ISSN:
1600-5724
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
A method of absolute scaling of diffraction data is proposed, based on the calculation of the sum of the intensity diffracted at low resolution (Bragg d spacing 〉 15 Å). This sum is proportional to the mean-square deviation of the scattering-length density in the unit cell, and this property is used to determine the scale factor. The method is applied to the case of neutron diffraction using contrast variation experiments with biological molecules, and it is used to check the validity of some assumptions concerning the system under study, such as the global rate of H/D exchange or the uniformity of scattering-length density in the molecules. The use of this method requires an asymptotic correction of the sum of intensity. This correction is based on Porod's law, whose application to diffraction experiments is discussed, in particular for contrast variation experiments. An analysis of the spherical average of the diffracted intensity as a function of the scattering vector, compared to isotropic solution scattering, allows the conditions of applicability of Wilson statistics to be specified at low and medium resolution, i.e. the random statistical model underlying the Wilson statistics in this scattering range to be defined.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0108767386099373
Permalink
