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Ultrafast fluorescence upconversion technique and its applications to proteins
Author(s) -
Chosrowjan Haik,
Taniguchi Seiji,
Tanaka Fumio
Publication year - 2015
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/febs.13180
Subject(s) - chromophore , photon upconversion , photochemistry , photoisomerization , chemistry , electron transfer , ionic bonding , fluorescence , crystallography , chemical physics , ion , organic chemistry , optics , physics , isomerization , catalysis
The basic principles and main characteristics of the ultrafast time‐resolved fluorescence upconversion technique (conventional and space‐resolved), including requirements for nonlinear crystals, mixing spectral bandwidth, acceptance angle, etc., are presented. Applications to flavoproteins [wild‐type ( WT ) FMN ‐binding protein and its W32Y, W32A, E13R, E13K, E13Q and E13T mutants] and photoresponsive proteins [ WT photoactive yellow protein and its R52Q mutant in solution and as single crystals] are demonstrated. For flavoproteins, investigations elucidating the effects of ionic charges on ultrafast electron transfer ( ET ) dynamics are summarized. It is shown that replacement of the ionic amino acid Glu13 and the resulting modification of the electrostatic charge distribution in the protein chromphore‐binding pocket substantially alters the ultrafast fluorescence quenching dynamics and ET rate in FMN ‐binding protein. It is concluded that, together with donor–acceptor distances, electrostatic interactions between ionic photoproducts and other ionic groups in the proteins are important factors influencing the ET rates. In WT photoactive yellow protein and the R52Q mutant, ultrafast photoisomerization dynamics of the chromophore (deprotonated trans‐p ‐coumaric acid) in liquid and crystal phases are investigated. It is shown that the primary dynamics in solution and single‐crystal phases are quite similar; hence, the photocycle dynamics and structural differences observed at longer time scales arise mostly from the structural restraints imposed by the crystal lattice rigidity versus the flexibility in solution.