Stereospecificity in triplet state photorearrangements. Oxa-di-.pi.-methane photorearrangement. Mechanistic studies in photochemistry

1974 ◽  
Vol 96 (24) ◽  
pp. 7554-7556 ◽  
Author(s):  
Rick L. Coffin ◽  
Richard S. Givens ◽  
Robert G. Carlson
Keyword(s):  
Triplet State ◽  
Mechanistic Studies

scholarly journals Mechanistic studies on the dehydrogenases of methylotrophic bacteria. 1. The influence of substrate binding to reduced trimethylamine dehydrogenase on the intramolecular electron transfer between its prosthetic groups

1982 ◽  
Vol 207 (2) ◽  
pp. 233-239 ◽  
Author(s):  
D J Steenkamp ◽  
H Beinert
Keyword(s):  
Triplet State ◽  
Intramolecular Electron Transfer ◽  
Methylotrophic Bacteria ◽  
Mechanistic Studies ◽  
Trimethylamine Dehydrogenase ◽  
Ph Values ◽  
Tetramethylammonium Chloride ◽  
Maximal Yield ◽  
Influence Of Substrate ◽  
Prosthetic Groups

The trimethylamine dehydrogenase of bacterium W3A1 is reduced with the formation of a triplet state in which two electrons, derived from the substrate, are distributed between the [4Fe-4S] cluster and 6-S-cysteinyl-FMN semiquinone. In titration experiments at pH 8.5 about 1.0 mol of dimethylamine or 0.5 mol of trimethylamine per mol of the enzyme is required to titrate the enzyme to an endpoint. At pH values less than 8.0, however, an excess of trimethylamine is required to obtain maximal yield of the g = 4 e.p.r. signal, characteristic of the triplet state, or maximal absorbance at 365 nm which indicates formation of the flavin semiquinone. The binding of 0.86 mol of trimethylamine per mol of the enzyme could be detected by a gel chromatographic method. When the enzyme is titrated with dithionite in the presence of tetramethylammonium chloride, an endpoint is reached after the uptake of two electrons which give rise to the triplet state, whereas three electrons are consumed in the absence of tetramethylammonium chloride to reduce the enzyme completely. The enzyme is inhibited noncompetitively by tetramethylammonium chloride and the slopes of double reciprocal plots are a concave upwards function of inhibitor concentration. The data indicate the presence of a binding site for the substrate and other amines on the reduced enzyme which enhances the proportion of enzyme in the triplet state.

Photochemical synthesis, 22. On photochemical cycloaddition: Cyclopentenone

1968 ◽  
Vol 46 (15) ◽  
pp. 2535-2547 ◽  
Author(s):  
P. de Mayo ◽  
J-P. Pete ◽  
M. Tchir
Keyword(s):  
Triplet State ◽  
Quantum Efficiency ◽  
Photochemical Synthesis ◽  
Triplet States ◽  
Mechanistic Studies ◽  
Rapid Reaction

Cyclopentenone has been added photochemically to a wide variety of olefins and the quantum efficiency determined. Mechanistic studies indicate a rapid reaction involving a triplet state by a process which is not stereospecific, but which does not allow complete equilibration. Evidence is provided which suggests that cyclopentenone reacts photochemically from two triplet states, but that only the higher leads to cycloaddition.

A nitroreductase-activatable near-infrared theranostic photosensitizer for photodynamic therapy under mild hypoxia

2020 ◽  
Vol 56 (43) ◽  
pp. 5819-5822
Author(s):  
Jing Zheng ◽  
Yongzhuo Liu ◽  
Fengling Song ◽  
Long Jiao ◽  
Yingnan Wu ◽  
...  
Keyword(s):  
Photodynamic Therapy ◽  
Triplet State ◽  
Near Infrared ◽  
Mild Hypoxia

In this study, a near-infrared (NIR) theranostic photosensitizer was developed based on a heptamethine aminocyanine dye with a long-lived triplet state.

Temporal and mechanistic studies on the resistance of glioma cells to temozolomide

2016 ◽  
Vol 228 (06/07) ◽  
Author(s):  
WP Roos ◽  
M Eich ◽  
S Quiros ◽  
AV Knizhnik ◽  
T Nikolova ◽  
...  
Keyword(s):  
Glioma Cells ◽  
Mechanistic Studies
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