Spectroscopic detection of DNA quadruplexes by vibrational circular dichroism.

The four-stranded G-quadruplex motif is a conformation frequently adopted by guanine-rich nucleic acids that plays an important role in biology, medicine, and nanotechnology. Although vibrational spectroscopy has been widely used to investigate nucleic acid structure, association of particular spectral features with the quadruplex structure has to date been ambiguous. In this work, experimental IR absorption and vibrational circular dichroism (VCD) spectra of the model quadruplex systems d(G)(8) and deoxyguanosine-5'-monophosphate (5'-dGMP) were analyzed using molecular dynamics (MD) and quantum-chemical modeling.

Isotope-labeled vibrational circular dichroism studies of calmodulin and its interactions with ligands.

In this work we have studied ligand-induced secondary structure changes in the small calcium regulatory protein calmodulin (CaM) using vibrational circular dichroism (VCD) spectroscopy. We find that, due to its chiral sensitivity, VCD spectroscopy has increased ability over IR spectroscopy to detect changes in the structure and flexibility of secondary structure elements upon ligand binding. Moreover, we demonstrate that the uniform isotope labeling of CaM with (13)C shifts its amide I' VCD band by about approximately 43 cm(-1) to lower wavenumbers, which opens up a spectral window to simultaneously visualize a bound target protein.

Fourier transform infrared/vibrational circular dichroism spectroscopy as an informative tool for the investigation of large supramolecular complexes of biological macromolecules.

A combination of ultraviolet (UV) and infrared (IR) absorption and circular dichroism (CD) spectroscopy was applied to investigate the structure and formation of large supramolecular DNA-protein complexes. This combination of techniques was used to overcome limitations of UV-CD (electronic, or ECD) spectroscopy due to considerable light scattering in such solutions. Based on the analysis of FTIR and UV-CD spectra, the interaction of DNA with nonhistone chromatin protein HMGB1 and linker histone H1 was studied.