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Dynamics of a membrane-bound tryptophan analog in environments of varying hydration: a fluorescence approach

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Abstract

Tryptophan octyl ester (TOE) represents an important model for membrane-bound tryptophan residues. In this article, we have employed a combination of wavelength-selective fluorescence and time-resolved fluorescence spectroscopies to monitor the effect of varying degrees of hydration on the dynamics of TOE in reverse micellar environments formed by sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in isooctane. Our results show that TOE exhibits red edge excitation shift (REES) and other wavelength-selective fluorescence effects when bound to reverse micelles of AOT. Fluorescence parameters such as intensity, emission maximum, anisotropy, and lifetime of TOE in reverse micelles of AOT depend on [water]/[surfactant] molar ratio (w o). These results are relevant and potentially useful for analyzing dynamics of proteins or peptides bound to membranes or membrane-mimetic media under conditions of changing hydration.

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Notes

  1. We have used the term maximum of fluorescence emission in a somewhat wider sense here. In every case, we have monitored the wavelength corresponding to maximum fluorescence intensity, as well as the center of mass of the fluorescence emission. In most cases, both these methods yielded the same wavelength. In cases where minor discrepancies were found, the center of mass of emission has been reported as the fluorescence maximum

Abbreviations

AOT:

Sodium bis(2-ethylhexyl) sulfosuccinate

REES:

Red edge excitation shift

TOE:

Tryptophan octyl ester

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Acknowledgements

This work was supported by the Council of Scientific and Industrial Research, Government of India. We thank YSSV Prasad and GG Kingi for technical help and members of our laboratory for critically reading the manuscript. AA acknowledges the Indian Council of Medical Research for the award of a Project Assistantship. DAK thanks the Council of Scientific and Industrial Research for the award of a Senior Research Fellowship.

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Correspondence to Amitabha Chattopadhyay.

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Chattopadhyay, A., Arora, A. & Kelkar, D.A. Dynamics of a membrane-bound tryptophan analog in environments of varying hydration: a fluorescence approach. Eur Biophys J 35, 62–71 (2005). https://doi.org/10.1007/s00249-005-0009-7

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