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Arjun K. Gopta 《数学物理学报(B辑英文版)》1999,19(1)
1IntroductionLetnbeanormalt--variatepopulationandXj,j=1,'',t(t23)bethej--thvariateinn.Letthesetofvariatesxl,''txtbepartitionedintoqmutuanyexclusivesubsetsofwhich.say,esubsetscontainexactlyonevariateandthereasoningk=q--esubsets(k21)containti,''ttkvariatesrespectively,wheref.22(y=1,''tk;e Z:=,t.=f).Nogeneralityislostinassumingthatthetvariatesareorderedsothatthefirst,belongtothe,subsetscontainingoneyaxiateeach,andnexttivariatesbelongto(I 1)--fhsubset,'',thelasttivariatestotheq--thsubset,whe… 相似文献
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L. S. Lussier C. Sandorfy H. OA L E-Thanh D. Vocelle 《Photochemistry and photobiology》1987,45(S1):801-808
Abstract— The Fourier-transform infrared spectra of chloroform-d solutions of conjugated imines CH3 CH=CHCH=NCH(CH3 )2 and CH3 CH2 CH=CHCH=CHCH=NCH(CH3 )2 and the related protonated species with HCl, HBr, HI, trichloro, dichloro, monobromo and monochloroacetic acids or propionic acid are presented. The effects of conjugation and protonation are examined. The results show that conjugation slightly increases the basicity of the Schiff bases. HCl, HBr and HI protonate the Schiff bases completely. The carboxylic acids protonate partially depending on their p K a , values. When the Schiff base contains two (or more) C=C bonds conjugated with C=N, the main C=C stretching band undergoes a strong intensification showing that sizeable dipole moment variations occur along the conjugated chain. 相似文献
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Anton Savitsky Oksana Gopta Mahir Mamedov John H. Golbeck Alexander Tikhonov Klaus M?bius Alexey Semenov 《Applied magnetic resonance》2010,37(1-4):85-102
Photosystem I (PS I) mutants from the cyanobacterium Synechocystis sp. PCC 6803 bearing point mutations to the axial ligands of A0A (M688NPsaA) and A0B (M668NPsaB) were studied by high-field W-band electron paramagnetic resonance (EPR) spectroscopy. It was found that the EPR observables of PS I from the M668NPsaB mutant were virtual identical to that of the wild type (WT), and are clearly distinct from the M688NPsaA mutant. In particular, the P 700 ·+ decay kinetics in the M688NPsaA mutant is significantly slower than in the WT or the M668NPsaB mutant. The analysis of the out-of-phase electron–electron dipolar electron spin echo envelope modulation shows that in the M668NPsaB mutant, the estimated distance of 26.0 ± 0.3 Å agrees well with the 25.8 Å distance for the P 700 ·+ A 1A ·? radical pair measured in the X-ray crystal structure. In the M688NPsaA mutant, two populations are found with estimated distances of 26.0 ± 0.3 and 25.0 ± 0.3 Å in a ratio of 0.7–0.3, which agree well with the 25.8 Å distance for the P 700 ·+ A 1A ·? radical pair and the 24.6 Å distance for the P 700 ·+ A 1B ·? radical pair measured in the X-ray crystal structure. The data confirm that under the experimental conditions employed in this work, which involve dark-adapted samples without the pre-reduction of the iron–sulfur clusters, electron transport in cyanobacterial PS I is asymmetrical at 100 K, with the majority of electron transfer taking place through the A-branch of cofactors. 相似文献
4.
Sarkisov OM Gostev FE Shelaev IV Novoderezhkin VI Gopta OA Mamedov MD Semenov AY Nadtochenko VA 《Physical chemistry chemical physics : PCCP》2006,8(48):5671-5678
The pulsed excitation of electronic levels coupled to specific nuclear modes by a 26 fs laser pulse at 706 nm creates a wavepacket in the nuclear space of photopystem I (PS I) of Synechocystis sp. strain PCC 6803 both in the ground state and in the one-exciton manifold. Fourier transform of transient decay curves shows several low frequency peaks. The most prominent Power Spectral Density (PSD) peaks are at omega = 49 cm(-1) and omega = 88 cm(-1). The peculiarity of the coherent wavepacket in the PS I of S. sp. strain PCC 6803 is the unique, long-lived 49 cm(-1) and 88 cm(-1) oscillations with decay times up to 10 ps. It was suggested that such a long-lived coherence is determined by a contribution of the ground state wavepacket. The dependence of these two PSD peaks on the probe wavelength resembles the profile of the transient absorption spectra of PS I. The pump-probe signal in the Soret region reflects the dynamics of the ground state wavepacket created by pulsed excitation of the Q(y)-band. It was shown that the multimode Brownian oscillator model allows a quantitative fit of the oscillatory patterns of the pump-probe signal to be obtained. 相似文献
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Jens Niklas Oxana Gopta Boris Epel Wolfgang Lubitz Mikhail L. Antonkine 《Applied magnetic resonance》2010,38(2):187-203
Photosystem I (PS I) contains two symmetric branches of electron transfer cofactors. In both the A- and B-branches, the phylloquinone
in the A1 site is π-stacked with a tryptophan residue and is H-bonded to the backbone nitrogen of a leucine residue. In this work,
we use optical and electron paramagnetic resonance (EPR) spectroscopies to investigate cyanobacterial PS I complexes, where
these tryptophan residues are changed to phenylalanine. The time-resolved optical data show that backward electron transfer
from the terminal electron acceptors to P700·+ is affected in the A- and B-branch mutants, both at ambient and cryogenic temperatures. These results suggest that the quinones
in both branches take part in electron transport at all temperatures. The electron-nuclear double resonance (ENDOR) spectra
of the spin-correlated radical pair P700·+A1·− and the photoaccumulated radical anion A1·−, recorded at cryogenic temperature, allowed the identification of characteristic resonances belonging to protons of the methyl
group, some of the ring protons and the proton hydrogen-bonded to phylloquinone in the wild type and both mutants. Significant
changes in PS I isolated from the A-branch mutant are detected, while PS I isolated from the B-branch mutant shows the spectral
characteristics of wild-type PS I. A possible short-lived B-branch radical pair cannot be detected by EPR due to the available
time resolution; therefore, only the A-branch quinone is observed under conditions typically employed for EPR and ENDOR spectroscopies. 相似文献
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