Raman Optical Activity of Biological Molecules - Emerging Raman Applications and Techniques in Biomedical and Pharmaceutical Fields - page 154

Fig. 7.2. Cartoon representation of the polypeptide backbone of a protein, illus-
trating the Ramachandran φ , ψ angles and the amino acid side chains R i

however, the sensitivity of UVCD is less than that for ROA due to its depen-
dence on electronic rather than vibrational transitions.

7.3 Instrumentation

As discussed above, a backscattering geometry is essential for the routine
measurement of ROA spectra of biomolecules. Backscattering ROA spectra
may be acquired using both the ICP and SCP measurement strategies, al-
though the designs of the corresponding instruments are completely different.
A backscattering ICP measurement strategy was utilized in Glasgow for many
years and provided a large number of biomolecular ROA spectra. A detailed
description of the optical layout of the Glasgow backscattering ICP ROA
instrument can be found elsewhere [24]. Typical laser power at the sample
is 700 mW and sample concentrations of proteins, carbohydrates and nu-

cleic acids are

∼

∼ 30-100 mg/ml while those of intact viruses are ∼ 5-30 mg/ml.

600-1700 cm − 1 are typ-

Under these conditions ROA spectra over the range ∼

ically obtained in ∼ 5-24 h for proteins and nucleic acids and ∼ 1-4 days for

intact viruses.
A completely new design of ROA instrument with significant advantages
inherent to the SCP strategy has recently been developed by Hug [19, 25].
This strategy cancels out the flicker noise arising from dust particles and