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Saturation Transfer Difference (saturation + transfer_difference)
Selected Abstracts13C-NMR detection of STD spectraMAGNETIC RESONANCE IN CHEMISTRY, Issue 2 2010Christoph Räuber Abstract We have investigated the use of 13C for the detection of saturation transfer difference (STD) NMR spectra. By detecting the STD spectrum in the 13C channel it is possible to eliminate the residual water signal in the STD-NMR spectrum. We have employed an INEPT transfer in order to shift the magnetization from the proton channel to 13C. As a sample system to check our method we have used human serum albumin and phenylalanine. We have shown that such a transfer can be accomplished and gives reasonable signal intensities. Copyright © 2009 John Wiley & Sons, Ltd. [source] Competition STD NMR for the detection of high-affinity ligands and NMR-based screeningMAGNETIC RESONANCE IN CHEMISTRY, Issue 6 2004Yu-Sen Wang Abstract The reported competition STD NMR method combines saturation transfer difference (STD) NMR with competition binding experiments to allow the detection of high-affinity ligands that undergo slow chemical exchange on the NMR time-scale. With this technique, the presence of a competing high-affinity ligand in the compound mixture can be detected by the disappearance or reduction of the STD signals of a low-affinity indicator ligand. This is demonstrated on a BACE1 (,-site amyloid precursor protein cleaving enzyme 1) protein,inhibitor system. This method can also be used to derive an approximate value, or a lower limit, for the dissociation constant of the potential ligand based on the reduction of the signal intensity of the STD indicator, which is illustrated on an HSA (human serum albumin) model system. This leads to important applications of the competition STD NMR method for lead discovery: it can be used (i) for compound library screening against a broad range of drug targets to identify both high- and low-affinity ligands and (ii) to rank order analogs rapidly and derive structure,activity relationships, which are used to optimize these NMR hits into viable drug leads. Copyright © 2004 John Wiley & Sons, Ltd. [source] Functional Characterization of the Recombinant N -Methyltransferase Domain from the Multienzyme Enniatin SynthetaseCHEMBIOCHEM, Issue 9 2007Till Hornbogen Dr. Abstract A 51 kDa fusion protein incorporating the N -methyltransferase domain of the multienzyme enniatin synthetase from Fusarium scirpi was expressed in Saccharomyces cerevisiae. The protein was purified and found to bind S -adenosyl methionine (AdoMet) as demonstrated by cross-linking experiments with 14C-methyl-AdoMet under UV irradiation. Cofactor binding at equilibrium conditions was followed by saturation transfer difference (STD) NMR spectroscopy, and the native conformation of the methyltransferase was assigned. STD NMR spectroscopy yielded significant signals for H2 and H8 of the adenine moiety, H1' of D -ribose, and SCH3 group of AdoMet. Methyl group transfer catalyzed by the enzyme was demonstrated by using aminoacyl- N -acetylcysteamine thioesters (aminoacyl-SNACs) of L -Val, L -Ile, and L -Leu, which mimic the natural substrate amino acids of enniatin synthetase presented by the enzyme bound 4,-phosphopantetheine arm. In these experiments the enzyme was incubated in the presence of the corresponding aminoacyl-SNAC and 14C-methyl-AdoMet for various lengths of time, for up to 30 min. N -[14C-Methyl]-aminoacyl-SNAC products were extracted with EtOAc and separated by TLC. Acid hydrolysis of the isolated labeled compounds yielded the corresponding N -[14C-methyl] amino acids. Further proof for the formation of N - 14C-methyl-aminoacyl-SNACs came from MALDI-TOF mass spectrometry which yielded 23,212 Da for N -methyl-valyl-SNAC, accompanied by the expected postsource decay (PSD) pattern. Interestingly, L -Phe, which is not a substrate amino acid of enniatin synthetase, also proved to be a methyl group acceptor. D -Val was not accepted as a substrate; this indicates selectivity for the L isomer. [source] Lectin-Based Drug Design: Combined Strategy to Identify Lead Compounds using STD NMR Spectroscopy, Solid-Phase Assays and Cell Binding for a Plant Toxin ModelCHEMMEDCHEM, Issue 3 2010Abstract The growing awareness of the sugar code,i.e. the biological functionality of glycans,is leading to increased interest in lectins as drug targets. The aim of this study was to establish a strategic combination of screening procedures with increased biorelevance. As a model, we used a potent plant toxin (viscumin) and lactosides synthetically modified at the C6/C6, positions and the reducing end aglycan. Changes in the saturation transfer difference (STD) in NMR spectroscopy, applied in inhibition assays, yielded evidence for ligand activity and affinity differences. Inhibitory potency was confirmed by the blocking of lectin binding to a glycoprotein-bearing matrix. In cell-based assays, iodo/azido-substituted lactose derivatives were comparatively active. Interestingly, cell-type dependence was observed, indicating the potential of synthetic carbohydrate derivative to interact with lectins in a cell-type (glycan profile)-specific manner. These results are relevent to research into human lectins, glycosciences, and beyond. [source] | ||||||||||