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F F Litvin

Publications and source records attributed to F F Litvin.

At least 37 records · Page 2Linked to original sources
PubMedDate not supplied

[Study of energy migration between native forms of chlorophyll at -196 degrees C by the method of sensitized fluorescence].

Mathematical decomposition of fluorescence spectra of chloroplasts and cells measured under monochromatic excitation in the regions of absorption maxima of the main native forms allowed the authors to calculate the efficiency of energy migration between forms. It is shown that 80--100% of absorbed quanta flow to the Chl 738/708 form (bean) in photosystem 1, whereas in photosystem 2, the Chl 695/690 and Chl 703/698 forms are terminal energy acceptors. Efficient backward energy transfer between the Chl 680/676 and Chl 686/682 forms and the existence of energy migration pathways passing one or two steps of the energy stairway formed by the energy levels of the chlorophyll forms are found. It is shown that chlorphyll b is not an intermediate link in the process of energy transfer from carotenoids to chlorophyll a. The intrinsic fluoresence quantum yields of the native forms are calculated.

Chlorophyll↗
PubMedDate not supplied

[Study of different types of chlorophyll a aggregates in solutions and films by absorption and luminescence derivative spectroscopy].

The second derivative of absorption, fluorescence and fluorescence excitation spectra of chlorophyll a in concentrated solutions and films was investigated. More than 14 forms of pigment aggregates, which can be divided into two types--with narrow 8-10nm) and wide (25-40nm) low temperature (-196 degrees C) spectra bands, were found. For the most part of the aggregated forms, the position and half width of the bands, as well as the Stokes shift and relative quantum yield were determined. The comparison of the spectral characteristics points to the indentity of the aggregates and corresponding native forms of Chl. a. It is shown that the universal relationship between absorption and fluorescence bands in applicable to the aggregates of the two types and the energy of resonance interaction between monomers in the aggregates is evaluated.

Alkanes↗
PubMedDate not supplied

[Dynamics of the biosynthesis of native chlorophyll forms from initial stages to the completion of the greening process in etiolated leaves].

The succession of the formation of the native chlorophill forms and the development of the energy migration between them was studied by means of the comparison of three spectrum types: absorption, fluorescence and fluorescence excitation, and of their second derivatives. Quantitatively the chlorophyll accumulation in 9 native forms was followed by means of mathematical disintegration of the spectra using computer.

Chlorophyll↗
PubMedDate not supplied

[Luminescence of bacteriorhodopsin in purple membranes from Halobacterium haolbium cells].

Red luminescence of purple membranes from Halobacterium halobium cells was found out, and its emission, excitation and polarization spectra were investigated. Simultaneous parallel measurements of absorption and luminescence changes in one sample brought about by the action of light were also carried out. The bands in the spectra can be attributed to a number of bacteriorhodpsin (BR) forms: BR(595,520), BR(650,575),BR(600-620), BR(700,625), BR(730,660) BR(780,695), where the number above is the position of the luminescence maxima, below--that of absorption. Proceding from the quantum yield of the luminescence (10(-3)) and of photoreaction (10(-1)) of BR, the photoisomerization rate constant of the latter was estimated (10(11) sec(-1). The temperature dependence of the luminescence quantum yield points to the existence of two or three quenching processes with different activation energies. BR phosphorescence was not observed in the region 500-1100 nm. High degree (36%) os luminescence polarization shows that there is no homogeneous energy transfer between BR molecules, or there is regularity in orientation of their dipoles. Energy migration from the bulk of carotenoids to BR was not found. However limited heterogeneous transfer between the different BR forms cannot be ruled out. The absence (or limitation) of migration indicated that there is a spatial separation of the chromophores. Data on possible participation of triplet states in the BR photoconversions are discussed.

Bacteriorhodopsins↗
PubMedDate not supplied

[Photoinduced inhibition and stimulation of respiration in cells of Halobacterium halobiums kinetics, action spectra, relationship to photoinduction of deltapH].

Along with the inhibition illumination also causes the stimulation of the respiration of H. halobium R1 cells. When light is switched off photoinhibition of respiration (PIR) decays much faster (tau 1/2=12 sec) than photostimulation (PSR) (tau 1/2=60 sec). This allows the evaluation of the contribution of the each phase into the total change of the respiration rate. PIR prevails in neutral and alkaline media (at pH 6.8 the amplitude ratio of PSR/PIR=0.3). At the same conditions light induced alkalization of the medium is observed, which at high light intensities is followed by acidification. The half rise time of PIR is 0.5 divided by 0.8 sec under excitation with short light flashes at 18C and pH 6.8. When pH of the medium is reduced the rate of dark respiration decreases, PSR amplitude increases, PIR is almost not changed and light-induced alkalinization of the medium decreases. At pH 5.5 PSR prevails: at light of 10(5) erg/(cm(2).s) the ratio PSR/PIR=2. The maximum value of PIR and PSR at 18C reaches 20-30 percent of the dark respiration level. Uncouplers (CCCP, DNF) and inhibitor (DCCD) of phosphorylation suppress PIR and light induced alkalinization of the medium and significantly (5-7 times at Ph 6.8) increase PSR and light induced acidification. The action spectra show that bacteriorhodopsin is responsible for all the observed light induced changes of O2 and H+ exchange; carotinoids do not participate in sensibilization. It is suggested that photophosphorylation is necessary for PIR and that PSR is caused by the rise of internal pH due to light induced efflux of protons mediated by bacteriorhodopsin.

Bacteriorhodopsins↗
PubMedDate not supplied

[Fluorescence of rhodopsins and its relation to primary processes of light energy transformation].

A new area of the investigation of visual and bacterial rhodopsins--fluorescence spectroscopy of the pigments is discussed. Fluorescence properties are considered in relation to photochemical transformations of the pigments at low temperatures. A number of fluorescent states of the pigments are described. It is shown that the excited states of bacteriorhodopsin and visual rhodopsin are characterized by a series of common features. The analysis of general properties of the pigments excited states allows a conclusion that the singlet excited states take part in the photoreaction. The photoreaction scheme is discussed in which structural changes of the chromophore take place already in the excited state.

Animals↗