As part of our investigation into the design and applications of proteolytic enzymes, we required a convenient method to attach peptides to the surface of a variety of materials. In this paper we report the synthesis and characterization of a class of peptide derivatized lipids (PDL's) that can be self-assembled into monomolecular films. These films can be used to control interfacial properties such as wetting and adhesion and provide a simple method to coat surfaces with amino acids.

Experiments have been made with a simple device consisting of two asymmetrically insulated electrodes separated by a thin electrolytic layer. This device has been found to exhibit a wide variety of transient potentials similar to those transmitted by biological synapses, thus suggesting the possibility of constructing a network of similar devices which simulates the behaviour of a biological neural network.

The polymeric matrix of mineralized tissues controls the form and structure of the mineral that is deposited. This matrix has an insoluble fraction which provides a structural framework for the mineralized tissue, and a soluble fraction which is rich in polyanionic macromolecules. One hypothesis envisages mineral being nucleated by an atomic dimensional matching between crystal lattice and anionic spacing in the polyanionic macromolecules. An alternate hypothesis considers that fixed polyanions provide a surface for an adsorbed layer, enriched in lattice ions by ionotropy, to induce mineral formation from the metastable body fluids.

We found that soluble matrix polyanions, immobilized by attachment to insoluble substrates, would induce mineral from metastable solutions. The insoluble substrates included natural and synthetic hydrogels not derived from mineralized tissues. Whether the polyanions were prepared from apatitic or CaCO3 tissues, the mineral induced was independent of the source and was determined by the composition of the solution. Other immobilized, calcium-binding, polyanionic macromolecules, obtained from non-mineralizing tissues, also induced mineral.

These and other data indicate that mineral induction by biological matrices is less specific than implied in the atomic dimensional matching extension of the epitaxial hypothesis.

The avian eggshell is one of the most rapidly mineralizing biological systems known. By understandi'ng the key components and steps in this process, we hope to provide relevant information for fabrication of ceramic composites. The calcification of the eggshell occurs in three main steps: 1) fabrication of an organic matrix, 2) nucleation of an inorganic phase on the organic matrix, and 3) space-filling growth of the calcite phase. The different layers of an eggshell can be separately isolated and studied. Three approaches have been used in our study of the eggshell: 1) characterization of the organization and chemical composition of the shell, 2) selective removal or blocking of particular components to improve the remineralization of demineralized shells, and 3) addition of new components to produce composite ceramics of different kinds. In this preliminary communication, the organization of the shell matrix and membranes and their association with the crystal phase, the immunohistochemical occurrence and distribution of types I and X collagen, and of different proteoglycans are reviewed. Also the preliminary findings of the remineralization of the intact or modified eggshell are presented. These experiments allow us to identify the essential steps in forming a natural composite ceramic.

As a simple model for biomineralization we are investigating the deposition of oxide particles into polymers by the in situ hydrolysis of oxides. By light scattering and electron microscopy we have observed the development of titania in polyvinylchloride. Hydrolysis is due to exposure to atmospheric moisture after film formation under very dry conditions. We believe of alkoxide initially phase separate and then are hydrolysed. Using a strongly Aolymer as a matrix for silica formation we present evidence for catalysis of particle -tby the matrix.

This study was initiated to investigate the structural response of the bessbeetle to determine potential advantageous ramifications and effects on the optimization of synthetic composite materials. The result of the micromechanics sensitivity study of various parameters are presented. Variables such as fiber size and shape, fiber volume fraction, ratio of modulus of elasticity of fiber over matrix, are changed one variable at a time, and the response quantities such as stress and tranverse modulus are presented.

Grass and horn keratin are presented as examples of biological materials which are notch-insensitive due to the presence of strong and stiff parallel fibres in a weaker more compliant matrix. A simple Voigt model is adequate to account for most of these properties. The biological significance of this morphology is explored: with grasses it affects the way animals graze, with horn keratin the behaviour of the horned animal maximises fracture control.

The processability of polypropylene fibers into composite materials was characterized by dynamic wettability measurements. Single fibers were immersed in a series of aqueous acidic solutions of chitosan. Variations in the wetting force, observed for progressive and successive immersions of the fibers in the liquid, indicated adsorption of species out of the solution or the presence of foreign materials on the surface of the solid. The value of the advancing wetting force was used to assess the coating of the fibers by the liquid. Data on the surface composition of the fibers were obtained by electron spectroscopy for chemical analysis. The conditions of preparation of the composite materials containing chitosan were determined from the correlation of the observations on wettability, surface composition and scanning electron microscopy.

Secretory proteins of Chironomus tentans larvae form insoluble fibers that are spun into threads used to construct underwater feeding and pupation tubes. The physical properties of spun fibers should reflect their protein constituents.

The disassembly and reassembly of secretory protein complexes in vitro were studied by solution turbidity, electron microscopy and circular dichroism spectroscopy. Secretory proteins were able to reform complexes with a similar morphology and dichroic spectrum to that of native complexes. These complexes are stabilized by electrostatic and disulfide bonds.

cDNA and genomic cloning indicate that spIs, the 1000-kDa secretory proteins, primarily consist of alternating “constant” and “subrepeat” regions. We synthesized and purified synthetic peptides for each region and used circular dichroism and infrared spectroscopy to measure their secondary structure. Constant peptide consists of α-helix and β-turn. Subrepeat peptide consists of poly(Gly) II-type helix and β-turn.

We conclude that spIs form the fibrous backbone of a novel biopolymer with alternating α-helices and poly(Gly)II helices punctuated by β-turns. Such fibers may have unique physical properties.

We have used transmitted polarized light microscopy to examine the fluid contents of silk glands taken from Bombyx mori silkworms and Nephila clavipes orb-weaving spiders. In the absence of shear, the secretions are optically isotropic. As the concentration is allowed to increase by evaporation, microstructures typical of the nematic liquid crystalline state are observed. Thus it appears that naturally spun silk becomes liquid crystalline en route to solidifying into fiber - which is advantageous to introducing and retaining global molecular alignment. This will facilitate the formation of strong, stiff fibers without the need for a significant post-spinning draw. We have also found that natural silk does not exhibit the defects in molecular alignment that are typical of synthetic polymer fibers spun from liquid crystalline solutions or melts.

Eye-lens alpha-crystallins are very peculiar In the sense that they present polydispersity, a quality most often shared by man made polymers. Quaternary structure studies reveal that these proteins are assembled from about 50 subunits of two kinds. We developped a mixed aggregation model which renders, for alpha-crystallins, both size and polydispersity, in accordance with data in the litterature. The initial stoichiometry controls stability in the aggregation process and should be a very sensitive parameter to monitor in mixed aggregations.

Silk-like proteins are a topic of long-standing scientific interest and recently are being considered for such uses as high performance fibers [1] and enzyme-immobilizing substrates [2]. The structure of silk (in particular, the metastable silk I form) is critical in understanding the formation and processing of these materials.

Computations provide a useful tool for the detailed modeling of the structures of fibrous proteins. Conformational energy calculations on representative model polypeptides have been used successfully to elucidate the structure of collagen [3]. We have applied this method to the study of the crystalline region of Bombvx mori silk fibroin [4].

A novel composite consisting of Ultra-High Molecular Weight Polyethylene, UHMWPE, and ashed bone has been evaluated for human implant applications. The structure and mechanical properties of this composite have been studied using x-ray diffractometry (XRD), scanning electron microscopy (SEM) and dynamic torsion tests. Dynamic properties of the composite and its role in the enhancement of bone ingrowth and damping of vibrations at bone-implant interface are discussed. The new composite offers a novel technique that can provide the desired biological and mechanical fixation in a total hip surgery.

The industrial process for extracting chitosan from low cost shellfish waste is well known. It comprises three basic steps: deproteinization, demineralization of the shells to yield chitin, followed by deacetylation of chitin to produce chitosan. However, the product obtained from the process often still contains many impurities. In general, these encompass minerals and carotenoids bonded to chitosan. The treatment of chitosan flakes with aqueous solutions of inorganic polybasic acids permits the removal of the impurities mentioned above. This paper describes an engineering-type procedure which develops a pure, colorless material having a controlled molecular weight.

Bone-forming cells fabricate a highly ordered collagen matrix (osteoid) which subsequently mineralizes. A variety of cell culture systems exist for osteogenic cells, yet none of these is optimal for the organized formation of a mineralized matrix. We have generated collagen substrates which have different degrees of fibrillar orientation, and have cultured osteogenic cells on these matrices. In this format, von Kossa-stained sections show that highly oriented collagen matrix starts to calcify in 6–7 days, while a random fibrillar matrix does not mineralize even after 21 days. Mineral has been detected only within the collagen matrix with a narrow, unmineralized region between the cells and the mineral.