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Spectroscopy of Photosynthetic Pigment-Protein Complex LHCII

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Gruszecki W., Zubik M., Luchowski R., Grudzinski W., Gryczynski Z., Gryczynski I.

Acta Physica Polonica A

2012

vol. 121

issue 2

397-400

Light-harvesting pigment-protein complex of photosystem II is the most abundant membrane protein in the biosphere, comprising more than half chlorophyll molecules. The protein plays a role of photosynthetic antenna, collecting solar radiation and transferring excitations towards the reaction centers, where electric charge separation takes place. Efficient excitation energy capture and transfer requires unique organization of the complex and unique photophysical properties of the accessory pigments: chlorophylls and carotenoids. LHCII is also a place where extremely harmful singlet oxygen may be generated, under strong illumination conditions. Several physical mechanisms have been found in LHCII, operating to protect the photosynthetic apparatus against light-induced damage, including chlorophyll triplet and singlet excitations quenching by carotenoids. In this paper we discuss the results of our recent studies, carried out with the application of several molecular spectroscopy techniques (electronic absorption, fluorescence, resonance Raman and FTIR), designed to investigate molecular mechanisms responsible for regulation of excitation density in LHCII. Among the most interesting findings are the light-induced molecular configuration changes of the LHCII-bound xanthophylls, leading to conformational rearrangements of the protein. These mechanisms are discussed in terms of excessive excitation quenching in the pigment-protein complex subjected to overexcitation. Such an activity seems to represent a vital regulatory process in the photosynthetic apparatus, at the molecular level, protecting plants against photodegradation.

Advances in Fluorescence Spectroscopy: Multi-Photon Excitation, Engineered Proteins, Modulation Sensing and Microsecond Rhenium Metal-Ligand Complexes

100%

Lakowicz J., Gryczynski I., Tolosa L., Dattelbaum J., Castellano F., Li L., Rao G.

Acta Physica Polonica A

1999

vol. 95

issue 1

179-196

The technology and applications of fluorescence spectroscopy are rapidly advancing. In this overview presentation we summarize some recent developments from this laboratory. Two and three-photon excitation have been observed for a wide variety of intrinsic and extrinsic fluorophores, including tryptophan, tyrosine, DNA stains, membrane probes, and even alkanes. It has been possible to observe multi-photon excitation of biopolymers without obvious photochemical or photo-thermal effects. Although not described in our lecture, another area of increasing interest is the use of engineered proteins for chemical and clinical sensing. We show results for the glucose-galactose binding protein from E. coli. The labeled protein shows spectral changes in response to micromolar concentrations of glucose. This protein was used with a novel sensing method based on the modulated emission of the labeled proteins and a long lifetime reference fluorophore. And finally, we describe a recently developed rhenium complex which displays a lifetime near 3ľs in oxygenated aqueous solution. Such long lifetime probes allow detection of microsecond dynamic processes, bypassing the usual nanosecond timescale limit of fluorescence. The result of these developments in protein engineering, sensing methods, and metal-ligand probe chemistry will be the increased use of fluorescence in clinical chemistry and point-of-care analyses.

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2 Acta Physica Polonica A

1 2012

1 1999

2 Gryczynski I.

1 Castellano F.

1 Dattelbaum J.

1 Grudzinski W.

1 Gruszecki W.

1 Gryczynski Z.

1 Lakowicz J.

1 Li L.

1 Luchowski R.

1 Rao G.

1 Tolosa L.

1 Zubik M.

Search results

Spectroscopy of Photosynthetic Pigment-Protein Complex LHCII

Advances in Fluorescence Spectroscopy: Multi-Photon Excitation, Engineered Proteins, Modulation Sensing and Microsecond Rhenium Metal-Ligand Complexes