Glucagon Affinity Absorbents: Selective Binding of Receptors of Liver Cell Membranes

AFFINITY chromatography has been used in the rapid isolation of enzymes, antibodies, antigens and other ligand-binding proteins^1–6. Selective adsorbents with biological specificity perhaps may best be used in the resolution and isolation of complex biological structures and important regulatory macromolecules present in cells in very low amounts. For example, polypeptide and steroid hormone receptors, drug receptors, transport proteins and repressor molecules may be well suited for study by this technique because they display specific binding functions with a high degree of affinity.     

Antimalarial Properties of Imipramine and Amitriptyline12

Dietary riboflavin deficiency is known to diminish malarial parasitemia. In this study, we determined whether imipramine and amitriptyline, drugs which inhibit riboflavin metabolism, have antimalarial efficacy. In addition, we evaluated whether these drugs, like other antimalarial agents, increase the hemolytic response to ferriprotoporphyrin IX (FP). The growth of Plasmodium falciparum (FCR3) in the absence and presence of these drugs (10 to 75 μM) was measured by determining (³H)hypoxanthine uptake by intraerythrocytic parasites for 48 h in RPMI 1640 medium. The uptake of (³H)hypoxanthine was significantly reduced in a dose-dependent manner by both imipramine and amitriptyline. The IC₅₀ values of imipramine and amitriptyline at 48 h were 56 and 45 μM, respectively. Both drugs enhanced hemolysis induced by FP (10 or 20 μM). No hemolysis by these drugs was detected in the absence of FP. It is concluded that the tricyclic antidepressants, imipramine and amitriptyline, possess substantial antimalarial properties.     

Plasma Membrane Glycoproteins of Ciona intestinalis Spermatozoa that Interact with the Egg1

In the ascidian Ciona intestinalis the species-specific interaction between the spermatozoon and the egg occurs between the vitelline coat (VC) of the egg and the plasma membrane of the apical part of the head of the spermatozoa. Concanavalin A (Con A)-binding sites are present on this area of the sperm surface. We used Con A to identify and isolate the spermatozoon plasma membrane components that may be involved in the interaction with the VC. These glycoproteins have been identified on SDS-PAGE of a sperm membrane fraction (SMF) enriched with the extermal proteins, after incubation of the gel with ³H-Con A. Affinity chromatography on Con A-agarose has been used for the purification of sperm plasma membrane proteins with and affinity for the lectin. The biological activity of the Con A-retained fraction was determined with binding and fertilization assays.     

Variations in the composition and properties of the gum exuded by Acacia karroo Hayne in different African locations*

The variation in chemical composition of 15 specimens of the gum exudate from Acacia karroo Hayne, obtained from four different African locations, has been investigated. The range of analytical values found (e.g., specific rotation + 36° to + 67°; uronic acid 10.3 to 18.1%; rhamnose 4 to 10%) reflect the well-known variability of this Acacia species. The major analytical difference concerns the unusually wide range of molecular weights observed, i.e., 1.5 × 10⁵ to 48 × 10⁵. The material of highest molecular weight, from trees infested with Cerambycid beetles, is consumed by bush-babies (Galagidae).     

The scaling of colony size with nest volume in termites: a role in population dynamics?

相似文献