8. Raman spectroscopy
Raman spectroscopy, in which the decay of vibration is observed after
strong excitation of the sample (mainly with a laser), is a variant of mid-IR
(FT-IR) spectroscopy. In contrast to IR spectroscopy which mainly highlights
primary protein structures, Raman spectroscopy mainly points
out modifications in secondary protein structures such as α-helix and
β-sheets and is known to be a rich source of information on amino acid
residues (Overman & Thomas, 1999). Smaller portions of sample are required,
compared with FT-IR, and instrumentation can be less expensive
and portable. Raman spectroscopy is relatively insensitive to water and
hence does not suffer fromwater interference, so Raman spectroscopy requires
little pretreatment of the sample without e.g. cryo-sectioning and