Slow Solvent Relaxation Dynamics of Nanometer Sized Reverse Micellar Systems Through Tryptophan Metabolite, Kynurenine

• Published in: Photochemistry and photobiology Vol. 88; no. 1; pp. 38 - 45
• Main Authors: Rakshit, Surajit, Goswami, Nirmal, Pal, Samir Kumar
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.01.2012
• Subjects: Fluorescence; Fluorescence Resonance Energy Transfer; Hydrogen bonds; Kynurenine - chemistry; Metabolites; Micelles; Nanoparticles; Photochemistry; Solvents - chemistry; Spectrophotometry, Ultraviolet
• ISSN: 0031-8655; 1751-1097
• DOI: 10.1111/j.1751-1097.2011.01007.x

Exploration of environmental dynamics using intrinsic biological probe tryptophan is very important; however, it suffers from various difficulties. An alternative probe, kynurenine (KN), has been found to be an efficient probe for the ultrafast dynamics in the biological environment (Goswami et al., [2010] J. Phys. Chem. B., 114, 15236–15243). In the present study, we have investigated the efficacy of KN for the exploration of relatively slower dynamics of biologically relevant environments. A detailed investigation involving UV–Vis, steady‐state/time‐resolved fluorescence spectroscopy and Förster resonance energy transfer (FRET) studies on KN compared to a well‐known solvation probe, H33258, a DNA‐minor groove binder in a model nonionic reverse micelle reveals that ultrafast internal conversion associated with the hydrogen‐bonding dynamics masks KN to become a dynamical reporter of the immediate environments of the probe. Our work explores the efficacy of kynurenine (KN), one of the tryptophan metabolites as a potential probe for the slow solvent relaxation dynamics in a restricted medium of neutral reverse micelles (RM). While picosecond‐resolved Förster resonance energy transfer study confirms the inclusion of the probe in the RM, details of the optical spectroscopic investigations reveal that ultrafast internal conversion associated with the hydrogen‐bonding dynamics masks KN to become a dynamical reporter of the immediate environments of the probe.