Transient Photochemistry of Neutral Red

Marks, Gary T; Lee, E D; Aikens, D. A.; Richtol, H. H.

doi:10.1111/j.1751-1097.1984.tb08185.x

Cited by 25 publications

(19 citation statements)

References 19 publications

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“…Despite its significant biological importance, photophysical and photochemical properties of NR have not been investigated extensively except a few recent literature reports (7)(8)(9)(10)(11)(12)(13), which unfortunately contain many contradictory and inconsistent results. One of the major reasons could be that in many of these studies the commercially available samples of NR were used without any purification.…”

Section: Introductionmentioning

confidence: 99%

Dual Solvatochromism of Neutral Red

Singh¹,

Pal²,

Bhasikuttan³

et al. 1998

Photochem & Photobiology

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Abstract— The effect of solvent polarity on the electronic absorption and fluorescence properties of neutral red (NR), a phenazine‐based dye of biological importance has been investigated in several neat and mixed solvents. An unusual dual solvatochromic behavior has been observed that reveals the existence of two closely spaced electronic excited states in NR. In low‐polarity solvents the fluorescence of the NR is mainly emitted from the localized excited state, whereas in high‐polarity solvents the emission from the charge transfer state dominates. The dipole moments of the localized and charge transfer states of NR have been estimated from the solvatochromic shifts. The dipole moment of the localized excited state (4.8 D) is only slightly higher than that of the ground state (2.0 D), while that of the charge transfer state is drastically higher (17.5 D). Fluorescence quantum yields and the life‐times of NR have been determined in different solvents and correlated with the solvatochromic shifts.

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Section: Introductionmentioning

confidence: 99%

Dual Solvatochromism of Neutral Red

Singh¹,

Pal²,

Bhasikuttan³

et al. 1998

Photochem & Photobiology

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“…A detailed investigation on the reduced radicals and the triplet state of NR is thus essential. Though there are a few reports on the reduced radicals and the triplet state characteristics of NR (8,17,18) in aqueous solutions, the results are again not very consistent in some respects. One of the major reasons for this could be the limited solubility of NR in water at a pH greater than about 8.…”

Section: Introductionmentioning

confidence: 80%

“…Fax: 91-22-5505151; e-mail: hpal@apsara.barc.ernet.in †Abbreviations: NR, neutral red; MS, aqueous-organic mixed solvent; ACP, acetophenone; BZ, benzene; OD, optical density. reports (7)(8)(9)(10)(11)(12) are often seen to have many contradictory and inconsistent results. In our recent two publications (13,14), we critically investigated the photophysical properties of NR and its cationic form (NRH ϩ ) and thus tried to remove some of the doubts in the reported results.…”

Section: Introductionmentioning

confidence: 99%

“…Neutral red also has application in radiation dosimetry (16). Reduced radicals of NR can be generated via the reductive quenching of the triplet state of the dye (8). A detailed investigation on the reduced radicals and the triplet state of NR is thus essential.…”

Section: Introductionmentioning

confidence: 99%

“…One of the major reasons for this could be the limited solubility of NR in water at a pH greater than about 8. This can cause unavoidable errors in the estimated parameters of the reduced radicals and the triplet states in aqueous solutions at higher pH, using flash photolysis and pulse radiolysis techniques (8,17,18).…”

Section: Introductionmentioning

confidence: 99%

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Studies on the Radiolytically Produced Transients of Neutral Red: Triplet and Reduced Radicals

Singh¹,

Pal²,

Sapre³

2007

Photochemistry and Photobiology

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The spectral and kinetic properties of reduced radicals and the triplet state of neutral red (NR), a phenazine‐based dye, have been investigated using pulse radiolysis technique. A mixed water–isopropanol–acetone solvent has been used to study the reduced radicals of NR for a wide pH range of about 1–13, due to limitation of solubility of the dye in aqueous solutions particularly above pH 8. From pH‐dependent absorption studies it has been established that the reduced radicals of NR can exist in four different prototropic forms in solution. Three pKa values for the corresponding prototropic equilibria have been estimated. The formation and decay rate constants of reduced radicals have also been measured. The triplet state characteristics of the dye have been investigated in neat benzene solutions, both in the presence and in the absence of triplet sensitizers. The T1→ Tn absorption spectrum and decay kinetics of the triplet state have been measured. The triplet state energy (ET) of NR in benzene have been estimated to be within 36–42 kcal mol−1, using an energy transfer method.

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The role of Yap1p and Skn7p‐mediated oxidative stress response in the defence of Saccharomyces cerevisiae against singlet oxygen

Brombacher

Fischer

Rüfenacht

et al. 2006

Yeast

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The production of the reactive oxygen species superoxide and hydrogen peroxide in Saccharomyces cerevisiae induces the expression of various defence genes involved in an oxidative stress response. Expression of many of these genes has been shown to be coordinated by two transcriptional regulators, Yap1p and Skn7p, either alone or in concert. Here, we investigated the role of the Yap1p and Skn7p-mediated stress response in the defence against singlet oxygen, a non-radical reactive oxygen species produced mainly by photosensitized reactions in illuminated cells. Both, a yap1 and skn7 mutant were highly sensitive to Rose Bengal, an exogenous photosensitizer producing singlet oxygen in the light. The expression of a Yap1p-dependent reporter gene was induced by increased singlet oxygen production, showing that singlet oxygen activates general oxidative stress response mechanisms required for the resistance against Rose Bengal treatment. This response was also slightly stimulated by light in the absence of the photosensitizer, possibly due to singlet oxygen production by endogenous photosensitizers. The expression pattern of four oxidative stress genes in a yap1, skn7 and wild-type strain and the sensitivity of the corresponding mutants exposed to different oxidative stress conditions proved a role of Yap1p and Skn7p in the defence against singlet oxygen. Similarities in the genetic responses against singlet oxygen and hydroperoxides suggest an overlap in the oxidative stress response against these reactive oxygen species.

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Transient Photochemistry of Neutral Red

Cited by 25 publications

References 19 publications

Dual Solvatochromism of Neutral Red

Dual Solvatochromism of Neutral Red

Studies on the Radiolytically Produced Transients of Neutral Red: Triplet and Reduced Radicals

The role of Yap1p and Skn7p‐mediated oxidative stress response in the defence of Saccharomyces cerevisiae against singlet oxygen

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