64 research outputs found
Structure–activity relationships of dinucleotides: Potent and selective agonists of P2Y receptors
Dinucleoside polyphosphates act as agonists on purinergic P2Y receptors to mediate a variety of cellular processes. Symmetrical, naturally occurring purine dinucleotides are found in most living cells and their actions are generally known. Unsymmetrical purine dinucleotides and all pyrimidine containing dinucleotides, however, are not as common and therefore their actions are not well understood. To carry out a thorough examination of the activities and specificities of these dinucleotides, a robust method of synthesis was developed to allow manipulation of either nucleoside of the dinucleotide as well as the phosphate chain lengths. Adenosine containing dinucleotides exhibit some level of activity on P2Y1 while uridine containing dinucleotides have some level of agonist response on P2Y2 and P2Y6. The length of the linking phosphate chain determines a different specificity; diphosphates are most accurately mimicked by dinucleoside triphosphates and triphosphates most resemble dinucleoside tetraphosphates. The pharmacological activities and relative metabolic stabilities of these dinucleotides are reported with their potential therapeutic applications being discussed
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Preparation and characterization of liver cells made permeable to macromolecules by treatment with toluene
Isolated individual liver cells were made permeable to charged molecules and macromolecules by treatment with toluene, and the properties of such cells were examined in detail. The optimal conditions of toluene treatment, as determined by assay of aminoacyl-tRNA synthetase activities, was 7 to 9% toluene for 2 min at 0 degrees. Conditions are also described for maintaining the treated cells for periods up to 1 hour. Toluene treatment was found to be as efficient as various disruptive methods for making internal enzymes accessible to exogenous substrates, and this was true for enzymes in the cytosol, membrane, or organelle fractions. Electron microscopic and biochemical examination of toluen-treated cells indicated that they were relatively intact and lost only small amounts of cellular constituents to the suspension medium. The data in this paper suggest that toluene treatment of individual cells might prove useful for studies of macromolecular synthesis in liver
A technique for generalizing temporal durations in relational databases
Abstract We address the problem of generalizing temporal data concerning durations extracted from relational databases. Our approach is based on a domain generMization graph that defines a partial order specifying the generalization relations for a duration attribute. This domain generalization graph is reusable (i.e., can be used to generalize any duration attribute), adaptable {i.e., can be extended or restricted as appropriate for particular applications), and transportable (i.e., can be used with any database containing a duration attribute)
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