The MCL-1 BH3 helix is an exclusive MCL-1 inhibitor and apoptosis sensitizer

available in PMC 2011 February 3.MCL-1 has emerged as a major oncogenic and chemoresistance factor. A screen of stapled peptide helices identified the MCL-1 BH3 domain as selectively inhibiting MCL-1 among the related anti-apoptotic Bcl-2 family members, providing insights into the molecular determinants of binding specificity and a new approach for sensitizing cancer cells to apoptosis.National Institutes of Health (U.S.) (NIH award 5RO1GM084181)National Institutes of Health (U.S.) (NIH grant 5P01CA92625)National Institutes of Health (U.S.) (Ruth L. Kirschstein National Research Service Award 1F31CA144566)Burroughs Wellcome Fund (Career Award

Raman optical activity instrument for studies of biopolymer structure and dynamics

The latest version of a multi-channel Raman optical activity (ROA) instrument implementing incident circular polarization (ICP) modulation within a in a backscattering geometry and optimized for measurements on biopolymers in aqueous solution is described. It is based on a fast single-stage, imaging (stigmatic) monochromator equipped with a high optical density holographic notch filter, a holographic transmission grating and a thinned back-illuminated thermoelectrically cooled charge-coupled device (CCD) detector with a high quantum efficiency. A large-aperture longitudinal electro-optic modulator (Pockels cell) is employed to switch between orthogonal circular polarization states in the incident laser radiation. A thick Lyot depolarizer is used for depolarization of the backscattered Raman radiation. This backscattering ICP CCD ROA design is currently realized with two prototype instruments dedicated to studies of the structure and dynamics of biopolymers in aqueous solution. Backscattered ICP ROA spectra of the following samples are presented as typical examples of the excellent performance characteristics: poly(L-glutamic acid) in α-helical and disordered conformations; bovine α-lactalbumin in native and acid molten globule states; human immunoglobulin; calf thymus DNA and both magnesium-bound and magnesium-free phenylalanine-specific transfer RNA; and filamentous bacterial viruses Pf1 and M13

Raman optical activity of filamentous bacteriophages: hydration of α-helices

We report the first observations of vibrational Raman optical activity (ROA) on intact viruses. Specifically, ROA spectra of the filamentous bacteriophages Pf1, M13 and IKe in aqueous solution were measured in the range ∼600–1800 cm−1. On account of its ability to probe directly the chiral elements of biomolecular structure, ROA has provided a new perspective on the solution structures of these well-studied systems. The ROA spectra of all three are dominated by signatures of helical elements in the major coat proteins, as expected from pre-existing data. The helical elements generate strong sharp positive ROA bands at ∼1300 and 1342 cm−1 in H2O solution, but in 2H2O solution the ∼1342 cm−1 bands disappear completely. The spectra are similar to those of polypeptides under conditions that produce α-helical conformations. Our present results, together with results from other studies, suggest that the positive ∼1342 cm−1 ROA bands are generated by a highly hydrated form of α-helix, and that the positive ∼1300 cm−1 bands originate in α-helix in a more hydrophobic environment. The presence of significant amounts of highly hydrated helical sequences accords with the known flexibility of these viruses. Differences of spectral detail for Pf1, M13 and IKe demonstrate that ROA is sensitive to subtle variations of conformation and hydration within the major coat proteins, with M13 and IKe possibly containing more non-helical structure than Pf1. The ROA spectra of Pf1 at temperatures above and below that at which a structural transition is known to occur (∼10 °C) reveal little difference in the protein conformation between the two forms, but there are indications of changes in DNA structure

Raman optical activity studies of the influence of water on structure and dynamics of proteins, viruses and nucleic acids

It has long been appreciated that water, the natural biological medium, plays a central role in determining both structure and function of biological molecules [1]. However, there remains a dearth of information on the mechanistic details. A promising technique for studying the effects of solvation on biomolecular structure and function is Raman optical activity (ROA), which measures vibrational optical activity by means of a small difference in the intensity of Raman-scattered light from chiral molecules in right- and left-circularly polarized incident light [2]. ROA can be more incisive than conventional vibrational spectroscopy in the study of biomolecules because only the few vibrational coordinates within a complicated normal mode which sample the skeletal chirality most directly make the largest contributions. Recent results on peptides, proteins and intact viruses suggest that ROA can distinguish α-helix in hydrophobic, amphipathic and fully solvated environments. Fully water-solvated α-helix appears to have an important functional role, and may be implicated in the conformational diseases. ROA studies of nucleic acids have provided evidence that deformations of water molecules couple strongly with some base stretching modes, and have revealed a new glasslike transition at ∼15–18 °C which might involve the formation of ordered water structure