Solvation Dynamics of Coumarin 480 in Micelles

Sarkar, Nilmoni; Datta, Anindya; Das, and Swati; Bhattacharyya, Kankan

doi:10.1021/jp960630g

Cited by 265 publications

(396 citation statements)

References 37 publications

(36 reference statements)

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“…10 One consistent conclusion of their studies is that there is not a one-to-one correspondence between steady-state spectra and the time-dependent Stokes shift function, S(t): ''...steady-state spectroscopy may not always be a good predictor for dynamical behavior.'' 14 Bhattacharyya and co-workers have measured the timedependent fluorescence of the dye molecule, Coumarin 480, in solventless zeolites, 4 aqueous micelles 5 and reverse micelles, 6 in water pools in a sol-gel matrix, 7 and vesicles. 8 They found that the long-time solvation dynamics depend strongly on the environment with a long-time decay of ϳ0.8 ns in the sol-gel matrix, 7 0.6 -2.4 ns in micelles ͑using different surfactants͒, 5 8 -12 ns in reverse micelles, 6 11 ns in vesicles, 8 and ϳ15.4 ns in the solventless zeolites.…”

Section: Experimental Workmentioning

confidence: 99%

“…14 Bhattacharyya and co-workers have measured the timedependent fluorescence of the dye molecule, Coumarin 480, in solventless zeolites, 4 aqueous micelles 5 and reverse micelles, 6 in water pools in a sol-gel matrix, 7 and vesicles. 8 They found that the long-time solvation dynamics depend strongly on the environment with a long-time decay of ϳ0.8 ns in the sol-gel matrix, 7 0.6 -2.4 ns in micelles ͑using different surfactants͒, 5 8 -12 ns in reverse micelles, 6 11 ns in vesicles, 8 and ϳ15.4 ns in the solventless zeolites. 4 ͑The solvent relaxation dynamics for Coumarin 480 in bulk aqueous solution takes place in 310 fs.…”

Section: Experimental Workmentioning

confidence: 99%

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Simulations of time-dependent fluorescence in nano-confined solvents

Thompson

2004

The Journal of Chemical Physics

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The time-dependent fluorescence of a model diatomic molecule with a charge-transfer electronic transition in confined solvents has been simulated. The effect of confining the solvent is examined by comparing results for solutions contained within hydrophobic spherical cavities of varying size ͑radii of 10-20 Å͒. In previous work ͓J. Chem. Phys. 118, 6618 ͑2002͔͒ it was found that the solute position in the cavity critically affects the absorption and fluorescence spectra and their dependence on cavity size. Here we examine the effect of cavity size on the time-dependent fluorescence, a common experimental probe of solvent dynamics. The present results confirm a prediction that motion of the solute in the cavity after excitation can be important in the time-dependent fluorescence. The effects of solvent density are also considered. The results are discussed in the context of interpreting time-dependent fluorescence measurements of confined solvent systems.

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Section: Experimental Workmentioning

confidence: 99%

Section: Experimental Workmentioning

confidence: 99%

Simulations of time-dependent fluorescence in nano-confined solvents

Thompson

2004

The Journal of Chemical Physics

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“…More recently, the 7-aminocoumarins have been used to probe dynamic fluctuations about a charge-transfer excited state for a wide variety of condensed-phase systems. These include polymers, 11,21 reverse and normal micelles, [3][4][5]22,23 semiconductor surfaces, 24 zeolites, 25 sol-gels, 7 vesicles, 6 proteins, 26 cyclodextrins, 9 and molten salts. 27,28 The coumarins can be detected on a single-molecule level 29 but will find only limited applications in this area because they photoreact after prolonged cycles of excitation/emission.…”

Section: Introductionmentioning

confidence: 99%

Time-Dependent Density Functional Theory Investigation of the Ground and Excited States of Coumarins 102, 152, 153, and 343

2002

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We present calculations of various properties of the ground and excited electronic states of coumarins 102, 152, 153, and 343. Using density functional theory (DFT) and time-dependent density functional theory (TDDFT), we examine the excitation energies to the S 1 and S 2 states, the ground and excited-state dipole moments, and the lowest ionization potentials of these coumarins. In the case of C153, we locate two distinct S 0 minima due to differing conformations of the julolidyl ring structure and compare properties for the syn and anti conformers. For C343, we examine the possibility of proton transfers in the ground and S 1 states of the system. We find that (1) DFT tends to overestimate the ground-state dipole moments in these systems, (2) excellent agreement is obtained between TDDFT and experimental vertical excitation energies, (3) TDDFT and CIS yield similar estimates of the dipole moment change between the S 0 and S 1 states, both of which are in the range of previous experimental estimates, (4) in each case, the S 2 state is at least 0.5 eV above the S 1 state for the ground-state geometry, and (5) proton transfer is not likely in the ground state of C343 but is only 0.18 eV higher in energy in the S 1 state. We also compare the DFT/TDDFT results with RHF/CIS, MP2, and INDO S/CI results. We find good agreement between MP2 and experimental ground-state dipole moments and good agreement between INDO S/CI and TDDFT gas-phase excitation energies.

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“…Furthermore, structural transitions can be induced in charged micelles at a given temperature by increasing the ionic strength of the medium or amphiphile concentration (Ikeda 1984;Porte and Appel 1984). The organization and dynamics of micellar environments, namely the core, the interface, and the immediate layers of water on the interface, have been investigated using experimental (Sarkar et al 1996;Maiti et al 1997;Rawat et al 1997;Rawat and Chattopadhyay 1999) and theoretical (MacKerell 1995) approaches. It is fairly well established now that practically all types of molecule have a surface-seeking tendency in micelles (due to very large surface area to volume ratio) and that the interfacial region is the preferred site for solubilization, even for hydrophobic molecules (Shobha et al 1989).…”

Section: Introductionmentioning

confidence: 99%

Effect of micellar charge on the conformation and dynamics of melittin

Raghuraman

Chattopadhyay

2004

Eur Biophys J

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Electrostatic interactions play a crucial role in modulating and stabilizing molecular interactions in membranes and membrane-mimetic systems such as micelles. We have monitored the change in the conformation and dynamics of the cationic hemolytic peptide melittin bound to micelles of various charge types, utilizing fluorescence and circular dichroism (CD) spectroscopy. The sole tryptophan of melittin displays a red-edge excitation shift (REES) of 3-6 nm when bound to anionic, nonionic, and zwitterionic micelles. This suggests that melittin is localized in a restricted environment, probably in the interfacial region of the micelles, and this region offers considerable restriction to the reorientational motion of the solvent dipoles around the excited state tryptophan in melittin. Further, the rotational mobility of melittin is considerably reduced in these micelles and is found to be dependent on the surface charge of micelles. Interestingly, our results show that melittin does not partition into cetyltrimethylammonium bromide (CTAB) micelles owing to electrostatic repulsion between melittin and CTAB micelles, both of which carry a positive charge. In addition, the fluorescence lifetime of melittin is modulated in micelles of different charge types. The lowest mean fluorescence lifetime is observed in the case of melittin bound to anionic sodium dodecyl sulfate (SDS) micelles. CD spectroscopy shows that micelles induce significant helicity to melittin, with maximum helicity being induced in the case of melittin bound to SDS micelles. Fluorescence quenching measurements using the neutral aqueous quencher acrylamide show differential accessibility of melittin in various types of micelles. Taken together, our results show that micellar surface charge can modulate the conformation and dynamics of melittin. These results could be relevant to understanding the role of the surface charge of membranes in the interaction of membrane-active, amphiphilic peptides with membranes.

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Solvation Dynamics of Coumarin 480 in Micelles

Cited by 265 publications

References 37 publications

Simulations of time-dependent fluorescence in nano-confined solvents

Simulations of time-dependent fluorescence in nano-confined solvents

Time-Dependent Density Functional Theory Investigation of the Ground and Excited States of Coumarins 102, 152, 153, and 343

Effect of micellar charge on the conformation and dynamics of melittin

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