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Multidimensional NMR Spectroscopy (multidimensional + nmr_spectroscopy)
Selected Abstractsm/p -Cresol,based t -BOC protected alternating "high ortho" copolymer as a possible e-beam resist: Characterization using multidimensional NMR spectroscopy,JOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2009Maneesh Sharma Abstract Synthesis of a m/p -cresol,based novolac resin and its subsequent esterification using di- tert -butyl dicarbonate (t -BOC) is described. The product has been characterized using techniques of FTIR spectroscopy, one dimensional 1H NMR, 13C NMR, and DEPT-135 spectra. Two dimensional NMR experiments like, COSY, HSQC, and HMBC have been used for exhaustive probing of the microstructural details of the derivatized copolymer. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Fast multidimensional NMR by polarization sharingMAGNETIC RESONANCE IN CHEMISTRY, Issue 1 2007Eriks Kup Abstract The speed of multidimensional NMR spectroscopy can be significantly increased by drastically shortening the customary relaxation delay between scans. The consequent loss of longitudinal magnetization can be retrieved if ,new' polarization is transferred from nearby spins. For correlation spectroscopy involving heteronuclei (X = 13C or 15N), protons not directly bound to X can repeatedly transfer polarization to the directly bound protons through Hartmann,Hahn mixing. An order of magnitude increase in speed has been observed for the 600 MHz two-dimensional HMQC spectra of amikacin and strychnine using this technique, and it also reduces the noisy F1 ridges that degrade many heteronuclear correlation spectra recorded with short recovery times. Copyright © 2007 John Wiley & Sons, Ltd. [source] A simple approach for phase-modulated single-scan 2D NMR spectroscopyMAGNETIC RESONANCE IN CHEMISTRY, Issue 10 2005Nikolas Salisbury Andersen Abstract Conventional NMR spectroscopy techniques require long acquisition times due to the recovery time between the repeated excitations necessary for each increment of the evolution times in the indirectly detected dimensions. Here we outline a pulse sequence element for gradient-assisted ultrafast multidimensional NMR spectroscopy using frequency-modulated ,chirp' pulses to generate phase-modulated magnetization in an indirectly detected spectral dimension. The potential of this sequence element is demonstrated by acquiring a correlation spectroscopy (COSY) spectrum in 96 ms. This new pulse sequence element is an extension of ultrafast spectroscopy techniques based on the generation of amplitude modulation of the NMR signal in the indirectly detected spectral dimensions. The use of phase modulation instead of amplitude modulation helps broaden the applicability and may provide an increase of sensitivity in some experiments due to the ability to distinguish between positive and negative frequency offsets relative to the carrier frequency of the sequence element. Copyright © 2005 John Wiley & Sons, Ltd. [source] Temperature-dependent structural changes in intrinsically disordered proteins: Formation of ,,helices or loss of polyproline II?PROTEIN SCIENCE, Issue 8 2010Magnus Kjaergaard Abstract Structural characterization of intrinsically disordered proteins (IDPs) is mandatory for deciphering their potential unique physical and biological properties. A large number of circular dichroism (CD) studies have demonstrated that a structural change takes place in IDPs with increasing temperature, which most likely reflects formation of transient ,,helices or loss of polyproline II (PPII) content. Using three IDPs, ACTR, NHE1, and Spd1, we show that the temperature-induced structural change is common among IDPs and is accompanied by a contraction of the conformational ensemble. This phenomenon was explored at residue resolution by multidimensional NMR spectroscopy. Intrinsic chemical shift referencing allowed us to identify regions of transiently formed helices and their temperature-dependent changes in helicity. All helical regions were found to lose rather than gain helical structures with increasing temperature, and accordingly these were not responsible for the change in the CD spectra. In contrast, the nonhelical regions exhibited a general temperature-dependent structural change that was independent of long-range interactions. The temperature-dependent CD spectroscopic signature of IDPs that has been amply documented can be rationalized to represent redistribution of the statistical coil involving a general loss of PPII conformations. [source] Structure of a (Cys3His) zinc ribbon, a ubiquitous motif in archaeal and eucaryal transcriptionPROTEIN SCIENCE, Issue 9 2000Hung-Ta Chen Abstract Transcription factor IIB (TFIIB) is an essential component in the formation of the transcription initiation complex in eucaryal and archaeal transcription. TFIIB interacts with a promoter complex containing the TATA-binding protein (TBP) to facilitate interaction with RNA polymerase II (RNA pol II) and the associated transcription factor IIF (TFIIF). TFIIB contains a zinc-binding motif near the N-terminus that is directly involved in the interaction with RNA pol II/ TFIIF and plays a crucial role in selecting the transcription initiation site. The solution structure of the N-terminal residues 2,59 of human TFIIB was determined by multidimensional NMR spectroscopy. The structure consists of a nearly tetrahedral Zn(Cys)3(His)1 site confined by type I and "rubredoxin" turns, three antiparallel ,,strands, and disordered loops. The structure is similar to the reported zinc-ribbon motifs in several transcription-related proteins from archaea and eucarya, including Pyrococcus furiosus transcription factor B (PfTFB), human and yeast transcription factor IIS (TFIIS), and Thermococcus celer RNA polymerase II subunit M (TcRPOM). The zinc-ribbon structure of TFIIB, in conjunction with the biochemical analyses, suggests that residues on the ,,sheet are involved in the interaction with RNA pol II/TFIIF, while the zinc-binding site may increase the stability of the ,,sheet. [source] | ||||||||||