Collagen heating

Fig. 6. The far ultraviolet rotatory dispersion of native calf skin collagen - in 0.01 molar acetic solution. The ultraviolet rotatory dispersion of the same preparation of calf skin collagen heated at 50 °C for 30 min, coded to 25 °C and measured immediately, O-O-O. Concentrations were between 0.0076 and 0.076%. Data from Blout et al.18a)...

Martin, M.L. Regan, C.M. (1988). The anticonvulsant sodium valproate specifically induces the expression of a rat glial heat shock protein which is identified as the collagen type IV receptor. Brain Res. 459, 131-137. 

The results of heat and water stress experiments (Table 12.3) show that these factors had no significant effects on nitrogen isotope ratios of bone collagen or hair. The mean collagen-diet difference (A Nco-d) values of the water-restricted litters ranged from 2.6 %o for group 10 on diet A (36°, water ad... 

Table 12,2. Experimental conditions, mean 5 N values and diet-tissue and tissue-tissue dilTerence values (A N) of rats not subjected to water stress and/or heat stress, Diet 8 N values are those of the protein source rather than the whole diet pellets. SD = standard deviation, co-d = collagen-diet, h-d = hair-dici, f-d = flesh-diet, co-f = collagen-flesh. 

Hair A Nh.heat-stressed rats is 3.0 0.41%o. That for unstressed rats is 3.4 0.46%o. 

Nagata, K., Saga, S. Yamada, K.M. (1986). A major collagen-binding protein of chick embryo fibroblasts is a novel heat shock protein. Journal of Cell Biology, 103, 223-9. 

Purely thermal denaturation of proteins requires much longer times collagen in moist heat below 120 °C needs 30 min to denature (Meyer et ah, 2005), wheat glutens must be subjected to 200-215 °C of dry heat for 72 min (Friedman et ah, 1987), and as mentioned above, whey proteins require at least 50 °C and 30 min for texturization without the use of extrusion processing. 

When collagen is heated, it is denaturated, losing its structure the polypeptide chains separate and unwind, and, as the collagen cools down, it soaks up surrounding water and forms gelatin. 

Fig. 1. (A) CD spectra of rat-tail collagen in native state, heat-denatured state, and in...

Table 36-1 lists some of the mechanisms important in governing the susceptibility of the PNS to disease and injury. Peripheral nerves, although toughened by their high content of collagen, are prone to injury to myelin by compression (e.g. carpal tunnel syndrome and tardy ulnar palsy) and to axons by excessive stretch (e.g. brachial plexopathy in newborn infants following a difficult delivery). Subcutaneous nerves, because of their exposed position, are also vulnerable to cold or heat injury. 

Pristane (2,6,10,14-tetramethylpentadecane) is a mineral oil known to induce arthritis, a disease also referred to as pristane-induced arthritis (PIA) [58], Susceptibility to PIA is MHC-haplotype dependent, in that DBA/1 (H2q) mice are susceptible whereas DBA/2 (H2d) are not, and is accompanied by a broad spectrum of autoantibodies, including anti-Rheuma Factor (RF), anti-collagen and antibodies to heat shock proteins (HSP). PIA is clearly immune dependent since nu/nu mice and irradiated mice do not develop PIA. PIA involves polyclonal T cell activation [59], particularly CD4+ cells [58], Intriguingly, mice can be protected from developing PIA by HSP65-specilic CD4+ Th2 cells [60],... 

Hydrolysis. To 0.50 ml of a protease solution or a dentin slice in 0.50 ml water was added 0.50 ml 12 M HCl. Nitrogen was blown over the solutions and the tubes were closed and heated at 111°C for 24 hours in a hot air oven. Aliquots were dried in triplicate in vacuo over NaOH for collagen determination and HPLC analysis. 

The reduction was done essentially as described previously (Robins, 1976). After several washings with 0.9% (w/v) sodium chloride, 0.05 M sodium phosphate, pH 7.4, at 4°C, the stirred demineralized root powder was reduced with 0.71 g sodium borohydride, an estimated one-twentieth of the collagen mass. After one hour, the solution was acidified (pH < 4, pH paper) to inactivate remaining borohydride. Thereafter, the pH was readjusted to 7.5. The solution was centrifuged and the pellets were hydrolyzed by heating for 24 hours at 112°C in 6 M HCl under N2 in bottles with Teflon-sided screw caps. The dark hydrolyzate was paper-filtered, evaporated under reduced pressure at 50°C, and mixed with 5 ml 0.1 M acetic acid. The hydrolyzate was assayed for hydroxyproline. 

When the collagen rod can be extracted in the native form it is soluble in acidic solutions, at room temperature. If the solutions are heated, the collagen is denaturated the chains lose their helical conformation. The characteristic temperature of this helix —> coil transition is around 36 C. The solution then contains principally single chains, but also some double and triple chains which were initially covalently bound and some sub-units of the single chains. This product is gelatin. 

An ultraviolet spectroscopic method was presented, and used for the assay of procaine and nitrofural in a multicomponent collagen sponge without prior separation of the drugs [33]. Crushed Collagen Sponge (0.1 g) was dissolved in 70 mL of 1 mM HCl, and heated for ten minutes. The solution was cooled, diluted to volume, mixed, filtered, whereupon the first 20 mL was discarded. The absorbance of the analyte solution was then measured at 290 and 373 nm (against 1 mM HCl) for procaine and nitrofural, respectively. 

Gelatin is obtained by heating collagen (the major intercellular protein constituent of the entire connective tissue of animal skins and bones) with water or dilute hydrochloric acid. Its production differs from that of glue in that (he raw materials are selected, cleaned and treated with especial care, so that the resulting product is practically Colotless... 

Polymers. In combination with various metal salts, sorbitol is used as a stabilizer against beat and light in poly(vinyl chloride) (qv) resins and, with a phenolic antioxidant, as a stabilizer in uncured styrene—butadiene mbber (qv) compositions and in polyolefins (see He AT STABILIZERS Olefin polymers Rubber compounding). Heat-sealable films are prepared from a dispersion of sorbitol and starch in water (255). Incorporation of sorbitol in collagen films gready restricts their permeability to carbon dioxide (256). 

Ascorbic acid (vitamin C), the antiscurvy vitamin, is used by the body to form and maintain intercellular and skeletal material such as the collagen of fibrous tissue and the matrix of bone, dentin, and cartilage. Milk and milk products are not considered a significant source of this vitamin and should not be relied upon as such. Freshly drawn cow s milk contains about 2 mg ascorbic acid per 100 g milk, but as vitamin C is heat labile and easily destroyed by oxidation, the vitamin C content of pasteurized milk is reduced to about 0.94 mg/100 g. 

---