PMID- 18402487
OWN - NLM
STAT- MEDLINE
DCOM- 20080717
LR  - 20131121
IS  - 1520-6106 (Print)
IS  - 1520-5207 (Linking)
VI  - 112
IP  - 17
DP  - 2008 May 1
TI  - Temperature dependence of electron transfer to the M-side bacteriopheophytin in 
      rhodobacter capsulatus reaction centers.
PG  - 5487-99
LID - 10.1021/jp800082m [doi]
AB  - Subpicosecond time-resolved absorption measurements at 77 K on two reaction 
      center (RC) mutants of Rhodobacter capsulatus are reported. In the D(LL) mutant 
      the D helix of the M subunit has been substituted with the D helix from the L 
      subunit, and in the D(LL)-FY(L)F(M) mutant, three additional mutations are 
      incorporated that facilitate electron transfer to the M side of the RC. In both 
      cases the helix swap has been shown to yield isolated RCs that are devoid of the 
      native bacteriopheophytin electron carrier HL (Chuang, J. I.; Boxer, S. G.; 
      Holten, D.; Kirmaier, C. Biochemistry 2006, 45, 3845-3851). For D(LL), depending 
      whether the detergent Deriphat 160-C or N-lauryl-N,N-dimethylamine-N-oxide (LDAO) 
      is used to suspend the RCs, the excited state of the primary electron donor (P*) 
      decays to the ground state with an average lifetime at 77 K of 330 or 170 ps, 
      respectively; however, in both cases the time constant obtained from 
      single-exponential fits varies markedly as a function of the probe wavelength. 
      These findings on the D(LL) RC are most easily explained in terms of a 
      heterogeneous population of RCs. Similarly, the complex results for 
      D(LL)-FY(L)F(M) in Deriphat-glycerol glass at 77 K are most simply explained 
      using a model that involves (minimally) two distinct populations of RCs with very 
      different photochemistry. Within this framework, in 50% of the D(LL)-FY(L)F(M) 
      RCs in Deriphat-glycerol glass at 77 K, P* deactivates to the ground state with a 
      time constant of approximately 400 ps, similar to the deactivation of P* in the 
      D(LL) mutant at 77 K. In the other 50% of D(LL)-FY(L)F(M) RCs, P* has a 35 ps 
      lifetime and decays via electron transfer to the M branch, giving P+HM- in high 
      yield (> or =80%). This result indicates that P* --> P(+)H(M)(-) is roughly a 
      factor of 2 faster at 77 K than at 295 K. In alternative homogeneous models the 
      rate of this M-side electron-transfer process is the same or up to 2-fold slower 
      at low temperature. A 2-fold increase in rate with a reduction in temperature is 
      the same behavior found for the overall L-side process P* --> P(+)H(L)(-) in 
      wild-type RCs. Our results suggest that, as for electron transfer on the L side, 
      the M-side electron-transfer reaction P* --> P(+)H(M)(-) is an activationless 
      process.
FAU - Chuang, Jessica I
AU  - Chuang JI
AD  - Department of Chemistry, Stanford University, Stanford, California 94305-5080, 
      USA.
FAU - Boxer, Steven G
AU  - Boxer SG
FAU - Holten, Dewey
AU  - Holten D
FAU - Kirmaier, Christine
AU  - Kirmaier C
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PT  - Research Support, U.S. Gov't, Non-P.H.S.
DEP - 20080411
PL  - United States
TA  - J Phys Chem B
JT  - The journal of physical chemistry. B
JID - 101157530
RN  - 0 (Imidoesters)
RN  - 0 (Pheophytins)
RN  - 0 (Photosynthetic Reaction Center Complex Proteins)
RN  - 17066-08-9 (N-lauryl iminodipropionate)
RN  - 17453-58-6 (bacteriopheophytin)
RN  - PDC6A3C0OX (Glycerol)
SB  - IM
MH  - Electron Transport
MH  - Glycerol/chemistry
MH  - Imidoesters/chemistry
MH  - *Models, Biological
MH  - Models, Molecular
MH  - Mutation
MH  - Phase Transition
MH  - Pheophytins/*chemistry/metabolism
MH  - Photosynthetic Reaction Center Complex Proteins/*chemistry/genetics/metabolism
MH  - *Rhodobacter capsulatus/genetics/metabolism
MH  - Spectrometry, Fluorescence
MH  - Spectrophotometry, Infrared
MH  - Temperature
MH  - Thermodynamics
EDAT- 2008/04/12 09:00
MHDA- 2008/07/18 09:00
CRDT- 2008/04/12 09:00
PHST- 2008/04/12 09:00 [pubmed]
PHST- 2008/07/18 09:00 [medline]
PHST- 2008/04/12 09:00 [entrez]
AID - 10.1021/jp800082m [doi]
PST - ppublish
SO  - J Phys Chem B. 2008 May 1;112(17):5487-99. doi: 10.1021/jp800082m. Epub 2008 Apr 
      11.