Soluble derivatives of feather keratin. 2. Molecular weight and conformation

Abstract

It has been shown (Fraser & MacRae, 1963) that solutions of unfractionated feather-keratin derivatives can be dried down into films that give welloriented X-ray-diffraction patterns containing many of the features associated with the microfibrillar structure of the native material. It was found that similar films could be obtained from the fractions described by . In most cases spontaneous birefringence developed around the edge of the film during drying. The X-ray-diffraction patterns yielded by these films when the X-ray beam passed parallel to the surface were similar to those of the unfractionated derivatives at low angles of diffraction, with a prominent meridional reflexion at 23A and equatorial reflexion at 33A. At wider angles the fractionated materials show strong layer lines at 4*8 and 2-4k and a series of equatorials which index as orders of a 33i spacing.The electron micrographs shown in Plate 1 were obtained by spraying a 1:1 (v/v) mixture of 0 05 % protein solution and 1 % phosphotungstate, pH 5 6, on to grids covered with a carbon-collodion fihm and using the negative-staining method of Brenner & Horne (1959). It is apparent from Plate 1 that, on drying, the fractionated derivatives spontaneously polymerize to form fibrils. The apparent thickness of the fibrils varies from 40 to 60 A at their narrowest part (arrow in Plate 1 b) to approx. 130A at their widest part, suggesting that they are helical with a pitch of approx. 1500 k. At first sight the fibrils appear to consist of two filaments coiled around each other to give a two-strand rope, but a ribbon containing three strands cannot be excluded at present. A feature is the tendency of the fibrils to aggregate laterally in precise register.

Keratin: Structure, mechanical properties, occurrence in biological organisms, and efforts at bioinspiration

“…Both exhibit very low content of histidine and methionine. It was also reported that the derivatives from reduced wool could be precipitated into high-sulfur and low-sulfur components [16]; while for feather rachis, only minor differences were found between the compositions of the various fractions and no evidence for high-or low-sulfur components was obtained [73].…”

“…For amino acid analysis, the acid hydrolysis of proteins and automated ion-exchange chromatography are used routinely [71]. The residue percent of wool (representing a-keratin) and feathers (representing b-keratin) are summarized in Table 5 [16,72,73]. It is clear that both show high content of half cystine (cysteine plus half cystine), which provides the disulfide bonds and distinguishes keratin as high-sulfur protein from other biopolymers.…”

Age and Gender Dependent Nutrient Composition of Feather and Feather-Free Body Fractions in Meat-Type Chickens

“…About 85% -90% of the total feather protein is feather keratin, a durable fibrous scleroprotein [11]. According to earlier reports [12] [13] [14] [15], scleroproteins in feathers, hairs, wool and horn contain a high percentage of N (15.0% to 16.8%).…”

The Complete Amino Acid Sequence of a Feather Keratin From Emu (Dromaius Novae-Hollandiae)

“…Schroeder et al (1957) isolated dito pentapeptides from partial acid hydrolysates of white turkey feather calamus. 1964a, 1964b), and a mean residue weight of 99·5 for the native protein, calculated from the amino acid analysis given by Harrap and Woods (1967), it was concluded that about 29 residues per molecule were in the ,8-conformation.…”

“…Suzuki (see addendum to this paper) has proved experimentally with infrared spectroscopy that the T3 section does in fact have a much increased percentage of j3-material and that j3-material is absent in other peptides. It is probably this section of the molecule which is responsible for the ready gel formation in solutions of feather proteins (Harrap and Woods 1967).…”