Home About us Contact
|
Home About us Contact | ||
|
|
||
Raman Optical Activity (raman + optical_activity)
Selected AbstractsUse of vibrational spectroscopy to study protein and DNA structure, hydration, and binding of biomolecules: A combined theoretical and experimental approachINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 5 2006K. J. Jalkanen Abstract We report on our work with vibrational absorption, vibrational circular dichroism, Raman scattering, Raman optical activity, and surface-enhanced Raman spectroscopy to study protein and DNA structure, hydration, and the binding of ligands, drugs, pesticides, or herbicides via a combined theoretical and experimental approach. The systems we have studied systematically are the amino acids (L -alanine, L -tryptophan, and L -histidine), peptides (N -4271 acetyl L -alanine N,-methyl amide, N -acetyl L -tryptophan N,-methyl amide, N -acetyl L -histidine N,-methyl amide, L -alanyl L -alanine, tri- L -serine, N -acetyl L -alanine L -proline L -tyrosine N,-methyl amide, Leu-enkephalin, cyclo-(gly- L -pro)3, N -acetyl (L -alanine)nN,-methyl amide), 3-methyl indole, and a variety of small molecules (dichlobenil and 2,6-dochlorobenzamide) of relevance to the protein systems under study. We have used molecular mechanics, the SCC-DFTB, SCC-DFTB+disp, RHF, MP2, and DFT methodologies for the modeling studies with the goal of interpreting the experimentally measured vibrational spectra for these molecules to the greatest extent possible and to use this combined approach to understand the structure, function, and electronic properties of these molecules in their various environments. The application of these spectroscopies to biophysical and environmental assays is expanding, and therefore a thorough understanding of the phenomenon from a rigorous theoretical basis is required. In addition, we give some exciting and new preliminary results which allow us to extend our methods to even larger and more complex systems. The work presented here is the current state of the art to this ever and fast changing field of theoretical spectroscopic interpretation and use of VA, VCD, Raman, ROA, EA, and ECD spectroscopies. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 [source] Identification of a human estrogen receptor ,-derived antiestrogenic peptide that adopts a polyproline II conformationJOURNAL OF PEPTIDE SCIENCE, Issue 7 2009Josef Kapitán Abstract Polyproline II (PPII) helix is an extended secondary structure present in a number of proteins. PPII-containing sequences mediate specific protein,protein interactions with partners containing appropriate cognate domains called PPII-recognizing domains (PRDs) and are involved in the activation of intracellular signaling pathways. Thus, the identification of PPII structures in proteins is of great interest, not only to explore molecular and physiological mechanisms, but also to elaborate new potential drugs. By revisiting X-ray crystal structures of liganded ,-type human estrogen receptor (ER,), we have identified an 11-residue PPII-helical sequence (D321AEPPILYSEY331) in the ligand-binding domain of the receptor. The data recorded by far-ultraviolet circular dichroism (far-UV CD), vibrational Raman optical activity (ROA) and differential scanning calorimetry (DSC) show that the corresponding peptide (Ac-DAEPPILYSEY-NH2) is particularly well structured in PPII, with the same proportion of PPII as observed from X-ray structures (,85%). In addition, studies carried out on ER,-negative Evsa-T breast cancer cells transiently co-transfected with a pcDNA3-ER, plasmid and a Vit-tk-Luc reporter gene revealed that the peptide antagonizes the estradiol-induced transcription providing perspectives for researching new molecules with antagonistic properties. Copyright © 2009 European Peptide Society and John Wiley & Sons, Ltd. [source] Raman optical activity of an achiral element in a chiral environmentJOURNAL OF RAMAN SPECTROSCOPY, Issue 9 2009Andrew M. Smith Abstract Raman optical activity (ROA) is a relatively new technique used to determine the structure of chiral molecules and is proving useful in the study of biological molecules such as proteins and DNA/RNA. Here, for the first time, we demonstrate the applicability of ROA as a technique to study achiral groups in chiral environments, detecting the induced chirality of N -(fluorenyl-9-methoxycarbonyl) (Fmoc) in a chiral self-assembled structure of Fmoc-dipeptides. This technique is therefore of interest to those studying self-assembled systems that adopt a chiral structure. Copyright © 2009 John Wiley & Sons, Ltd. [source] Observation of SERS effect in Raman optical activity, a new tool for chiral vibrational spectroscopyJOURNAL OF RAMAN SPECTROSCOPY, Issue 12 2006Salim Abdali Abstract A new tool for chiral vibrational spectroscopy is reported here. A surface enhanced effect was observed using Raman optical activity (ROA). This observation opens new possibilities for ROA as a tool for vibrational spectroscopy. The combination of surface enhanced effect (SE) and ROA into surface enhanced Raman optical activity (SEROA) takes this tool to another level, where a single molecule may be studied with respect to chirality, secondary structure and fold determination. ROA has been able to provide information about important dynamics in molecular understanding. Until recently, however, ROA measurements required a longer exposure and higher concentration of the sample. With SEROA these obstacles can be overcome because both studies on single molecule, i.e. very low concentration, and faster acquisition of the signal can be carried out. In the present, work silver colloids were mixed with solution, in which a pentapeptide, Met-Enkephalin, was dissolved. SEROA signals were recorded and the results are reported here. Copyright © 2006 John Wiley & Sons, Ltd. [source] Renaissance in chiroptical spectroscopic methods for molecular structure determinationTHE CHEMICAL RECORD, Issue 2 2007Prasad L. Polavarapu Abstract Two of the chiroptical spectroscopic methods, namely optical rotatory dispersion (ORD) and electronic circular dichroism (ECD), have been around for several decades. But their use in determining the absolute configuration and predominant conformation is gaining renewed interest with the availability of quantum mechanical methods for predicting ORD and ECD. Two other methods, namely vibrational circular dichroism (VCD) and vibrational Raman optical activity (VROA), are relatively new and offer convenient approaches for deducing the structural information in chiral molecules. With the availability of quantum mechanical programs for predicting VCD and VROA, these methods have attracted numerous new researchers to this area. This review summarizes the latest developments in these four areas and provides examples where more than one method has been used to confirm the information obtained from individual methods. © 2007 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 7: 125,136; 2007: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.20117 [source] Calculated Raman Optical Activity Signatures of Tryptophan Side ChainsCHEMPHYSCHEM, Issue 15 2008Christoph R. Jacob Dr. Raman optical activity: The different local chirality of an adjacent group can cause a different sign of the ROA intensity of an amino-acid side chain (here tryptophan, see picture centre), even though the normal mode is unchanged. Calculated spectra clearly confirm that ROA spectroscopy can be utilized to determine the absolute conformation of tryptophan side chains in proteins (see figure, left and right). [source] Theoretical Determination of the Vibrational Raman Optical Activity Signatures of Helical Polypropylene ChainsCHEMPHYSCHEM, Issue 11 2006Ewa Lamparska Abstract Raman and vibrational Raman optical activity (VROA) spectra of helical conformers of polypropylene chains are simulated using ab initio methods to unravel the relationships between the vibrational signatures and the primary and secondary structures of the chains. For a polypropylene chain containing three units, conformational effects are shown to lead to more acute signatures for VROA than for Raman spectra. In addition to regular polypropylene chains, which can display right and left helicities with the same probability, chirality and therefore helicity are enforced by substituting one chain end with a phenyl group. The simulations predict that the threefold helical structures, which correspond to (TG)N conformations of the backbone, have a specific VROA backward signature in the form of an intense couplet around 1100 cm,1. This couplet is associated with collective wagging and twisting motions, while most of its intensity comes from the anisotropic invariants combining normal coordinate derivatives of the electric dipole,electric dipole polarizability and of the electric dipole,magnetic dipole polarizability. A similar signature has already been found in model helical polyethylene chains, whereas it is very weak in forward VROA. [source] Determination of absolute configuration,An overview related to this Special IssueCHIRALITY, Issue 5 2008Stig Allenmark Abstract Rapid progress in asymmetric synthesis stimulated a further development of methods and techniques for the determination of absolute configuration of chiral molecules. In recent years the direct methods, i.e. X-ray diffraction analysis, circular dichroism (vibrational and electronic), Raman optical activity, optical rotation measurements, as well as indirect methods for relative configuration assignment with the use of NMR spectroscopy or enzymatic transformations, are receiving increasing attention not only by specialists in the field but also by synthetic and structural chemists alike. This paper provides a short overview of the methods currently used, as well as references to contributions collected in this Thematic Issue of Chirality. Chirality, 2008. © 2008 Wiley-Liss, Inc. [source] | ||||||||||