Keratin in skin is softer than keratin in nail because keratin in skin has:
Less number of disulphide bonds
Less number of salt bridges
High sodium content
Different affinity for water
A i.e. Less number of disulphide bondsKeratin in skin is softer than keratin in nail, horn & hooves because skin keratin has less number of disulfide bondsQ between Cys residues of adjacent polypeptide chains.