ABSTRACT
Vibrational circular dichroism (VCD) is a measurement of the differential absorption of left and right circularly polarized light (ΔA = AL − AR) by molecular vibrational transitions, typically in the infrared (IR) region of the spectrum [1-10]. As an absorption technique, it samples the same transitions as in IR spectra; however, its intensity (ΔA) must arise from chiral interactions of molecular bonds in an asymmetric molecule, polymer, or medium. For small molecules, the resulting spectral pattern is often a characteristic of the three-dimensional configuration of the atoms bound within the molecule. For biopolymers this “absolute” configuration is not an unresolved question that needs to be answered experimentally. Amino acids in proteins normally all have an L configuration, and the ribose rings in DNA and RNA all have the same configuration. Polysaccharides are more complex, yet absolute configuration is typically not the driving structural issue even for such systems.
