Keratin homogeneity in the tail feathers of Pavo cristatus and Pavo cristatus mut. alba.
Bottom Line: In the final structure, the crystalline beta-cores are fixed by the rest of the keratin molecule.The hydrophobic residues of the beta-core are locked into a zip-like arrangement.Structurally there is no difference between the blue and the white bird.
Affiliation: University of Vienna, Faculty of Physics, Strudlhofgasse 4, A-1090 Vienna, Austria.Show MeSH
Mentions: Each such feather (Fig. 2A) of about 2 mm diameter at the base and 1 m length is produced once a year, amounting to a production rate of about 1 cm/day during the winter–spring growth period. The diameter of the feather keeps increasing (Fig. 2B), which amounts to ever increasing production volumes per day. Although the geometry changes considerably, the quality of the material produced remains surprisingly uniform. Weiss and Kirchner (submitted for publication) showed that Young’s modulus of the cortex varies at most ten percent between tip and calamus, say between November and March. The purpose of this note is to check how the mechanical constancy is based on structural constancy. Is the keratin and its structural arrangement the same between tip and calamus? Does the diffraction pattern change? The structure of the feather keratin molecule is not perfectly known. Moreover, the arrangements of the crystallized β-sheets (Fraser and Parry, 2008) concerns from proline to proline only 31 amino acids (3.3 kDa) of the 98 amino acids (9.8 kDa) of the entire molecule. If, and how the rest of the molecule, after all two thirds and consisting of a 20 amino acids long N-terminus and a 47 amino acids long C-terminus, are crystallized and leave a mark on the diffraction pattern has remained open to speculation.
Affiliation: University of Vienna, Faculty of Physics, Strudlhofgasse 4, A-1090 Vienna, Austria.