Neutron small angle scattering of hemoglobin.

Neutron small angle scattering experiments were performed on human hemoglobin in various mixtures of Hz0 and DzO. It was possible to observe the inter-particle effect without corrections for resolution and to verify the first minimum and the secondary maximum in accordance with the theoretical scattering curve. The accuracy in determining the radius of gyration has been improved over that determined in previous neutron small angle scattering studies. With respect to hydrogen deuterium exchange it was possible to observe the kinetics of the slow exchanging protons with an accuracy of 30 protons. Finally a new and much more precise method for the determination of particle volumes was developed. With this method the density of the scattering lengths of the solvent was altered by varying its DtO content, and, using a real zero point method, that mixing ratio was determined at which the small angle scattering of the solution vanishes. From the mixing ratio the volume of the nonhydrated hemoglobin was obtained as 84,000 f 2,000 A3.