UMLS:C0027960 - FACTA Search

Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Target Concepts:

Query: UMLS:C0027960 (mole)
21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The one-electron oxidation of a reduced nitroxide (2,2,6,6-tetramethyl-1,4-dihydroxypiperidine, TOLH), detected by ESR, was used to resolve and quantify oxidants arising from the reaction of heme proteins with hydroperoxides, including chelatable iron released subsequent to oxidative cleavage of the porphyrin ring. Released iron was distinguished from protein radicals and ferryl heme by analyzing TOLH oxidation in the presence of different chelating agents. Metmyoglobin (metMb) treatment with one mole of H2O2 per mole of heme produced protein-bound oxidants that oxidized about two molecules of TOLH per heme. Some of the oxidizing species responsible for TOLH oxidation were highly persistent (t1/2 for the decay was 3 hrs at 25 degrees C). Iron release, metMb bleaching and the catalysis of Fenton-type chemistry were compared in metMb solutions treated with tert-butyl hydroperoxide (tBH). Iron release required about five-fold higher hydroperoxide concentrations than did metMb bleaching. Alkoxyl and methyl radical production was catalyzed by iron released from metMb but not by protein-bound iron in oxidized metMb solutions treated with tBH and ascorbic acid. The results suggest that ascorbate-mediated hydroxyl and alkoxyl radical production by hydroperoxide-treated metMb is due to released iron and that the protein-bound non-heme iron that arises during bleaching is at most a weak Fenton reagent.
...
PMID:Hydroxyl and alkoxyl radical production by oxidation products of metmyoglobin. 839 72

The Cd2+ binding to human erythrocyte spectrin tetramer (SPT) was studied by the ultrafiltration method. The results indicate that the Cd2+ binding depends on Cd2+ concentration in a biphasic feature. Thus, it is different from the Tb(3+)-SPT reaction. The biphasic feature is in accordance with the results of fluorescence and circular dichroism (CD) studies on Cd(2+)-SPT complex. The data were analyzed by the Scatchard method. At the first stage (the mole ratio of Cd2+/SPD < 45), there are two types of Cd2+ binding sites, with the binding sites and corresponding binding constants determined as: n1 = 6, K1 = 3.3 x 10(5) M-1; n2 = 8, K2 = 9.1 x 10(4) M-1. At the second state (Cd2+/SPD > 45), the Cd2+ binding manifests a positive cooperative effect. The interaction between Cd2+ and maleimide spin labeled (MSL) SPT was studied by the ESR method. The results were fitted with the multiple equilibrium model, and one Cd2+ high-affinitive binding site with association constant 9.61(7) x 10(5) M-1 was obtained. The conjugation of maleimide with thiol group results in the decrease of Cd2+ high-affinitive binding sites from 6 to 1. This demonstrated that the thiol groups of SPT were involved in the high binding sites. The increase of mobile fraction of MSL in low Cd2+ concentration revealed that Cd2+ binding to SPT induces a significant conformation change of MSL-SPT. The rotation correlation time of MSL attached to SPT varied from 4.4 x 10(-9) to 6.5 x 10(-9) sec.
...
PMID:The ultrafiltration and ESR study of Cd2+ binding to human erythrocyte spectrin. 853 Sep 19

The induction of base damage products in gamma-irradiated DNA, hydrated between 2.5 and 32.8 moles of water per mole of nucleotide (tau), was investigated using the gas chromatography/mass spectrometry-selected ion monitoring technique. In general, the yields of the measured base damage products were found to be dependent on the extent of the hydration when the DNA was irradiated under nitrogen. At low hydrations (tau < or = 13), the highest yields of the measured products were found for 7,8-dihydro-8-oxo-guanine, 5,6-dihydrothymine and, to a lesser extent, 2,6-diamino-4-oxo-5-formamidopyrimidine, products which are consistent with the base radicals found in low-temperature ESR studies. At higher hydrations (tau < or = 13), changes in DNA conformation and an increase in the attack of bulk water radicals on DNA play a significant role in the formation of radiation-induced DNA base damage products. Additional findings in our study include: (1) the sum of the yields of the products formed from electron-loss centers is greater than the sum of the yields of the products formed from electron-gain centers, indicating that there might be other electron-gain products which have not been identified; (2) the combined yield for the base damage products and the release of unaltered bases at tau < or = 13 is constant, implying that radiation damage in the tightly bound water molecules of the primary hydration layer causes DNA damage (quasi-direct effect) that is similar to the damage caused by direct ionization of the DNA (direct effect); and (3) the yields of the individual base damage products that were formed from electron-loss centers can be modeled on the basis of both the known reactions that lead to the formation of the initial charged base radicals in irradiated DNA, and the known reactions that involve the conversion of these initial DNA radicals into their respective nonradical end products.
...
PMID:Radiation-induced DNA damage as a function of hydration. II. Base damage from electron-loss centers. 892 98

Reactions of LEC (Long-Evans rats with a cinnamonlike coat color) rat liver Cu(I)-metallothioneins (MTs) with HgCl2 or K3Fe(CN)6 were investigated by ESR spectroscopy and generation of hydroxyl radicals was demonstrated using the ESR spin trap, 5,5-dimethyl-1-pyrroline N-oxide (DMPO). When Cu(I)-MTs were incubated with more than one equivalent mole HgCl2 or K3Fe(CN)6 to Cu+ bound to MTs, strong signals due to Cu2+ appeared. ESR spectra, which were a combination of the DMPO-OH adduct signal and a six-line signal, were observed in the reaction of Cu(I)-MTs with HgCl2, whereas no oxygen radical signal was seen with K3Fe(CN)6. The DMPO-OH signal intensity was greater in the presence of SOD while the signal disappeared in the presence of catalase. The results suggest that addition of HgCl2 causes the liberation of cuprous ions from MTs followed by a reaction with oxygen, leading to hydroxyl radical formation through a Fenton-type Haber-Weiss reaction.
...
PMID:Metal-induced hydroxyl radical generation by Cu(+)-metallothioneins from LEC rat liver. 907 Aug 42

Native beta-lactoglobulin (Blg) binds 1 mole of palmitic acid per mole of protein with a dissociation constant of 0.6 microM for the primary fatty acid binding site. Chemical modification of Cys 121, which lies at the external putative hydrophobic binding site of Blg, does not affect retinol or 4,4'-bis 1-(phenylamino)-8-naphthalenesulfonate (bis-ANS) binding to the protein, indicating that the incorporated appendages do not perturb the internal hydrophobic site within the beta-barrel of Blg (i.e., the retinoid site is unaffected). On the other hand, methylation of Cys 121, reduces the affinity of Blg for palmitic acid by 10-fold as monitored by intrinsic fluorescence. Modification of the Cys 121 with methylmethanethiosulfonate or a thiol-specific spin label appears to either further weaken or totally eliminate fatty acid binding, respectively, due to steric hindrance. Furthermore, this binding pattern has been independently verified using a spin labeled fatty acid analog and monitoring ESR as well as by bis-ANS fluorescence when bound to the protein. These results suggest that fatty acids bind at the "external site" of beta-lactoglobulin, between the sole alpha-helix and the beta-barrel. In addition, structural stability studies of native and chemically modified Blg appear to confirm this observation as well.
...
PMID:Mapping fatty acid binding to beta-lactoglobulin: Ligand binding is restricted by modification of Cys 121. 951 70

We previously suggested that hydroxyl free radical (-OH) production may play a role in carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). MNNG-induced gastric cancer in rats and human gastric carcinoma occur most often in the antral mucosa and rarely in the normal fundic mucosa. We hypothesized that regional differences in anti-oxidant activity may be responsible. In the present study, we examined anti-oxidant activity by comparing the relative rates of reduction of a nitroxide free radical, 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy (Tempol), in the antral and fundic mucosa of male Wistar rats using ESR. The relative rate of Tempol reduction was significantly slower in the antral portion of the wall than in the fundic portion when Tempol [4 x 10(-6) mole/mg wet weight of gastric wall] in HEPES buffer (pH 7.4) was spread over the mucosal surface of a section of the gastric wall. Addition of a sulfhydryl group modulator, N-ethylmaleimide, to the mucosal surface before treatment with Tempol removed the significant difference observed in the rates of reduction in the antral and fundic portions of the gastric wall. No signals were detected in the muscle layer. Our results indicate that the relative rate of free radical reduction by sulfhydryl groups was significantly slower in the antral mucosa than in the fundic mucosa. We therefore conclude that a regional difference in the rates of reduction of free radicals by sulfhydryl groups may result in the site susceptible to development of MNNG-induced gastric cancer.
...
PMID:Slow rate of free radical scavenging in the gastric antral mucosa of male Wistar rats: a possible mechanism of gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine. 953 85

Redox reactions were carried out in aerobiosis and anaerobiosis between NAD(P) dimers or NAD(P)H and pyrroloquinoline quinone (PQQ) in different buffers. The buffer system and pH significantly affected the oxidation rates of nucleotides and the ESR signal intensity of the PQQ(*) radical formed in anaerobiosis by comproportion between the quinone and quinol forms. The relative reactivity of the four nucleotides toward PQQ was affected by pH and buffer nature. PQQ, which behaves as an electron shuttle from nucleotides to oxygen, was first converted to PQQH(2) and then rapidly reoxidized by oxygen, with formation of hydrogen peroxide. Both NAD(P) dimers and NAD(P)H consumed 1 mol of oxygen per mole of reacted molecule of pyridine nucleotide, yielding 1 or 2 mol of NAD(P)(+) from NAD(P)H or from NAD(P) dimers, respectively. Chelating agents such as EDTA and phytate strongly decreased the reaction rate and the PQQ(*) radical signal intensity. Kinetics carried out in the presence of metal ions showed instead an increased reaction rate in the order Ca(2+) >> Mg(2+) > Na(+) >> K(+). Spectrofluorimetric measurements of PQQ with increasing concentrations of Ca(2+) showed a fluorescence quenching and shift of the maximum emission toward lower wavelengths, while other metal ions showed minor effects, if any. Therefore, it is demonstrated that Ca(2+) binds to PQQ, probably forming a complex which is more reactive with both one-electron (NAD(P) dimers) or two-electron donors (NAD(P)H) in nonenzymic reactions. It is important to recall that Ca(2+) was already found to play active role in PQQ-containing enzymes.
...
PMID:Role of calcium in the reaction between pyrroloquinoline quinone and pyridine nucleotides monomers and dimers. 1044 92

Die Kelders Cave 1, South Africa, has provided more than 150,000 taxonomically identifiable mammal and tortoise bones from Middle Stone Age (MSA) and Later Stone Age (LSA) deposits. Cape dune mole-rats dominate the mammal sample, and they appear to have been accumulated mainly by people during the LSA occupation and mainly by eagle owls in the MSA. In sharp contrast to the LSA fauna, the MSA sample contains extralimital ungulates that imply relatively moist, grassy conditions. The large mean size of the MSA mole-rats also points to greater humidity, while the large size of the gray mongooses implies cooler temperatures. The sum supports luminescence and ESR dates that place the MSA occupation within the early part of the Last Glaciation (global isotope stage 4). The Die Kelders ungulate bones support those from Klasies River Mouth in suggesting that MSA people obtained dangerous terrestrial prey much less frequently than their LSA successors, probably because MSA people lacked the bow and arrow and other projectile weapons. The Die Kelders tortoise bones constrain the extent of climatic change, since their abundance indicates that warm, dry days remained common, at least seasonally. The tortoises tend to be much larger in the MSA layers than in the LSA ones, suggesting that MSA people collected tortoises less intensively, probably because MSA populations were relatively sparse.
...
PMID:Middle and Later Stone Age large mammal and tortoise remains from Die Kelders Cave 1, Western Cape Province, South Africa. 1062 2

The phase behavior of mixed lipid dispersions representing the inner leaflet of the cell membrane has been characterized by X-ray diffraction. Aqueous dispersions of phosphatidylethanolamine:phosphatidylserine (4:1 mole/mole) have a heterogeneous structure comprising an inverted hexagonal phase H(II) and a lamellar phase. Both phases coexist in the temperature range 20-45 degrees C. The fluid-to-gel mid-transition temperature of the lamellar phase assigned to phosphatidylserine is decreased from 27 to 24 degrees C in the presence of calcium. Addition of sphingomyelin to phosphatidylethanolamine/phosphatidylserine prevents phase separation of the hexagonal H(II) phase of phosphatidylethanolamine but the ternary mixture phase separates into two lamellar phases of periodcity 6.2 and 5.6 nm, respectively. The 6.2-nm periodicity is assigned to the gel phase enriched in sphingomyelin of molecular species comprising predominantly long saturated hydrocarbon chains because it undergoes a gel-to-fluid phase transition above 40 degrees C. The coexisting fluid phase we assign to phosphatidylethanolamine and phosphatidylserine and low melting point molecular species of sphingomyelin which suppresses the tendency of phosphatidylethanolamine to phase-separate into hexagonal H(II) structure. There is evidence for considerable hysteresis in the separation of lamellar fluid and gel phases during cooling. The addition of cholesterol prevents phase separation of the gel phase of high melting point sphingomyelin in mixtures with phosphatidylserine and phosphatidylethanolamine. In the quaternary mixture the lamellar fluid phase, however, is phase separated into two lamellar phases of periodicities of 6.3 and 5.6 nm (20 degrees C), respectively. The lamellar phase of periodicity 5.6 nm is assigned to a phase enriched in aminoglycerophospholipids and the periodicity 6.3 nm to a liquid-ordered phase formed from cholesterol and high melting point molecular species of sphingomyelin characterized previously by ESR. Substituting 7-dehydrocholesterol for cholesterol did not result in evidence for lamellar phase separation in the mixture within the temperature range 20-40 degrees C. The specificity of cholesterol in creation of liquid-ordered lamellar phase is inferred.
...
PMID:Cholesterol favors phase separation of sphingomyelin. 1125 9

Redox properties of metallothioneins (MTs) and Cu in the cytosol from Long-Evans Cinnamon (LEC) rat livers 13 weeks after birth were investigated. MTs from LEC rat livers contain 8 g atoms of Cu and 1 g atom of Zn per mole of protein (Cu(I)8-MTs). Titration of Cu(I)8-MTs with CuCl2 indicates that Cu(I)8-MTs were able to reduce further 2-g atoms of cupric ions per mole MTs as bound form. Hg2+-induced hydroxyl radical generation from Cu(I)8-MTs was demonstrated by ESR using the spin trap, 5,5-dimethyl-1-pyrroline N-oxide (DMPO). The intensity of DMPO-OH signal from Cu-loaded MTs was increased with the increasing number of Cu in MTs. The used cytosol fraction contained 1.37 mM total Cu and 5 mM DTNB titrable-SH groups has a potential to reduce 2 mM CuCl2. No ESR signal due to Cu2+ was also detected with LEC rat liver cytosol, whereas strong Cu2+ signal appeared by the addition of HgCl2. The rate constants for the reaction of Cu(I)8-MTs with superoxide and hydroxyl radicals were estimated to be 2 x 10(6) and > or = 10(12) M(-1)s(-1), respectively, from competition kinetics. Cu2+-catalyzed oxidation of DNA was strongly inhibited both in the presence of Cu-unsaturated MTs and GSH. The results suggest that Cu(I)8-MTs from LEC rat livers just before hepatitis still act as antioxidants.
...
PMID:Cu-metallothioneins (Cu(I)8-MTs) in LEC rat livers 13 weeks after birth still act as antioxidants. 1137 Aug 44

<< Previous 1 2 3 4 5 Next >>