Search results for "medium"
showing 10 items of 3746 documents
EXPERIENCES OF STRUCTURE ANALYSES OF CHLOROPHENOL DIMERS AND TRIMERS FOUND IN DIFFERENT SAMPLES
1982
ABSTRACT Chlorophenol formulations (Kymi/Kymmene Co., wood preservatives), sawmill wood waste samples and different waste treatment product samples were analyzed for oligomeric by-products of the polychlorinated phenols. Structure types for 26 phenolic dimers, 45 neutral dimers and 13 phenolic trimers were determined by GC/MS. Types of one tetrachloro and one hexachloro compound detected remained unknown. Contents of by-products in chlorophenol formulations varied greatly depending on their production method. Chemical treatment of wastes with NaClO and NaOH lowered their contents of chlorophenols and phenolic dimers, but did not change (NaOH) or increased (NaClO) the contents of neutral dim…
Folding in vitro of light-harvesting chlorophyll a/b protein is coupled with pigment binding.
2002
The major light-harvesting chlorophyll a/b protein (LHCIIb) of the plant photosynthetic apparatus is able to self-organise in vitro. When the recombinant apoprotein, Lhcb1, is solubilised in the denaturing detergent sodium (or lithium) dodecylsulfate (SDS or LDS) and then mixed with chlorophylls and carotenoids under renaturing conditions, structurally authentic LHCIIb forms. Assembly of functional LHCIIb, as indicated by the establishment of energy transfer between complex-bound chlorophyll molecules, occurs in two apparent kinetic steps with time constants of 10 to 30 seconds and 50 to 300 seconds, depending on the reaction conditions. Here, we use circular dichroism (CD) in the far-UV ra…
Purification and identification of chlorophyll c1 from the green alga Mantoniella squamata
1987
Abstract The prasinophycean alga Mantoniella squamata contains besides chlorophyll a and b a third chlorophyll c -like pigment in its light-harvesting antenna. This third chlorophyll was purified by reverse phase and polyethylene chromatography in order to identify its chemical structure. The absorption and fluorescence spectra were measured not only from the doubly purified pigment, but also from its Mg-free derivates. The spectra were compared with those of authentic chlorophyll c and of Mg-2,4-desethyl-2,4-divinylpheoporphyrin a 5 monomethyl ester which was isolated from Rhodobacter capsulata . The results show that the pigment from Mantoniella agrees best with chlorophyll c 1 . In order…
Preparation of Native and Recombinant Light-Harvesting Chlorophyll-<I>a/b </I>Complex
2004
Procedures to isolate native light-harvesting chlorophyll-a/b complex (LHCIIb) and to reconstitute recombinant LHCIIb are described. Separation of trimeric from monomeric forms and free pigment by sucrose density-gradient ultracentrifugation can be applied to both native and reconstituted complexes. The preparations are characterized by their pigment composition, protein pattern, and spectral properties.
Methodical Studies in the Separation of Chlorophyll-Protein Complexes by Polyacrylamide Gel Electrophoresis
1980
Summary Chlorophyll-protein complexes from thylakoids of Sinapis alba plants were separated, using Tris-HCl and Tris-borate buffer in the sodium dodecyl sulphate acrylamide gel electrophoresis. In the electrophoretogram with Tris-borate buffer, 6 bands could be characterized in the gel pattern. In addition to the three major green zones (P-700-chlorophyll a-protein, light-harvesting chlorophyll a/b-protein, free pigment zone), which were also observed in experiments with the Tris-HC1 buffer, three further bands (LHCP 1 , LHCP 2 , CPa) were electrophoretically separated. An elongation of the electrophoretical period resulted especially in a decrease of the proportion of the light-harvesting …
Comparative analysis of the composition of two chlorophyll-b-containing light-harvesting complexes.
1990
The major light-harvesting complexes from Mantoniella squamata (Prasinophyceae) and from Chlorella fusca (Chlorophyceae) were analyzed with respect to polypeptide composition and pigmentation. It was found that the polypeptides of Mantoniella are smaller than those of Chlorella and bind twice the amount of pigment. We assume that the amount of pigment per polypeptide is of ecological as well as of taxonomical importance.
Influence of Heavy Metal Concentration on Chlorophyll Content in Pleurozium schreberi Mosses
2020
Abstract The aim of biomonitoring is assessment of environment condition. Biomonitoring studies with the use of mosses focus mainly on analytes accumulation and determining elements’ concentrations in the study area. It is often forgotten that a bioindicator should be alive during biomonitoring studies (which can be determined by, e.g., analysis of chlorophyll content). The objective of the carried out research was an assessment of the influence of selected heavy metals concentration: Ni, Cu, Zn, Cd and Pb accumulated by Pleurozium schreberi mosses during 3-month exposition within active biomonitoring, on their vitality, assessed by an analysis of a and b chlorophyll concentrations. The stu…
Pigment binding of photosystem I light-harvesting proteins.
2002
Light-harvesting complexes (LHC) of higher plants are composed of at least 10 different proteins. Despite their pronounced amino acid sequence homology, the LHC of photosystem II show differences in pigment binding that are interpreted in terms of partly different functions. By contrast, there is only scarce knowledge about the pigment composition of LHC of photosystem I, and consequently no concept of potentially different functions of the various LHCI exists. For better insight into this issue, we isolated native LHCI-730 and LHCI-680. Pigment analyses revealed that LHCI-730 binds more chlorophyll and violaxanthin than LHCI-680. For the first time all LHCI complexes are now available in t…
Water soluble chlorophyll binding protein of higher plants: A most suitable model system for basic analyses of pigment–pigment and pigment–protein in…
2011
Abstract This short review paper describes spectroscopic studies on pigment–pigment and pigment–protein interactions of chlorophyll (Chl) a and b bound to the recombinant protein of class IIa water soluble chlorophyll protein (WSCP) from cauliflower. Two Chls form a strongly excitonically coupled open sandwich dimer within the tetrameric protein matrix. In marked contrast to the mode of excitonic coupling of Chl and bacterio-Chl molecules in light harvesting complexes and reaction centers of all photosynthetic organisms, the unique structural pigment array in the Chl dimer of WSCP gives rise to an upper excitonic state with a large oscillator strength. This property opens the way for thorou…
The Light-Harvesting Chlorophyll a/b Complex Can Be Reconstituted in Vitro from Its Completely Unfolded Apoprotein
2003
The major light-harvesting chlorophyll a/b protein (LHCIIb) of higher plants is one of the few membrane proteins that can be refolded in vitro. During folding, the apoprotein is assembled with pigments to form a structurally authentic and functional pigment--protein complex. All reconstitution procedures used so far include solubilization of the apoprotein in sodium dodecyl sulfate (SDS) where the protein adopts approximately half of its alpha-helical folding present in the native structure. This paper shows that this preformed alpha-helix is not a prerequisite for LHCIIb folding in vitro. The apoprotein can also be reconstituted starting from a solution in guanidinium hydrochloride (Gnd) w…