In this report, the substitution of the oxygen group (=O) of Tetraphenylcyclopentadienone with =CR
2
group (R = methyl ester or nitrile) was found to have tuned the electro-optical properties of the molecule. Although both groups are electrons withdrawing in nature, their absorption from UV-vis spectra analysis was observed to have been blue-shifted by methyl ester substitution and red-shifted by nitrile substitution. Interestingly, these substitutions helped to enhance the overall intensity of emission, especially in the context of methyl ester substitution whereby the emission was significantly boosted at higher concentrations due to hypothesized restrictions of intramolecular motions. These observations were explained through detailed descriptions of the electron withdrawing capability and steric properties of the substituents on the basis of density functional theory calculations.
The primary reaction
mechanism of cytochrome c (Cyt c) was elucidated for two redox forms of ferric
(oxidized) and ferrous (reduced) Cyt c by measuring
their transient absorption (TA) spectra using a homemade sub-10 fs
broadband NUV laser pulses system. The TA traces measured in the broad
probe wavelength region were analyzed by the global analysis method
to study the electronic dynamics. The difference of relaxation dynamics
dependent on the excitation bandwidth enabled us to elucidate that
the 2.5 ps component in ferrous Cyt c can be assigned
to intramolecular vibration energy redistribution and not to vibrational
cooling, which was not clear until this work. The temporal resolution
of 10 fs observes TA signal modulation caused by the molecular vibration
in the time domain, which can be used to calculate the instantaneous
frequency of the molecular vibration mode. The observed vibrational
dynamics has visualized that the heme structure changes in 0.8 ps
for ferric Cyt c and in >1.0 ps for ferrous Cyt c. These estimated lifetimes of vibrational dynamics reflect
vibrational relaxation in the ground state of ferric Cyt c and electronic transition from the S2 state to the S1 state in ferrous
Cyt c, respectively.
In this study, we investigated the ultrafast dynamics of bacteriorhodopsins (BRs) from Haloquadratum walsbyi (HwBR) and Haloarcula marismortui (HmBRI and HmBRII). First, the ultrafast dynamics were studied for three HwBR samples: wild-type, D93N mutation, and D104N mutation. The residues of the D93 and D104 mutants correspond to the control by the Schiff base proton acceptor and donor of the proton translocation subchannels. Measurements indicated that the negative charge from the Schiff base proton acceptor residue D93 interacts with the ultrafast and substantial change of the electrostatic potential associated with chromophore isomerization. By contrast, the Schiff base proton donor assists the restructuring of the chromophore cavity hydrogen-bond network during the thermalization of the vibrational hot state. Second, the ultrafast dynamics of the wild-types of HwBR, HmBRI, and HmBRII were compared. Measurements demonstrated that the hydrogen-bond network in the extracellular region in HwBR and HmBRII slows the photoisomerization of retinal chromophores, and the negatively charged helices on the cytoplasmic side of HwBR and HmBRII accelerate the thermalization of the vibrational hot state of retinal chromophores. The similarity of the correlation spectra of the wild-type HmBRI and D104N mutant of HwBR indicates that inactivation of the Schiff base proton donor induces a positive charge on the helices of the cytoplasmic side.
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