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Influence of fluctuations in electron density on the excess small‐angle X‐ray scattering from dilute solutions of macromolecules
Author(s) -
Carpenter Dewey K.,
Mattice Wayne L.
Publication year - 1977
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1977.360160106
Subject(s) - macromolecule , chemistry , electron density , radius , electron , scattering , electron scattering , solvent , small angle x ray scattering , crystallography , physics , quantum mechanics , organic chemistry , biochemistry , computer security , computer science
The influence on the excess scattering function P (μ) of flutuations in the electron density ρ within a macromolecule is treated, to the approximation that the solvent is a structureless medium of constant electron density ρ 0 . The results for P (μ) and the apparent value of the mean square radius R app 2 , can be expressed as functions of the excess electron density Δρ: P (μ) = X (μ) + (Δρ) −1 Y (μ) + (Δρ) −2 Z (μ) and R app 2 = R x 2 + (Δρ) −1 R y 2 + (Δρ) −2 R z 2 , where X (μ) and R x 2 depend only on the shape of the macromolecule, while Y (μ) and R y 2 as well as Z (μ) and R z 2 depend on the shape and the fluctuations in ρ. By varying the electron density of the solvent, the contributions of the shape and the internal structure of the macromolecule can be resolved. The quantities R x 2 , R y 2 , and R z 2 are evaluated for seven models to illustrate the relative importance of these contributions for representative structures.