scholarly journals Chromophore Assignment in C-Phycocyanin from Mastigocladus laminosus

1987 ◽  
Vol 42 (3) ◽  
pp. 258-262 ◽  
Author(s):  
S. Siebzehnrübl ◽  
R. Fischer ◽  
H. Scheer
Keyword(s):  
Circular Dichroism ◽  
Binding Sites ◽  
Specific Binding ◽  
Reactive Site ◽  
Spectral Changes ◽  
Mastigocladus Laminosus ◽  
Specific Binding Sites ◽  
Close Proximity ◽  
Circular Dichroïsm ◽  
Unambiguous Assignment

C-phycocyanin from the cyanobacterium, Mastigocladus laminosus, and its subunits have been treated with ρ-chloromercuribenzenesulfonate (PCMS). A single reactive site was found on the 13- subunit, and assigned to the single free cystein-β109. The concomitant spectral changes (absorp­tion, fluorescence, circular dichroism), together with the known close proximity of cys-β109 to chromophore β82, allowed an unambiguous assignment of the three spectrally, biochemically and functionally different chromophores to specific binding sites on the two peptide chains (α84: 616-618, β82: 622-624, β153: 598-600 nm).

scholarly journals Intermediates of reversible photochemistry of phycoerythrocyanin α from Mastigocladus laminosus probed by low temperature absorption and circular dichroism spectroscopy

1999 ◽  
Vol 1 (1) ◽  
pp. 25-30 ◽  
Author(s):  
Kai-Hong Zhao ◽  
Hugo Scheer
Keyword(s):  
Circular Dichroism ◽  
Low Temperature ◽  
Circular Dichroism Spectroscopy ◽  
Spectral Changes ◽  
Mastigocladus Laminosus ◽  
Circular Dichroïsm

The reversible photochemistry of theα-subunit of phycoerythrocyanin (α-PEC) has been measured by low temperature absorption and circular dichroism in the range of 125K to 295 K. Below 185 K, the photochemistry is nearly silent; above 205 K, the photochemistry increases gradually without an indication of intermediates, and between 185 to 205K spectral changes in absorption and circular dichroism indicate an intermediate and/or changes in the interaction(s) between the chromophore and its environment.

Cytochemical and Subcellular Organization of the Shoot Apical Meristem of Dry and Germinating Jack Pine Embryos

1974 ◽  
Vol 4 (1) ◽  
pp. 39-54 ◽  
Author(s):  
A. J. Mia ◽  
D. J. Durzan
Keyword(s):  
Shoot Apex ◽  
Binding Sites ◽  
Specific Binding ◽  
Tritiated Water ◽  
Jack Pine ◽  
Specific Binding Sites ◽  
Close Proximity ◽  
Seed Reserves ◽  
Food Reserves ◽  
Rna And Dna

Water added to dry seeds of jack pine evoked changes at the shoot apex which reflected the mobilization and consumption of food reserves for the synthesis of new protoplasm and for the formation of the prospective shoot. In shoot apices the distal zone contained large cells having nuclei with low affinity for stains. Flank and subapical zones had smaller cells with densely stained nuclei. These features did not alter during imbibition nor after the first wave of mitosis at 96 h when radicles emerged from seeds. Cells in the distal zone divided rarely. Mitosis, most abundant in subapices, decreased acropetally to the distal zone.In dry seeds, protein bodies and amyloplasts increased in size and frequency per cell from the distal zone in the basipetal direction towards the flanks and subapical zone. During imbibition most proteinaceous reserves, rich in arginine N, disappeared from all cells of the shoot apex. Lipid bodies in distal cells were small, numerous, and disappeared slowly as germination proceeded. Proplastids, mitochondria, and unidentified pleomorphic bodies were distributed in close proximity to the nucleus particularly in apical cells.Products of imbibed tritiated water (nonexchangeable tritium), and tritiated D-glucose, thymine, thymidine, and uracil were localized at the shoot apex and revealed assimilatory patterns consistent with cytochemical zonation. The covalent incorporation of tritium from water, while spread through most cells, was greatest in nuclei of flank and subapical cells. The radioactivity from glucose was found mainly in cell walls. Labelling by uracil, thymine, and thymidine by salvage mechanisms was especially abundant in nuclei of the flanks. These events coincided with dense RNA and DNA staining during germination. Collectively, observations indicated that at the flanks, water and seed reserves were concentrated at specific binding sites for the synthesis and dispersion of macromolecules before the visual production of leaf primordia.

scholarly journals Specific Binding of Rubidium in Chlorella

1962 ◽  
Vol 45 (5) ◽  
pp. 959-977 ◽  
Author(s):  
Dan Cohen
Keyword(s):  
Active Transport ◽  
Binding Sites ◽  
Specific Binding ◽  
High Concentration ◽  
External Concentration ◽  
Specific Binding Sites ◽  
Dense Suspension ◽  
Concentration Of Ions ◽  
The Individual ◽  
A Site

Specific binding sites for potassium, which may be components of the carriers for active transport for K in Chlorella, were characterized by their capacity to bind rubidium. A dense suspension was allowed to take up Rb86 from a low concentration of Rb86 and a high concentration of ions which saturate non-specific sites. The amount bound was derived from the increase in the external concentration of Rb86 following addition of excess potassium. The sites were heterogeneous. The average affinity of Rb and various other ions for the sites was determined by plotting the degree of displacement of Rb86 against log molar concentration of the individual ions. Interpolation gave the concentration for 50 per cent displacement of Rb, which is inversely related to affinity. The order of affinity was not changed when the cells were frozen, or boiled either in water or in 70 per cent ethanol. The affinity is maximal for ions with a crystalline radius of 1.3 to 1.5 A and a high polarizability, and is not related to the hydrated radius or valency. It is suggested that binding groups in a site are rigidly arranged, the irregular space between them being 2.6 to 3.0 A across, so that affinity is high for ions of this diameter and high polarizability.

Studies of the uptake of macromolecules by cells. I. Uptake of proteins by cells of the Ehrlich–Lettré ascites carcinoma

1968 ◽  
Vol 46 (12) ◽  
pp. 1443-1450 ◽  
Author(s):  
Y. C. Choi ◽  
E. R. M. Kay
Keyword(s):  
Nucleic Acid ◽  
Cell Membrane ◽  
Binding Sites ◽  
Specific Binding ◽  
Protein Uptake ◽  
Specific Binding Sites ◽  
Model Protein ◽  
Uptake Process ◽  
Kinetics Of ◽  
Protein Treatment

The uptake of protein by cells of the Ehrlich–Lettré ascites carcinoma was characterized kinetically by using hemoglobin as a model protein. An attempt was made to show that the process is not an artefact due to nonspecific adsorption of protein to the cell membrane. The kinetics of the uptake process suggested that an interaction exists between the exogenous protein and specific binding sites on the membrane. Acetylation of hemoglobin enhanced the rate of uptake of this protein. Treatment of cells with neuraminidase, phospholipase A, and Pronase resulted in an inhibition of protein uptake. The experimental evidence for the uptake of hemoglobin was supported by evidence that L-serine-U-14C-labelled hemoglobin is transported into the cytoplasm and utilized subsequently, resulting in labelling of the nucleic acid nucleotides.

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