Three-state denaturation of α-lactalbumin by guanidine hydrochloride

摘要: Abstract The reversible unfolding of α-lactalbumin by guanidine hydrochloride has been studied at 25.0 °C means ultraviolet circular dichroism measurements. non-coincidence the apparent transition curves obtained from ellipticity changes far (222 nm) and near (270 nm 296 wave-lengths demonstrates presence least one intermediate in denaturation process. aromatic residues which contribute to Cotton effects 270 appear be exposed solvent first stage a two-stage process, while helical regions polypeptide chain destroyed second stage. Earlier work demonstrated an acid between two compact forms α-lactalbumin, native (neutral pH) form form. Results presented here suggest that is produced as total neutral pH. Lysozyme are known have similar primary structures expected tertiary structures, but several differences their properties described. comparison transitions lysozyme provides result compatible with although free energy stabilization state 3 5 kcal/mol smaller for than lysozyme. pH dependence reaction can described terms abnormal histidyl carboxyl residues. stable process may cause difference dynamic character proteins thus provide reasonable interpretation chemical reactivity.