cis—trans Isomerization of Organic Molecules and Biomolecules: Implications and Applications

Dugave, Christophe; Demange, Luc

doi:10.1002/chin.200338260

Cited by 88 publications

(140 citation statements)

References 1 publication

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“…In t ‐DMASBT, the TICT state is formed by the rotation of the smaller dimethylamino group, but the competing torsional rotation around the olefinic double bond involves the rotation of dimethylanilino group or the benzothiazole group. Fluorescence quantum yields of trans‐ stilbene were also shown to be temperature and viscosity dependent due to the twisting motion about the central bond of phenyl ring . Although the fluorescence quantum yield decreases with increase in temperature, it increases with increase in viscosity.…”

Section: Resultsmentioning

confidence: 99%

Photoisomerization of trans‐2‐[4′‐(Dimethylamino)styryl]benzothiazole

Mishra

Thangamani

Chatterjee

et al. 2012

Photochem & Photobiology

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Photoreaction of trans-2-[4'-(dimethylamino)styryl]benzothiazole (t-DMASBT) under direct irradiation has been investigated in dioxane, chloroform, methanol and glycerol to understand the mechanism of photoisomerization. Contrary to an earlier report, isomerization takes place in all these solvents including glycerol. The results show that restriction on photoisomerization leads to the increase in fluorescence quantum yield in glycerol. The results are consistent with the theoretically simulated potential energy surface reported earlier using time-dependent density functional theory (TDDFT) calculations. DFT calculations on cis isomers under isolated condition have suggested that cis-B conformer is more stable than cis-A conformer due to hydrogen-bonding interaction. In the ground state, cis-DMASBT is predominantly present as cis-B. The fluorescence spectra of the irradiated t-DMASBT suggested that photoisomerization follows not the adiabatic path as proposed by Saha et al., but the nonadiabatic path.

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Section: Resultsmentioning

confidence: 99%

Photoisomerization of trans‐2‐[4′‐(Dimethylamino)styryl]benzothiazole

Mishra

Thangamani

Chatterjee

et al. 2012

Photochem & Photobiology

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“…It has been reported 1968) that the isomerisation may be induced by UV light in vivo, as has been demonstrated in vitro (Koenigs et al, 1993;Zheng et al, 1999). Photoisomerisation of the E-double bond, in p-coumarate, has been studied using yellow protein that ultimately mediates a phototactic response to blue light in certain purple bacteria Ectothiorhodospira (Ryan et al, 2002;Dugave and Demange, 2003). Feeding Melilotus officinalis shoots with E-ocoumaric acid-2-14 C in both dark and light conditions showed much more radioactivity in the coumarins isolated from shoots exposed to light than in the coumarins isolated from shoots kept in the dark.…”

Section: The E-z-cinnamic Acid Isomerisation Stage In Different Plantsmentioning

confidence: 97%

Biosynthesis of scopoletin and scopolin in cassava roots during post-harvest physiological deterioration: The E-Z-isomerisation stage

et al. 2008

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Two to three days after harvesting, cassava (Manihot esculenta Crantz) roots suffer from post-harvest physiological deterioration (PPD) when secondary metabolites are accumulated. Amongst these are hydroxycoumarins (e.g. scopoletin and its glucoside scopolin) which play roles in plant defence and have pharmacological activities. Some steps in the biosynthesis of these molecules are still unknown in cassava and in other plants. We exploit the accumulation of these coumarins during PPD to investigate the E-Z-isomerisation step in their biosynthesis. Feeding cubed cassava roots with E-cinnamic-3,2',3',4',5',6'-d(5) acid gave scopoletin-d(2). However, feeding with E-cinnamic-3,2',3',4',5',6'-d(6) and E-cinnamic-2,3,2',3',4',5',6'-d(7) acids, both gave scopoletin-d(3), the latter not affording the expected scopoletin-d(4). We therefore synthesised and fed with E-cinnamic-2-d(1) when unlabelled scopoletin was biosynthesised. Solely the hydrogen (or deuterium) at C2 of cinnamic acid is exchanged in the biosynthesis of hydroxycoumarins. If the mechanism of E-Z-cinnamic acid isomerisation were photochemical, we would not expect to see the loss of deuterium which we observed. Therefore, a possible mechanism is an enzyme catalysed 1,4-Michael addition, followed by sigma-bond rotation and hydrogen (or deuterium) elimination to yield the Z-isomer. Feeding the roots under light and dark conditions with E-cinnamic-2,3,2',3',4',5',6'-d(7) acid gave scopoletin-d(3) with no significant difference in the yields. We conclude that the E-Z-isomerisation stage in the biosynthesis of scopoletin and scopolin, in cassava roots during PPD, is not photochemical, but could be catalysed by an isomerase which is independent of light.

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“…1 Muitos desses processos apresentam aplicações industriais, como a fotocatálise, ou aplicações biomédicas, como as sondas fluorescentes para o diagnóstico de imagem. 2 Muitos compostos apresentam características fluorescentes, dentre esses compostos, encontram-se os derivados de naftoquinonas. 3 Esses compostos, de origem natural, apresentam diversas aplicações biológicas, como antitumorais, antifúngica, antimalárica, entre outras.…”

Section: Introductionunclassified