Thermal analysis ofortho- andpara-cortical cells isolated from wool fibers

Abstract

The nature of the bimodal denaturation endotherm, which has been observed for some α‐keratin materials, was investigated in order to evaluate the validity of the two conflicting theories to interpret the phenomenon. Ortho‐ and para‐cortical cells were isolated from Merino wool and subjected to measurements by differential scanning calorimetry in water at elevated temperatures (80–170°C). The results show for the isolated cell fractions denaturation peaks at 138°C (ortho) and 144°C (para) that are with respect to their location and temperature difference in good agreement with the results obtained for the whole fiber material. The denaturation enthalpy of the para‐ (21 J/g) was found to be higher than of the ortho‐cortical cells (17 J/g) in contrast to expectations from electron diffraction studies. The fact that both of these values are higher than for the whole fiber (15 J/g) is attributed to the removal of the cuticle prior and to the enzymatic digestion of some further material during cell separation. The results give unequivocal evidence for the validity of the ortho/para‐hypothesis for the interpretation of the endothermic denaturation doublet of keratins. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1991–1995, 1998

Thermal analysis of merino wool fibres without internal lipids

“…In the present 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 a-form crystallines in the domains of ortho-and para-cortical cells as affirmed by Wortmann and Deutz 17,18 and by the results of Manich et al 28 The last part of our study was focused on the determination of pore size of treated wools to analyze the possible pore modification due to lipid extraction. The technique used was thermoporometry, which is based on the determination of the melting temperature of imbibed water for different pore sizes.…”

“…15,21 For Merino wool the endotherm is often bimodal. Wortmann and Deutz confirmed that ortho-cortical cells have a lower melting point than para-cortical cells, 18 which could account for the bimodal peak. Cao et al 15 have investigated the origin of this bimodal endotherm and have presented an alternative interpretation, in which the bimodal peak arises from the overlapping of the melting endotherm of aform crystallites with the thermal degradation of other histological components.…”

“…19 A number of researchers have studied the melting peak of a-form crystallites in merino wool. Some analyses of wool have been performed in an excess of water, [17][18][19][20] others in the absence of water, 16,20 and Cao et al have used oil as a thermal medium. 15,21 For Merino wool the endotherm is often bimodal.…”

“…Wool fibers have been studied by this technique in several papers. [15][16][17][18][19] 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 has influence in DSC analysis 19 ), and to the moisture sensibility of the thermal transitions. 20 The differences in DSC parameters can be related to differences in the matrix material, that is the nonhelical parts of the intermediate filaments (IFs), the material between the IFs, and all other amorphous, morphological components.…”

Wanted, dead and alive: Why a multidisciplinary approach is needed to unlock hair treatment potential

“…Cortical cells containing variable intensity macrofibrils exhibit differences in thermal behaviour, most clearly in extreme cases such as fine wool . This is a clear indication of differences in quaternary structure and chemical bonding.…”