Collagen salt-extracted

G13. Gross, J., Studies on the formation of collagen. IV. Effect of vitamin C deficiency on the neutral salt-extractible collagen of skin. J. Exptl. Med. 109, 557-569 (1959). 

Tig. 0. Chromatograms on CM cellulose of denatured soluble collagens obtained by sequential extractions of human infant skin with 1 M NaCl, 0.5 M acetic acid (two times), and 5 M guanidine hydrochloride. The column was eluted at 40 C and pH 4.8 with a salt gradient. Note that collagens ere extracted by ecid.s and guanidine which are not extracted by salt. (Courtesy Bornstein and Piez, 1964.)... 

Certain solutions, such as dilute alkali buffers, salt solutions, and acid buffers, are each able to extract a small proportion of collagen from collagenous material. These solutions contain collagen as the individual triple helices. Such soluble (tollagens can have no covalent intermolecular cross-links. This has been brought out in Table I taken from a review on collagen by Honnann (1960b). 

Nikkari and Kulonen (1962) noted that acid-soluble lathyritic collagen exhibited an elevated a/jS ratio only when a prior NaCl extraction was omitted. Lathyrism, therefore, only causes an increased amount of salt-soluble collagen and does not affect any acid-soluble collagen that may already be present. 

Newly formed collagen extracted with cold, aqueous NaCl solutions consists of three equal-sized chains (a-components) of two different composition types ( -l and -2). The two chains of similar composition are the a-1 chains. The a-2 chain differs from the a-1 in a number of amino acids, particularly hydroxyproline, proline, lysine, and histidine (26). As the collagen molecule matures, the a-chains crosslink intramo-lecularly in pairs this older protein can be readily extracted with acidic solutions such as dilute acetate and citrate buffer, but not with salt solutions. The crosslinked chains are called /3 components the crosslinks are probably covalent bonds (26) that arise by condensation of the side chains of strategic lysyl residues after enzymatic oxidative deamination. Older collageil also forms intermolecular bonds, but the nature of this crosslink has not yet been determined (27). 

Nevertheless, solutions of molecules can be prepared from both types of tissue by extraction with weak acids or neutral salts. Structural changes due to heat can be conveniently followed in these solutions by observing changes in viscosity and optical rotation. The underlying assumption in such studies is that the molecules are free of interactions with one another in contrast to the close interaction in the solid native state. For most soluble collagens the specific rotation and intrinsic viscosity rj, of dilute neutral solutions are almost temperature independent, until a particular value is reached at which... 

Soluble coUi en Collagen molecules that can be extracted with salts and dilute acids. Soluble collagen molecules contain the telopeptides. 

Collagen from various sources (fish bladder, calf skin, and rat tail tendon) can be extracted, solubilized, and purified. The purified preparation can be made to reaggregate in the form of the native fibrils (640-700 A) with the typical axial repeat and intraperiod fine structure. By appropriate physicochemical treatment, these longer fibers can be broken down to smaller fibrils (220 A). The fibers can then be dispersed into a calcifying medium, and the deposition of the calcium salt, or nucleation, can be followed either by X-ray crystal diffraction methods or electron microscopy. These studies demonstrated that only the long (640-700 A) axial repeat fibers could induce nucleation. 

The amount of bound water (studied by H n.m.r. spectroscopy) and the extended molecular conformation appear to be responsible for the anti-freeze properties of a glycoprotein from the Antarctic fish Dissostichus mawsoni. Chemical modification has shown that the carbohydrate moiety of the glycoprotein component of the (Na + K )ATPase in membrane preparations of the salt glands from dog fish does not contribute to the catalytic activity of the enzyme. One of two glycoproteins extracted from squids (Sepia officinalis) resembles collagen. ... 

Polar linkages seem to be the principal basis of association of the components of ground substance with the insoluble tissue components, for most of the dissolved components of ground substances and some of the fibrous elements are readily extracted by salt solutions or weak alkalies. Some type of interaction seems very probable, for extracted soluble collagen can be reversibly precipitated into several types of characteristic fibrils, the forms of which depend upon the precipitating conditions and upon the presence... 

As already stated, the polyphenols are firmly bormd to the collagen in leathers which have been subjected to vegetable tanning. In the TFG of a leather sample we may therefore expect that this bond will be broken and that fragmentation of both the tannin and the collagen will occur. Fig. 10 ows the TFG of an animal in treated only with chromium salts (chrome-tanned leather). For comparison. Fig. 11 pves the TFG of a chrome leather that has been further tanned with mimosa extract the characteristic, prominent zones of resorcinol (3) and pyrocatechol (2) show up clearly. The typical products of thermolysis of vegetable tanned and unfinished leathers are compiled in Table 5. 

The connective tissues and liquids of HA, as a rule, exist firstly as chondroitin sulfates in association with collagen [27,28] and other glycosaminoglycans. Purification methods must therefore include the purification of HA from these impurities. An extraction of hyaluronate with water and aqueous salt solutions is accompanied with the presence of a large amount of impurities of protein nature, other polysaccharides, nucleic acids, lipids and lipoproteins. The limitation of the protein removal fermentative methods... 

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