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Updated: May 23, 2026

Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy
Published on: June 27, 2014
First observation of ultrafast intramolecular proton transfer rate between electronic ground states in solution
Yuichi Masuda1, Tomoko Nakano, Midori Sugiyama
1Department of Chemistry, Faculty of Science, Ochanomizu University, Bunkyo-ku, Tokyo 112-8610, Japan. masuda.yuichi@ocha.ac.jp
Abstract:
Despite the importance of ultrafast (time scale exceeding 10(-11) s) intramolecular proton transfer (PT) events between electronic ground states in solution, experimental determination of the rates of such reactions has not yet been accomplished because of the limitations of the utilized methods. The objective of this study was to evaluate the PT rates of intramolecular O···H···O hydrogen-bonded systems in solution through the (1)H spin-lattice relaxation times of the hydroxyl protons, induced by the (1)H-(17)O dipolar interactions (T(1dd)(OH)), taking into account the contribution of the OH reorientational motion to T(1dd)(OH). Solutions of the benzoic acid dimer (BA dimer), 1-benzoyl-6-hydroxy-6-phenylfulvene (Fulvene), and dibenzoylmethane (DBM) were chosen as test systems. For Fulvene in CCl(4), the PT time, τ(PT), was deduced to be 7 × 10(-11) s. In the case of the BA dimer in CCl(4), the τ(PT) value was considerably greater than the OH reorientational correlation time, τ(R(OH)) = 4.3 × 10(-11) s. In contrast, the experimental results for DBM in CCl(4) indicated that the proton is located about midway between the two oxygen atoms, that is, the PT potential energy surface is a single well or a double well with a PT barrier near or below the zero-point energy.
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