1: Biophys J  1981 Oct;36(1):277-96 

Time-dependent absorption anisotropy and rotational diffusion of proteins in
membranes.

Kawato S, Kinosita K Jr.

The decay of flash-induced absorption anisotropy, r(t), of a chromophore in a
membrane protein is closely correlated with rotational diffusion of the protein
in the membrane. We develop a theory of time-dependent absorption anisotropy
which is applicable to both linear chromophores and planar chromophores which
have two different absorption moments at right angles to one another. The theory
treats two types of rotational diffusion of membrane proteins: one is rotation
of the whole protein about the normal to the plane of the membrane, and the
other is restricted wobbling of the whole or part of the protein molecule. In
the former case, r(t) is determined by a rotational diffusion coefficient and an
angle between the absorption moment(s) and the normal to the plane of the
membrane. Rotation of rigid transmembrane proteins can be described by this
treatment. In the latter case, r(t) is characterized by a wobbling diffusion
coefficient and the degree of orientational constraint. This treatment may be
applicable to independent wobbling of the hydrophilic part of membrane proteins.
We further show that, for linear and circularly degenerate chromophores, the
effect of the excitation flash intensity on r(t) can be accounted for by a
constant scaling factor.

PMID: 7284553 [PubMed - indexed for MEDLINE]