Abstract
An angular displacement-enhanced heterodyne polarimeter has been employed to investigate the interplay between trifluoroethanol (TFE) and glycerol on the thermal denaturation of type I collagen. The concentration of the collagen solution was fixed at 0.341 (mg/mL), and was heated from 25 °C to 55 °C. TFE solutions with concentrations of 5%, 10%, 15%, 20%, 40% and 80% (v/v) were prepared and the phase change was recorded for the determination of thermal denaturation. It was observed that the thermal denaturation temperature (Td) is decreased with increasing TFE concentration due to the partial cleavage of the triple-helical structure. With TFE concentration higher than 20% (v/v), the degree of optical rotation appears to be nearly the same, reflecting that the collagen triple helices have been completely destructed. Moreover, the addition of glycerol in inhibiting the thermal denaturation of collagen is investigated. It has been shown that glycerol can improve the thermal denaturation of both collagen and TFE-mixed collagen. Experimental results show that, in the presence of 2 M glycerol, the Td of collagen remained at around 41.9 °C, meanwhile the Td of 20% (v/v) TFE-mixed collagen is significantly restored to 32.8 °C.
Highlights
Collagen is the major component of the human proteome and plays a key role in the structural connection of tissues, such as ligaments, tendons, ocular sclera, bone, and skin
It was further investigated that the combined effect of glycerol and urea with concentration ranged from 1 to 3 M; the results clearly showed that the thermal denaturation induced by urea was improved by the addition of glycerol
The present results indicate that TFE affects the optical rotation and decreases the denaturation temperature due to the disruption of the inter-strand hydrogen bonding
Summary
Collagen is the major component of the human proteome and plays a key role in the structural connection of tissues, such as ligaments, tendons, ocular sclera, bone, and skin. In the preparation of these biomaterials, trifluoroethanol (TFE) is used as a co-solvent. Shanmugam et al [4] have summarized the effect of TFE induced in proteins, which can stimulate the conformational transition between random coil, α-helix, and β-sheet in proteins and peptides. Shanmugam et al [4] investigated the effect of TFE on type I collagen structure using circular dichroism (CD) and Fourier transfer infrared (FTIR) spectroscopy techniques. The results of thermal melting revealed that the stability of triple helix in collagen was decreased even at a low concentration of TFE (5%, v/v) by the observation of decreased optical density [4]. The results of the turbidity measurements revealed that the collagen structure is dissociated by inhibiting the fibril formation under the circumstance of higher TFE concentration [4]
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