Understanding the molecular structure of wool - the changing shape of keratin

The principal component of hair is a protein molecule called keratin. All protein molecules consist of long chains of small molecular units, the amino acids, of which there are 20 different kinds. Each keratin molecule in hair consists of many hundreds of amino acid units, arranged in an irregular order, although not a random one by analogy, the letters in this sentence are in an irregular order, but the sentence has meaning. The order in keratin determines how the molecules fit together, giving the hair strength and flexibility.

The long chains of keratin could be compacted, called the alpha-form (shown left) or stretched out, called the beta-form (shown right). Using his X-ray analysis, Astbury showed that the elasticity or stretchiness of wool fibres was due to the compacted alpha-keratin protein fibres unfolding into the more extended beta-form.

Click here to see an animation of how the compacted alpha-keratin protein molecule unfolds into the extended beta-form.

Click here to listen to Astbury describing the keratin transition

From the lecture 'How to Swim with a Molecule for a Tail' given at Wayne State University, 10th October, 1953

Whilst this discovery was of great interest to the textile industry, its real significance was that it showed how the macroscopic properties of biological materials could be understood in terms of changes in the shape of their constituent protein molecules.

This was to lead to a novel approach to understanding biological systems, that Astbury referred to as molecular biology.

Royal Society logo
History of the World in 100 Objects logo
British Society for History of Science logoThackray Museum logo

Copyright and Legal | Accessibility |Privacy | Freedom of information
Copyright 2010 University of Leeds