Related Experiment Video
Updated: Jul 14, 2026

Spatial Separation of Molecular Conformers and Clusters
Published on: January 9, 2014
On the behavior of indole-containing species sequestered within reverse micelles at sub-zero temperatures
Chase A Munson1, Lee Kelepouris, Gary A Baker
1Department of Chemistry, Natural Sciences Complex, University at Buffalo, The State University of New York, Buffalo, NY 14260-3000, USA.
Abstract:
We report on the effects of temperature (+30 to -100 degrees C) on the fluorescence from N-acetyl tryptophanamide (NATA) and human serum albumin (HSA) sequestered within Aerosol-OT (AOT) reversed micelles. NATA reports simultaneously from the polar and non-polar side of the reverse micelle interface. As the sample temperature decreases, the relative fraction of NATA molecules associated with the polar side increases. This redistribution process is characterized by DeltaH = -14.8 +/- 0.6 kJ/mol and DeltaS = -54 +/- 2 J/(K mol). The activation energy for thermal quenching (E(a,TQ)) associated with the polar side NATA molecules is 6.7 kJ/mol before the micelles have shed water and 1.0 kJ/mol after water shedding (below approximately -20 degrees C). The time-resolved fluorescence intensity decay for tryptophan-214 in HSA is triple exponential. We suggest that these lifetimes arise from three indole residue conformations in equilibrium. Cooling the sample causes a freezing-in of the least quenched conformer; the other conformers are frozen out. The E(a,TQ) value for the shortest lifetime component is 6 kJ/mol. The E(a,TQ) for the long and intermediate lifetime components are equivalent (approximately 1.5 kJ/mol).
More Related Videos
Related Concept Videos
¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR
π Electron Effects on Chemical Shift: Overview
Inductive Effects on Chemical Shift: Overview
Induced Electric Dipoles
Since the absolute value of potential energy holds no physical meaning, its zero value can be chosen as per...
Entropy and Solvation
Sublimation

