The casein milk proteins and the brain proteinsa-synuclein and tau have been described as natively unfolded with ran-domcoil structures,which, inthecaseofa-synucleinandtau, have a propensity to form the ®brils found in a number of neurodegenerative diseases. New insight into the structures of these proteins has been provided by a Raman optical activity study, supplemented with di erential scanning cal-orimetry, of bovineb-andj-casein, recombinant humana-, b-andc-synuclein,