Th. Joo et al., DYNAMICS IN ISOLATED BACTERIAL LIGHT-HARVESTING ANTENNA (LH2) OF RHODOBACTER-SPHAEROIDES AT ROOM-TEMPERATURE, Journal of physical chemistry, 100(6), 1996, pp. 2399-2409
The underlying dynamics of the B800 absorption band in isolated LH2 of
Rb. sphaeroides at room temperature is studied by transient absorptio
n, transient grating, and photon echoes using 30 fs pulses. The energy
transfer time from B800 to B850 is determined to be 800 fs, similar t
o the value reported previously. The three pulse stimulated photon ech
o identifies several important contributions to the B800 absorption li
ne shape and thereby the dynamics of the system involved: several low
frequency intramolecular vibrations; ultrafast bath (solvent and prote
in) responses, and static inhomogeneity longer than the time scale of
B800 to B850 energy transfer make significant contributions. Transient
absorption decay is nonexponential as found previously. It is argued
that the fast component in the two-exponential analysis of the transie
nt absorption signal originates from vibrational relaxation within the
B800 absorption band. Calculations of the nonlinear signals based on
the optical transition frequency correlation function, M(t), including
all three contributions (intramolecular vibrations, ultrafast bath (s
olvent and protein) responses, and static inhomogeneity) are presented
, and a form for M(t) is obtained by fitting the three pulse photon ec
ho experimental data.