ABSTRACT
Anabaena azollae, a presumptive isolate from Azolla filiculoides, was immobilized in polyurethane foam, hydrophilic polyvinyl foam and alginate. When viewed by low-temperature scanning electron microscopy a thick mucilage layer covered the surface of both cells and matrix; this closely resembles the mode of attachment of the symbiont Anabaena in the Azolla leaf cavity. The heterocyst frequency of the immobilized A. azollae doubled relative to free-living cells and reached a level of 14-17%. Immobilization induced increases in both hydrogen production via nitrogenase or hydrogenase and in the rates and stabilization of acetylene reduction (N2-fixation). Ammonia production by immobilized cells with L-methionine-D,L-sulfoximine (MSX) is greater than that of freeliving cells. Immobilized cells without MSX were, however, able to excrete ammonium at lower rates thus emulating the characteristic of the symbiotic cyanobacteria (A. azollae) in the leaf cavity of Azolla.
ABSTRACT
In an attempt to solve the controversy about the evaluation of the molar absorption coefficient of PChl(ide), this coeffecient is estimated in this work by using an original experimental approach. The calculated molar absorption coefficient of PChl(ide) is 30.4.10(3) l mole(-1) cm(-1) at 626 nm in acetone 80%; it is close to that derived from the specific absorption coefficient of Koski and Smith when assurning that the pigment extracted by these authors was the esterified pigment: PChl. Sets of equations for the quantification of Chl(ide) a, Chl b and PChl(ide) in 80% acetone extracts are derived.
ABSTRACT
In an attempt to solve the controversy about the evaluation of the molar absorption coefficient of PChl(ide), this coefficient is estimated in this work by using an original experimental approach. The calculated molar absorption coefficient of PChl(ide) is 30.4.10(3) 1 mole(-1) cm(-1) at 626 nm in acetone 80%; it is close to that derived from the specific absorption coefficient of Koski and Smith when assuming that the pigment extracted by these authors was the esterified pigment: PChl. Sets of equations for the quantification of Chl(ide) a, Chl b and PChl(ide) in 80% acetone extracts are derived.
ABSTRACT
Distribution of proteins, protochlorophyllide and photoactivity was studied in fractions obtained from bean etioplast membranes purified by linear or discontinuous sucrose density gradient centrifugation. The polypeptide pattern of two selected membrane fractions was examined by means of polyacrylamide gel electrophoresis. Both fractions contained the doublet of molecular weights 34.000-35.000 characteristic of NADPH-Protochlorophyllide oxido-reductase but differed by accompanying proteins. When both fractions were illuminated, protochlorophyllide was photoreduced in chlorophyllide fluorescing at 688 nm. During a subsequent 30 min. dark period, the emission peak shifted rapidly up to 678 nm in one of the fractions while it moved slowly to 683 nm in the other one. The possible occurrence of two phototransformable protochlorophyllide-complexes is discussed. Delta-aminolevulinic acid pretreatment of etiolated leaves led to an increase in the amount of proteins in the etioplast membranes.
Subject(s)
Chlorophyll/analogs & derivatives , Chloroplasts/ultrastructure , Intracellular Membranes/ultrastructure , Plant Proteins/isolation & purification , Plants/ultrastructure , Protochlorophyllide/isolation & purification , Cell Fractionation , Light , Molecular Weight , PhotosynthesisABSTRACT
77 K absorption and fluorescence spectra are measured during incubation of etiochloroplast isolated from pine cotyledons and suspended in buffers with or without various co-factors (GSH, ATP, CoA Abbreviations: PChl(ide) = protochlorophyll(ide); PChlideF657 = protochloro-phyllide-lipoprotein complex with fluorescence maximum at 657 nm; Chl(ide) = chlorophyll(ide); PEG = polyethylene glycol; DCIP = 2-6-dichlorophenol indophenol; ALA = \gd aminolevulinic acid; ATP = adenosine 5\t' triphosphate; CoA = coenzyme A; NADPH = nicotinamide-adenine dinucleotide phosphate, reduced. ) and NADPH. It is shown that, in the absence of co-factors, rapid spectral changes due to denaturation of the protein-pigment complexes occur. The spectral changes differ according to whether denaturation occurs in the light or in the dark. The rate of denaturation of the Ch1-protein complexes is significantly lowered when co-factors are added and a protective effect of NADPH on the PChlide-protein complexes was observed.
ABSTRACT
Etiochloroplasts isolated from dark-grown pine cotyledons fed with δ-aminolevulinic acid (ALA Abbreviations: ALA=\Gd-aminolevulinic acid; Chl(ide) = chlorophyll(ide); PChlide = protochlorophyllide; PChlideA636, PChlideA650=forms of protochlorophyllide absorbing light maximally at the wavelength indicated in nm; PChlideF635, PChlideF657=PChlide forms exhibiting a fluorescence maximum at the wavelength indicated; ALA-Pchlide=PChlide formed by an exogenous ALA treatment; NADPH = nicotineamide adeninedinucleotide phosphate. ) contain, in addition to the chlorophyll forms, two protochlorophyllide complexes which emit fluorescence around 635 nm and 657 nm respectively (ALA-PChlideF635 and PChlideF657). By a combination of light flashes and periods of darkness, it is possible to phototransform PChlideF657 and thereafter, if NADPH is added to the system, to re-form this pigment-complex from the pool of ALA-PChlideF635 during the dark periods. The process of phototransformation followed by the re-formation of PChlideF657 in the presence of NADPH can be obtained in vitro five to six times consecutively. The role of NADPH in the formation of the PChlideF657 complex is discussed.
