Collagen Backbone Research Articles

Collagen‐Poly(methyl methacrylate) graft copolymers: Effect of aqueous organic solvent system and salts on copolymer composition

AbstractCollagen‐poly(methyl methacrylate) (PMMA) graft copolymers were prepared in a number of aqueous/organic solvent systems and in the presence of neutral salts using ceric ammonium nitrate as initiator. The composition of the collagen‐methyl methacrylate graft copolymers was studied by hydrolyzing the collagen backbone and measuring the molecular weights of the grafted PMMA branches. In water/methanol grafting media the molecular weights of the PMMA branches showed a maximum at a methanol concentration of 25% and then decreased with further increase in methanol concentration. Even though the percent grafting registered a sharp fall with increasing concentration of methanol, the number of grafting sites remained more or less constant and was almost the same as that obtained in aqueous medium. Other aqueous/organic solvent systems gave more grafted chains than those prepared in water alone, and these were of lower molecular weight. Anions such as sulphate and chloride were found to have more influence than nitrate in decreasing the number of grafting sites.

Dentin matrix collagen: evidence for a covalently linked phosphoprotein attachment.

Oxidative degradation of decalcified bovine dentin matrix with alkaline sodium metaperiodate solubilizes a substantial part of the matrix. The soluble portion includes a fraction containing more than 75% of the covalently-bound phosphorus present in the native dentin. Preparative scale electrophoresis of the solubilized dentin on polyacrylamide gels led to the isolation of a group of four strongly anionic components (I–IV). Analyses showed each component to be a protein characterized by a high content of phosphate groups, serine and aspartic acid, and, with one exception (II), small amounts of proline and hydroxyproline. Each component contained one residue of hydroxylysine per mole. In addition to the periodate resistant hydroxylysine, III and IV also contained periodate resistant glucose and galactose. On the basis of the presence of hydroxyproline in varying amount, and hydroxylysine on a mole per mole basis, it is suggested that components I, III and IV consist of collagen backbone fragments linked to a phosphoprotein moiety with a high content of serine and aspartic acid. The periodate-resistant hexoses and the hydroxylysine probably represent the linkage point. Component II is a phosphoprotein moiety essentially free of a collagen fragment. These data provide direct evidence that dentin collagen contains a covalently bound non-collagen polypeptide attachment of highly acidic character.

Characterization of the collagen–vinyl graft copolymers prepared by the ceric ion method. I. Solution properties

AbstractGraft copolymerization of vinyl monomers on to collagen was carried out by the ceric ion method. The grafted vinyl polymer chains were isolated by both acid and enzymatic hydrolysis of the collagen backbone in order to characterize the graft copolymers. Proof of grafting was obtained through the detection of amino acid endgroups in the grafts isolated by both the methods. The grafts isolated gave the characteristic blue color normally associated with the presence of amino acids. The presence of amino acid endgroups was further confirmed by dinitrophenylation of the isolated grafts. The absorption spectra of the dinitrophenylated(DNP) grafts showed absorption maximum in the ultraviolet region of 340–360 mμ, characteristic of DNP‐amino acids. Soluble collagen grafted with polyacrylamide(PAA) formed fibrils on heating to 37°C at neutral pH but, unlike the native collagen, these fibrils did not redissolve on cooling at 2°C. These results show that the redispersion property of soluble collagen was impaired, probably by attachment of the PAA side chains to the collagen molecule. The turbidimetric titration behavior of the grafts, their general behavior of swelling in different solvents, and the intrinsic viscosity of the copolymers in mixed solvents also provided additional proof of grafting.

Raman spectroscopy of calcified tissue.

Laser Raman spectra of ox tibia and of reconstituted rat tail tendon have been obtained and have been compared with the infrared spectra of calcified tissue and collagen. The most intense Raman bands in the calcified tissue originate from the symmetric phosphate modes; however, several of the backbone and side chain modes of collagen are also apparent. There is some evidence that both proline and phenylalamine in the collagen contribute to the spectrum. The Raman spectrum of reconstituted, collagen was difficult to separate from the fluorescence background. Only six distinct bands could be obtained, divided between peptide and sidechain modes. Differences between reconstituted and calcified collagen spectra may originate from partial denaturation of the former in the laser beam. Other differences seem to be genuine chemical manifestations.