Excited state proton transfer of pyranine in a γ-cyclodextrin cavity

Mondal, Sudip Kumar; Sahu, Kalyanasis; Sen, Pratik; Roy, Durga; Ghosh, Subhadip; Bhattacharyya, Kankan

doi:10.1016/j.cplett.2005.07.001

Cited by 103 publications

(156 citation statements)

References 35 publications

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“…Mondal et al investigated ESPT of HPTS in -cyclodextrin (-CD) cavity using picosecond and femtosecond fluorescence spectroscopy. 44 They showed that the recombination of the geminate ion pair accelerates but the initial proton-transfer step and the dissociation of the geminate ion pair slow down inside -CD. Sahu in a CTAB micelle.…”

Section: Proton and Electron Transfer In A Confined Systemmentioning

confidence: 99%

Ultrafast Dynamics in Biological Systems and in Nano-Confined Environments

Sahu

Mondal

Ghosh

et al. 2007

Bulletin of the Chemical Society of Japan

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Ultrafast chemical dynamics in a nano-confined system is very different from that in a bulk liquid. In this account, we give an overview on recent femtosecond study on dynamics of ultrafast chemical processes in the nanocavity of a biological system. Dynamics in a biological system crucially depends on the location of the fluorescent probe. We show that one can study solvation dynamics in different regions (i.e. spatially resolve) by variation of the excitation wavelength. We discuss two interesting cases of how structure affects dynamics. First, solvation dynamics of two protein folding intermediates of cytochrome c is found to be differ significantly in the ultrafast initial part (<20 ps). Second, methyl substitution of the OH group in a cyclodextrin is shown to slow down the initial part of solvation dynamics quite dramatically. The most interesting observation is the discovery of the ultraslow component of solvation dynamics which is 100-1000 times slower compared to bulk water. The electron-and proton-transfer processes in a nano-confined system are found to be markedly retarded because of slow solvation and structural constraints. Close proximity of the reactants in a confined system is expected to accelerate dynamics of bi-molecular processes. This is illustrated by ultrafast fluorescence resonance energy transfer (FRET) in %1 ps time scale between a donor and an acceptor in a micelle. Finally, it is demonstrated that the decay of fluorescence anisotropy provides structural information (e.g. size of a cyclodextrin inclusion complex) and may be used to detect formation of a nano-aggregate.

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Section: Proton and Electron Transfer In A Confined Systemmentioning

confidence: 99%

Ultrafast Dynamics in Biological Systems and in Nano-Confined Environments

Sahu

Mondal

Ghosh

et al. 2007

Bulletin of the Chemical Society of Japan

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“…Adding a luminescent dye as a probe makes it possible to measure intracellular pH values [18] and proton transfer. [19] Py has been used as a fluorescent probe for monitoring the gelation of polyacrylamide-sodium alginate composites and sol-gel transition properties of κ-carrageenan. [20,21] The cation effect on the thermal transition of iota carrageenan has been performed by a photon transmission technique, [22] and activation energies were found to be strongly correlated to the CaCl 2 content in the system.…”

Section: Introductionmentioning

confidence: 99%

Effect of Calcium Ion Concentration on Small Molecule Desorption from Alginate Beads

Evingür

Kaygusuz

Erim

et al. 2014

Journal of Macromolecular Science, Part B

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Spherical alginate beads were prepared by ionotropic gelation of sodium alginate through the use of calcium ions. Pyranine (Py) was added to the alginate solution as a small molecule probe for fluorescence studies. Desorption of Py in water from the alginate beads cross-linked with calcium ions was studied by using the steady state fluorescence technique. The fluorescence emission intensity (I) from Py was monitored during the desorption process at 512 nm using the time drive mode of the spectrofluorometer. The increase in I was attributed to Py release from the beads. The Fickian diffusion model was used to calculate the desorption coefficients, D, which were found to be increased up to 3% (w/v) CaCl2 concentration in the beads, and then decreased with a further increase of CaCl2 content. On the other hand, the encapsulation efficiency of Py in the calcium alginate beads presented the reverse behavior compared to D. It was observed that, when the content of CaCl2 was increased, the incubation time, t(0), for the start of desorption increased

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“…There are two classes of such photoprotolytic processes. The first class is excited-state intermolecular proton-transfer reactions (ESPT) [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16], in which the proton is transferred to a solvent molecule, in most cases water. The molecules in this class are called photoacids.…”

Section: Introductionmentioning

confidence: 99%