A large geometric distortion in the first photointermediate of rhodopsin, determined by double-quantum solid-state NMR.
Double-quantum magic-angle-spinning NMR experiments were performed on 11,12-(13)C(2)-retinylidene-rhodopsin under illumination at low temperature, in order to characterize torsional angle changes at the C11-C12 photoisomerization site. The sample was illuminated in the NMR rotor at low temperature (~120 K) in order to trap the primary photointermediate, bathorhodopsin. The NMR data are consistent with a strong torsional twist of the HCCH moiety at the isomerization site. Although the HCCH torsional twist was determined to be at least 40°, it was not possible to quantify it more closely. The presence of a strong twist is in agreement with previous Raman observations. The energetic implications of this geometric distortion are discussed.
School of Chemistry, University of Southampton, SO17 1BJ, Southampton, UK. mariac@soton.ac.uk
Maria
M
Concistrè
Ole G
OG
Johannessen
Neville
N
McLean
Petra H M
PH
Bovee-Geurts
Richard C D
RC
Brown
Willem J
WJ
Degrip
Malcolm H
MH
Levitt
D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D011789:Quantum Theory; D012243:Rhodopsin / Q000737:chemistry*; D013696:Temperature
C015017:bathorhodopsin; D012243:Rhodopsin