Polarized Spectroscopy with Fluorescent Biomolecular Building Blocks

Book chapter, 2016

© 2016 by John Wiley & Sons, Inc. All rights reserved. This chapter considers linear dichroism (LD), magnetic circular dichroism (MCD), and Forster resonance energy transfer (FRET) and how these phenomena are related to and may report on transition moment orientations and on molecular structure. MCD is an asset in combination with LD and fluorescence anisotropy for the deciphering of transition moment directions in biophysically important chromophores, and many examples of applications are found among nucleobases. A property corresponding to the absorption anisotropy (linear dichroism) for emission is the fluorescence anisotropy. The amino acid tryptophan, with indole as its photoactive aromatic chromophore, is the most frequently used natural fluorescent probe in biophysical contexts, due to its relatively high fluorescence quantum yield and well-resolved absorption profile in the near-UV. The single-molecule fluorescence-detected linear dichroism (smFLD) method is a useful complement to smFRET since it can help to avoid misinterpretation of false smFRET signals.