Absorption Spectroscopy to Determine Macromolecule Structural Changes

Abstract

Definition The UV-visible absorption spectrum of a biomolecule is the combination of the electronic transitions of all of its component parts or chromophores. The spectrum thus depends on the electronic structures of its component parts, which in turn depends on their environment. Thus, e.g., the absorbance of a tryptophan chromophore that is buried in the hydrophobic core of the protein will be at least slightly different from that of an exposed tryptophan. Two particularly useful applications of UV absorption spectroscopy to probe structural changes are outlined below.

Macromolecule Condensation Measuring a UV-visible spectrum with an absorption spectrometer may be used to follow the condensation of a macromolecule sample into particles, though what is actually being probed is scattering of the light rather than absorption. A monotonic increase in absorbance signal outside the absorption bands of the molecules being studied is observed as condensation takes place. In the case of DNA,...