Infrared spectroscopy is a useful technique for the determination of
conformation
and orientation of membrane-associated proteins and lipids. The technique
is
especially powerful for detecting conformational changes by recording spectral
differences before and after perturbations in physiological solution. Polarized
infrared measurements on oriented membrane samples have revealed valuable
information on the orientation of chemical groupings and substructures
within
membrane molecules which is difficult to obtain by other methods. The
application of infrared spectroscopy to the static and dynamic structure
of proteins
and peptides in lipid bilayers is reviewed with some emphasis on the importance
of sample preparation. Limitations of the technique with regard to the
absolute
determination of secondary structure and orientation and new strategies
for
structural assignments are also discussed.