Paramagnetic relaxation probe

Paramagnetic Relaxation Probes Spin Labeling of Apomyoglobin... 

The EPR linewidths of Gd(III) complexed with cacodylate buffer and bovine albumin serum have been obtained which were consistent with the action of Gd(III) as a paramagnetic relaxation probe with the same protein [44]. A host of inorganic and organic ligands including amino acids and nucleotides complexed with Gd(III) were studied and two types of peaks were observed (i.e.) narrow symmetric peaks and broad asymmetric peaks [45],... 

Hilty et alP have used spin labels to study protein-lipid interactions in mixed micelles containing dihexanoylphosphatidylcholine and the E. coli outer-membrane protein X (OmpX). As paramagnetic relaxation probes, they used several different nitroxide spin labels attached to the lipid as well as Gd-DOTA, which remains in the aqueous phase. Spectral perturbations were monitored in TROSY and ID H NMR spectra. 

Paramagnetic ion probes have been successfully used to study the binding characteristics and solution conformations of a number of biochemically important molecules. These include vitamin D, (533) penicillins, (534) and the antibiotics tetracycline, (535-537) vancomycin, (632) and bacitracin. (633) Antibodies and antibody fragments (immunoglobulins, IgG) have been studied by proton relaxation enhancement methods when lanthanide ions, particularly Gd(m), are bound to the proteins. (746-748). 

Other paramagnetic ions that can be incorporated in the porphyrin ring include Mn(iii), Fe(iii), Co(ii), Ni(ii), Cu(ii), and Ag(ii). Of these ions Co(ii) is the best shift probe, and Fe(iii) and Mn(iii) the best relaxation probes. This whole series of ion probes was used to study a variety of porphyrin-calTeine complexes. (655) Shift and line-broadening data suggest that the solution structures are of the plane-to-plane type with the metal situated above nitrogen-9 of the caffeine ring. 

Paramagnetic shift and relaxation probes are proving of great benefit in studying the structures, dynamics, and permeabilities of... 

NMR Spectrometry. Liquid phase and NMR spectra were recorded on a Varian XL300 NMR spectrometer at carbon and nitrogen resonant fi equencies of 75.4 and 30.4 MHz, respectively, using a 10 mm broadband probe. Quantitative NMR spectra of the unreacted fulvic and humic acid samples were recorded in DMSO-d6, 99.9 atom % as previously described (23). INEPT (24) and ACOUSTIC (25) N NMR spectra were recorded on the aniline-reacted fulvic and humic acids. Refocussed INEPT (proton decoupled) spectra were recorded as previously described (9). ACOUSTIC spectra, with the exception of the bimessite catalyzed sample, were recorded with the use of paramagnetic relaxation reagent (100-200 mg chromium (III) acetylacetonate). Acquisition parameters included an 18,656.7 Hz spectral window (613.7 ppm), 0.5-s acquisition time, 45° pulse angle, 2.0-s pulse delay, and t delay of 0.1 ms. Neat formamide in a 5 mm NMR tube, assumed to be 112.4 ppm, was used as an external reference standard for all spectra. N NMR chemical shifts are reported in ppm downfield of ammonia, taken as 0.0 ppm. 

Paramagnetic Species Shift Reagents and Relaxation Probes. 130... 

Hyde et al. [236] have reviewed the spin-probe-spin-label method, which was first described by Leigh [60] to determine the distance between a spin probe (a paramagnetic metal ion) and a spin label (usually a nitroxide). This theory is also applicable to two interacting metal ions one a fast relaxing probe and the other a slower relaxing label . The experimental observable is usually the decreased intensity of the slower relaxing label, C. If C and the relaxation time, T, of the spin probe are known, then the distance, r, between probes may be obtained from the relationship... 

The use of the ATP resonances as the reporter has been described recently. Reduction of the ATP STD NMR signals by a competitive inhibitor, permitted a direct measurement of the inhibitor K, with respect to the natural substrate ATP. After this initial measurement, the assay was combined with paramagnetic relaxation enhancement effect. In a second step, Maganese ions were added to the samples, which turned the Mg2+/ATP complex into a paramagnetic probe. The proximity of a potential non-ATP competitive compound can be inferred [81]. 

Groves, J.T. and K.V. Shalyaev (1998). Paramagnetic H-NMR relaxation probes of stereoselectivity in metalloporphyrin catalyzed olefin epoxidation. Chirality 10, 106-119. 

Du et have determined the magnitude and orientation of the paramagnetic susceptibility tensor of the cyanomet complex of an 02-avid hemoglobin from the trematode Paramphistomum epiclitum. They used proton hyperfine chemical shifts and paramagnetic relaxation enhancements to probe the chemical bonding at the metal center. 

In many respects, equilibrium physical measurements could be considered most valuable. Nuclear magnetic resonance (NMR) spectra (T, paramagnetic relaxation) were used to probe cooperativity of midazolam with testosterone and a-NF [1388], Atkins and his associates [1389] used a single-molecule fluorescent approach to show allosteric effects of one ligand on the dissociation rate of another substrate, Nile red. Nile red is an allosteric fluorescent substrate and has utility for such studies [1390] evidence could also be obtained for a second binding site [ 13 91 ]. 

Nickel. NMR paramagnetic relaxation enhancement in [Ni(en)2(OH2)2] has been probed theoretically. NMR data have also been reported for nickel complexes of a benzopyrrole chelate/ NF complexes of l,5-(benzimidazol-2-yl)-3-thiapentane, NF complexes of dissymmetric tertiary amines,and [Ni Pb( l-Et02C- 1-NC-ethylene- 12,2-dithiolate)2 ]. ... 

High-resolution H n.m.r. spectroscopy has been used to probe the conformations of a number of o-ribofuranosylamine derivatives and such rigid molecules as 2,2 -cyclonucleosides and nucleoside 3, 5 -phosphates in aqueous solution. H N.m.r. spectroscopy has also been used to study details of the intramolecular association and conformations of a- and j8-linked pyridine ribo-nucleosides and their 5 -phosphates. The results were analysed in terms of base-D-ribose, o-ribose-side-chain, and base-side-chain interactions and the conformational restraints imposed by the cis HO-2-HO-3 interaction in jS-nucleo-tides and the additional cis HO-2 -base interaction in a-nucleotides. H N.m.r. measurements - including measurements of nuclear Overhauser effects and paramagnetic relaxations effected by Mn + cations - have been used to investigate the preferred conformation about the jV-glycosidic bond of 8-amino-, 8-methyl-amino-, and 8-dimethylamino-adenylic acid, all of which competitively inhibit the coenzyme NADH in the reaction with chicken-muscle lactate dehydrogenase. The primary and secondary amines were shown to prefer anti conformations, whereas the tertiary amine prefers a syn conformation. 

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