Biological materials, specific binding

By contrast, the kinetics of transport across a biological membrane usually does not exhibit such a linear dependence on AC. Instead, the rate approaches an asymptote at high concentration differences, much as the rate of an enzymatic reaction approaches a maximum rate at high substrate concentrations (fig. 17.24d). This behavior suggests that the transport protein has a specific binding site for the material that it transports. The overall rate of transport is limited by the number of these sites in the membrane, and thus fits an... 

Determination of specific binding of the labelled peptides to biological materials was carried out with D341 Med human medulloblastoma cells derived from a tumour biopsy from a patient with a cerebellar medulloblastoma, which expresses high levels of somatostatin receptors. The cells were maintained as a continuous cell line in 10% foetal calf serum and zinc option media in a humidified atmosphere (37°C, 5% CO,). 

Gel chromatography on Sephadex LH-20 offers good separation of biologically active forms of vitamin A both in standard solutions and in biological materials [153]. Holasova and Blattn [154] studied specific binding of an active form of vitamin A, retinol, to retinol receptors. 

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