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At least 793 records · Page 44Linked to original sources
PubMed1965

The chemical structure of pemptoporphyrin.

1. Pemptoporphyrin dimethyl ester was further purified on an alumina column and then crystallized from chloroform and methanol with melting point 215-218 degrees . The absorption spectra in the visible and ultraviolet with molar extinction coefficients are presented. 2. The nuclear-magnetic-resonance spectrum of pemptoporphyrin dimethyl ester in deuterochloroform solution is reported, together with those of several other porphyrins. 3. One vinyl and one hydryl group were found at positions 2 and 4 (or 4 and 2) in the molecule. The structure of pemptoporphyrin is 2(4)-hydryl-1,3,5,8-tetramethyl-4(2)-vinyldeuteroporphyrin IX. 4. Reduction of pemptoporphyrin dimethyl ester with resorcinol gave deuteroporphyrin IX dimethyl ester.

Journal Article↗
PubMed1967

Enzymic glucosylation of phenols.

1. A transglucosylase fraction has been obtained from the mycelium of Aspergillus niger. 2. The preparation will transfer alpha-d-glucopyranosyl residues from maltose and other alpha-d-glucopyranosides to phenolic and alcoholic hydroxyl groups and to carboxylic acid groups. 3. alpha-Isomaltosides and alpha-maltosides are formed when resorcinol and catechol are used as acceptors. 4. pH precipitation and DEAE-cellulose chromatography were used to resolve the activity into two fractions. The properties, in particular polyol inhibition, of one of these fractions have been examined in detail.

Alcohols↗
PubMed1980

Maleylacetate reductase from Trichosporon cutaneum.

The enzyme catalysing the reduction of maleylacetate to 3-oxoadipate was purified 150-fold from Trichosporon cutaneum, induced for aromatic metabolisms by growth with resorcinol as a major carbon source. The enzyme separated upon electrofocusing into three species with PI values 4.6, 5.1 and 5.6. They had similar catalytic properties and the same molecular weight.

Chemical Phenomena↗
PubMed2005

Flexibility in substrate recognition by thimet oligopeptidase as revealed by denaturation studies.

Thimet oligopeptidase (TOP) is a soluble metalloendopeptidase belonging to a family of enzymes including neurolysin and neprilysin that utilize the HEXXH metal-binding motif. TOP is widely distributed among cell types and is able to cleave a number of structurally unrelated peptides. A recent focus of interest has been on structure-function relationships in substrate selectivity by TOP. The enzyme's structural fold comprises two domains that are linked at the bottom of a deep substrate-binding cleft via several flexible loop structures. In the present study, fluorescence spectroscopy has been used to probe structural changes in TOP induced by the chemical denaturant urea. Fluorescence emission, anisotropy and collisional quenching data support a two-step unfolding process for the enzyme in which complete loss of the tertiary structure occurs in the second step. Complete loss of activity and loss of catalytic Zn(II) from the active site, monitored by absorption changes of the metal chelator 4-(2-pyridylazo)-resorcinol, are also connected with the second step. In contrast, the first unfolding event, which is linked to changes in the non-catalytic domain, leads to a sharp increase in kcat towards a 9-residue substrate and a sharp decrease in kcat for a 5-residue substrate. Thus a conformational change in TOP has been directly correlated with a change in substrate selectivity. These results provide insight into how the enzyme can process the range of structurally unrelated peptides necessary for its many physiological roles.

Enzyme Stability↗
PubMedDate not supplied

BioGlue: albumin/glutaraldehyde sealant in cardiac surgery.

BioGlue is a commercially available sealant manufactured by Cryolife (Atlanta, GA) as a hemostatic adjunct for cardiac and vascular surgery. This type of sealant has evolved conceptually from the gelatin resorcinol formalin glue (GRF or "French Glue") in the sense that it is devised not only to act a sealant but also as an agent to strengthen friable tissues, particularly in acute aortic dissection. In fact, the initial availability of BioGlue in the United States was under an FDA humanitarian device exemption for use in acute aortic dissection. This novel regulatory strategy expedited clinical use of BioGlue in acute aortic dissection and was permissible because of the small number of patients (less than 4000 per annum) in the potential treatment population. In this article, we will discuss the mechanism of action and composition of this agent, preclinical experience, the results of a prospective randomized trial as well as the results of our initial experience with BioGlue at MGH.

Animals↗
PubMed1996

Evidence for the existence of ganglioside molecules in the antigen of Entamoeba histolytica.

Gangliosides were found to be present in Entamoeba histolytica. They were extracted from lyophilized trophozoites of the pathogenic strain HM-1:IMSS and purified by high performance thin-layer chromatography. Two resorcinol-positive bands, comigrating with GM2 and GD1a were demonstrated, revealing the existence of ganglioside molecules in Entamoeba histolytica. The GM2 content, determined as lipid-bound sialic acid, was 1.5 micrograms/10(8) amoebae, the content of the GD1a comigrating band was 0.32 microgram/10(8) amoebae. The identity of the GM2 comigrating band was confirmed by TLC immunostaining, using the monoclonal anti-GM2 antibody GMB28. Furthermore, six out of ten anti-amoeba positive sera selectively reacted with the GM2 comigrating band, as revealed by immunostaining on TLC plates. Absorption tests revealed that preincubation of anti-amoeba positive sera with standard GM2 was followed by a significant decrease in the reaction with amoeba trophozoites by indirect immunofluorescence. These results demonstrate that a GM2 comigrating component of Entamoeba histolytica may be one of the antigens responsible for the appearance of circulating antibodies in patients with amoebiasis.

Absorption↗
PubMed1996

L-DOPA up-regulates glutathione and protects mesencephalic cultures against oxidative stress.

Incubation with L-DOPA induced a rise in GSH level in cultures of fetal rat mesencephalon, mouse neuroblastoma (Neuro-2A), human neuroblastoma (SK-N-MC), pig kidney epithelial cells (LLC-PK1), and glia from newborn rat brain, but not C6 glioma cells or neuronal cultures (no glia) from the mesencephalon. The pure neuronal cultures were destroyed by incubation with L-DOPA; added ascorbic acid or superoxide dismutase protected the cells. Washout of L-DOPA after 48 h amplified the rise in GSH content in mixed cultures (neurons plus glia). Examination of structure-activity relationships for elevating GSH levels in responsive cell types revealed that autooxidizable compounds (alpha-methyl-DOPA, dopamine, apomorphine, catechol, and hydroquinone) behaved similarly to L-DOPA, whereas structural analogues that cannot undergo autooxidation (3-O-methyl-DOPA, tyrosine, 2,4-dihydroxyphenylalanine, and resorcinol) failed to elevate GSH levels. Therefore, up-regulation of GSH appears to be a response to a mild oxidative stress. When mixed mesencephalic cultures were exposed to a strong oxidant stress by incubation with tert-butyl hydroperoxide, a loss in viability was seen. Cultures pretreated with L-DOPA or hydroquinone were protected from loss of viability. However, when cultures were pretreated with both L-DOPA and ascorbate, which prevents the rise in GSH level, protection was lost, in accord with the failure to up-regulate GSH. These results show that the up-regulation of cellular GSH evoked by autooxidizable agents is associated with significant protection of cells. Glia play an essential role in the response of mesencephalic cell cultures. An ability to up-regulate GSH may serve a protective role in vivo.

Animals↗
PubMed1998

In vitro studies of ferritin iron release and neurotoxicity.

The increase in brain iron associated with several neurodegenerative diseases may lead to an increased production of free radicals via the Fenton reaction. Intracellular iron is usually tightly regulated, being bound by ferritin in an insoluble ferrihydrite core. The neurotoxin 6-hydroxydopamine (6-OHDA) releases iron from the ferritin core by reducing it to the ferrous form. Iron release induced by 6-OHDA and structurally related compounds and two other dopaminergic neurotoxins, 1-methyl-4-phenylpyridinium iodide (MPP+) and 1-trichloromethyl-1,2,3,4-tetrahydro-beta-carboline (TaClo), were compared, to identify the structural characteristics important for such release. 1,2,4-Trihydroxybenzene (THB) was most effective in releasing ferritin-bound iron, followed by 6-OHDA, dopamine, catechol, and hydroquinone. Resorcinol, MPP , and TaClo were ineffective. The ability to release iron was associated with a low oxidation potential. It is proposed that a low oxidation potential and an ortho-dihydroxyphenyl structure are important in the mechanism by which ferritin iron is mobilized. In the presence of ferritin, both 6-OHDA and THB strongly stimulated lipid peroxidation, an effect abolished by the addition of the iron chelator deferoxamine. These results suggest that ferritin iron release contributes to free radical-induced cell damage in vivo.

1-Methyl-4-phenylpyridinium↗
PubMedDate not supplied

The effect of storage on the ganglioside content of human platelets.

Gangliosides are glycolipids which contain sialic acid and are found in the membranes of mammalian cells. By analogy with recent studies of other cells, it is possible that gangliosides play a role in the membrane functions and in vivo survival of platelets. In order to determine if ganglioside destruction plays a role in the storage-induced loss of platelet viability and function (storage lesion), the ganglioside content of platelets was measured after 24 and 96 hours of storage. Samples were taken from platelet concentrates that were stored either on a flat-bed shaker (n = 6) or on a circular rotator (n = 6). Total ganglioside content was determined colorimetrically from the total lipid extracts of purified platelet pellets using the Svennerholm resorcinol method. Ganglioside GM3 content was determined by Folch partitioning, high performance thin-layer chromatography, and densitometric scanning. Ganglioside content, measured as microgram of lipid-bound sialic acid per 10(10) platelets, was significantly decreased (p less than 0.005) between 24 and 96 hours of storage, whether measured as total or GM3 ganglioside. The mean values +/- SEM at 24 and 96 hours of storage were 9.4 +/- 0.6 and 6.7 +/- 0.6, respectively (n = 12 for each). These data indicate that storage causes irreversible loss of membrane ganglioside, which may be detrimental to the function and in vivo survival of platelets.

Blood Platelets↗
PubMed2003

Prenylated flavonoids from the roots of Sophora flavescens with tyrosinase inhibitory activity.

Prenylated flavonoids containing the resorcinol moiety were isolated as tyrosinase inhibitors from the roots of Sophora flavescens by activity-guided fractionation. Among the 12 compounds isolated, kuraridin, kurarinone and norkurarinol showed stronger inhibitory potencies (IC 50 = 1.1, 1.3 and 2.1 microM, respectively) than that of kojic acid (IC 50 = 11.3 microM), a well known tyrosinase inhibitor. Substitution of a lavandulyl or hydroxylavandulyl group at the C-8 position and a methoxy or hydroxy group at the C-5 position are essential for the inhibitory effect.

Flavonoids↗
PubMed1984

Tunicamycin blocks neuritogenesis and glucosamine labeling of gangliosides in developing cerebral neuron cultures.

Fetal cerebral neurons at the initiation of active neurite outgrowth in culture incorporate 4-fold more [3H]glucosamine into glycoproteins than into the cellular lipid fraction. After 8 days or longer, when a well-developed fiber network is apparent, lipids are labeled more extensively than the glycoproteins. Labeling of the latter is inhibited 95% and 89% by 0.5 microgram of tunicamycin per ml added to 1-day-old and 8-day-old cultures, respectively. Labeling of glycolipids is inhibited 30% in 1-day-old and 86% in 8-day-old cultures. Tunicamycin blocks incorporation of glucosamine label into practically all ganglioside species except for a resorcinol-positive, sialidase-sensitive band tentatively identified as GQ1b tetrasialoganglioside (Svennerholm ganglioside nomenclature). It also substantially reduces binding of 125I-labeled tetanus toxin to intact cells. There is 14% and 27% reduction in the total ganglioside sialic acid content in 1-day-old and 8-day-old cells treated for 24 hr with 0.5 microgram of tunicamycin per ml, but no substantial compositional changes are encountered. Tunicamycin blocks neurite outgrowth when added to cells soon after plating but causes no retraction or losses of fibers once the fiber network is established. Therefore, inhibition of neurite outgrowth by tunicamycin is not due to an effect on cellular gangliosides but can be correlated to an inhibition of protein glycosylation.

Animals↗
PubMed1985

On the mechanisms of induction of cancer-protective enzymes: a unifying proposal.

Induction of detoxification enzymes is a major mechanism whereby a wide variety of chemical agents protect rodents against neoplastic, mutagenic, and other toxicities of carcinogens. The enzyme NAD(P)H:(quinone acceptor) oxidoreductase (EC 1.6.99.2) can protect against the toxicities of quinones and is a useful marker for protective enzyme induction. Quinone reductase can be induced in murine Hepa 1c1c7 hepatoma cells and 3T3 embryo fibroblasts by compounds that are chemoprotectors in vivo, including some phenolic antioxidants, azo dyes, aromatic diamines, and aminophenols. Structurally dissimilar catechols (1,2-diphenols) and hydroquinones (1,4-diphenols) induce quinone reductase in these systems, but resorcinol (1,3-diphenol) and its substituted analogues are inactive. Furthermore, only aromatic 1,2- and 1,4-diamines and aminophenols are inducers, whereas the 1,3-diamines are completely inactive. These findings suggest that the functional capacity to form quinones or quinone-diimines, rather than the precise structure, is essential for inductive activity and that the generation of the signal for enzyme induction depends upon oxidation-reduction lability. The observations that some chemoprotective compounds (e.g., azo dyes, beta-naphthoflavone) induce both cytochromes P-450 and quinone reductase, whereas others (e.g., tert-butylhydroquinone) induce only quinone reductase, can be reconciled by the fact that inducers of the first type are metabolized by P-450 enzymes to form products that are functionally similar to compounds of the second type.

Animals↗
PubMed1998

A carboxyl-terminal Cys2/His2-type zinc-finger motif in DNA primase influences DNA content in Synechococcus PCC 7942.

The DNA primase gene, dnaG, has been isolated from the cyanobacterium Synechococcus PCC 7942. It is not part of a macromolecular synthesis operon but is co-transcribed with pheT and located adjacent to the metallothionein divergon, smt. At the carboxyl terminus of this DnaG is a Cys2/His2 zinc-finger motif. The carboxyl-terminal 91 residues bound 65Zn and 0.95 g atom of Zn2+ mol-1 were detected with 4-(2-pyridylazo)resorcinol. Following exposure to Cd2+, 0.95 g atom of Cd2+ was displaced by 2 equivalents of p-(hydroxymercuri) phenylsulfonate mol-1, while only 0.03 g atom of Cd2+ was displaced mol-1 polypeptide missing the carboxyl-terminal (residue 592 onward) zinc-finger motif. Zn2+ caused an increase in intensity, and a reduction in wavelength, of Trp fluorescence at the tip of the predicted zinc-finger, while EDTA caused the converse. Cells containing a single chromosomal codon substitution (C597S), altering the zinc-finger, were generated by exploiting Zn2+-sensitive smt mutants and the proximity of dnaG to smt. Cells in which smt and dnaG(C597S) had integrated into the chromosome were selected via restored Zn2+ tolerance. Synechococcus PCC 7942 and its dnaG(C597S) mutant grew at equivalent rates, but the latter had a reduced number of chromosomes.

Base Sequence↗
PubMed2000

Flavonoid 6-hydroxylase from soybean (Glycine max L.), a novel plant P-450 monooxygenase.

Cytochrome P-450-dependent hydroxylases are typical enzymes for the modification of basic flavonoid skeletons. We show in this study that CYP71D9 cDNA, previously isolated from elicitor-induced soybean (Glycine max L.) cells, codes for a protein with a novel hydroxylase activity. When heterologously expressed in yeast, this protein bound various flavonoids with high affinity (1.6 to 52 microm) and showed typical type I absorption spectra. These flavonoids were hydroxylated at position 6 of both resorcinol- and phloroglucinol-based A-rings. Flavonoid 6-hydroxylase (CYP71D9) catalyzed the conversion of flavanones more efficiently than flavones. Isoflavones were hardly hydroxylated. As soybean produces isoflavonoid constituents possessing 6,7-dihydroxy substitution patterns on ring A, the biosynthetic relationship of flavonoid 6-hydroxylase to isoflavonoid biosynthesis was investigated. Recombinant 2-hydroxyisoflavanone synthase (CYP93C1v2) efficiently used 6,7,4'-trihydroxyflavanone as substrate. For its structural identification, the chemically labile reaction product was converted to 6,7,4'-trihydroxyisoflavone by acid treatment. The structures of the final reaction products for both enzymes were confirmed by NMR and mass spectrometry. Our results strongly support the conclusion that, in soybean, the 6-hydroxylation of the A-ring occurs before the 1,2-aryl migration of the flavonoid B-ring during isoflavanone formation. This is the first identification of a flavonoid 6-hydroxylase cDNA from any plant species.

Base Sequence↗
PubMed1983

A sensitive method for simultaneous determination of airborne organolead compounds. Part I: Chromatographic separation and chemical reaction detection.

Reversed phase high performance liquid chromatography coupled to a sensitive chemical reaction detector has been developed for the separation and detection of inorganic lead and organolead compounds. The separation of Pb2+, Me3Pb+, Et3Pb+, Me4Pb, and Et4Pb can be achieved within 50 minutes. The eluate from the column flows continuously through a system of mixing coils where the lead species are transformed into compounds which undergo complexation with 4-(2-pyridylazo)resorcinol. The red-coloured complex is detected spectrophotometrically at 546 nm. In the lower measuring range of 0.3 to 1.5 nmol (abs.) for the five compounds linear calibration curves are obtained. The requirements and characteristics of the separation and post-column reactions are illustrated and the linearity, reproducibility, and sensitivity of the system area discussed.

Air↗
PubMed2003

Substituent effects in the BF3-mediated acylation of phenols with cinnamic acids.

2',4'-Dihydroxy-4-nitrochalcone was obtained by BF3 etherate acylation of resorcinol with 4-nitrocinnamic acid. Instead, when p-methoxycinnamic or p-coumaric acids were used, the main product of the reaction was the coumarin umbelliferone, while no chalcone was present. These effects are commented in relation to the nature of the substituent present on the cinnamic acid moiety.

Acylation↗
PubMed2004

Toxicity of some phenolic derivatives--in vitro studies.

Cytotoxicity of 5 phenol derivatives (phenol, catechol, resorcinol, hydroquinone and phloroglucinol) was tested using a mouse 3T3 fibroblast cell line. Its relationships with structural and physicochemical properties were investigated. Linear regression analysis and Pearson's correlation coefficient were used to characterise the relationship between cytotoxicity (expressed by IC(50) values) and physicochemical parameters of compounds or their toxicity in vivo expressed by LD(50) values. The studies showed that physicochemical properties of compounds seemed to have less influence on their cytotoxic potency than structural properties. Cytotoxicity of the compounds probably depends on the number of -OH groups and their location in the aromatic ring more than on physicochemical properties of compounds. The best correlation was obtained for IC(50) values and LD(50) values determined following rabbit skin administration and experimental skin irritation score.

3T3 Cells↗
PubMed1976

Dermal carcinogenicity study by mouse-skin painting with 2,4-toluendediamine alone or in representative hair dye formulations.

The chronic toxicity of 2,4-toluenediamine (2,4-TDA) alone or in conbination with a hair dye complex (2,5-toluenediamine, p-phenylenediamine, and resorcinol) was studied in Swiss-Webster mice of both sexes by a skin-painting technique. The predominant neoplasms seen in these mice were primary pulmonary adenomas and adenocarcinomas. Skin neoplasms were seen in most groups of mice, including untreated control mice. Statistical analysis of the incidences of skin neoplasms among the various groups of mice did not show any significant differences. The 2,4-TDA alone or mixed with the hair dye complex did not produce any abnormal proliferation and maturation of the squamous epithelium of the skin. The 2,4-TDA under our experimental conditions was found to be nontoxic and noncarcinogenic to the skin of mice.

9,10-Dimethyl-1,2-benzanthracene↗