Picosecond Time-resolved Fluorescence Studies Research Articles

Conformational change due to reduction of cytochrome-c oxidase in lauryl maltoside: picosecond time-resolved tryptophan fluorescence studies on the native and heat modified enzyme

Detailed fluorescence studies on bovine heart cytochrome-c oxidase (CcO) has been carried out in lauryl maltoside solution. Steady-state fluorescence of the tryptophan residues of the enzyme showed that the fluorophores are embedded deep inside the hydrophobic protein cavity. Time resolved studies of tryptophan fluorescence of native and heat treated CcO have been carried out in both reduced and oxidised forms using synchronously pumped pulsed picosecond dye laser and single photon counting technique. Decay of the tryptophan fluorescence have been fitted using discrete four exponential model. Amplitude distribution of lifetimes also showed four distinct regions in the analysis of the decay profiles by maximum entropy method (MEM). The results indicate that controlled heat treatment of CcO affects the conformation of the enzyme near the active centers which makes it incapable of active proton pumping while the electron transfer property is still conserved. Reduction of the native CcO is associated with a large conformation change in lauryl maltoside near the active centers which is not observed in case of CcO encapsulated in vesicles. Reduction of the heat treated enzyme was found to have a conformation different from the reduced native CcO.

Salt effects on a proton transfer reaction of excited 1-naphthol in a solid/liquid interface layer: A picosecond time-resolved total internal reflection fluorescence study

Analyses of the excited-state proton transfer reaction of 1-naphthol in sapphire/water interface layers have been performed using fluorescence decay data obtained by a picosecond time-resolved total internal reflection fluorescence spectroscopy. The rate constant of the excited-state proton transfer reaction, k 1, of 1-naphthol in an interface layer was reduced as compared to that in a bulk aqueous solution. Addition of NaCl to aqueous solution of 1-naphthol resulted in a decrease in k 1 for both in the interface layer and in the bulk solution, suggesting that a proton acceptor from excited 1-naphthol is not a single water molecule but a water cluster and that water clusters in an interface layer are also destroyed by NaCl.

Picosecond time-resolved fluorescence studies on photoinhibition and double reduction of Q A in photosystem II

The influence of double reduction of Q A, the secondary electron acceptor in Photosystem (PS) II, on the primary events of PS II electron transport was studied by picosecond time-resolved fluorescence measurements in isolated PS II membranes. The double reduction was achieved either by chemical treatment or by strong anaerobic illumination. In the presence of doubly reduced Q A fluorescence decay from the PS II reaction centres showed a dominant amount of a fast phase (150–250 ps) similar to open PS II. In addition to two further components of 600 ps and 2–3 ns, a long-lived component of about 10 ns was observed which is characteristic of the doubly reduced state only. The data indicate efficient primaru charge separation as well as the presence of a long-lived radical pair when Q A is doubly reduced. From these results it is concluded that the electrostatic effect of the two electrons on Q A 2−, which is expected to strongly suppress primary charge separation, is neutralized, most likely by protonation at or near the Q A site. Analysis of the decay curves in the framework of the exciton/radical pair equilibrium model indicates the formation of a relaxed radical pair state. Fluorescence quenching due to aerobic photoinhibition was shown to arise from the increase of a fast decaying (300–320 ps) component at the expense of the more slowly decaying components during the photoinhibitory treatment. No long-lived component in the range of about 10 ns was observed in case of aerobic photoinhibition. It is concluded that, in contrast to the anaerobic photoinhibition, no doubly reduced Q A is accumulated during the aerobic photoinhibitory treatment.

Inhomogeneous Aggregation of a Merocyanine Dye at the Solid/Liquid Interface Layer. A Picosecond Time-Resolved Total Internal Reflection Fluorescence Study

Abstract Fluorescence spectra and their rise and decay dynamics of a merocyanine dye in the interface layer have been studied as a function of penetration depth of the evanescent wave intensity by total internal reflection fluorescence spectroscopy. The aggregation of the dye was enhanced in the interface layer of up to ≈ 100 nm thickness compared to the bulk solution.

Excited-state proton transfer of 1-naphthol in liquid—solid interface layers. Picosecond time-resolved total internal reflection fluorescence study

Picosecond time-resolved total internal reflection fluorescence spectroscopy was applied to analyze the proton transfer reaction of 1-naphthol in water—sapphire interface layers. The rate constant of the proton transfer reaction from excited neutral species became slow in the interface layer as compared with that in the bulk aqueous solution. The anomaly observed up to the penetration depth of 100 nm was interpreted in terms of rotational fluctuations of water aggregates in the interface layer.

Excitation energy relaxation of oxacyanine in Langmuir-Blodgett monolayer films: picosecond time-resolved fluorescence studies

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTExcitation energy relaxation of oxacyanine in Langmuir-Blodgett monolayer films: picosecond time-resolved fluorescence studiesNaoto Tamai, Hiroshi Matsuo, Tomoko Yamazaki, and Iwao YamazakiCite this: J. Phys. Chem. 1992, 96, 16, 6550–6554Publication Date (Print):August 1, 1992Publication History Published online1 May 2002Published inissue 1 August 1992https://doi.org/10.1021/j100195a009RIGHTS & PERMISSIONSArticle Views82Altmetric-Citations37LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-Alerts

Microviscosity in polyacrylamide gels with pendant triphenyl-methane leuco derivatives: picosecond time-resolved fluorescence study

Picosecond fluorescence dynamics of triphenylmethane dyes bonded to polyacrylamide gels before and after swelling was studied by a single-photon timing technique. Microviscosity in the gels after swelling was estimated to be 10–11 cP by examining the viscosity dependence of fluorescence dynamics of malachite green in various alcohols. The results were interpreted in terms of structured stiff water in a microcavity of the gels.

A picosecond time-resolved fluorescence study on the biliprotein, phycocyanin 645

Phycocyanin 645, a photosynthetic chromoprotein isolated from a cryptomonad, has been studied by picosecond time-resolved fluorescence by comparing the results of excitation at three wavelengths, 565, 585 and 615 nm. These excitation wavelengths were selected to correspond as closely as possible using our instrumentation to the maxima of three of the four bands found by deconvolution of the absorption spectrum. These three deconvolution bands — 558, 585 and 624 nm — corresponded to the absorption maxima of chromophores that transfer their excitation energies at very high efficiencies to the lowest-energy chromophore. The fourth, lowest-energy, deconvolution band was at 650 nm, and this chromophore provided the main fluorescence emission of the protein. The decay kinetics for 565 and 615 nm excitation were at 8.9 and 14.7 ps, respectively, but excitation at 585 nm gave rise to a faster component at about 2 ps. Careful statistical analysis was performed to verify that the decays obtained by the various excitations were significantly different. These results were discussed in terms of a model in which the 585 nm and 650 nm bands were strongly coupled and shared delocalization energy. The remaining two bands — 558 and 624 nm — probably transferred excitons to the 650 nm band by very weak dipole coupling. If we assume the delocalization hypothesis to be valid, the 2 ps decay would be a measure of the internal conversion between the high- and low-energy exciton states of the delocalized pair.

Highly selective rotational isomerization of 2-vinylanthracene in the excited singlet state. Picosecond time-resolved fluorescence study

Time-resolved fluorescence spectra and fluorescence kinetics of 2-vinylanthracene in benzene were measured by the picosecond time-correlated single-photon counting technique. Upon 316 nm laser excitation, one rotamer was selectively excited and underwent one-way isomerization to the other rotamer within their lifetimes in the excited singlet state.

Excitation energy relaxation of rhodamine B in Langmuir-Blodgett monolayer films: Picosecond time-resolved fluorescence studies

Excitation energy relaxation of N,N′-dioctadecylrhodamine B incorporated in Langmuir-Blodgett monolayers has been studied with a picosecond time-resolved fluorescence spectrophotometer. Relaxation of singlet excitation energy in a monomolecular layer was interpreted in terms of (1) energy migration among different sites with a fractal-like distribution which are energetically or spatially disordered and (2) energy trapping by higher aggregates.

Excitation-energy redistribution in the cryptomonad alga Cryptomonas ovata

We have studied the redistribution of excitation energy in the cryptomonad alga Cryptomonas ovata. Low-temperature fluorescence emission spectra from cells preilluminated with light 1 and light 2 show that preferential excitation of Photosystem II (PS II) leads to decreased fluorescence emission from chlorophyll (Chl) a associated with PS II relative to the emission following the preferential excitation of Photosystem I (PS I). The fluorescence change is indicative of a light-state transition by the cells. However, comparision of measurements of the kinetics of P-700 photooxidation by cells fixed with glutaraldehyde following illumination with light 1 or light 2 shows that the relative activity of PS I is lower in cells fixed in light 2. This is in contrast to the expectation for cells in State 2. Excitation spectra for the fluorescence emission from PS II Chl a show that preferential excitation of PS II leads to a decreased probability for energy transfer from phycoerythrin and Chl c 2 to PS II when compared to cells in which PS I is preferentially excited. This result is in accordance with recent picosecond time-resolved fluorescence studies (Bruce, D., Biggins, J., Charbonneau, S. and Thewalt, M. (1987) in Progress in Photosynthesis Research (Biggins, J., ed.), Vol. II, pp. 777–780, Martinus Nijhoff, Dordrecht) and we, therefore, suggest that C. ovata does not undergo a classical light-state transition. However, preferential excitation of PS II or PS I appears to cause pigment-protein conformational changes which change the probability for energy transfer from phycoerythrin to PS II, and we suggest that this may be a mechanism for photoprotection of PS II. Studies of the kinetics of excitation-energy redistribution, and of the effects of electron-transport inhibitors and uncouplers of photophosphorylation indicate that the mechanism for excitation-energy redistribution in C. ovata and phycobilisome-containing organisms may be similar.

Picosecond time-resolved fluorescence study of the antenna system isolated from Mastigocladus laminosus Cohn. IL Constituent biliproteins in various forms of aggregation

Picosecond time-resolved fluorescence study of the antenna system isolated from Mastigocladus laminosus Cohn. IL Constituent biliproteins in various forms of aggregation

Picosecond time-resolved fluorescence study of the antenna system isolated from Mastigocladus laminosus Cohn. I. Functionally intact phycobilisomes

Picosecond time-resolved fluorescence study of the antenna system isolated from Mastigocladus laminosus Cohn. I. Functionally intact phycobilisomes

Picosecond time-resolved fluorescence studies of intramolecular heteroexcimers

Intramolecular heteroexcimer formation processes in the excited state of p-(CH 3) 2N-C 6H 4-(CH 2) 3-(9-anthryi) (A 3) as well as p-(CH 3) 2N-C 6H 4-(CH 2) 3-(1-pyrenyl)(P 3 in hexane and 2-propanol have been investigated by means of picosecond time-resolved fluorescence measurements.

A picosecond time-resolved fluorescence study of s-tetrazine vibrational relaxtion in solution

The v 6a v' = 1 vibrational relaxation rate of s-tetrazine in n-hexane solution was measurer with high reliability using a picosecond streak camera. Calibration and means for accurate data processing are described in detail. We find that although weakly coupled, its vibrational relaxation occurs within 8 ps.

Picosecond time-resolved fluorescence studies of poly(N-vinylcarbazole) using a pulse-radiolysis technique

The formation processes of two distinct excimers of poly(N-vinylcarbazole)(PVCZ) have been directly observed by using a picosecond single-pulse radiolysis system with 10 ps time resolution. The primary processes of radiation-induced excitation in the polymer solutions have been studied. A so-called second excimer (λmax of fluorescence = 375 nm) of PVCZ is almost completely formed immediately after a 10 ps electron pulse. Most of the sandwich-type excimer (λmax of fluorescence = 420 nm) is formed in several nanoseconds. Most of the second excimer was confirmed to be formed directly in preexisting sites. Most of the sandwich-type excimer was confirmed to be formed through structural change of the excited carbazolyl and the ground-state carbazolyl chromophore to the sandwich conformation. Both the concentration of the preexisting trap sites and the efficiency of energy migration along the polymer chain before relaxation or solvation of the excited state are considered to be most important in the formation of the second excimer. Most of the primary excited states of PVCZ in irradiated toluene solutions of PVCZ are formed immediately after the 10 ps electron pulse. These very fast formation processes of excited states of solute molecules agree with the recent experimental results observed in irradiated hydrocarbon solutions of aromatic molecules in the picosecond time domain.

Picosecond time-resolved fluorescence study of chlorophyll organisation and excitation energy distribution in chloroplasts from wild-type barley and a mutant lacking chlorophyll b

Picosecond time-resolved fluorescence spectroscopy has been used to investigate the fluorescence emission from wild-type barley chloroplasts and from chloroplasts of the barley mutant, chlorina f-2, which lacks the light-harvesting chlorophyll a/b-protein complex. Cation-controlled regulation of the distribution of excitation energy was studied in isolated chloroplasts at the F 0 and F m levels. It was found that: 1. (a) The fluorescence decay curves were distinctly non-exponential, even at low excitation intensities (<2 × 10 14 photons · cm −2). 2. (b) The fluorescence decay curves could, however, be described by a dual exponential decay law. The wild-type barley chloroplasts gave a short-lived fluorescence component of approximately 140 ps and a long-lived component of 600 ps ( F 0) or 1300 ps ( F m) in the presence of Mg 2+; in comparison, the mutant barley yielded a short-lived fluorescence component of approx. 50 ps and a long-lived component of 194 ps ( F 0) and 424 ps ( F m). 3. (c) The absence of the light-harvesting chlorophyll a/b-protein complex in the mutant results in a low fluorescence quantum yield which is unaffected by the cation composition of the medium. 4. (d) The fluorescence yield changes seen in steady-state experiments on closing Photosystem II reaction centres ( F m/ F 0) or on the addition of MgCl 2 (+Mg 2+/−Mg 2+) were in overall agreement with those calculated from the time-resolved fluorescence measurements. The results suggest that the short-lived fluorescence component is partly attributable to the chlorophyll a antenna of Photosystem I, and, in part, to those light-harvesting-Photosystem II pigment combinations which are strongly coupled to the Photosystem I antenna chlorophyll. The long-lived fluorescence component can be ascribed to the light-harvesting-Photosystem II pigment combinations not coupled with the antenna of Photosystem I. In the case of the mutant, the two components appear to be the separate emissions from the Photosystem I and Photosystem II antenna chlorophylls.