Elastic resolution spectroscopy: A method to study molecular motions in small biological samples

Few biological molecules are available in quantities, 200-400 mg, that are required for quasi-elastic neutron scattering analysis. We show that the time correlation function of molecular motions can be extracted with much less material using only the strong scattering intensity at zero energy transfer. The time axis is introduced by varying the width of the instrumental resolution function, which is achieved using multiple-chopper time-of-flight spectrometers. The elastic intensity decreases with increasing energy resolution due to molecular motions in the sample. The technical feasibility of ERS is demonstrated with 23 mg of hydrated myoglobin in comparison with the standard approach.