Multiple denaturational transitions in fibrillar collagen

Abstract

SynopsisThe heat denaturation of pepsinized bovine nonfibrillar and fibrillar collagen was studied by differential scanning calorimetry. For fibrillar preparations that had been rapidly precipitated with stirring at low ionic strength, then resuspended a t physiological ionic strength, multiple denaturational transitions were observed. At heating rates of 10"C/min, melting endotherms occurred a t about 44,50,53, and 57OC. Fibrillar collagen that was slowly gelled without stirring a t physiological ionic strength exhibited a similar series of endothems, but the lower melting transitions were less conspicuous. In contrast, nonfibrillar bovine collagen in acidic solution showed only a single denaturational transition at 40°C. Nonfibrillar solutions a t pH 7, to which inhibitors of fibrillogenesis were added, showed a major endotherm as high as 46'C. These results suggest that reconstituted fibrillar collagen contains a heterogeneous fibril population, possibly including molecules in a nonfibrillar state. It was proposed that the multiple melting endotherms of such preparations were due to sequential melting of molecular and fibril classes, each with a distinct melting temperature. The fibrillar classes may represent three or more types of banded and nonbanded species that differ from each other in packing order, collagen concentration, and possibly also in fibril width and level of cross-linking.

Temperature induced denaturation of collagen in acidic solution

“…Equation (4) Figure 1 shows the temperature dependence of specific heat capacity (C p ) of the collagen in acetic acid at different heating rates. As reported before, 15,16 at any heating rate, a bimodal transition with a major peak at T m $ 408C and a shoulder at T s $ 328C are observed. As the heating rate increases from 0.5 to 1.338C/min, both of them shift to higher temperatures, indicating that they involve kinetic effect.…”

“…It has been suggested that collagen forms several distinct fibrillar species, and each of them has a characteristic melting temperature. 16 Since all the species consist of the same collagen molecules, it is impossible that some species have a reversible melting but the others have an irreversible one. The reversibility of the shoulder transition indicates that it is not due to the denaturation of a certain collagen species.…”

“…[15][16][17][18] Privalov and Tiktopulo suggested some predenaturational conformation of collagen before the denaturation, 15 but there was no further interpretation. Wallace et al 16 proposed that such multiple transitions are because of sequential melting of distinct classes of molecules and fibrillar species formed by the reconstituted collagen. However, such fibrillar species have not been directly observed.…”

“…6 So far, the denaturational transition process has been extensively examined by circular dichroism (CD), [7][8][9][10] fluorescence depolarization, 11 a combination of size exclusion chromatography and light scattering (LS), 12,13 NMR, 14 and differential scanning calorimetry (DSC). [15][16][17][18][19][20][21][22][23][24] However, there still remain some unsolved problems about the fibrillation and the stabilization of the triple helices in the denaturation.…”

Features of Collagen Matrix Reconstructed with Proteodermatan sulfate from Pigskin Insoluble Collagen

“…Wallace et a/. 31 ) suggested that the very thin fibrils from an acid soluble collagen solution denaturated below 50°C, consistent with our finding. McPherson et al 32 l recognized that the addition of heparin to collagen fibrillar suspensions promotes the growth in fibril diameter and make fibrils grow to a higher stability on DSC.…”