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Updated: Jan 20, 2026

Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy
Published on: June 27, 2014
Probing Charge-Transfer and Short-Lived Triplet States of a Biosensitive Molecule, 2,6-ANS: Transient Absorption and
Mohan Singh Mehata1, Yang Yang2, Keli Han2
1Laser-Spectroscopy Laboratory, Department of Applied Physics, Delhi Technological University, Bawana Road, Delhi 110042, India.
Abstract:
We report the existence of a short-lived triplet electronic state of 2,6-ANS (2-anilinonaphthalene-6-sulfonic acid), which, together with nonplanar (NP) and planar [charge-transfer (CT)] states, is produced following photoexcitation; these results are based on nanosecond transient absorption and time-resolved decays. The short-lived triplet state has a lifetime of ∼126 ns and is observed via triplet-triplet (T-T) transitions after exciting 2,6-ANS with a pump laser pulse of 355 nm (probe wavelength range of 360-500 nm). Moreover, the CT state, which is very close to the NP state produced from the locally excited state/NP state, emits active fluorescence with a lifetime of ∼11 ns. The solvent plays a major role in the rotation of the phenylamino group during the conversion of the NP state to the CT state, and vice versa. Intersystem crossing occurs from the CT state. Thus, investigating the triplet state together with the CT/NP states of 2,6-ANS, a commonly used probe for sensing proteins and other biomolecules, is highly relevant and helps reveal its photoexcitation dynamics.
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