Wool samples in vacuo, as well as samples sealed with various amounts of water, were studied by differential thermal analysis (DTA). In all cases, a phase-transition endotherm, often a doublet, was observed. The temperature of the first peak T m depends on the amount of water present, heating rate, level of disulfide reduction, and type of keratin fiber. Parallel x-ray studies showed that the conformation of the polypeptide chains in samples at room temperature, after heating to the completion of the endotherm, depended on the first three of these parameters. T m was 142°C for a Merino wool heated at 3.8°C/min in a sealed tube with an amount of water greater than 80% of the dry weight of the wool and, after fusion, the sample showed no x-ray reflections other than a diffuse ring at 9.8A and the usual halo at 4.15Å. Cystine-reduced samples similarly treated and unreduced samples sealed with 7-10% of water subsequently gave a sharp arc at 4.65A, indicating the presence of partially disoriented β-crystallites. Relative entropies of transition were computed from the DTA curves and showed a correlation with the x-ray results. For instance, when the relative entropy was low the x-ray patterns showed loss of the α-form and appearance of the β-form, but when the relative entropy of transition was high, the α-pattern was replaced by one showing no specific ordered form.

No abstract

The specific heat of rat tail teiidoii :it varioiis water coiiteiits was measured as a function of temperatiire. The resiiltiiig graphs showed peaks arising from 1 he melting, near .?0"C, of heliral m:itei'ial iii the collagen, :tiid from the nieltiiig of absorbed water iii ihc range -40°C to 0°C. The heal of meliiiig of helical material was 11.7 cal per gram of dry iendoii. I)etermiiiatioti of the heat niid temperatiire of fiisioii o f i he absorbed water allowed rwoliition of the water i n t o forir states i i i the w s e of teidoti before deiiaturatioii, :tiid three slates after deii:ttiiratioii. The foiii,hlates ;ire ( 2 ) water not freexable 011 cooliiig to -iO"C, (2) freex:il)le wnler 15-iih boih Iie:ii :tiid ienipc~xtiire of fiisioii differelit froin the v:tliies for ordii1:it.y wsiter, (.j) f i w z : h l e \wiei' with the heat of frisioii of ordiiiary w:i.ter, h i t :I differelit teinper:ttrire of fiisioii, atid ( 4 ) water iiot distiiiguished from ordinary water. The forirth state was abseiit. i i i deiiatrired t,eiidoii. The resiilts are dismissed i i i terms of in(8re:isiiiK size of cliisiers of nhsorbed water moleviiles. 0 ]!I71 by John Wiley & Soils, Iiic.

SynopsisMeasurements of specific heat of wool-water systems were made a t approximately 5°C intervals over the temperature range -70 to 100°C. Ten ditrerent samples were used, each with a dieerent amount of absorbed water in the range from dryness to saturation at 0°C. The graph of specific heat against temperature for dry wool is precisely linear over the complete temperature range, suggesting that thermal mot ion is entirely vibrational. When absorbed water is present the data can be conveniently discussed i n terms of behavior below and above an amount of absorbed water of 22.7 g in 100 g of wool (22.7% of absorbed water). Below 22.7% there is only one temperature range in which the results indicate an appreciable transition in heat absorbing properties. The temperature of transition depends on water content but is higher than 0°C. Above 22.7% a second transition appears in the range -30 to 0°C and grows rapidly larger with increase of water content. The first transition is tentatively ascribed to a slightly cooperative breakdown of polar bonds in wool, and the second to a process analogous to melting in the absorbed water. The results are discussed in these terms as well as with reference to specific heat theories, the heat absorption of the wool component and the water component, and enthalpy differences between the various samples.

When a keratin fibre is extended in water, held, and dried, a stress develops in the fibre. This stress is minimal for an extension of approximately 2%. The strain dependence of developed stress, and some properties of fibres at strains in the region of 2%, are discussed in terms of postulated hydrogenbond formations. Data are included on swelling, on deuterium for hydrogen exchange in strained fibres, on recovery of length, and on attempts to determine stress against strain curves under conditions in which fibre regain remained constant while the curves were determined.