Oxygen Quenching of Fluorescence in Solution: An Experimental Study of the Diffusion Process

Ware, William R.

doi:10.1021/j100809a020

Cited by 1,280 publications

(600 citation statements)

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“…There are several factors that can contribute to quenching. Oxygen has been demonstrated to be a collisional quencher with an efficiency of 1 per collision [13]. The overall quenching effect of the oxygen depends on its local concentration, the diffusion constant in the medium, and the lifetime of the fluorescent molecule.…”

Section: Discussionmentioning

confidence: 99%

Packing of phospholipid vesicles studied by oxygen quenching of Laurdan fluorescence

Parasassi

Gratton

1992

J Fluoresc

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Steady-state fluorescence oxygen quenching experiments were performed on phospholipid vesicles where 2-dimethylamino-6-1auroylnaphthalene (Laurdan) was inserted. The quenching efficiency was found to be much higher in vesicles in the liquid-crystalline phase with respect to the gel phase, by a factor of about 50. Since the oxygen solubility in the two phospholipid phases can differ at most by a factor of 4 based on literature values, we concluded that oxygen diffusion must be responsible for the great difference in the quenching efficiency. A relatively high quenching efficiency was also found in vesicles composed of equimolar gel and liquid-crystalline phospholipids. Simulations were performed using the linear superposition of the properties of the pure phases to demonstrate that, in the case of vesicles composed of coexisting phases, the diffusional properties of oxygen in each phase are largely modified by the presence of the other. The addition of 10 mol% cholesterol to the gel phase rendered Laurdan fluorescence approximately as quenchable as in the equimolar mixture of the two phases. This result points out that molecules such as cholesterol, which introduce packing defects in the bilayer, favor oxygen diffusion. From the oxygen quenching experiments and using the properties of generalized polarization, the rate of Laurdan dipolar relaxation can be estimated.

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Section: Discussionmentioning

confidence: 99%

Packing of phospholipid vesicles studied by oxygen quenching of Laurdan fluorescence

Parasassi

Gratton

1992

J Fluoresc

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“…The Stern-Volmer plot of the CM14 and CM15 is presented in Figure 6. The results in Table 3 showed that Kq were much greater than the limiting diffusion rate constant of the biomolecule (2.0 x 10 10 mol L −1 S− 1 ), which indicated that the probable quenching mechanism of BSA-CM14 and BSA-CM15 interactions was initiated by complex formation rather than by dynamic collision [48].…”

Section: Albumin Binding Assaymentioning

confidence: 98%

Versatility of 7-Substituted Coumarin Molecules as Antimycobacterial Agents, Neuronal Enzyme Inhibitors and Neuroprotective Agents

Kapp

Visser

Sampson

et al. 2017

Preprint

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An in vitro medium-throughput screen using M. tuberculosis H37Rv was employed to screen an in-house library of structurally diverse compounds for antimycobacterial activity. From this initial screen, eleven 7-substituted coumarin derivatives with confirmed monoamine oxidase-B and cholinesterase inhibitory activities, demonstrated growth inhibition of more than 50% at a 50 µM concentration. This prompted further exploration of all the 7-substituted coumarins in our library, nineteen in total, as potential antimycobacterial agents. Four derivatives showed promising antimycobacterial activity with MIC99 values of 8.31 -29.70 µM and 44.15 -57.17 µM on M. tuberculosis H37Rv in independent assays using Gaste-Fe and 7H9 + OADC media, respectively. These compounds were found to bind to albumin which may explain the variations in MIC between the two assays. Preliminary antimycobacterial evaluation of moxifloxacin resistant M. tuberculosis show that these compounds are able to maintain their activity in fluoroquinolone resistant mycobacteria. Analysis of structure activity relationships for antimycobacterial versus neuronal enzyme inhibitory activity indicate that structural modification on position 4 and/or 7 of the coumarin scaffold may be utilized to improve selectivity towards either inhibition of neuronal enzymes or antimycobacterial effect. Cytotoxicity evaluations of the compounds indicate moderate cytotoxicity with slight selectivity towards mycobacteria. Further neuroprotective assays on SH-SY5Y human neuroblastoma cells indicate significant neuroprotection for selected compounds irrespective of their neuronal enzyme inhibitory properties. These coumarin molecules are thus interesting lead compounds that may provide insight into the design of new antimicrobacterial and/or neuroprotective agents.

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“…A capacidade de supressão de oxigênio singlete pelos carotenóides ocorre via um mecanismo de transferência de energia envolvendo a excitação do carotenóide ao estado triplete de mais baixa energia (1), sendo este, por sua vez, desativado pelo eficiente decaimento não radiativo para o estado fundamental (2) 37,[50][51][52][53] . 54 .…”

Section: Sensibilização E Supressão De Oxigênio Singlete Por Carotenóunclassified

Fotofísica de carotenóides e o papel antioxidante de b-caroteno

Cardoso¹

1997

Quím. Nova

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PHOTOPHYSICS OF CAROTENOIDS AND THE ANTIOXIDANT ROLE OF β-CAROTENE.Carotenoid polyenes play a wide role in nature and their photophysical properties make of these pigments a focus of research in photochemistry, photobiology and photomedicine. Some aspects of the singlet and triplet states and, their interaction with molecular and singlet oxygen and free radicals are briefly reviewed in this article.Keywords: carotenoids; β-carotene; singlet oxygen. DIVULGAÇÃO INTRODUÇÃODe todos os pigmentos naturais, os carotenóides são provavelmente os de maior ocorrência, podendo ser encontrados em animais, plantas e microorganismos. São pigmentos altamente coloridos, insaturados e lipofílicos, apresentando uma variedade de cores desde o amarelo até o vermelho. Os carotenóides são responsáveis pela coloração apresentada por muitos insetos, pássaros, peixes e crustáceos. Por exemplo, são responsá-veis pelas cores do salmão, da truta e do peixe dourado, pela plumagem rosa dos flamingos e, pela mudança de cor da lagosta, quando submetida ao aquecimento, em função da liberação de um carotenóide,astaxantina (I), que está inicialmente associado à uma proteína.E-Mail: cardoso@iq.ufrj.br Quase todos os carotenóides são derivados de tetraterpenos (C 40 ) com o esqueleto hidrocarbônico consistindo em oito unidades isoprenóides. Na natureza, os carotenóides surgem a partir da reação de acoplamento "cauda-cauda" do análogo C20 do pirofosfato de farnesila, levando inicialmente à formação do fitoeno (Figura 1); este por sua vez, através de reações de desidrogenação, ciclização e oxidação, dará origem a uma variedade de pigmentos C 40 , como por exemplo, os abundantes β-caroteno (II) e licopeno (III). Esta classe de pigmentos também inclui certos compostos formados pelo rearranjo deste esqueleto, ou pela remoção formal de parte desta estrutura. Carotenóides formados somente por átomos de carbono e hidrogênio são chamados de carotenos, enquanto os derivados contendo um heteroátomo, como por exemplo oxigênio, são chamados de xantofilas 1 . O carotenóide mais conhecido é o β-caroteno, pigmento responsável pela cor característica da cenoura que corresponde à pró-vitamina A mais abundante e de maior atividade, sendo convertido em vitamina A 1 pela quebra oxidativa da dupla ligação central e posterior redução bioquímica do aldeído (Figura 2). Os carotenóides destacam-se em outras áreas da medicina além da nutricional, sendo utilizados no tratamento de certas doenças de pele, como por exemplo na fotoporfíria eritropoié-tica. Estudos recentes indicam uma possível atividade anticancerígena como também a provável participação como moduladores das respostas imunológicas 2,3 . Na área comercial os carotenóides já há alguns anos vêm sendo utilizados como colorantes e antioxidantes, principalmente em alimentos pois,

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Oxygen Quenching of Fluorescence in Solution: An Experimental Study of the Diffusion Process

Cited by 1,280 publications

References 4 publications

Packing of phospholipid vesicles studied by oxygen quenching of Laurdan fluorescence

Packing of phospholipid vesicles studied by oxygen quenching of Laurdan fluorescence

Versatility of 7-Substituted Coumarin Molecules as Antimycobacterial Agents, Neuronal Enzyme Inhibitors and Neuroprotective Agents

Fotofísica de carotenóides e o papel antioxidante de b-caroteno

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