Andrey A. Demidov

Deconvolution of C-phycocyanin beta-84 and beta-155 chromophore absorption and fluorescence spectra of cyanobacterium Mastigocladus laminosus.

Absorption and fluorescence spectra of the C-phycocyanin beta-subunit were quantitatively deconvoluted into component spectra of the beta-84 and beta-155 chromophores. The deconvolution procedure was based on a theoretical treatment of polarization properties. Four kinds of spectra (absorption, emission, emission polarization, and excitation polarization) measured on C-phycocyanin isolated from the cyanobacterium Mastigocladus laminosus were used as the experimental data set. Without any assumption of spectral shape, the absorption and fluorescence spectra of both chromophores were unambiguously resolved and their fluorescence quantum yields were evaluated. By combining the spectra of the alpha-subunit, independently measured, with the resolved spectra of the beta-subunit, the fluorescence and fluorescence polarization spectra and the fluorescence quantum yield of the monomer were estimated; they agree with experimental values to within an acceptable error. Further, the matrix of energy transfer rates in the monomer was estimated; it gave a significantly different result (by up to 40%) from previously estimated ones.

Fluorescence polarization of triple-chromophore complexes with energy transfer.

The formula for the determination of a fluorescence polarization degree is derived for triple-chromophore complexes with energy transfer: P = (3B - 1 + 2A)/(3 + B + 4A). In this formula B = q(12) cos(2)(?(12)) + q(13) cos(2)(?(13)) + q(23) cos(2)(?(23)) and parameters A and q(ij) are dependent on the kinetic parameters of energy exchange and the chromophore spectroscopic parameters. The angle ?ij is the angle between the transition dipole moments of the i and j chromophores. The formula was tested for the particular case of the C-phycocyanin (C-PC) of the blue-green algae Agmenellum quadruplicatum, which contain three chromophores, α-84, β-84, and β155. Polarized spectra were calculated for both the emission and the excitation spectra of C-PC β subunits and monomers.

Determination of Chlorophyll a and Pheophytin a Concentrations in Acetone Extracts by Laser Fluorometry

We have used the technique of laser fluorometry for chlorophyll a and pheophytin a measurements in 90% acetone/water extracts of sea-water phytoplankton. In our method, the acetone Raman signal is used as an internal standard. We have shown that use of the second harmonic of a pulsed Nd:YAG laser (λ = 532 nm) makes it possible to measure pigment concentrations as low as 10 ng/L. It creates favorable conditions for high-efficiency analysis of the phytoplankton pigments in the oligotrophic areas of the world ocean and for investigations of the feed process of individual zooplankton samples.

Lidar mapping of phytoplankton and organic matter distributions in the Baltic Sea

The results of simultaneous lidar monitoring of phytoplankton (PP) and organic matter (OM) horizontal distributions in the subsurface layer of the Baltic Sea are presented in the paper. A special shipboard lidar system has been developed. Total length of the monitoring route was 8390 km. The horizontal distributions of near-surface PP and OM for the second half of May and the first ten days of June were reconstructed using the data obtained. The polluted areas near the industrially active regions were detected. Diurnal rhythms of PP fluorescence were measured in situ by lidar. It proved the necessity of adjustment of lidar data for such diurnal variations. The temporal divergence of detected structures was explored. For most parts of the area, averaged time of divergence for phytoplankton horizontal distribution was estimated as 1.2% per day.