NMR STUDIES OF MEMBRANE STRUCTURE AND DYNAMICS

In broad terms, the goal of this research is to obtain a better
understanding of membrane structural properties and their
relationship to biological function. These basic studies will
contribute significantly to general medical research as well as to
research in heart and muscle diseases. New experimental and
theoretical methods will be developed for the study of the
structural and dynamic properties of lipid bilayers and their
interactions with cholesterol and integral membrane proteins. A
series of different lipid bilayers and membranes containing the
Ca2+-ATPase from sarcoplasmic reticulum will be investigated using
nuclear magnetic resonance (NMR) techniques. Deuterium NMR will
be used to derive order parameters for the individual bond segments
of the lipid and protein molecules in the liquid-crystalline state
to yield new structural information. The dependence of the spin-
lattice relaxation rates on the segmental ordering, resonance
frequency, and bilayer orientation will be studied using one- and
two-dimensional (2-D) NMR methods. The results will then be used
to critically evaluate different theoretical models for the
molecular dynamics of lipid bilayers. The experimental studies
will include detailed investigations of the influences of acyl
chain length, polar head group, and degree of hydration on bilayer
physical properties. Similar studies of phospholipid membranes
containing cholesterol or the Ca2+-ATPase will be performed.
Carbon-13 NMR studies of phospholipid bilayers and biomembranes
will be conducted at natural abundance or with isotopically
enriched samples using novel solid-state techniques. Dipolar
tensors will be determined from 2-D NMR experiments to derive order
parameters for the individual bond segments of the lipid and
protein moieties. The carbon-13 NMR studies will also involve
spin-lattice relaxation rate measurements in the laboratory- and
rotating-coordinate frames. In addition, high-resolution proton
and carbon-13 NMR studies of the Ca2+-ATPase and its 20 kD tryptic
fragment in detergent micelles and membranes will be carried out.
From these results, a unified picture for the structural dynamics
of membranes will be developed. Finally, NMR studies of membranes
containing the Ca2+-ATPase will be correlated with studies of their
ATP-hydrolyzing and calcium translocating activities to relate
their structural and dynamic properties to function.