Terahertz radiation from bacteriorhodopsin reveals correlated primary electron and proton transfer processes

G. I. Groma, J. Hebling, I. Z. Kozma, G. Váró, J. Hauer, J. Kuhl, E. Riedle

Research output: Contribution to journalArticle

30 Citations (Scopus)

Abstract

The kinetics of electrogenic events associated with the different steps of the light-induced proton pump of bacteriorhodopsin is well studied in a wide range of time scales by direct electric methods. However, the investigation of the fundamental primary charge translocation phenomena taking place in the functional energy conversion process of this protein, and in other biomolecular assemblies using light energy, has remained experimentally unfeasible because of the lack of proper detection technique operating in the 0.1- to 20-THz region. Here, we show that extending the concept of the familiar Hertzian dipole emission into the extreme spatial and temporal range of intramolecular polarization processes provides an alternative way to study ultrafast electrogenic events on naturally ordered biological systems. Applying a relatively simple experimental arrangement based on this idea, we were able to observe light-induced coherent terahertz radiation from bacteriorhodopsin with femtosecond time resolution. The detected terahertz signal was analyzed by numerical simulation in the framework of different models for the elementary polarization processes. It was found that the principal component of the terahertz emission can be well described by excited-state intramolecular electron transfer within the retinal chromophore. An additional slower process is attributed to the earliest phase of the proton pump, probably occurring by the redistribution of a H bond near the retinal. The correlated electron and proton translocation supports the concept, assigning a functional role to the light-induced sudden polarization in retinal proteins.

Original languageEnglish
Pages (from-to)6888-6893
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume105
Issue number19
DOIs
Publication statusPublished - May 13 2008

Fingerprint

Terahertz Radiation
Bacteriorhodopsins
Protons
Electrons
Light
Proton Pumps
Proteins

Keywords

  • Coherent terahertz emission
  • Excited-state kinetics
  • Nonlinear spectroscopy
  • Sudden polarization
  • Ultrafast charge separation

ASJC Scopus subject areas

  • Genetics
  • General

Cite this

Terahertz radiation from bacteriorhodopsin reveals correlated primary electron and proton transfer processes. / Groma, G. I.; Hebling, J.; Kozma, I. Z.; Váró, G.; Hauer, J.; Kuhl, J.; Riedle, E.

In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 105, No. 19, 13.05.2008, p. 6888-6893.

Research output: Contribution to journalArticle

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