| Abstract
| - The dipole moments of α- and γ-chymotrypsins aredetermined using the dielectric constant measurement.The results are roughly comparable to those of electric dichroismmeasurements despite the principle andmethodology of these two techniques are entirely different.Nevertheless, the differences which exist betweenthem seem to be beyond the experimental error. The cause ofdisagreement appears to be, at least partially,due to the difficulty of finding the correct internal field. A newtheory which is based on an ellipsoidalparticle surrounded by a hydration shell is discussed. The modelwas found to improve the agreement markedly.Additionally, in order to corroborate the observed dipole momentswith numerical computations, the dipolemoments of α- and γ-chymotrypsins were calculated using proteindata bases. The dipole moment of smallproteins consists of two major components, the moment due to fixedsurface charges and the core momentdue to polar chemical bonds. The calculation of the surface chargedipole moment consists of two parts: (1)computation of the pK shifts of polar groups in proteins and(2) computation of the dipole moments usingcorrected pK's. The core moment was calculated as thevectorial summation of polar group moments in thebackbone and side chains. The agreement between measured andcalculated dipole moments is excellent.
|
