A variety of structural techniques, including IR spectroscopy, reveals
that thermal denaturation of bacteriorhodopsin follows a given pathwa
y (successively rearrangement of helical structures, extensive deuteri
um exchange, and finally protein aggregation) irrespective of heating
rate, pH or ionic strength conditions, In all cases, thermal denaturat
ion leads to a 'compact denatured state' which retains a large proport
ion of ordered structure.