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Fang J, Zhang B, Asai H. Chemical modification of contractile 3-nm-diameter filaments in Vorticella spasmoneme by diethyl-pyrocarbonate and its reversible renaturation by hydroxylamine. Biochem Biophys Res Commun 2003; 310:1067-72. [PMID: 14559224 DOI: 10.1016/j.bbrc.2003.09.121] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
A peritrich ciliate possesses a zooid and a long stalk consisting of a bundle of 3-nm-diameter filaments. Glycerinated stalks can contract in the presence of free Ca(2+) and re-extend in the absence of free Ca(2+). In the present study, we demonstrated that histidine residue(s) played a critical role in spasmoneme contraction by using glycerinated stalk of Vorticella. Concentration-dependent inhibition of spasmoneme contraction was observed in the presence of reversible histidine-modifying reagent named diethyl-pyrocarbonate (DEPC). In addition, the contractility degree of DEPC-modified spasmoneme could be partially restored by hydroxylamine treatment. The 244nm absorption of modified spasmoneme protein(s) increased with rising DEPC concentration and decreased following the addition of hydroxylamine treatment. Adding Ca(2+) before DEPC modification could prevent the spasmoneme contraction from inhibition of DEPC. Those results suggested that histidine residues were actively involved in spasmoneme contraction. Ca(2+)-binding ability of spasmin was not inhibited by DEPC modification, which suggested that the essential histidine residues were not on the calcium-binding site of spasmin.
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177
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Kuznetsova S, Knaff DB, Hirasawa M, Lagoutte B, Sétif P. Mechanism of Spinach Chloroplast Ferredoxin-Dependent Nitrite Reductase: Spectroscopic Evidence for Intermediate States. Biochemistry 2003; 43:510-7. [PMID: 14717606 DOI: 10.1021/bi035662q] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Nitrite reductases found in plants, algae, and cyanobacteria catalyze the six-electron reduction of nitrite to ammonia with reduced ferredoxin serving as the electron donor. They contain one siroheme and one [4Fe-4S] cluster, acting as separate one-electron carriers. Nitrite is thought to bind to the siroheme and to remain bound until its complete reduction to ammonia. In the present work the enzyme catalytic cycle, with ferredoxin reduced by photosystem 1 as an electron donor, has been studied by EPR and laser flash absorption spectroscopy. Substrate depletion during enzyme turnover, driven by a series of laser flashes, has been demonstrated. A complex of ferrous siroheme with NO, formed by two-electron reduction of the enzyme complex with nitrite, has been shown to be an intermediate in the enzyme catalytic cycle. The same complex can be formed by incubation of free oxidized nitrite reductase with an excess of nitrite and ascorbate. Hydroxylamine, another putative intermediate in the reduction of nitrite catalyzed by nitrite reductase, was found to react with oxidized nitrite reductase to produce the same ferrous siroheme-NO complex, with a characteristic formation time of about 13 min. The rate-limiting step for this reaction is probably hydroxylamine binding to the enzyme, with the conversion of hydroxylamine to NO at the enzyme active site likely being much faster.
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178
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Iwata Y, Koseki H. Decomposition of hydroxylamine/water solution with added iron ion. JOURNAL OF HAZARDOUS MATERIALS 2003; 104:39-49. [PMID: 14602398 DOI: 10.1016/s0304-3894(03)00233-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Decomposition hazards of hydroxylamine (HA)/water solution with and without the addition of iron ion were studied in this paper. Tests were conducted to obtain information about decomposition hazards of HA/water solution following the United Nations recommendations on the transport of dangerous goods. When the heat accumulation storage test was conducted using HA50 wt.%/water solution without the addition of iron ion, the self-accelerating decomposition temperature (SADT) was 80 degrees C. Therefore, HA50 wt.%/water solution was not classified with self-reactive substances following the United Nations recommendations on the transport of dangerous goods. Decomposition hazards of HA50 wt.%/water solution with added iron ion were investigated. The concentration of iron ion in sample of HA50 wt.%/water solution without the addition of iron ion was below 1.0 ppm. The range of the concentration of iron ion in sample of HA50 wt.%/water solution with added iron ion was between 1.0 and 5.4 ppm. The thermal stability of HA50 wt.%/water solution decreased by the addition of iron ion in the heat accumulation storage test. HA50 wt.%/water solution with the addition of iron ion was classified with self-reactive substances following the United Nations recommendations on the transport of dangerous goods. The intensity of the thermal decomposition of HA50 wt.%/water solution increased by the addition of iron ion in the Koenen test.
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179
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Hou WC, Lee MH, Hsu FL, Lin YH. Inhibitory activities of semicarbazide-sensitive amine oxidase and angiotensin converting enzyme of pectin hydroxamic acid. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2003; 51:6362-6366. [PMID: 14518968 DOI: 10.1021/jf034463a] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Solutions of 100 mL of 1% commercial pectin each with a different degree of esterification (DE), DE94, DE65, and DE25, were reacted with 100 mL of 2 M alkaline hydroxylamine (pH 12.0) at room temperature for 4 or 18 h. These pectin hydroxamic acids (PHAs; DE94T4, DE94T18, DE65T4, and DE25T4) were used to test the inhibitory activities against semicarbazide-sensitive amine oxidase (SSAO) and angiotensin-converting enzyme (ACE). Compared to different DE pectins (DE94, DE65, and DE25), the PHAs of DE94T4, DE94T18, DE65T4, and DE25T4 showed different inhibition activities against SSAO or ACE. Commercial pectins with different DE values showed negligible SSAO or ACE inhibitions. The order of SSAO inhibition was DE65T4 > DE94T18 approximately DE25T4 >> DE94T4. However, the order of ACE inhibition was DE94T4 > DE94T18 >> DE65T4 > DE25T4. The SSAO activity staining or ACE-hydrolyzed products on TLC chromatogram also confirmed the inhibitory activities of PHAs against SSAO or ACE.
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180
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Yamazaki SI, Itoh S. Kinetic Evaluation of Phenolase Activity of Tyrosinase Using Simplified Catalytic Reaction System. J Am Chem Soc 2003; 125:13034-5. [PMID: 14570470 DOI: 10.1021/ja036425d] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A very simple tyrosinase reaction system has been developed using borate anion as a trapping agent of catechols and hydroxylamine as an external reductant to evaluate the phenolase activity without the interference of catecholase activity. Reactivities of variously para-substituted phenols in this system were compared directly to those of the phenols in the model reactions, demonstrating that the enzymatic oxygenation reaction of phenols proceeds via the same mechanism as the model reaction, that is, electrophilic aromatic substitution mechanism.
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181
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Davies SJ, Ayscough AP, Beckett RP, Bragg RA, Clements JM, Doel S, Grew C, Launchbury SB, Perkins GM, Pratt LM, Smith HK, Spavold ZM, Thomas SW, Todd RS, Whittaker M. Structure-activity relationships of the peptide deformylase inhibitor BB-3497: modification of the methylene spacer and the P1' side chain. Bioorg Med Chem Lett 2003; 13:2709-13. [PMID: 12873499 DOI: 10.1016/s0960-894x(03)00532-8] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Structural modifications to the peptide deformylase inhibitor BB-3497 are described. In this paper, we describe the initial SAR around this lead for modifications to the methylene spacer and the P1' side chain. Enzyme inhibition and antibacterial activity data revealed that the optimum distance between the N-formyl hydroxylamine metal binding group and the P1' side chain is one unsubstituted methylene unit. Additionally, lipophilic P1' side chains that closely mimic the methionine residue in the substrate provided compounds with the best microbiological profile.
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182
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Wang C, Lyon DY, Hughes JB, Bennett GN. Role of hydroxylamine intermediates in the phytotransformation of 2,4,6-trinitrotoluene by Myriophyllum aquaticum. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2003; 37:3595-3600. [PMID: 12953871 DOI: 10.1021/es030010a] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Phytotransformation studies of 2,4,6-trinitrotoluene (TNT) were conducted using Myriophyllum aquaticum to clarify the role of initial intermediates of TNT transformation in the complex product distributions reported previously. 2-Hydroxylamino-4,6-dinitrotoluene (2HA46DNT) and 4-hydroxylamino-2,6-dinitrotoluene (4HA26DNT) were the initial intermediates of TNT phytotransformation. 2HA46DNT and 4HA26DNT were both abiotically transformed to 4,4',6,6'-tetranitro-2,2'-azoxytoluene (2,2'azoxy) and 2,2',6,6'-tetranitro-4,4'-azoxytoluene (4,4'azoxy) and also phytoreduced to the related amines 2-amino-4,6-dinitrotoluene (2A46DNT) and 4-amino-2,6-dinitrotoluene (4A26DNT). To further elucidate the initial steps of this TNT phytotransformation pathway, the transformations of known intermediates (including 2HA46DNT, 4HA26DNT, 2A46DNT, 4A26DNT, 2,2'azoxy, and 4,4'azoxy) were monitored in plant systems. The transformation rates were measured, and kinetic analysis using pseudo-first-order models was used to evaluate the relative rates of competing reactions. The formation of the azoxy products was determined to be more rapid than the formation of the amine products. Both the azoxy and amine products were subject to uptake and further transformation by the plant.
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183
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Bui CT, Babon JJ, Lambrinakos A, Cotton RGH. Detection of mutations in DNA by solid-phase chemical cleavage method. A simplified assay. Methods Mol Biol 2003; 212:59-70. [PMID: 12491903 DOI: 10.1385/1-59259-327-5:059] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/28/2023]
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184
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Vanderesse R, Thevenet L, Marraud M, Boggetto N, Reboud M, Corbier C. Alpha-aminoxy acids as building blocks for the oxime and hydroxylamine pseudopeptide links. Application to the synthesis of human elastase inhibitors. J Pept Sci 2003; 9:282-99. [PMID: 12803495 DOI: 10.1002/psc.452] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The aminoxy acids NH2-O-C(alpha)HR-CO2H are much more easily obtained in the enantiomerically pure form than the analogous hydrazino acids NH2-NH-C(alpha)HR-CO2H, and it has been shown that the isosteric amidoxy psi[CO-NH-O] and hydrazide psi[CO-NH-NH] amide surrogates Induce two quite similar gamma-like folded structures. An aminoxy acid can also be N-coupled to a peptide aldehyde to give the aldoxime psi[CH = N-O] link or to a peptide ketone to form the ketoxime psi[CR= N-O] link. The former can be further reduced into the hydroxylamine psi[CH2-NH-O] link which gives rise to reduced amidoxy peptides. The structural properties Induced by these amide surrogates were studied, using IR and NMR spectroscopy, paying particular attention to the Z/E-isomerism of the oxime link. In order to investigate their inhibitory potency, the three amide surrogates were introduced in the Pro3-Val4 and Val4-Ala5 position of Z-Ala1-Ala2-Pro3-Val4-Ala5-Ala6-NHiPr, a substrate which is cleaved in the Val4-Ala5 position by human leukocyte elastase (HLE). The [Val4psi[CO-NH-O]Ala5] analogue was still a substrate, while the [Pro3psi[CO-NH-O]Val4] and [Val4psi[CH = N-O]Ala5] pseudopeptides acted as HLE competitive inhibitors.
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185
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Cabail MZ, Pacheco AA. Selective one-electron reduction of Nitrosomonas europaea hydroxylamine oxidoreductase with nitric oxide. Inorg Chem 2003; 42:270-2. [PMID: 12693206 DOI: 10.1021/ic025779n] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Hydroxylamine oxidoreductase (HAO) from the autotrophic bacterium Nitrosomonas europaea catalyzes the 4-e- oxidation of NH2-OH to NO2-. The e- are transferred from NH2OH to an unusual 5-coordinate heme known as P460, which is the active site of HAO, and from there to an array of seven c-type hemes. NO., generated by laser flash photolysis of N,N'-bis(carboxymethyl)-N,N'-dinitroso-1,4-phenylenediamine, is found to act as a 1-e- donor to HAO. Most likely NO. binds P460 to yield a [Fe(NO)]6 moiety, which then hydrolyzes to give the reduced enzyme and NO2-. The [Fe(NO)]6 moiety is also a plausible final intermediate in the oxidation of NH2OH.
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186
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Kataoka H, Horiyama S, Yamaki M, Oku H, Ishiguro K, Katagi T, Takayama M, Semma M, Ito Y. Anti-inflammatory and anti-allergic activities of hydroxylamine and related compounds. Biol Pharm Bull 2002; 25:1436-41. [PMID: 12419955 DOI: 10.1248/bpb.25.1436] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The anti-inflammatory activities of several novel oximes and O-acyl oximes that we synthesized have been reported based on carrageenan-induced rat foot-pad swelling assay and histamine-induced rat vascular permeability assay. A cyclooxygenase (COX)-1 inhibitory effect has also been reported for 4'-piperidinoacetophenone and 4'-morpholinoacetophenone oximes and their O-acyl derivatives. To further search for more effective non-steroidal anti-inflammatory or anti-allergic drugs, 1-hydroxylamino-1-(4'-piperidinophenyl) ethane (P-HA) and 1-hydroxylamino-1-(4'-morpholinophenyl) ethane (M-HA) were synthesized from the corresponding oximes with sodium cyanoborohydride, and N,O-diacetyl hydroxylamines (P-HA-Ac and M-HA-Ac) were prepared from these hydroxylamines using acetyl chloride. These hydroxylamines and N,O-diacetyl hydroxylamines clearly exhibited inhibitory effects on mouse carrageenan-induced foot-pad swelling induced by oral administration (150, 37.5 mg/kg). An oral dose of P-HA-Ac (150 mg/kg) significantly inhibited the mouse anaphylactic reaction to ovalbumin measured by the abdominal wall (AW) method. Percutaneous administration of P-HA and M-HA significantly inhibited 2,4-dinitrofluorobenzene (DNFB)-induced contact hypersensitivity reaction (type IV) in mice at a dose of 0.5 and 0.1 mg/ear, respectively. All tested hydroxylamines and N,O-diacetyl hydroxylamines clearly inhibited both COX-1 and COX-2 enzyme activities with IC(50) values of 1.9-28.7 and 1.6-2.9 micro M against COX-1 and COX-2, respectively. Hydroxylamines (P-HA and M-HA) also showed a 5-lipoxygenase inhibitory effect.
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187
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Bui CT, Rees K, Lambrinakos A, Bedir A, Cotton RGH. Site-selective reactions of imperfectly matched DNA with small chemical molecules: applications in mutation detection. Bioorg Chem 2002; 30:216-32. [PMID: 12392702 DOI: 10.1016/s0045-2068(02)00019-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The last decade has witnessed many exciting scientific publications associated with site-selective reactions of small chemical molecules with imperfectly matched DNA. Typical examples are carbodiimide, hydroxylamine, potassium permanganate, osmium tetroxide, chemical tagging probes, biotinylated, chemiluminescent and fluorescent probes, and all of them selectively react with imperfectly matched DNA. More recently, some therapeutic agents including DNA intercalating drugs and groove binders have been found to promote the in vivo repair system to recognize and repair the mismatch more effectively. The results have established a novel method for detection of mismatches. Development of new chemical reactions for detection of imperfectly matched DNA and mutations is a rapidly growing field and has attracted significant interest of scientists from both chemical and biological fields and it is the main focus of this review.
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188
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Mazumdar A, Bandyopadhyay D, Bandyopadhyay U, Banerjee RK. Probing the role of active site histidine residues in the catalytic activity of lacrimal gland peroxidase. Mol Cell Biochem 2002; 237:21-30. [PMID: 12236583 DOI: 10.1023/a:1016540303300] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The role of active site histidine residues in SCN- oxidation by lacrimal gland peroxidase (LGP) has been probed after modification with diethylpyrocarbonate (DEPC). The enzyme is irreversibly inactivated following pseudo-first order kinetics with a second order rate constant of 0.26 M(-1) sec(-1) at 25 degrees C. The pH dependent rate of inactivation shows an inflection point at 6.6 indicating histidine derivatization. The UV difference spectrum of the modified vs. native enzyme shows a peak at 242 nm indicating formation of N-carbethoxyhistidine. Carbethoxyhistidine formation and associated inactivation are reversed by hydroxylamine indicating histidine modification. The stoichiometry of histidine modification and the extent of inactivation show that out of five histidine residues modified, modification of two residues inactivates the enzyme. Substrate protection with SCN- during modification indicates that although one histidine is protected, it does not prevent inactivation. The spectroscopically detectable compound II formation is lost due to modification and is not evident after SCN- protection. The data indicate that out of two histidines, one regulates compound I formation while the other one controls SCN- binding. SCN- protected enzyme is inactive due to loss of compound I formation. SCN- binding studies by optical difference spectroscopy indicate that while the native enzyme binds SCN- with the Kd of 15 mM, the modified enzyme shows very weak binding with the Kd of 660 mM. From the pH dependent binding of SCN-, a plot of log Kd vs. pH shows a sigmoidal curve from which the involvement of an enzyme ionizable group of pKa 6.6 is ascertained and attributed to the histidine residue controlling SCN- binding. LGP has thus two distinctly different essential histidine residues - one regulates compound I formation while the other one controls SCN- binding.
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189
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Orellana MS, López V, Uribe E, Fuentes M, Salas M, Carvajal N. Insights into the interaction of human liver arginase with tightly and weakly bound manganese ions by chemical modification and site-directed mutagenesis studies. Arch Biochem Biophys 2002; 403:155-9. [PMID: 12139964 DOI: 10.1016/s0003-9861(02)00204-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Diethyl pyrocarbonate (DEPC) caused a loss in the ability of inactive subunits of wild-type and H141F mutant human liver arginase (EC 3.5.3.1) to be reactivated by Mn(2+). The effect was reversed by hydroxylamine and involved a residue with a pK(a) of 6.5+/-0.1. Half activation with Mn(2+) was sufficient for total resistance of H141F and full activation was not impeded by a previous incubation of the half-active species with DEPC. The H101N and H126N mutants expressed 60 and 82% of the wild-type activity, respectively, without changes in K(m) for arginine or K(i) for lysine inhibition. After dialysis against EDTA, H126N was inactive in the absence of added Mn(2+) and contained <0.1 Mn(2+)/subunit, whereas H101N was half active and contained 1.2+/-0.1 Mn(2+)/subunit. Results support the concept that a weakly bound metal ion is needed only for conversion of active species to a more active active state.
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190
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Ilangovan G, Li H, Zweier JL, Kuppusamy P. In vivo measurement of tumor redox environment using EPR spectroscopy. Mol Cell Biochem 2002; 234-235:393-8. [PMID: 12162459] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/26/2023]
Abstract
Solid tumors are characterized by a number of physiological properties such as occurrence of significant hypoxia, large amounts of cellular reducing equivalents, compromised blood-flow and low pH, all of which are distinctly different from normal tissues. Tumor therapeutic regimens such as radiation or chemotherapy attempt to exploit these physiological differences between normal and malignant tissue. Thus, methods that can detect these subtle differences would greatly aid in devising appropriate treatment strategies. Low-frequency in vivo electron paramagnetic resonance (EPR) spectroscopy is capable of providing non-invasive measurements of these parameters in tumors. This requires the use of appropriate exogenously injected free radical reporter molecules (probes), such as nitroxides. In the present study we performed measurements of nitroxide metabolism in RIF-1 murine tumors, in vivo, and demonstrated that the rate of nitroxide decay correlated with the tumor redox environment. The results showed the existence of significantly higher reducing environment in the tumor tissue compared to normal tissue. The dependence of the tumor redox status on the intracellular GSH levels and tissue oxygenation was investigated. The measurement of redox status and its manipulation may have important implications in the understanding of tumor growth and therapy.
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191
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Kowal AT. Anharmonic vibrational spectra of hydroxylamine and its 15N, 18O, and deuterium substituted analogs. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2002; 58:1055-1067. [PMID: 11942392 DOI: 10.1016/s1386-1425(01)00581-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Vibrational self-consistent field (VSCF) and correlation-corrected vibrational self-consistent field (CC-VSCF) methods were used to compute the anharmonic frequencies of fundamentals, overtones, and combination transitions of natural abundance hydroxylamine, 15NH2OH, NH2(18)OH, ND2OD, ND2OH, and NH2OD isotopomers at second order Møller-Plesset perturbation theory (MP2) in basis sets of triple-zeta quality. Frequencies of the fundamental transitions observed in the gas phase spectrum were reproduced by CC-VSCF treatment within 20 cm(-1) in TZV(d,p) and TZV(2d,2p) basis sets, and the change of basis set composition had only minor effect on the frequencies of the computed fundamentals. CC-VSCF computed wave numbers of overtone and combination transitions were typically within 1-40 cm(-1) of the gas phase band positions, except for those resulting from multiple excitations of v2, v3, and v7 fundamentals, because of a strong mutual coupling between these modes. Integral transition intensities calculated at MP2 level closely followed those of experimental spectrum, including intensity decrease in v1, 2v1, 3v1 progression, and 30-fold intensity increase of 2v8 in respect to that of v8 fundamental. The frequency of the OH torsional fundamental was found to be strongly dependent on the mode-mode interaction potential among v9 and v1, v7, v2, v4, v5 modes. Band shifts resulting from 15N, 18O and complete 2H substitutions were reproduced almost quantitatively by CC-VSCF computation in TZV(d,p) basis. Computed anharmonic isotope frequency shifts were different from those obtained in the harmonic approximation and no scaling procedure seemed capable of performing their interchange.
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192
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Laitonjam WS, Rajkumar TS, Chingakham BS. Synthesis of some A- and D-ring fused steroidal pyrazoles, isoxazoles and pyrimidines. Steroids 2002; 67:203-9. [PMID: 11856544 DOI: 10.1016/s0039-128x(01)00146-5] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The preparation of steroidal heterocycles containing pyrazole, isoxazole and pyrimidine rings fused to the 2,3- and 16,17-positions of the steroid nucleus is described. These were prepared by the reaction of hydrazine, hydroxylamine and guanidine, respectively, with 2-ethoxymethylene-3-oxo- or 16-ethoxymethylene-17-oxo- or 2-bis(methylthio)methylene-3-oxo- or 16-bis(methylthio)methylene-17-oxo-steroids.
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Abstract
Steroidal nucleoside analogs were synthesized starting from testosterone. By reduction of the oxime of 17 beta-hydroxy-androst-4-en-3-one (testosterone), a mixture of the two amino epimers of C-3 were obtained. The 3 alpha-amino-androst-4-en-17 beta-ol was crystallized in 73% yield and coupled with 5-amino-4,6-dichloropyrimidine to give 3 alpha-(5'-amino-4'-chloro-pyrimidin-6'-yl)amino-androst-4-en-17 beta-ol. This compound was treated with triethyl orthoformate in acid media to give the corresponding purinyl steroid adduct 3 alpha-(6'-chloro-purin-9'-yl)-androst-4-en-17 beta-ol in 98% yield. This substance, in turn, was converted with good yield into the 6'-thio, 6'-methylamino, and 6'-diethyl aminopurinyl derivatives through nucleophilic reactions at C-6 of the purine nucleus.
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Sudo Y, Iwamoto M, Shimono K, Kamo N. Association of pharaonis phoborhodopsin with its cognate transducer decreases the photo-dependent reactivity by water-soluble reagents of azide and hydroxylamine. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1558:63-9. [PMID: 11750265 DOI: 10.1016/s0005-2736(01)00423-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
pharaonis phoborhodopsin (ppR; also pharaonis sensory rhodopsin II, psRII) is a receptor of the negative phototaxis of Natronobacterium pharaonis. In halobacterial membrane, ppR forms a complex with its transducer pHtrII, and this complex transmits the light signal to the sensory system in the cytoplasm. In the present work, the truncated transducer, t-Htr, was used which interacts with ppR [Sudo et al. (2001) Photochem. Photobiol. 74, 489-494]. Two water-soluble reagents, hydroxylamine and azide, reacted both with the transducer-free ppR and with the complex ppR/t-Htr (the complex between ppR and its truncated transducer). In the dark, the bleaching rates caused by hydroxylamine were not significantly changed between transducer-free ppR and ppR/t-Htr, or that of the free ppR was a little slower. Illumination accelerated the bleach rates, which is consistent with our previous conclusion that the reaction occurs selectively at the M-intermediate, but the rate of the complex was about 7.4-fold slower than that of the transducer-free ppR. Azide accelerated the M-decay, and its reaction rate of ppR/t-Htr was about 4.6-fold slower than free ppR. These findings suggest that the transducer binding decreases the water accessibility around the chromophore at the M-intermediate. Its implication is discussed.
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195
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Nishiyama T, Tamekuni H, Tachibana T, Kitamura H, Saito S. Antioxidative activity of hydroxylamines. ESR spectra of radicals derived from hydroxylamines. Free Radic Res 2001; 35:895-905. [PMID: 11811540 DOI: 10.1080/10715760100301391] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The antioxidative activity of hydroxylamines was evaluated for the oxidation of tetralin at 61 degrees C and linoleic acid micelles in an aqueous dispersion at 37 degrees C, induced by an azo initiator. The antioxidative efficacy of the hydroxylamines for the oxidation of tetralin was smaller than that of alpha-tocopherol. However, the hydroxylamines showed more potent antioxidative activity than that of the alpha-tocopherol against the oxidation of linoleic acid micelles. On the basis of the results of an ESR study and the oxidation product obtained, it is suggested that active position in hydroxylamines depend not only on hydroxyl hydrogen-atom, but also on the allylic hydrogen atom.
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Perálvarez A, Barnadas R, Sabés M, Querol E, Padrós E. Thr90 is a key residue of the bacteriorhodopsin proton pumping mechanism. FEBS Lett 2001; 508:399-402. [PMID: 11728460 DOI: 10.1016/s0014-5793(01)03080-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mutation of Thr90 to Ala has a profound effect on bacteriorhodopsin properties. T90A shows about 20% of the proton pumping efficiency of wild type, once reconstituted into liposomes. Mutation of Thr90 influences greatly the Schiff base/Asp85 environment, as demonstrated by altered lambda(max) of 555 nm and pK(a) of Asp85 (about 1.3 pH units higher than wild type). Hydroxylamine accessibility is increased in both dark and light and differential scanning calorimetry and visible spectrophotometry show decreased thermal stability. These results suggest that Thr90 has an important structural role in both the unphotolysed bacteriorhodopsin and in the proton pumping mechanism.
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197
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Salmon L, Prost E, Merienne C, Hardré R, Morgant G. A convenient preparation of aldonohydroxamic acids in water and crystal structure of L-erythronohydroxamic acid. Carbohydr Res 2001; 335:195-204. [PMID: 11578635 DOI: 10.1016/s0008-6215(01)00210-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Hydroxamic acids derived from aldonic acids, namely aldonohydroxamic acids, have become an increasingly important class of inhibitors of enzymes involved in the metabolism of carbohydrates. We now report the straightforward preparation of various types of aldonohydroxamic acids by a new methodology involving the use of commercial 50% aqueous hydroxylamine as the source of the free base hydroxylamine that reacts directly with the corresponding aldonolactone dissolved in water. The reaction proceeds almost instantaneously in water at room temperature, yielding generally pure products in quantitative yield. To date, this methodology is probably the most facile and efficient way to synthesize aldonohydroxamic acids. We also determined by X-ray diffraction analysis the first crystal structure of a free aldonohydroxamic acid reported to date. Crystals of L-erythronohydroxamic acid belonged to the monoclinic system, space group P2(1), a=5.511(3), b=7.556(1), c=8.071(3) A, beta=109.10 degrees, and Z=2.
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198
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Iwamoto M, Sudo Y, Shimono K, Kamo N. Selective reaction of hydroxylamine with chromophore during the photocycle of pharaonis phoborhodopsin. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1514:152-8. [PMID: 11513812 DOI: 10.1016/s0005-2736(01)00380-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Phoborhodopsin (pR; also called sensory rhodopsin II, sRII) is a receptor of negative phototaxis of Halobacterium salinarum, and pharaonis phoborhodopsin (ppR; also pharaonis sensory rhodopsin II, psRII) is a corresponding protein of Natronobacterium pharaonis. These receptors contain retinal as a chromophore which binds to a lysine residue via Schiff base. This Schiff base can be cleaved with hydroxylamine to loose their color (bleaching). In dark, the bleaching rate of ppR was very slow whereas illumination accelerated considerably the bleaching rate. Addition of azide accelerated the decay of the M-intermediate while its formation (decay of the L-intermediate) is not affected. The bleaching rate of ppR under illumination was decreased by addition of azide. Essentially no reactivity with hydroxylamine under illumination was observed in the case of D75N mutant which lacks the M-intermediate in its photocycle. Moreover, we provided illumination by flashes to ppR in the presence of varying concentrations of azide to measure the bleaching rate per one flash. A good correlation was obtained between the rate and the mean residence time, MRT, which was calculated from flash photolysis data of the M-decay. These findings reveal that water-soluble hydroxylamine reacts selectively with the M-intermediate and its implication was discussed.
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199
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Wylie DC, Voloch M, Lee S, Liu YH, Cannon-Carlson S, Cutler C, Pramanik B. Carboxyalkylated histidine is a pH-dependent product of pegylation with SC-PEG. Pharm Res 2001; 18:1354-60. [PMID: 11683252 DOI: 10.1023/a:1013006515587] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
PURPOSE Pegylation of therapeutic protein usually results in a mixture of monopegylated proteins with differing sites of modification. With rh-interferon-alpha2A pegylation, we have found that this heterogeneity includes two classes of pegylation site chemistry, the relative proportions of which can be adjusted by reaction pH. METHODS The effect of pegylation reaction pH on the relative proportion of three peaks produced was investigated. Products were purified and characterized by peptide mapping, chemical stability to neutral hydroxylamine, and biologic activity. RESULTS Reactions at basic pH levels produced a mixture of products pegylated at lysine residues as has been observed elsewhere. However, the dominant product of reactions at mildly acidic levels of pH showed distinct chemistry and higher cytopathic effect activity. The primary site of modification at this pH was His34. We developed a quantitative assay using sensitivity to neutral hydroxylamine to measure the proportion of urethane bonds involving carboxyalkylated histidines. This assay showed that histidine was pegylated preferentially at low pH levels with another protein, rh-Interleukin-10. CONCLUSIONS Reaction pH can be used to select the preferred pegylation site chemistry.
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Ren J. Chemical mismatch cleavage analysis by capillary electrophoresis with laser-induced fluorescence detection. Methods Mol Biol 2001; 163:231-9. [PMID: 11242948 DOI: 10.1385/1-59259-116-7:231] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
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