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.

scholarly journals Solubilization and characterization of substance P-binding sites from chick brain membranes

1988 ◽  
Vol 252 (2) ◽  
pp. 545-551 ◽  
Author(s):  
H P Too ◽  
M R Hanley
Keyword(s):  
Substance P ◽  
Binding Sites ◽  
Specific Binding ◽  
Chick Brain ◽  
High Concentration ◽  
Brain Membrane ◽  
Brain Membranes ◽  
Specific Binding Sites ◽  
Octyl Glucoside

Sites binding monoiodinated-Bolton-Hunter-reagent-labelled substance P were solubilized from 1-day-old-chick brain membrane by using non-ionic detergents (1% digitonin/1% n-octyl glucoside) and a high concentration of NaCl (0.5 M). The solubilized preparation retained the pharmacological properties of the high-affinity binding sites found in the native membrane. The high density of specific binding sites (approximately 2 pmol of binding sites/mg of protein) suggests that the chick brain membranes may be a useful source for the purification of the substance P-binding sites.

Arachidonate Transfer Between Platelets and Lipoproteins

1992 ◽  
Vol 68 (06) ◽  
pp. 719-726 ◽  
Author(s):  
Ingrid I Surya ◽  
Gertie Gorter ◽  
Jan Willem N Akkerman
Keyword(s):  
Binding Sites ◽  
Specific Binding ◽  
Human Platelets ◽  
Temperature Sensitive ◽  
High Concentration ◽  
Prolonged Incubation ◽  
Specific Binding Sites ◽  
Lipid Exchange ◽  
Exchange Processes ◽  
Platelet Functions

SummaryAlthough platelets have specific bindingsites for LDL and HDL, it is doubtful whether lipoproteins modulate platelet functions via receptor-mediated processes. We investigated platelet-lipoprotein interaction during prolonged incubation with concentrations of LDL and HDL that saturate the bindingsites within a few minutes. When [3H]arachidonate-labeled human platelets were incubated for 4 h with lipoproteins, part of the 3H-radioactivity transferred to LDL and to a lesser extent to HDL. The transfer was temperature-sensitive, unaffected by modification of lysine in LDL or indomethacin treatment of the platelets, and almost irreversible. [3H]arachidonate transfer to lipoproteins could be mimicked by incubating platelets with a high concentration of fatty acid free albumin. This showed, that the loss of 3H-radioactivity reflected a decrease in endogenous arachidonate, leading to impaired aggregation, secretion and thromboxane B2 formation in platelets after stimulation with thrombin but not with arachidonate. Thus, the decrease in platelet functions seen after long incubation with HDL is caused by depletion of platelet arachidonate. Despite an even stronger arachidonate depletion by LDL, this lipoprotein initiated arachidonate metabolism and secretion independent of specific binding sites for LDL on the platelet. Surprisingly, the major part of the secretion was preserved when the formation of prostaglandin endoperoxides/ thromboxane A2 was inhibited with indomethacin. These findings argue against a role for LDL and HDL receptors in the modulation of platelet functions and are more in favor of lipid exchange processes between platelets and lipoproteins.

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.

Microbial Receptor Assay for Rapi d Detection and Identification of Seven Families of Antimicrobial Drugs in Milk: Collaborative Study

1988 ◽  
Vol 71 (2) ◽  
pp. 304-316 ◽  
Author(s):  
Stanley E Charm ◽  
Ruey Chi
Keyword(s):  
Binding Sites ◽  
Specific Binding ◽  
Scintillation Counter ◽  
Collaborative Study ◽  
False Negative ◽  
Penicillin G ◽  
Specific Binding Sites ◽  
Receptor Assay ◽  
Relative Standard ◽  
Standard Deviations

Abstract A microbial competitive receptor assay for detecting residues of antibiotic families in milk was studied collaboratively by 13 laboratories. The drugs and levels (ppb) tested in this study i nclude penicillin G, 4.8; cephapirin, 5.0; cloxacillin, 100; tetracycline, 2000; chlortetracycline, 2000; oxytetracycline, 2000; erythromycin, 200; lincomycin, 400; clindamycin, 400; sulfamethazine, 75; sulfamethoxazole, 50; sulfisoxazole, 50; streptomycin, 1000; novobiocin, 50; and chloramphenicol, 800. In this method, microbial cells added to a milk sample provide specific binding sites for which 14C or 3H libeled drug competes with drug residues in the sample. The UC or H binding to the specific binding sites is measured in a scintillation counter and compared with a zero standard milk. If the sample is statistically different from the zero standard, it is positive. The assay takes about 15 min. The binding reaction occurs between the receptor site and the drug functional group, so all members of a drug family are detected. In this case, beta-lactams, tetracyclines, macrolides, aminoglycosides, novobiocin, chloramphenicol, and sulfonamides, including/^-aminobenzoic acid (PABA) and its other analogs, are detectable. The incidence of false negative determinations among samples is about 1%; the incidence of false positives is about 3%. For negative cases, the relative standard deviations for repeatability ranged from 0 to 5% and for reproducibility from 0 to 6%. For positive cases, relative standard deviations ranged from 0 to 13% for repeatability and from 0 to 14% for reproducibility. The method has been adopted official first action.

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