scholarly journals The enzymic degradation of l-serine O-sulphate. Mechanism of the reaction

1972 ◽  
Vol 128 (1) ◽  
pp. 41-46 ◽  
Author(s):  
N. Tudball ◽  
P. Thomas
Keyword(s):  
Hydrogen Atom ◽  
Carbon Atom ◽  
Rose Bengal ◽  
Incubation Medium ◽  
Tritiated Water ◽  
Competitive Inhibitor ◽  
Histidine Residues ◽  
Photo Oxidation ◽  
Rapid Inactivation ◽  
Mechanism Of The Reaction

1. During the enzyme-catalysed degradation of l-serine O-sulphate no exchange occurs between the hydrogen atom attached to the α-carbon atom of the substrate and the tritiated water of the incubation medium. 2. The participation of an intermediate carbanion has been demonstrated in the degradation by performing the reaction in the presence of tetranitromethane. 3. Photo-oxidation of the enzyme in the presence of Rose Bengal led to a rapid inactivation of enzyme with the concomitant loss of four histidine residues/molecule. 4. Rose Bengal was also a non-competitive inhibitor of the enzyme.

scholarly journals The inhibition of glutamate dehydrogenase by l-serine O-sulphate and related compounds and by photo-oxidation in the presence of Rose Bengal

1971 ◽  
Vol 123 (3) ◽  
pp. 421-426 ◽  
Author(s):  
N. Tudball ◽  
P. Thomas
Keyword(s):  
Amino Acid ◽  
Methyl Ester ◽  
Glutamate Dehydrogenase ◽  
Rose Bengal ◽  
Amino Acid Analysis ◽  
Inhibitory Effects ◽  
Irreversible Inhibitor ◽  
Photo Oxidation ◽  
Rapid Inactivation ◽  
Related Compounds

1. Glutamate dehydrogenase was inhibited by l-serine O-sulphate, β-chloro-l-alanine, O-phospho-l-serine and β-chloro-l-alanine methyl ester. With the exception of β-chloro-l-alanine methyl ester which was an irreversible inhibitor, it was possible to reverse the inhibitory effects by dialysis. 2. Both NAD+ and glutamate afford some protection against the inhibition due to the methyl ester. No change in the normal stimulatory effect exhibited by ADP was observed in the presence of β-chloro-l-alanine methyl ester but the effect due to GTP was modified. 3. Irradiation of glutamate dehydrogenase in the presence of Rose Bengal produced rapid inactivation. Amino acid analysis of the inactivated enzyme showed that eight histidine residues had been destroyed in the process.

A Raman Spectroscopy Study of the Chloromethyl Group Attached to an Aliphatic Hydrocarbon Chain

1973 ◽  
Vol 27 (1) ◽  
pp. 27-30 ◽  
Author(s):  
T. S. Wang ◽  
J. J. Mannion
Keyword(s):  
Raman Spectroscopy ◽  
Hydrogen Atom ◽  
Carbon Atom ◽  
Chlorine Atom ◽  
Hydrocarbon Chain ◽  
Aliphatic Hydrocarbon ◽  
Rotational Isomer ◽  
Spectroscopy Study ◽  
Chloromethyl Group ◽  
Infrared Studies

The chloromethyl group (—CH2Cl) attached to a normal hydrocarbon chain gives rise to two characteristic Raman bands near 660 and 730 cm−1. The band at 660 cm−1, which is very intense, is assigned to a stretching mode of the C-Cl linkage when the chlorine atom is trans to a hydrogen atom. The less intense peak at 730 cm−1 is assigned to the same mode of the rotational isomer with the chlorine atom trans to a carbon atom. These assignments are consistent with those reported in infrared studies. In contrast to almost equal intensities for both bands in the infrared, the band at 660 cm−1 proved to be the strongest by far in Raman spectra.

Mechanism and stereochemistry of enzymic reactions involved in porphyrin biosynthesis

1976 ◽  
Vol 273 (924) ◽  
pp. 117-136 ◽  
Keyword(s):  
Schiff Base ◽  
Hydrogen Atom ◽  
Carbon Atom ◽  
Pyridoxal Phosphate ◽  
Hydrogen Atoms ◽  
Bond Forming ◽  
Aminolaevulinic Acid

5-Aminolaevulinate synthetase catalyses the condensation of glycine and succinyl-CoA to give 5-aminolaevulinic acid. At least two broad pathways may be considered for the initial C—C bond forming step in the reaction. In pathway A the Schiff base of glycine and enzyme bound pyridoxal phosphate ( a ) undergoes decarboxylation to give the carbanion ( b ) which then condenses with succinyl-CoA with the retention of both the original C2 hydrogen atoms of glycine. In pathway B, loss of a C2 hydrogen atom gives another type of carbanion ( c ) that reacts with succinyl-CoA. Evidence has been presented to show that the initial C—C bond forming event occurs via pathway B which involves the removal of the pro R hydrogen atom of glycine. Subsequent mechanistic and stereochemical events occurring at the carbon atom destined to become C5 of 5-aminolaevulinate have also been delineated.

scholarly journals Effect of reverse micelles on the Rose Bengal-sensitized photo-oxidation of 1- and 2-hydroxynaphthalenes

Redox Report ◽  
2004 ◽  
Vol 9 (4) ◽  
pp. 199-205 ◽  
Author(s):  
Marta Luiz ◽  
M. Alicia Biasutti ◽  
Norman A. García
Keyword(s):  
Rose Bengal ◽  
Reverse Micelles ◽  
Photo Oxidation ◽  
The Rose

Aril Azines. II. Hydrogenation of p-Tolil Monoazine

1975 ◽  
Vol 53 (5) ◽  
pp. 748-752 ◽  
Author(s):  
Peter Yates ◽  
E. M. Levi
Keyword(s):  
Hydrogen Atom ◽  
Carbon Atom ◽  
Sodium Borohydride ◽  
Sodium Methoxide ◽  
Major Product ◽  
Lead Tetraacetate ◽  
Ring Closure ◽  
Carbonyl Carbon Atom ◽  
Carbonyl Carbon ◽  
Independent Synthesis

Hydrogenation of p-tolil monoazine (1b) over palladium-on-charcoal gives as the major product 4,5-dihydro-5-(p-toluyl)-3,4,5-tri-(p-tolyl)-1H-pyrazol-4-ol (2b), which has previously been obtained by treatment of 1b with sodium methoxide. Several minor products are formed, which include p-tolualdehyde, p-toluic acid, and p-toluamide, p-tolunitrile, p-tolualazine, and 3,4,5-tri-(p-tolyl)-4H-pyrazo-4-ol (9). The structure of the last compound, which is also formed on reduction of 1b with sodium borohydride, was established by its independent synthesis from 1,2,3-tri-(p-tolyl)-1,3-propanedione by oxidation with lead tetraacetate followed by treatment with hydrazine. It is suggested that 2b arises via reduction of a C=N bond of 1b and aldol ring closure. The minor hydrogenation products are of interest in that their formation involves C—C hydrogenolysis; it is suggested that this is initiated by addition of a hydrogen atom to a carbonyl carbon atom of 1b.

Tryptophan Photo-Oxidation by Clay-Adsorbed Sensitizers

Clay Minerals ◽  
1988 ◽  
Vol 23 (2) ◽  
pp. 205-212 ◽  
Author(s):  
J. Cenens ◽  
R. A. Schoonheydt
Keyword(s):  
Methylene Blue ◽  
Excited State ◽  
Rose Bengal ◽  
External Surface ◽  
Adsorption Site ◽  
Photo Oxidation ◽  
Dye Aggregation ◽  
Wyoming Bentonite

AbstractThe photo-oxidation of tryptophan (TRP), photosensitized by methylene blue (MB) exchanged on hectorite, Wyoming bentonite and laponite is strongly influenced by three factors: (i) Fe(III) in the structure, which quenches the excited state of MB; (ii) the adsorption site of MB, as photo-oxidation only takes place with MB on the external surface; (iii) dye aggregation, which reduces the yield. Rose bengal (RB), chemically anchored on the external surface of Barasym does not sensitize the photo-oxidation of TRP.

Probing Mechanisms of Aryl–Aryl Bond Cleavages under Flash Vacuum Pyrolysis Conditions

2014 ◽  
Vol 67 (9) ◽  
pp. 1279 ◽  
Author(s):  
Edward A. Jackson ◽  
Xiang Xue ◽  
Hee Yeon Cho ◽  
Lawrence T. Scott
Keyword(s):  
Hydrogen Atom ◽  
Carbon Atom ◽  
Bond Cleavage ◽  
Experimental Results ◽  
Phenyl Radicals ◽  
Flash Vacuum Pyrolysis ◽  
Vacuum Pyrolysis ◽  
Competing Pathways

Several biaryls have been subjected to flash vacuum pyrolysis (FVP) at 1100°C and 0.8–0.9 hPa. Product compositions are reported for the FVP of 9-phenylanthracene (1), 2-bromobiphenyl (5), biphenyl (8), 1,10-diphenylanthracene (12), 9-(2-naphthyl)anthracene (17), and 9,9′-bianthracenyl (20). The experimental results have been used to evaluate four possible mechanistic pathways for the cleavage of aryl–aryl bonds under these conditions: (1) the ‘explosion’ of substituted phenyl radicals; (2) hydrogen atom attachment to an ipso-carbon atom of the biaryl followed by C–C bond cleavage; (3) direct homolysis; and (4) loss of a fragment as an aryne. None of these mechanisms by itself successfully accommodates all of the experimental facts. The data suggest that aryl–aryl bond cleavages under FVP conditions involve at least two different mechanistic pathways and that the relative contributions of the competing pathways probably vary from one biaryl to the next.

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