Characterizing keratins using high‐pressure differential scanning calorimetry (HPDSC)

Abstract

SYNOPSISApplying differential scanning calorimetry (DSC) for temperatures up to 18O"C, the denaturation transition of the a-helical material of various keratins in excess water was studied at conditions of equilibrium water vapor pressure (high-pressure DSC) . The results show a generally cystine content and material invariate denaturation range of 20-30°C with peak temperatures around 140°C. Though analysis of variance and multiple comparison tests show a pronounced inhomogeneity of the enthalpy data, the results generally support the material invariance of the denaturation enthalpy and hence of the helix content of the keratins. The denaturation enthalpy for the helical coiled-coil-structures in the intermediate filaments is determined as AH = 6.5-7.8 kJ/mol. A significant positive correlation was found between the denaturation temperatures and the cystine content. It is concluded, that the helix denaturation temperatures are kinetically controlled by the amount and/or the chemical composition of the surrounding nonhelical matrix, and that the double-peak endotherms observed for wool and other keratins originate from two cell types that are sufficiently different in sulfur content to allow endotherm separation. In the case of wool the cell types can be identified as "ortho-" and "paracortical" cells.

Lipid Role in Wool Dyeing

“…In this work, weakly marked endotherms were obtained in all the samples studied with small enthalpy differences. Therefore, it seems that our results may lend support to the melting endotherm corresponding to the differential melting behavior of the -form crystallines in the domains of ortho-and para-cortical cells as affirmed by Wortmann et al (Wortmann & Deutz, 1993 and by the results of Manich et al ). An additional part of our study was focused on the determination of pore size of treated wools in order to analyse the possible pore modification due to lipid extraction.…”

“…DSC is a method commonly used to determine crystallinity in polymers and involves measuring the melting enthalpy. Wool fibres have been studied by this technique in several papers (Cao et al, 1997;Spei & Holzem, 1987;Wortmann & Deutz, 1993Wortmann, 2005). There are currently difficulties in accurately measuring the melting transition of wool owing to the fibrous nature of the sample, (for exemple the level of cystine content could have an influence on DSC analysis (Rivett, 1991), and to the moisture sensibility of the thermal transitions (Haly & Snaith, 1967).…”

Keratin made micro-tubes: The paradoxical thermal behavior of cortex and cuticle

“…DSC investigations of keratin fibres in the dry state show an endothermic effect, sometime a doublet, which at 10 K/min heating rate ranges from 230 to 260°C [4,7,8].…”

“…The endothermic effect is generally attributed to the thermal denaturation of the -helix which makes the crystalline part of the keratin fibre [5,6,8,9].…”

Caracterização físico-química e analítica de fibras capilares e ingredientes cosméticos para proteção

“…Quanto mais elevada for a densidade de ligações cruzadas nas IFAPs, maior será sua viscosidade e mais prejudicada será a transição hélice/folha nas IFs e viceversa (WORTMANN et al 1993;WORTMANN et al 1998;WORTMANN et al 2002).…”