SMALL-ANGLE NEUTRON-SCATTERING FROM LYSOZYME SOLUTIONS IN UNSATURATEDAND SUPERSATURATED STATES (SANS FROM LYSOZYME SOLUTIONS)

Small angle neutron scattering (SANS) method was used to study lysozym e solutions, with particular interest in an understanding of the cryst allization process at the initial stage. It is found that (1) in the u nsaturated solution, the protein molecules aggregate with a continuous increase in size when NaCl concentration is increased, and (2) in the supersaturated solution, an irreversible change, superimposed on the former process, occurs when the supersaturation is realized. These fac ts indicate the usefulness of SANS in detecting changes of protein mol ecules in solution on the nanometer scale. The reliability of the SANS results are indicated by (1) comparing them with those of small angle X-ray scattering (SAXS), and (2) comparing the effect of D2O and H2O as solvent. Since the interparticle interaction is essential in the cr ystallization process and a simple Guinier plot analysis is not allowe d, a more rigorous framework of analyzing data with interference funct ion is developed, through which both average interparticle distance an d particle size are estimated.