Evaluation of the Q
                            
                                y
                             absorption band maximum in a light-harvesting complex of the bacterial photosynthetic center Thermochromatium tepidum

A novel dispersive liquid-liquid semi-microextraction (DLLsME) procedure for copper(II) preconcentration is proposed. The system containing copper(II) and 6,7-dihydroxy-2,4-diphenylbenzopyrylium chloride (DHDPhB), after addition a mixture of chloroform and methanol becomes cloudy and the formation of the organic phase was observed immediately. The optimal conditions of DLLsME were found to be: pH 5, absorption band maximum was 570 nm, 1 cm3 of 1 × 10–3 mol/dm3 of DHDPhB, and mixed extractant containing 1 cm3 of chloroform and 1 cm3 of methanol. Under optimal conditions, the calibration plot was linear in the range of copper(II) concentration 4.32–65 μg/dm3 and the limit of detection was 1.29 μg/dm3. The rocks and tap water samples were successfully analyzed according to the suggested procedure with RSD no more than 4.9%.

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Manifestation of protein conformations in the B850 absorption band of light-harvesting complex LH2

Chemical Physics ◽

10.1016/j.chemphys.2013.06.010 ◽

2013 ◽

Vol 423 ◽

pp. 9-14 ◽

Cited By ~ 9

Author(s):

Julius Meldaikis ◽

Oksana Zerlauskiene ◽

Darius Abramavicius ◽

Leonas Valkunas

Keyword(s):

Absorption Band ◽

Light Harvesting ◽

Protein Conformations ◽

Light Harvesting Complex

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Macroorganisation and flexibility of thylakoid membranes

Biochemical Journal ◽

10.1042/bcj20190080 ◽

2019 ◽

Vol 476 (20) ◽

pp. 2981-3018 ◽

Cited By ~ 8

Author(s):

Petar H. Lambrev ◽

Parveen Akhtar

Keyword(s):

Light Harvesting ◽

Current Knowledge ◽

Three Dimensional ◽

Photosynthetic Apparatus ◽

Dynamic Responses ◽

State Transitions ◽

Photochemical Quenching ◽

Light Harvesting Complex ◽

Complex Ii ◽

Light Harvesting Complex Ii

Abstract The light reactions of photosynthesis are hosted and regulated by the chloroplast thylakoid membrane (TM) — the central structural component of the photosynthetic apparatus of plants and algae. The two-dimensional and three-dimensional arrangement of the lipid–protein assemblies, aka macroorganisation, and its dynamic responses to the fluctuating physiological environment, aka flexibility, are the subject of this review. An emphasis is given on the information obtainable by spectroscopic approaches, especially circular dichroism (CD). We briefly summarise the current knowledge of the composition and three-dimensional architecture of the granal TMs in plants and the supramolecular organisation of Photosystem II and light-harvesting complex II therein. We next acquaint the non-specialist reader with the fundamentals of CD spectroscopy, recent advances such as anisotropic CD, and applications for studying the structure and macroorganisation of photosynthetic complexes and membranes. Special attention is given to the structural and functional flexibility of light-harvesting complex II in vitro as revealed by CD and fluorescence spectroscopy. We give an account of the dynamic changes in membrane macroorganisation associated with the light-adaptation of the photosynthetic apparatus and the regulation of the excitation energy flow by state transitions and non-photochemical quenching.

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