Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q9UMR3 (NMR)
 150,598 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The pH-dependence of RNAase A and of Ntau-carboxymethylhistidine-12-RNAase (ribonucleate 3'-pyrimidino-oligonucleotidohydrolase) catalysis was studied. Apparent acid dissociation constants were obtained by least squares analysis of the kinetics data. These dissociation constants were compared with pKa values of model imidazole compounds, and with pKa values of histidine residues 12 and 119 on the protein. The shapes of the kcat versus pH profiles for RNAase A and its carboxymethyl derivative are very similar, from which it is concluded that the mechanism of catalysis is closely similar in the two proteins. Apparent pKa values obtained from the kinetic data are higher for the carboxymethylated protein than for RNAase A, as are the pKa values of residues 12 and 119. The similar shifts are consistent with the conclusions that both these residues are functionally significant in native and modified enzyme, and that an unblocked tau-nitrogen on histidine-12 is not essential for activity. From the enzyme's catalytic dependence on pH, and the NMR determined pKa values we propose that histidine 12 and 119 function catalytically in their basic and acidic forms respectively.
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PMID:Catalytic activity of Ntau-carboxymethylhistidine-12 ribonuclease: pH dependence. 1 11

The conformations of cysteamine, thiazolidine, and thiazolidine-4-carboxylic acid were determined in aqueous solutions using NMR spectroscopy. At physiological pH, the population ratio of gauche- and trans-conformers was 3:1. The gauche-rotamer is probably responsible for the antiradiation activity and acts through metal chelation involving sulfur and nitrogen atoms. The puckering of the thiazolidine ring was calculated using NMR coupling constants. The observed results were compared with those obtained in the solid state using X-ray diffraction.
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PMID:Conformational studies of antiradiation agents by NMR: cysteamine and its derivatives. 1 12

Reversible unfolding of bovine chymotrypsinogen A in 2H2O either by heating at low pH or by exposure to 6 M guanidinium chloride results in the exchange of virtually all the nitrogen-bound hydrogens that give rise to low-field 1H NMR peaks, without significant exchange of the histidyl ring Cepsilon1 hydrogens. These preexchange procedures have enabled the resolution of two peaks, using 250-MHz correlation 1H NMR spectroscopy, that are attributed to the two histidyl residues of chymotrypsinogen A. Assignments of the Cepsilon1 hydrogen peaks to histidine-40 and -57 were based on comparison of the NMR titration curves of the native zymogen with those of the diisopropylphosphoryl derivative. Two histidyl Cepsilon1 H peaks were also resolved with solutions of preexchanged chymotrypsin Aalpha. The histidyl peaks of chymotrypsin Aalpha were assigned by comparison of NMR titration curves of the free enzyme with those of its complex with bovine pancreatic trypsin inhibitor (Kunitz). The NMR titration curves of histidine-57 in the zymogen and enzyme and histidine-40 in the zymogen exhibit two inflections; the additional inflections were assigned to interactions with neighboring carboxyl groups: aspartate-102 in the case of histidine-57 and aspartate-194 in the case of histidine-40 of the zymogen. In bovine chymotrypsinogen A in 2H2O at 31 degrees C, histidine-57 has a pK' of 7.3 and aspartate-102 a pK' of 1.4, and the histidine-40-aspartate-194 system exhibits inflections at pH 4.6 and 2.3. In bovine chymotrypsin Aalpha under the same conditions, the histidine-57-aspartate-102 system has pK' values of 6.1 and 2.8, and histidine-40 has a pK' of 7.2. The results suggest that the pK' of histidine-57 is higher than the pK' of aspartate-102 in both zymogen and enzyme. A significant difference exists in the structure and properties of the catalytic center between the zymogen and activated enzyme. In addition to the difference in pK' values, the chemical shift of histidine-57, which is highly abnormal in the zymogen (deshielded by 0.6 ppm), becomes normalized upon activation. These changes may explain part of the increase in the catalytic activity upon activation. The 1H NMR chemical shift of the Cepsilon1 H of histidine-57 in the chymotrypsin Aalpha-pancreatic trypsin inhibitor (Kunitz) complex is constant between pH 3 and 9 at a value similar to that of histidine-57 in the porcine trypsin-pancreatic trypsin inhibitor complex [Markley, J.L., and Porubcan, M. A. (1976), J. Mol. Biol. 102, 487--509], suggesting that the mechanisms of interaction are similar in the two complexes.
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PMID:Zymogen activation in serine proteinases. Proton magnetic resonance pH titration studies of the two histidines of bovine chymotrypsinogen A and chymotrypsin Aalpha. 3 98

The coordination of the glycyl-L-tyrosinate . Pd(II) complex to adenosine 5' -diphosphate (ADP) and adenosine 5' -triphosphate (ATP) has been studied using 13C, 1H NMR and electronic spectral methods. Two dominant species have been found in solution, a monomeric ternary complex with Gly-Tyr . Pd(II) bound to the N-1 purine nitrogen and a dimer in which two dipeptide . Pd(II) complex molecules are coordinated to the nucleotide by N-1 and N-7 nitrogens. Monomeric ternary complexes having metal coordination to N-7 were not detected. The influence of the aromatic ring of tyrosine upon the chemical shifts for the bonded nucleotide molecule suggest that the plane of the purine ring and of the Gly-Tyr . Pd(II) complex are almost perpendicular to each other.
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PMID:Coordination of Gly-Tyr . Pd(II) complex to ATP and ADP nucleotides. 3 30

The first chemical synthesis of 2-aminoimidazo[1,2-a]-s-triazin-4-one (8), the corresponding nucleoside and nucleotide, and certain related derivatives of a new class of purine analogues containing a bridgehead nitrogen atom is described. Condensation of 2-amino-4-chloro-6-hydroxy-s-triazine (2) with aminoacetaldehyde dimethyl acetal followed by the ring annulation gave the guanine analogue 8. A similar ring annulation of 4-(2,2-dimethoxyethylamino)-s-triazine-2,6-dione (5) gave imidazo[1,2-a]-s-triazine-4,6-dione (9). Direct glycosylation of the trimethylsilyl derivative of 8 with 1-O-acetyl-2,3,5-tri-O-benzoyl-beta-D-ribofuranose in the presence of stannic chloride, followed by debenzoylation, gave the guanosine analogue 2-amino-8-(beta-D-ribofuranosyl)imidazo[1,2-a]-s-triazin-4-one (12b), which on deamination gave the xanthosine analogue 13. Phosphorylation of 12b gave 2-amino-8-(beta-D-ribofuranosyl)imidazo[1,2-a]-s-triazin-4-one 5'-monophosphate (II). The anomeric configuration has been determined unequivocally by using NMR of the 2',3'-O-isopropylidene derivate 10 and the site of ribosylation has been established by using 13C NMR spectroscopy. These compounds were tested against type 1 herpes, type 13 rhino, and type 3 parainfluenza viruses in tissue culture. Moderate rhinovirus activity was observed for several compounds at nontoxic dosage levels.
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PMID:Imidazo[1,2-a]-s-triazine nucleosides. Synthesis and antiviral activity of the N-bridgehead guanine, guanosine, and guanosine monophosphate analogues of imidazo[1,2-a]-s-triazine. 21 63

The synthesis of carrier ampholytes suitable for isoelectric focusing is described. The mixture of hexamethylenetetramine (HMTA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA) and pentaethylenehexamine (PEHA) ampholytes closely resembles commercial Ampholine, and covers the pH range 3-9.5. We have been able to detect focused ampholytes in a gel slab, taking advantage of their different refractive indices, and to assess their relative amounts along the pH gradient. PEHA ampholytes contain up to 20% of chromophoric structures, with two UV peaks at 368 and 315 nm, in a pH-dependent equilibrium, associated with a very weak nitrogen function having a pK of 1.1. This could be the pK6 of the last amino group in PEHA. However, NMR spectra failed to reveal any nitrogen heterocyclic structure formed during the synthesis. This mixture of ampholytes exhibits good conductivity, produces smooth pH gradients and allows sharp protein separations in the pH range 3-9.5. Their synthesis is very easy and their cost is extremely low. Their availability sould make feasible large-scale preparative isoelectric focusing, and attract more interest to continuous-flow techniques, where large amounts of ampholytes are required.
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PMID:Characterization of synthetic carrier ampholytes for isoelectric focusing. 23 18

A number of new fluorine-containing 1,2,4-triazolo[4,3-b]pyridazines have been synthesized by the condensation of 4-amino-(4H)-1,2,4-triazole with appropriate fluorinated beta-diketones in glacial acetic acid. All synthesized compounds were characterized by their m.p.'s, nitrogen analysis, IR, 1H NMR and 19F NMR. A representative number of compounds was screened for their CNS activity and found to be mild stimulants.
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PMID:Possible psychopharmacological agents. Part 9: Synthesis and CNS activity of some new fluorine-containing 1,2,4-triazolo[4,3-b]pyridazines. 54 48

Analytical methods were developed to determine whether there was less than one ppm of II in IV. Purified IV contained a compound with the same GC retention time as authentic II on OV-17 and Silar 10C columns, using a FID or a nitrogen/phosphorus detector. The GC-coupled mass spectra contained major peaks at m/e 251 and 167 and the GC-coupled methane CI spectra gave the quasi-molecular ion, m/e 282. However, the CI selected ion monitor indicated three compounds at m/e 282. The nitrosamine II was separated from IV by HPLC on muBondapak C18. The GC-coupled mass spectra of the HPLC nitrosamine fraction had peaks at m/e 251 and 167 and other peaks for a compound of greater MW than II, although the GC retention times were the same. Evidence for II and a decrease in the detection limit to one ppm was obtained with a TEA interfaced with a HPLC. To determine if II was formed from IV, it was exposed to ozone at -78 degrees C in methylene chloride. The DSC, IR and NMR of the product were coincident with those of the standard of II. In other experiments, IV in methylene chloride was exposed to light and dry air in the presence and absence of methylene blue. The PMR and 13C NMR of the product formed in the presence of methylene blue were the same as that of II. It is postulated that this nitrosamine was formed by a singlet oxygen mechanism.
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PMID:The analysis and source of 1-diphenylmethyl-4-nitrosopiperazine in 1-diphenylmethyl-4-[(6-methyl-2-pyridyl) methyleneamino]piperazine: a case history. 68 Jul 47

The copper(I) complexes of peptides containing sulfhydryl and imidazole groups have been investigated in aqueous solution by proton magnetic resonance (1H NMR). The N-mercaptoacetyl-L-histidine coordinates through the sulfhydryl sulfur and imidazole nitrogen atoms to form the unique 1:1 Cu(I) complex species containing bridged imidazole. The sulfhydryl and imidazole groups are adequate ligands for not only Cu(II) but also Cu(I). The 1H NMR spectra show that the peptide nitrogen group is not involved in complex formation of Cu(I) with N-mercaptoacetyl-L-histidine and 3-mercaptopropionyl-L-histidine. The results have been discussed with respect to the protein ligands for 'blue' copper centers.
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PMID:Proton-magnetic-resonance study of copper(I) complexes with peptides containing sulfhydryl and imidazole groups as possible model ligands for copper proteins. 91 6

N,N-Dimethylaminoethyl acrylate (acryl-DMA) was synthesized as a tertiary nitrogen choline acetyltransferase (ChAc) inhibitor which would be able to penetrate biological membranes to inhibit ChAc in the nerve terminal. The synthesis from dimethylaminoethanol and acrylyl chloride was described and the hydration with times in an aqueous medium measured by NMR spectroscopy was presented. The autohydrolysis in water was found to be 1.75 x 10(-8) mol/min at pH 7.4 and 5.0 mM concentration. The enzymatic hydrolysis was unaffected by cholinesterases. Acryl-DMA was capable of inhibiting ChAc extracted from rat brain with I50 of 5.02 x 10(-4) M. The inhibition was reversible and displayed uncompetitive kinetics with respect to both substrates, choline and acetyl-CoA. Neither the hydrolysis nor the hydration products of acryl-DMA could inhibit ChAc. Although acryl-DMA was hydrated rapidly and completely within 1 hr at high pH (9.0), the time course of inhibition ability of acryl-DMA in aqueous medium at physiological pH was found to decrease rather slowly and by 36% in 1 hr, indicating that acryl-DMA can survive from hydration at physiological pH. Acryl-DMA was also tested for its ability to block electrically induced muscle contractions in both isolated skeletal and smooth nerve-muscle preparations. The ED50's obtained were less than 5 x 10(-4) M in both cases.
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PMID:Chemistry and biological activities of N,N-dimethylaminoethyl acrylate, a choline acetyltransferase inhibitor. 108 11


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