title: Time-resolved infrared spectroscopic techniques as applied to channelrhodopsin.
abstract: Among optogenetic tools, channelrhodopsins, the light gated ion channels of the plasma membrane from green algae, play the most important role. Properties like channel selectivity, timing parameters or color can be influenced by the exchange of selected amino acids. Although widely used, in the field of neurosciences for example, there is still little known about their photocycles and the mechanism of ion channel gating and conductance. One of the preferred methods for these studies is infrared spectroscopy since it allows observation of proteins and their function at a molecular level and in near-native environment. The absorption of a photon in channelrhodopsin leads to retinal isomerization within femtoseconds, the conductive states are reached in the microsecond time scale and the return into the fully dark-adapted state may take more than minutes. To be able to cover all these time regimes, a range of different spectroscopical approaches are necessary. This mini-review focuses on time-resolved applications of the infrared technique to study channelrhodopsins and other light triggered proteins. We will discuss the approaches with respect to their suitability to the investigation of channelrhodopsin and related proteins.
authors.affiliation: Experimentelle Biophysik, Institut für Biologie, Humboldt-Universität zu Berlin Berlin, Germany.
authors.forename: Eglof
authors.initials: E
authors.lastname: Ritter
authors.affiliation: Methods for Material Development, Helmholtz-Zentrum für Materialien und Energie GmbH Berlin, Germany.
authors.forename: Ljiljana
authors.initials: L
authors.lastname: Puskar
authors.affiliation: Institut für medizinische Physik und Biophysik, Charité - Universitätsmedizin Berlin Berlin, Germany.
authors.forename: Franz J
authors.initials: FJ
authors.lastname: Bartl
authors.affiliation: Methods for Material Development, Helmholtz-Zentrum für Materialien und Energie GmbH Berlin, Germany ; Fachbereich Physik, Freie Universität Berlin Berlin, Germany.
authors.forename: Emad F
authors.initials: EF
authors.lastname: Aziz
authors.affiliation: Experimentelle Biophysik, Institut für Biologie, Humboldt-Universität zu Berlin Berlin, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Hegemann
authors.affiliation: Methods for Material Development, Helmholtz-Zentrum für Materialien und Energie GmbH Berlin, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Schade
keywords: FTIR; IR-spectrometer; channelrhodopsin; infrared spectroscopy; retinal proteins; time-resolved spectroscopy