A symposium sponsored by the Division of Industrial and Engineering Chemistry of the American Chemical Society, ACS 207th NATIONAL MEETING
San Diego
March 14-17, 1994
ORGANIZER:
C. Steven Sikes
The Mineralization Center
Department of Biological Sciences
University of South Alabama
Mobile, Alabama 36688
PHONE: 205/460-6352
FAX: 205/460-7642
INTERNET: SIYES@MOE.CHEM.USOUTHAL.EDU
LOCATION: Meetings: San Diego Conference Center Host Hotel: Embassy Suites
DATES: Monday RM., March 14 through Thursday, March 17,1994
COSPONSORS: Alabama Department of Economic and Community Affairs
The Mississippi-Alabama Sea Grant Consortium
The NSF/Alabama EPSCoR Program
Rohm and Haas Company
The University of South Alabama
The purpose of the symposium is to provide a forum for discussion of polyamino acids and related materials. Sidney W. Fox will deliver the keynote address. Professor Fox originated the work on thermal polymerization of amino acids some 40 years ago, the previous 20 years already including influential studies of amino acids and other compounds. From the beginning, his interests covered polyamino acids both as the possible basis of the emergence of life and as novel, useful materials. Uses covered in the symposium include such topics as ceramics, antifreezes, pathological calcification, antibiotics, corrosion inhibitors, fibers, elastics, adhesives, drug delivery, antiscalants, dispersants, biodegradability, anti-aging compounds, memory enhancement, artificial skin,. and others.
Monday, March 14, 1994
R.S. Young, Presiding
1:25 - Introductory Remarks
1:30- Thermal Polyamino Acids and Life: Experiments, Premises, Applications. S.W Fox
2:15 - Break
2:30 - Syntheses and Characterization of Thermal Polyamino Acid Prepared under Possible Prebiotic Reaction Pathways. K. Harada
3:00 - Prebiotic Polyamino Acids and the Origin of Protobiological Information. K. Dose
3:30 - Domain Protolife: Link Between Molecular and Biological Evolution. A. Pappelis*, S.W Fox
4:00 - Break
4:15 - Non-Random Sequence in Thermal Polyamino Acids. R Melius
4:45 - Liquid Crystalline Mesophases in Living Organisms. M. Ho
There will be a reception at the Embassy Suites hotel on Monday evening from 7 to 10 PM for participants and guests. At the reception at 8 PM, Dr. Henry King Stanford, President Emeritus of the University of Miami, will introduce Dr. Sid Fox who will then make a more informal presentation including personal recollections about his life and work.
Tuesday, March 15, 1994
J.H. Yopp, Presiding
7:55 - Introductory Remarks
8:00 - Thermal Heterocomplex Molecules from Amino Acids and Their Affinity Toward Various Monomers. K. Matsuno
8:30 - Proteinoid Potpourri. D.L. Rohlfing
9:00 - The Chemistry of Thermal Glycoproteins and Thermal Metalloproteins. P.R. Bahn
9:30 - Synthesis of Homo- and Copoly(Amino Acid)s by Direct Polycondensation. J.Z. Yang, E.C. Buruiana, R.M. Ottenbrite*
10:00 - Break
10:30 - Electrical Properties of Thermal Polyamino Acids. A.T. Pol
11:00 - Electrical Signal Activity in Membranous Vesicles of Thermal Polyamino Acids and Lecithin. B. Yu*, M. O'Keefe, S. Fox
11:30 - Primary and Tertiary Structures in Branched Proteinoids. R. Rosen
Lunch
J.H. Yopp, Presiding
1:25 - Introductory Remarks
1:30 - Dose-Dependent Anticalcification Effect of 2-Amino, Oleic Acid for Glutaraldehyde Crosslinked Bioprosthetic Tissues. W Chen*, J.D. Kim, F.J. Schoen, R.J. Levy
2:00 - Pathologic Calcification of Glutaraldehyde-Preserved Bioprosthetic Heart Valves. C.L. Webb
2:30 - Proteinoids - A Novel Drug Delivery System. S.J. Milstein
3:00 - Break
3:30 - Epidermal Growth Factor Controlled Delivery Systems Potentially Suitable for Enhanced Skin Regeneration. J.G. Winterowd
4:00 - A Family of Hydrophobic Peptides Containing Both D- and L-Amino Acids from Bombina orientalis. B.W. Gibson*, C. Moore, D. Tang, D. Medzihradszky, M. Tullius, R. Mandrell
4:30 - Recent Progress in the Development of Cecropin- and Melittin-Like Antibiotic Peptides. R.E.W. Hancock*, D. Wade
Wednesday, March 16, 1994
A.P. Wheeler, Presiding
7:55 - Introductory Remarks
8:00 - Kinetic and Thermal Characterization of the Hydrolysis of Polysuccinimide to Polyaspartate. J. Mosig, C.H. Goodin*, A.M. Atencio, B. Ballino, A.P. Wheeler
8:30 - Characterization of Thermally Prepared Polyamino Acids by Potentiometric Titration. E, Kokufuta
9:00 - The Effect of Calcium Ions on the Conformation of Thermally Polymerized Poly alpha, beta-Aspartic Acid. I.R. Collins, A. Wierzbicki, T.R. Edwards, C.S. Sikes, W.J. Benton*
9:30 - Break
10:00 - Modeling of Molecule-Surface Interactions. J.D. Madura
10:30 - Antifreeze Proteins. R.E. Feeney*, Y. Yeh
11:00 - Nonequilibrium Polymer Antifreezes. C.A. Knight
11:30 - A Molecular Modelling Study of the Winter Flounder Antifreeze Peptide as a Potential Hydrate Inhibitor. A.R. Edwards
Lunch
A.P. Wheeler, Presiding
1:25 - Introductory Remarks
1:30 - Fermentation of Marine Bacteria for Production of Novel Biomaterials. D.M. Manyak*, R.M. Weiner
2:00 - The Effects of Manganese on the Biosynthesis of gamma-Poly(Glutamic Acid) by Bacillus licheniformis, ATCC 9945A. A. Cromwick, G.A. Birrer, R.A. Gross*
2:30 - Controlled Nanostructure by Folding of Repetitive Polypeptides Synthesized in Escherichia coli. A.D. Parkhe*, M.J. Fournier, T.L. Mason, D.A. Tirrell
3:00 - Break
3:30 - A Unifying Mechanism for Diverse Energy Conversions and its Relevance to Protein Evolution in Living Organisms. D.W. Urry
4:00 - Highly Repetitive Proteins - Structure, Function, Genetics. C. Mello, S. Fossey, K McGrath, S. Arcidiacono, K. Senecal, M. Naldrett, J. Price, D.L. Kaplan*
4:30 - Spider Silk, Ancient Biomaterial for the Future. R.V. Lewis
Thursday, March 17,1994
A. Wierzbicki, Presiding
7:55 - Introductory Remarks
8-00- Enzymatic Production of Amino Acids. G.J. Calton
8:30 - Establishment of Industrial Production of L-Phenylalanine by Microorganisms. Y. Choi
9:00 - Coral Matrix Protein Fractions as Inhibitors of Corrosion and Scaling. E.M. Mueller*, C.S. Sikes
9:30 - Break
10:00 - Biodegradable Poly (Aspartic Acid) Detergent Polymers. M.B. Freeman, Y.H. Paik, G. Swift*, S.K. Wolk, K.M. Yocom
10:30 Biodegradation of Polyaspartate: Effect of Synthetic Methods. G. Schornick*, M. Kroner, R. Lungershausen
11:00 - The Biodegradability of Sodium Poly (alpha, beta-D,L-Aspartate). A.P. Wheeler*, D.D. Alford, L.P. Koskan
11:30 - Synthesis, Characterization and Biodegradation of Materials based on Poly(Amino Acids). F. Rypacek
Lunch
J.D. Madura, Presiding
1:25 - Introductory Remarks
1:30 - Commercially Useful Corrosion Properties of Polyaspartic Acid. D.J. Kalota*, D.C. Silverman
2:00 - Comparison of Polyamino Acids to Acrylic Acid Polymers for Industrial Water Treatment. W.H. Hann
2:30 - Processing of Complex Ceramics with the Aid of Biopolymers and Biomonomers. I.A. Aksay
3:00 - Break
3:30 - Relationship between Crystal Growth Inhibition of HA and In Vivo Anticalculus Effect. A. Gaffar*, E.C. Moreno, R.J. Gambogi, J. Afflitto
4:00 - Stereospecific Growth Control of Calcium Carbonate Crystals by Proteins and Polypeptides. A. Wierzbicki*, C.S. Sikes
4:30 - Biomineral Matrix Proteins as Models for Polyamino Acids. C.S. Sikes*, A.P, Wheeler
S.W. Fox, Coastal R.D. Institute, Univ. South Alabama, Mobile, AL 36688
Thermal polyamino acids (TPs) serve as precursors to protocells. Both TPs and laboratory protocells have properties of life, and also provide biomedical applications. Contrary to frequent assumption, TPs are found to be highly nonrandom; for either origins theory or utility, this attribute is essential. Thermal copolycondensation of amino acids occurs at terrestrial temperatures with inclusion of aspartic acid and/or glutamic acid. The TPs are ordered by their precursor amino acids instead of by DNA/RNA. Lysine-rich TPs catalyze formation of internucleotide bonds in water. In addition to numerous enzymatic activities, the TPs organize themselves (1959) into protocells having characteristics of life defined in Webster's Dictionary: metabolism, growth, reproduction, and responsiveness to stimuli. The results have led also to revised evolutionary theory, to explanation of the origins of neurons and their networks, and to applications: biocompatible materials for water purification, blood plasma expanders, nutritional materials, a new mode of drug delivery, antiaging of cells in culture, and memory enhancement in mice.
Aided by NASA, NFCR, the Longevity Foundation, and others.
K- Harada, Department of Liberal Arts, Shoin Women's University, Shinohara, Nada-ku, Kobe, 657, Japan.
In this study, a possible reaction pathway for the formation of protein-like copolyamino acids from gaseous starting materials is presented. The sequence of the reaction pathway is composed of four steps. These are 1) formation of fumaronitrile, 2) hydrolysis of fumaronitrile to, thermal precursors of aspartic acid such as ammonium fumarate or malate, 3) thermal copolycondensation of the precursors of aspartic acids with various other amino acids, and 4) formation of microspheres from the resulting copolyamino acids. Steps 2), 3) and 4) were demonstrated experimentally. The materials and the conditions used in this study could be regarded as prebiological. The thermal copolycondensation is also a convenient synthetic method of preparing aspartic-acid-containing various copolyamino acids.
K. Dose, Institute for Biochemistry, FB 19, J. Gutenberg University, D-55099 Mainz, Germany.
Individual amino acids interact in a non-random fashion both during carbodiimide-mediated peptide synthesis and thermal polymerization at 160 degrees C to 180 degrees C. In aqueous solution (during carbodiimide- mediated peptide synthesis) sequence selection is largely controlled by the reactivity of the individual amino acid residues. During thermal condensation, however, selection is largely achieved due to the stability ("survival") of the fittest intermediate (natural selection). In both types of polymerization reactions glutamic acid is readily converted into pyroglutamic acid that tends to occupy the N-terminal position of the growing polymer. Some mechanisms for the various polymerization processes will be presented. Evidence is summarized indicating that prebiotic polyamino acids may have served as carriers of protobiological information.
Aristotel Pappelis*, Southern Illinois University, Carbondale, and Sidney W. Fox, University of South Alabama, Mobile.
Cosmogenesis began with the Big Bang and proceeded through physical, chemical, and biological evolution. The emergence of life from thermal proteins (endogenously ordered polyamino acids), protocells (self-organized thermal proteins with attributes of life), and metaprotocells (protocells that can use light to synthesize ATP, can conduct nonribosomal protein synthesis, and can synthesize polynucleotides) yielded the prokaryotic cells of organisms in the Domains Bacteria and Archaea. Plants, animals, fungi, and protists (organisms of eucaryotic cells in the Domain Eucarya) evolved from the latter. We propose that protocellular activities, including protein-directed genetic information that led to a more modern DNA-based information system, are the link between chemical and biochemical unity of protolife and modern life, that this wholeness is part of nature encompassed by cosmogenesis, and that the mind of man can comprehend this unity. These experimental observations have been shown to relate to areas of human expression (science, philosophy, religion, etc.).
Paul Melius, Department of Chemistry, Auburn University, Auburn,. Alabama 36849
Thermal polymers of three to eight amino acids have been prepared by reaction at 180 to 200 degrees centigrade. All the mixtures contained glutamic acid and the polymers were ninhydrin negative, which indicates that there is no free amino group in the polymers. This has been shown to be due to a pyroglutamyl group at the N-terminus of the polymers. Glutamic acid has been shown not to be at the C-terminus of the polymers. Some sequencing information has been obtained of fragments of these polymers. All the evidence is consistent with a non-random sequence in the polyamino acid polymers.
Mae-Wan Ho, Bioelectrodynamics Laboratory, Open University, Walton Hall Milton Keynes, MK7 6AA, U.K.
I describe a novel technique that optimizes the detection of small birefringences over all polarization directions, and hence enables us to obtain, for the first time, high resolution and high contrast coloured images of entire, living, moving organisms based on visualizing coherent liquid crystalline mesophases in living tissues. This technique is particularly useful for monitoring coherent motions in phase ordered polymers, and will also have applications in characterizing and identifying subtly different mesophases that polymers can adopt under different conditions.
Koichiro Matsuno, Department of BioEngineering, Nagaoka University of Technology, Nagaoka 940-21, Japan.
Thermal heterocomplex molecules made by heating the mixture of aspartic acid and proline consist of two different species, whose molecular weights are roughly 4000 (called DPI) and 1400 daltons, respectively. DPI molecules aggregate themselves in their aqueous suspension and form microspherical structures. Microspherical structures thus formed exhibit an affinity toward monomeric amino acid, histidine. On average, one DPI molecule is found to adsorb 0.25 molecules of histidine in the saturated condition. DPI microspheres also exhibit an affinity toward nucleoside, adenosine. The saturated adsorption of adenosine per DPI molecule is found to be 0.4 molecules : These observations suggest a possibility that thermal heterocomplex molecules from amino acids would provide an evolutionary stage for promoting and enhancing the synthesis of polymers abiotically.
Duane L. Rohlfin Department of Biological Sciences, University of South Carolina, Columbia, SC 29208
Several studies on thermally prepared polyamino acids, or proteinoids (ptds), will be summarized and include:
Ptds containing controllably varied proportions of histidine catalyze the hydrolysis of p-nitrophenyl acetate, up to ten-fold faster than free histidine. The ptds were largely inactivated by heating in buffer. When stored dry, they were stable for years.
Ptds form at 65-85 degrees C (cf. 170 degrees C) when reactants are heated for weeks (cf. hours).
The presence of sand during polymerization enhances yields and influences some properties of ptds. Syntheses at low atmospheric pressure are similarly influenced.
Optically active ptds result from L-amino acids (AAs). Racemization of various AAs ranged from 100% to only 16%, and was influenced in part by other co-present AAs.
Glycine-rich ptds form from reactants conforming to analyses of extraterrestrial samples or reported product of simulated prebiotic syntheses. Most of these-ptds contain nonproteinous AAs; some ptds were made from only nonproteinous AAs.
Lysine-rich ptds form microspheres that resemble Oparin's coacervate droplets but contrast with acidic-ptd microspheres. The extent of formation of microspheres of both types was influenced by some of several tested types of enveloping atmospheres.
Peter R. Bahn, Bahn Biotechnology Co., RR1 Box 261, Woodlawn, Illinois 62898 USA
The Proteinoid Theory of the Origin-of-life, created and developed by Sidney W. Fox over the last four decades, represents the most extensive, experimentally verified theory of molecular evolution to have been generated in the modern scientific era. The Proteinoid Theory postulates that thermal copolyamino acids were the first proteins to appear on the Primitive Earth. The Proteinoid Theory also postulated that the thermal cyclization of glutamic acid to pyroglutamic acid and the thermal polymerization of aspartic acid to polyaspartic acid were the original chemical initiator reactions leading to protein synthesis on the primitive Earth. The Formose Reaction, in which formaldehyde is polymerized to monomeric carbohydrates, is thought to account for the original synthesis of sugars on the Primitive Earth. When sugars are included in a mixture of thermally polymerizing amino acids, thermal glycoproteins appear to be synthesized. Thermal glycoproteins constitute an experimental model for the first glycoproteins to appear on the Primitive Earth. Metals are currently believed to be products of stellar nucleosynthesis. When metal chloride salts are included in a mixture of thermally polymerizing amino acids, thermal metalloproteins appear to be synthesized. Thermal metalloproteins constitute an experimental model for the first metalloproteins to appear on the Primitive Earth.
J.Z. Yang, E.C. Buruiana, and R.M. Ottenbrite*, Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284
Synthetic poly(amino acids)s have been prepared mainly by thermal polymerization (Fox) or via NCA (Leuchs). Recently, a convenient approach was studied involving direct polycondensation of amino acids. In this study, diphenyl phosphoryl azide (DPPA) was used as a reagent for the direct condensation. The polymerization was carried out by stirring the monomer/ solvent mixture at room temperature in the presence of DPPA and triethylamine (TEA). Homo- and copolymers were obtained from a-amino acids such as aspartic and glutamic acids, phenylalanine and tyrosine in reasonable yields. The molecular weights of the poly(amino acid)s were about 37,000. The yields as well as the molecular weights of the polymers were dependent on [DPPAI/[Monomer] and [TEA]/[Monomer] ratios. Copolymers with molecular weights from 4,900 to 36,700 were also obtained from the direct copolycondensation of a-amino acids with other a, o)--amino acids. The direct polycondensation is a viable approach to synthesize poly(amino acid)s.
Alexander.T. Pol, Department of Biomedical Engineering, College of Engineering, University of Miami, Coral Gables, FL 33124-0621
Electrical properties of double-layer membranous vesicles, assembled from thermal polyamino acids (proteinoids) were measured using conventional electrophysiological technique. It has been found that there exist in such structures membrane polarization and oscillations resembling neuronal action potentials and transmembrane channel gate currents. Both the "resting" and "action" potentials of the vesicles were influenced by light, pH of the salt environment, potassium transmembrane difference, and electrical stimulation resulting in the switching of transmembrane electrical polarization.
These electrical properties are determined by the electrical charge of the constituent chemical groups of the polymers and their orientation within the membrane.
Obtained data indicate that material modeling of the neuron and chemical assembly of computer switching elements is possible.
Bi Yu*, Michael O'Keefe, and Sidney Fox, Coastal Research & Development Institute and Mineralization Center, University of South Alabama, Mobile, 36688
The properties of proteinoid microspheres have been catalogued since before 1970. Special attention has been paid since then to the responses of the microspheres to light. Patterns of electrical signals depend upon the composition of the thermal polyamino acids (TPs) in combination with lecithin. [TPs are known also as proteinoids (ptds).] When lecithin is included in the microsphere with either (phe)-rich equimolar TP or (leu)rich equimolar TP (LTPs) an almost flat baseline results from the microelectrode resting in the suspension. When the microelectrode penetrates an LTP vesicle and then is withdrawn repeatedly, activity is found to correlate with the penetration. Duration and amplitude of the spiking with the material contained has been studied. These and other experiments (Vaughan et al, 1987) indicate that the activity resides in the TP membrane and not in the lecithin, although inclusion of lecithin affects the quantitative response.
R. Rosen, Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia, B311 4117
In linear, biologically active polypeptides, there is a sharp distinction between primary structure or sequence, held together by strong covalent (peptide) bonds, and a tertiary or folded structure. The latter is presumed to bear the biological activities in the form of active sites and epitopes. The discovery of proteinoid by Sidney Fox has indicated that the same monomers can be assembled into other polymers, not exclusively peptide-bonded, with some unique activities (e.g., microsphere formation). Since linear polypeptides are not known to behave in this way, attention is drawn to branching of proteinoid polymers. In this note, we shall consider the analogs of folding in branched structures, and the roles of equilibria between folded and denatured structures, in relation to origin-of-life questions.
W. Chen*, J.D. Kim, F.J. Schoen, R.J. Levy, Div. Pediatric Cardiology, Univ. Michigan Med. Center, Ann Arbor, MI 48109-0576
Post-implant calcific degeneration is a frequent cause of most clinical failures of bioprosthetic heart valves (BPHV) fabricated from glutaraldehyde cross-linked porcine aortic valves. Our main objective was to study the dose-dependent anticalcification mechanism of amino oleic acid (AOA) covalently bound to both cusps and aortic wall tissues. The diffusion of calcium ions across both cusp and aortic wall tissues was evaluated, and the results demonstrated that there was aAOA dose-dependent retardation of calcium ion penetration. Studies were also performed to determine the stability of AOA binding, and the results revealed that a significant amount of AOA remained bound to the BPHV tissue after 8 months. AOA inhibition of BPHV calcification was found to be dose dependent with maximum AOA level resulting in the lowest calcium levels. The significance of AOA binding on tissue was determined by either blocking or reducing its free aldehyde residues, using either lysine or NaBH,, respectively, prior to AOA treatment. The tissue (experimental and control) calcium levels after 60 days of implant were comparable. It is concluded that AOA inhibition of calcification may be related to the duration of exposure.
Catherine L. Webb, Division of Pediatric Cardiology, The Children's Memorial Hospital, Northwestern University, Chicago, Illinois 60614
Calcific degeneration of glutaraldehyde-preserved bioprosthetic heart valves causes significant complications in patients with valvular heart disease. Strategies which have been employed for inhibition of pathologic calcification include tissue pretreatment with detergents, diphosphonates, trivalent cations, and polyaspartate, but they are limited because of lack of long-term effect. The mechanism of this calcification is not completely understood. We reasoned that similar processes may operate in physiologic mineralization (bone, teeth) as well as dystrophic calcification of biprosthetic heart valves. Several noncollagenous proteins - osteopontin, bone-acidic glycoprotein-75, and osteonectin - have been identified in association with mineralizing bone and teeth. Due to their high acidity and negative charge, they could provide a mineral source by binding calcium ions. This talk will discuss: 1) the identification of specific noncollagenous proteins in pathologically calcified glutaraldehyde - preserved bovine pericardium in the rat subdermal model, 2) immunohistochemistry over the duration of the rat subdermal implant, and 3) identification of invading immune cells in these rat subdermal implants using flow cytometry. The results suggest new possibilities for specific therapeutic interventions directed at extending bioprosthetic heart valve longevity.
Sam J. Milstein, Emisphere Technologies, Inc., 15 Skyline Drive, Hawthorne, New York 10532
We have developed a novel drug delivery system composed of thermally condensed amino acids (proteinoids). These proteinoids have unusual properties in that they undergo a phase transition that is pH determined. For the oral delivery of therapeutic compounds we have developed a family of proteinoids that at acidic pH values manifest themselves as hollow microspheres ranging in size from 0.3 to 10 microns. At neutral or basic pH values, the microspheres spontaneously dissolve.
We have tested in vivo the delivery in our microspheres of proteins, mucopolysaccharides and small organic compounds. Successful results have been demonstrated in 6 animal species including primates.
In addition, the delivery system has demonstrated the capacity to deliver viral antigens offering the possibility of a generic oral immunization vehicle.
Jack G. Winterowd, Polymers Group, Weyerhaeuser Co., Tacoma, WA 98477
We have developed a hydrophilic film which could potentially be used as a bandage to increase the rate of skin regeneration in burn victims. The film is primarily composed of small amounts of epidermal growth factor (EGF) protein embedded in a matrix of chitosan. The chitosan is degraded by lysozyme, which is present at the wound site. This alleviates the need to painfully and destructively remove used covering from the wound site. The kinetics of the drug rate for different variations of this film will be compared to state of the art delivery systems for the EGF protein.
B.W. Gibson*, C. Moore, D. Tang, D. Medzihradszky, M. Tullius and R. Mandrell, Department of Pharmaceutical Chemistry, University of California, San Francisco CA 94143
Previously we had reported the isolation and characterization of a family of amphipathic antimicrobial peptides from the skin of Bombina orientalis (Asian Toad). After sequencing the cDNA encoding the precursors to these antimicrobial peptides a second family of hydrophobic peptides were found that were encoded on the C-terminus of the precursors. To confirm this possibility, the skin secretions of B. orientalis were thoroughly examined and a set of peptides isolated that had the expected masses. LSIMS analysis of the skin secretions revealed several pairs of peptides eluting at different HPLC retention times with the same mass and amino acid sequence as determined by both Edman and tandem (MS/MS) analyses. To determine the basis for their structural differences, we carried out a more extensive sequencing effort using thermolysin, carboxypeptidase Y and amino peptidase M digestions in combination with HPLC and MS/MS analysis. Our studies found these peptides to contain N-terminal isoleucine in both the normal L-configuration as well as the unexpected D-configuration in nearly equal abundance, as confirmed by synthesis. The biological value of such a modification is suggested from the lack of proteolytic action seen in the arninopeptidase M experiment, thus providing a means to stabilize these peptides. Circular dichroism studies suggest a type II 0-turn structure. Biological assays of these peptides, however, showed very little antibiotic or hemolytic activity, and investigations are underway to assay for antifungal, anti-viral or even mastoparan-like cytotoxic activities.
R.E.W. Hancock*, Canadian Bacterial Diseases Network, UBC Campus, Vancouver, B.C. Canada, V6T 1Z4; D. Wade, Protein Engineering Network of Centres of Excellence, 720 Heritage Medical Research Centre, University of Alberta, Edmonton, Alberta T6G2S2
The cecropins are a group of peptides, 31-39 amino acids in length, that were originally isolated from pupae of the silkmoth, Hyalophora cecropia. Mehttin, a peptide of 26 amino acids, is the major toxic component in the venom of the honeybee, Apis mellifera. Both types of peptides are basic (net charge = +3 to +8), amphipatic, and amidated at their carboxyl terminals. Both have potent, broad spectrum, antibacterial activities, and melittin is toxic to eukaryotic cells. Many analogs and combinations of the amino acid sequences of these peptides have been synthesized in an attempt to create an antibiotic with enhanced activity and reduced toxicity. Mechanistic studies indicated that the mode of action may involve the formation of ion channels in cellular plasma membranes. Recent work has focused on: developing the smallest analog that retains full activity, determining structures in solution, the use of genetic engineering to clone and express these peptides, and further investigation of the mechanism of action.
J. Mosig(1), C.H. Gooding*(1), A.M. Atencio(2), B. Ballino(2), and A.P. Wheeler(3). Departments of Chemical Engineering (1) and Biological Sciences (3), Clemson University, Clemson, South Carolina 29634 and Donlar Corporation(2), Bedford Park, Illinois 60501.
Large-scale thermal polymerization of aspartic acid is under development for the production of polyaspartate (PA) because of a growing interest in biodegradable polyanions. These polymers can be used as water treatment and detergent additives and as superabsorbents. The process of synthesis usually involves two steps: thermal polycondensation of aspartic acid to polysuccinimide, (PS) and base hydrolysis to the imide to form (x, 0,D,L-PA. The PS has been produced on a commercial scale. However, prior to this work the hydrolysis had not been studied sufficiently to optimize conditions for scale up. An empirical rate model for hydrolysis was developed based on a tbeoretical shrinking-core model and data from laboratory scale titrations of PS with NaOH at varying temperatures and pH's. The model combined with measurements of the specific surface area and heat of hydrolysis of PS and the specific heat of PA solutions as well as microscopy of PS during hydrolysis provides a base for designing large-scale hydrolyses of PS.
Etsuo Kokufuta, Institute of Applied Biochemistry, University of Tsukuba, Tsukuba, Ibaraki 305, Japan
The following three polyamino acids were prepared by thermal polycondensation: poly(aspartic acid), copoly(glutamic acid, alanine), and poly(lysine). These thermally prepared polyamino acids were characterized by means of potentiometric titration, which was performed at different ionic strengths using aqueous NaOH and HCI solutions as the standard titrants. The intrinsic dissociation constants (pK-int) of carboxyl and amino groups in the thermal polyamino acids were studied using different analytical methods; from these studies the ratio of the alpha- and omega-linkages of the amino acid residues were estimated. It was found that the thermal poly(aspartic acid) consisted of aspartyl residues with both alpha- and omega-carboxyl groups (pK-int=3.2 plus or minus 0.1 for alpha-COOH; pK-int=4.3 plus or minus 0.1 for beta-COOH), while the copoly(glutamic acid, alanine) contained only alpha-COOH (pK-int=3.9 plus or minus 0. 1). The lysyl residues in the thermal poly(lysine) has mainly alpha-amino groups (pK-int =7.4 plus or minus 0. 1). These results are discussed in connection with the formation mechanism of the aspartyl, glutamyl, and lysyl residues in the polyamino acids during the thermal polycondensation.
Ian R. Collins (1), Andrzej Wierzbicki (2), Tony R. Edwards (3), C. Steven Sikes (4), and William J. Benton* (5). BP International, Group Research and Engineering (1), Sunbury, UK, Dept. of Chemistry, University of South Alabama (2), Mobile, Alabama, USA, BP Exploration, Production Operations Branch (3), Sunbury, UK, Dept. of Biological Sciences (4), University of South Alabama, Mobile, Alabama, USA BP Exploration (5), Westport Technology Center International, 6700 Portwest Drive, Houston, Texas, 77024 USA.
Thermally polymerized poly alpha, beta-aspartic acid (Mw = 4400) consists of 70-80% of the beta-form. The added carbon atom from the beta-form. of aspartic acid in the peptide backbone provides added rotational freedom which determines the tertiary conformation. This structure differs from the well known helicoids and beta sheets of the alpha-form of polyaspartic acid. The solution pH and the addition of divalent ions such as calcium influence the macromolecular hydrodynamics and the resultant tertiary conformation. Dynamic and static light scattering, and viscometry have shown that the tertiary conformation changes with increasing pH from an essentially random coil to an extended structure. The addition of calcium ions in the lower pH range (ca. 4.5) extends the molecule from a random coil-like structure to a rigid rod-like structure. Molecular modeling of these effects has been attempted to identify the specific tertiary structure, the functionality and the degree of association in the presence of divalent ions.
Jeffrey D. Madura, University of South Alabama, Department of Chemistry, Mobile Alabama, 36688-0002
Molecular recognition at interfaces is a concept of central importance in physics, chemistry and biology. This concept is manifest in crystals which, in their different functions and forms, are basic components of the world surrounding us, from minerals, ceramics, and microelectronic components, to bones, shells, and teeth. Experimentally, molecular recognition is explained through thermodynamics, kinetics and now atomic microscopy techniques such as scanning tunneling microscopy and atomic force microscopy. From these methods molecular interactions can be inferred. With recent advances in quantum mechanics and statistical mechanics along with computer hardware and software developments we can now address molecular interactions at interfaces on a molecular level. How the methods M computational chemistry can be used to probe these interactions will be discussed. Application of these methods to the interaction between the winter flounder antifreeze peptide and ice will be discussed.
R.E. Feene* and Y. Yeh, University of California, Davis, CA 95616
Since the early observations of a physiologist (Scholander et al. Physiol. Zool. 26:67, (1953)) that there was something in Arctic fish blood that caused abnormally low freezing temperatures, extensive progress has been made in characterization and understanding of the mechanism of action of the responsible proteins and peptides. A most plausible hypothesis is the noncolligative kinetic adsorption process of these proteins at the ice-solution interface. Found in fish, insects and plants, the main ones studied are the glycoproteins (AFGP) and a non-glycoprotein (AFP) from fish. Both species have two-thirds of amino acid composition as alanine. At or below the freezing temperature, their function is manifested in altering the growth habits of crystals. Needle-like spicules or higher concentration of AFGP near the prismatic surface affects the size of the gas bubbles extruded from a growing ice crystal. AFGP molecules also have very strong capacity to inhibit grain boundary migration and growth in recrystallization. Under these conditions, AFGP-8 (MW=2700) is at least as effective as AFGP-4 (MW=18,000) as measured by their activation energies against grain growth.
C.A. Knight, National Center for Atmospheric Research, Boulder, CO 80307
A variety of natural peptides and glycopeptides adsorb strongly at the ice-water interface and exert profound effects upon ice formation. Their molecular weights range from a few thousand to about 100,000, and evidence shows that the adsorption is virtually irreversible. The adsorption is crystallographically specific, evidently requiring a structural match between the adsorbed molecules and the ice surface, and different antifreezes have different adsorption planes. Detailed models have been constructed of the adsorption of several of the antifreezes, and it is clear that the antifreeze molecules reside in the surface, accounting for the permanence of the bonding. These materials actually prevent crystal growth over an appreciable supercooling range. Models of how this happens exist but are not quantitative, so there is no theoretical estimate of the limit of this kind of effect. Poly (vinyl alcohol) also has these effects.
Dr. Antony R. Edwards BP Exploration, Sunbury Research Centre, Chertsey Road, Sunbury-On-Thames Middlesex, England Gas hydrates are crystalline solids that have an ice like appearance and consist of two or more components. Free water molecules hydrogen bond to form polyhedral "cages" which are occupied by one or more small gas molecules such as methane. Hydrate formation can cause serious problems in oil and gas production by blocking pipelines, valves and other process equipment. Hydrate formation will occur when conditions of high pressure and low temperature reach respective threshold values. The problem is becoming more important as natural gas and gas-condensate resources are discovered in areas of deep cold water and on-shore colder climates. At present hydrate formation is prevented by using thermodynamic inhibitors such as methanol and triethylene glycol. These methods are expensive and can cause process difficulties. Arctic and Antarctic fish such as the Winter Flounder kinetically inhibit ice formation in their body fluids by using AntiFreeze Polypeptides (AFP's). Both experimental and modeling work has been carried out that show that these molecules adsorb onto the ice surface and inhibit growth. Molecular modeling calculations have been performed that show a preferential adsorption site for the winter flounder peptide (HPLC-6) on the 11001 face of the type 1 gas hydrate. The adsorption energies compare favourably with those of Wen and Laursen (1992) for the same molecule on the 12021) face of the ice 1h structure. Calculations show that there are 15 hydrogen bonds between the peptide and the gas hydrate water lattice compared to 13 for the molecule adsorbed onto ice. It is proposed that the Fish AFP would be an effective kinetic gas hydrate inhibitor.
David M. Manyak* (1) and Ronald M. Weiner (2), Oceanic Biosciences Corp. (1), Hanover, MD 21076 and Department of Microbiology (2), University of' Maryland, College Park, MD 20742
Marine organisms, including marine bacteria, produce a variety of polymeric biomaterials having unique properties and potential industrial applications. As with other natural biopolymers, a major hurdle to commercializing these materials is the availability of a renewable supply of raw material at a sufficiently low cost. Our group has been developing adhesive polymers from benthic: marine bacteria that bond to wetted surfaces underwater. The biofilms that these bacteria produce consist of exopolysaccharides (EPS), some with integral peptide residues. We have developed methods for low-cost fermentation of marine bacteria in order to scale up production of the EPS. A cost- and performance-optimized culture medium was selected from among several dozen evaluated. Cell counts as high as 10-to-the-twelfth /ml were achieved, and growth was supported for a variety of marine strains tested to date. Large-scale fermentation of marine bacteria is a promising approach for producing commercially valuable biopolymers for industrial applications.
Anne-Marie Cromwick, Gregory A. Birrer and Richard A. Gross*, Department of Chemistry, University of Massachusetts Lowell, 1 University Ave., Lowell, MA 01854
B. licheniformis ATCC 9945A was cultivated in shake flasks using citrate, glutamate and glycerol as carbon sources. The effect of the media MnSO4 concentration over a range between 0.0 to 615 micromolar was studied. The number of viable cells increased for all concentrations of MnSO4 from approximately 10-to-the-fifth to 10-to-the ninth cfu/ml. by the early stationary phase. However, after 50 h, the cell viability decreased rapidly for relatively lower (0.615 and 0 micromolar) MnS04 concentrations. Gamma-PGA volumetric productivity increased from approximately 5 to 15 g/L for corresponding increases in MnSO4 concentration from 0 to 61.5 micromoles and then decreased at higher MnS04 concentrations. The molecular weight decreased with time at all observed MnSO4 concentrations but at a greater rate and to a greater extent with increasing MnS04 concentration. In addition, at 615 and 0 micromolar MnSO4 the [L]-isorneric content of the glutamate repeat units in gamma-PGA was approximately 10 and 50%, respectively. X-ray diffraction analyses of these two samples showed identical d-spacings, suggesting the absence of a stereocomplex crystalline from 13 NMR on gamma-PGA which contained 50% [L]-glu suggests that at least some of the polymer chains formed are stereocopolymers.
A.D. Parkhe* (1), Maurille J. Fournier (2), Thomas L. Mason (2) and David A. Tirrell (1) Departments of Polymer Science and Engineering (1), and Biochemistry and Molecular Biology (2), University of Massachusetts, Amherst, MA 01003 USA
Polypeptide 1 comprising alternating beta-sheet-forming hexapeptides ((AG)3 and (GA)3 ) and turn-forming diads (EG) has been designed on the basis of protein sequence-structure relationships. DNA encoding I has been cloned in pET-3a (an expression plasmid). Subsequently, the polypeptide has been expressed in E. coli and a purification scheme has been developed to yield pure 1. The product of this scheme of synthesis and purification is monodisperse 1 with precise sequence and chirality. Polymer I has been crystallized by stirring a solution of 1 in 70% formic acid for 48 h. X-ray diffraction analysis suggests formation of beta sheet domains. The folding habit of the chains has been elucidated by blending I with a 13C-enriched analogue of 1 followed by FTIR spectroscopy. These data suggest chain folding by adjacent re-entry and lamellar morphology.
Dan W. Urry Lab. of Molecular Biophysics, Univ. of Alabama at Birmingham, VH 300; Birmingham, AL 35294-0019.
Living organisms evolved by developing the capacity to access available energy forms and by converting them into life-sustaining forms of energy. The forms of energy which living organisms utilize can be listed in terms of six intensive variables of free energy; these are: 1) mechanical force, 2) temperature, 3) pressure, 4) chemical potential, 5) electrochemical potential, and 6) electromagnetic radiation. A single mechanism, that of controlling the temperature at which hydrophobic folding and assembly occur in model proteins, has been shown to be capable of interconverting these energy forms. In particular, all of the five pairwise energy conversions coupled to mechanical force development due to folding have been demonstrated using elas4tic matrices formed on crosslinking the model proteins. The elastic matrix can be swollen at 20 degrees C and can contract on raising the temperature to 40 degrees C, lifting weights more than a thousand times its dry weight. This is the conversion of thermal energy into mechanical work. Without changing the temperature and with proper design, the above energy inputs can change the temperature, Tt, at which the thermally driven contraction occurs. If for example, Tt is greater than 37 degrees C, the matrix will be swollen at 37 degrees C; but when an input lowers the value of Tt 15 degrees to 20 degrees C, that input drives contraction and performs work. This is called the DeltaTt- mechanism of energy conversion. Only small changes in protein composition are required to make the protein responsive to different energy inputs at a given temperature; this design process is readily available to protein evolution.
C. Mello, S. Fossey, K. McGrath, S. Arcidiacono, K. Senecal, M. Naldrett, J. Prince, D. Kaplan*, Biotechnology Division, US Army Natick Research, Development and Engineering Center, Natick, Massachusetts 01760-5020
Biological systems employ highly repetitive motifs in some proteins to provide a range of function. The use of this approach may offer benefits in terms of material properties as well as adaptability/evolution issues. These designs can also lead to problems for the host in terms of specialization in biosynthetic processes and bioprocessing, and problems related to genetic manipulation of these systems. These issues will be explored with data collected from native spider silk and elastomeric resilin proteins, and with synthetic proteins designed based on coiled-coil heptad repeats and on spider silk. Topics to be covered include the characterization of repeats present in the native proteins, issues of secondary structure, genetic coding, and cloning issues. Strategies to utilize these types of protein repeats towards the design, biosynthesis and processing of new types of protein polymers will be presented.
Randolph-V.-Lewis Dept. of Molecular Biology, U. of Wyoming, Laramie, Wyoming 82071-3944
Spider dragline silk is one of the strongest materials known, with tensile strengths of 300,000 psi and an elasticity of over 30%, resulting in an energy to break of 150,000 J/kg. We have shown it is composed of two different proteins, Spidroins 1 and 2, which provide both the tensile strength and elasticity. Fourier transform infrared spectroscopy (FTIR), circular dichroism (CD), fiber X-ray diffraction and bound and free water content were used to examine the fibers and the proteins. Based on the protein sequences, we have proposed structures for both proteins which are consistent with current biophysical data and can explain the mechanical properties of the fiber. These structures consist of extended beta-sheet structure in the poly-Ala regions and linked beta-turns in the Gly rich regions which from the crystalline (hard) and elastic (soft) segments respectively. Data from the other spider silks indicate different protein sequences lead to distinctly different physical properties. However, each protein has some sequence similarity to other silk proteins.
Gary J. Calton, SRCHEM, Inc., 5331 Landing Road, Elkridge, MD 21227
The last decade saw a revolution in the production of amino acids due to the need for large quantities of specific amino acids in large quantities in high enantiomeric purity. Both L-aspartic acid and L-phenylalanine went from a level of use of 100 MT/yr to >5000 MT/yr. The resulting markets drove a number of venture based chemical firms to research novel methods of production. The enzymatic and microbial routes showed a clear superiority to achieve the required enantiomeric purity. Improvements in immobilization techniques provided clear superiority in cost of production. Developments in the effective economic use of enzymes and microbes will be illustrated using the most effective methods of immobilization available. The production of L-aspartic acid, of interest due to the ability of polyaspartic acid to provide an environmentally benign, yet effective inhibition of crystallization of calcium salts, provides an astounding illustration of the power of the microbe.
Young-Bok Choi, Miwon Co., Ltd., Seoul, Korea
Production of L-phenylalanine is the subject of academic and industrial interest because it is essential in production of aspartame. A tyrosine auxotrophic mutant, MVYTC27, of Escherichia coli, which accumulated 2.3 grams of L-phenylalanine per liter, was improved by a genetic procedure. A selected mutant, NPvVWJ304, accumulated 21 grams of L-phenylalanine per liter, but the production of L-phenylalanine was unstable due to loss of plasmid DNA from the host strain during fermentation, and the production rate of L-phenylalanine decreased at about 30 g/L concentration of L-phenylalanine. The final mutant, now used commercially, MWOR274, improved from MWWJ304, produced 27 g/L of L-phenylalanine. Increased yield of L-phenylalanine by MWOR247 may have been effected by increased resistance to high osmotic pressure in culture. MWOR274 has advantages as follows: (A) The growth is very good even in an excess of sorbitol or sodium chloride, and (B) The production of L-phenylalanine (LPA) does not decrease even after a high concentration LPA accumulates in culture.
Erich M. Mueller* and C. Steven Sikes, The Mineralization Center, University of South Alabama, Mobile, AL 36688
Protein fractions from oyster shell matrix, and their synthetic analogs, have previously been demonstrated to inhibit the formation of calcium salts and to inhibit steel corrosion in sea water. Protein fractions isolated from corals demonstrated similar activity. Fractions from Montastrea annularis skeletal matrix were particularly efficacious inhibitors of steel corrosion in high calcium formation waters. Amino acid analysis of the fractions demonstrated that aspartic and glutamic acids were the predominant amino acids present, a finding consistent with studies of other biomineral matrices. In vitro studies have also associated the polyanionic moieties with inhibition of scale formation. The addition of several different non-acidic amino acids to polyaspartate chains can improve anti-scaling activity but does not appear to significantly enhance corrosion inhibition. Thus, the polyanionic nature of the molecules appears to be primarily responsible for corrosion inhibition but the structure-function relationships between anti-corrosion and antiscaling activities are not identical.
M.B. Freeman, Y.H. Paik, G. Swift*, S.K. Wolk, YM. Yocom., Rohm and Haas Company, Spring House, Pennsylvania 19477
For close to a decade, biodegradable polymeric carboxylic acids have been the "holy grail" of the detergent industry as replacements for the widely used polymers of acrylic acid and copolymers of acrylic acid and maleic acid. While these polymers are not known to be harmful to the environment, the detergent industry has a long history of promoting the use of the most environmentally acceptable products in their detergent formulations. In this regard, the goals for biodegradable polymeric carboxylic acids are high; total biodegradation to gaseous products, biomass, and salts in the shortest time possible. There is a preference for completion of biodegradation in a few days, such that the polymers never enter environmental compartments beyond a sewage treatment plant. A new class of proprietary poly(aspartic acids) described in this paper, having molecular weights (Mw) in the range 4000 to 30,000 daltons, meet this difficult goal.
Q. Schornick, M. Kroner, R. Lungershausen, BASFAG, 67056 Ludwigshafen, Germany
The request for environmentally beneficial polymers has prompted the search for biodegradable polymers for many applications. Polyanionic proteins are known to disperse particles and control mineral growth. Potential applications include use as detergent, paint additive and in water treatment. One example for such a polyanionic protein is polyaspartate for which several synthetic routes are described in literature. This talk will discuss the effect of synthetic methods on biodegradation behavior of polyaspartate. Following OECD guideline 302B studies have been undertaken using activated sludge from a waste water treatment plant and monitoring DOC reduction. Polyaspartate synthesized in phosphoric acid shows a DOC reduction >95% whereas thermally polymerized polyaspartate starting from L-aspartic acid or maleic anhydride/ammonia yields only a level of 70% or 60%, respectively. These reduced biodegradation levels are attributed to a by-product detected by 13C-NMR.
A.P. Wheeler* (1), D.D. Alford (1)and L.P. Koskan (2). Department of Biological Sciences (1), Clemson University, Clemson, South Carolina 29634 and Donlar Corporation (2), Bedford Park, Illinois 60501
The search for biodegradable polymers has led workers to consider the use of poly(alpha, beta-D, L-aspartate) in water treatment, paper processing and as a detergent and paint additive. Therefore, a detailed study of the biodegradation of the polymer was undertaken. PA was produced by NaOH hydrolysis of a polysuccinimide synthesized by thermal polymerization of aspartic acid. PA was incubated with both dilute effluent and activated sludge from a waste water treatment plant. Low biomass effluent experiments show changes in molecular size of PA concomitant with oxygen demand induced by the polymer, suggesting susceptibility of the polymer to proteolysis. Low biomass sludge experiments yielded >70% mineralization of 10-20 mg/L PA by 28 days, suggesting that a significant portion of the polymer was quite labile. High biomass sludge experiments using 14C-PA at 1 mg/L revealed 30-40% mineralization and 95% removal of PA from solution in less than 5 days, followed by a much slower rate of CO2 evolution. Accordingly, it may be concluded that PA would be subject to degradation in a waste water treatment plant and would not appear in the plant effluent.
F. Rypacek*, J. Pytela, R. Kotva and V. Skarda, Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, 16206 Prague, Czech Republic
Synthetic poly(amino acid) derivatives are investigated as fully biodegradable polymers. Homopolymers and random or block copolymers of glutamic acid esters and amides can be prepared in a broad range of structural modifications either through copolymerization of respective NC-anhydrides and/or selective chemical reactions of side chains. Water-soluble polymers, neutral or ionic, are biodegradable by endo- and exo-peptidases. The enzyme specificity and the rate of degradation can be adjusted during the synthesis by copolymerization with other amino acids or by side chains modifications. Methods used for evaluation of their biodegradation are discussed. Copolymers with various biodegradation specificity are designed for controlled release systems as crosslinked hydrogels and block-copolymer micelles. The role of structural features of polymers and the specificity of their degradation for the performance of the delivery systems is discussed.
D. J. Kalota* and D. C. Silverman, Monsanto Company, 800 N. Lindberg Blvd., St. Louis, Mo 63167
Concern about environmental, health and regulatory issues has resulted in efforts to identify non-toxic and biodegradable water-based replacements for traditional products. Successful candidates will likely be multifunctional. In many water-based commercial applications the ability to inhibit corrosion is important. A study of the corrosion properties of aspartic acid and polyaspartic acid showed that they effectively inhibited the corrosion of steel at pH's above 9.6. The uniformity of the corrosion improved with higher concentrations and, for aspartic acid, under the dynamic conditions of a rotating cylindrical electrode in a device for estimation corrosion by measuring electrical impedance. Under static conditions pitting was reduced by using higher concentrations.
William M, Hann, Rohm and Hass Company, Spring House Laboratories, Spring House, PA 19477
Polymers based on acrylic acid and other synthetic vinyl addition monomers have been used for more than three decades to inhibit scale and enhance corrosion inhibition in a multitude of industrial water treatment applications. Recently, polymers based on L-aspartic acid have been suggested for use in many of the same applications. Comparisons between these two broad classes of polymers in tests modeling industrial water treatment processes are reported and explanations are offered for some of the differences found between them.
Ilhan A. Aksa Department of Chemical Engineering and Princeton Materials Institute, Princeton University, Princeton, NJ, USA 08544
The technique most commonly utilized in ceramics manufacturing is based on powder consolidation. Pores between the powders are then eliminated through heat treatment at elevated temperatures. In contrast, the processing of biologically produced ceramics always starts with a complex fluid system in which organic templates act as the nucleation sites for the ceramic phase. Growth of complex and fully dense ceramic structures (with ceramic contents close to 100%) occur through infiltration of liquid ceramic precursors into the complex fluid matrix. We contend that this process methodology provides a valuable alternative for the processing of ceramic matrix composites with complex structures where the deliberately introduced architectural details start at molecular level and work upwards in scale to micro- and macroscopic dimensions. Another important aspect of the biological processes is that they provide clues on environmentally benign process methods. This presentation will attempt to illustrate that synthesis and processing methods utilized by biological systems can be mimicked to develop organic/inorganic composites. Examples will include commercially important composites for ferroelectric applications.
A. Gaffan*, E.C. Moreno, R.J. Gambogi and J. Afflitto, Colgate-Palmolive Technology Center, 909 River Road, Piscataway, NJ, Forsyth Dental Center., Boston, MA
Dental calculus (tartar) is a hard crystalline deposit on tooth surfaces. It is mainly composed of basic calcium phosphate salts such as hydroxyapatite (HA). We have compared a variety of inhibitors on nucleation and crystal growth of HA in-vitro and in-vivo to ascertain the relationship between the adsorption of the inhibitors onto HA crystals and effect on in vivo calculus deposition onto teeth. Supersaturated calcium and phosphate (3mM) solutions at pH 7.4 under nitrogen atmosphere were used to study nucleation. The nominal composition of the solution for a seeded crystal growth experiment was 1.06 mM Ca and 0.63 mM P-i at pH 7.4 with a degree of saturation of 8.5 with respect to HA. The results of the experiments with pyrophosphate ion, (PP), peroxydi-phosphate (PDP) and phytate indicated that the crystal growth inhibition was related to the adsorption to the inhibitors onto specific growth sites on the surface of crystals. This was true with the above inorganic inhibitors, polymeric inhibitors, proteins and polyamino acids. Data will be presented to show the relationship between the adsorption parameters on HA of inhibitors; the number of adsorption sites, and the in-vivo anticalculus effect.
A. Wierzbicki* and C.S. Sikes, Department of Chemistry and Department of Biological Sciences, University of South Alabama, Mobile, AL 36688.
An evolutionarily developed ability to modify morphology of crystal material to serve specific functions has been achieved in nature by means of matrix proteins. Stereospecific interactions of these acidic proteins with crystal surfaces are used to control crystal growth. The nature of this stereospecifity is analyzed, for oyster shell proteins and polyaspartate interactions with calcium carbonate crystals, using Atomic Force Microscopy and molecular modeling.
C.S. Sikes*(1), and A.P. Wheeler (2). (1) The University of South Alabama, Mobile, AL 36688, USA (2) Clemson University, Clemson, SC 29613-1903, USA.
The polyanionic proteins from biological minerals like shells, bones, and teeth are powerful regulators of crystallization. Primary structural features such as separate domains of negatively charged and hydrophobic residues each contribute to this regulation. These features are already being put to work in the design of polyamino acids for use, for example, as antiscalants and corrosion inhibitors in water treatment and as dispersants in detergents. Cell-recognition sequences and hinge regions are additional components of primary structure with potential as new-polymer design elements. Secondary and higher level matrix structures also are being investigated with a view to synthetic functional correlates. It can be concluded that biomineral matrix proteins will continue to be useful in identifying novel polymeric materials.