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661.
The development of carbohydrate-based therapeutics has been frustrated by the low affinities that characterize protein-carbohydrate complexation. Because of the oligomeric nature of most lectins, the use of multivalency may offer a successful strategy for the creation of high-affinity ligands. The solid-phase evaluation of libraries of peptide-linked multivalent ligands facilitates rapid examination of a large fraction of linker structure space. If such solid-phase assays are to replicate solution binding behavior, the potential for intermolecular bivalent binding on bead surfaces must be eliminated. Here we report the solid-phase synthesis and analysis of peptide-linked, spatially segregated mono- and bivalent ligands for the legume lectin concanavalin A. Bead shaving protocols were used for the creation of beads displaying spatially segregated binding sequences on the surface of Tentagel resins. The same ligands were also synthesized on PEGA resin to determine the effect of ligand presentation on solid-phase binding. While we set out to determine the lower limit of assay sensitivity, the unexpected observation that intermolecular bivalent ligand binding is enhanced for bivalent ligands relative to monovalent ligands allowed direct observation of the level of surface blocking required to prevent intermolecular bivalent ligand binding. For a protein with binding sites separated by 65 A, approximately 99.9% of Tentagel(1) surface sites and 99.99% of the total sites on a PEGA bead must be blocked to prevent intermolecular bivalent binding. We also report agglutination and calorimetric solution-phase binding studies of mono- and bivalent peptide-linked ligands. 相似文献
662.
Carroll A. Snyder Mark A. Thorn James E. Klijanowicz Philip L. Southwick 《Journal of heterocyclic chemistry》1982,19(3):603-607
Treatment of easily prepared l-substituted-4-benzylidene-2,3-dioxopyrrolidines with ammonium formate produces 1,2,4,6,7,8-hexahydro-2,6-disubstituted-8-aryldipyrrolo [3,4-b:3′,4′-e]pyridine-3,5-diones (II), usually in yields of 50 to 60%. Aromatization of the dihydropyridine ring of the hexahydroderivatives II yields corresponding 1,2,6,7-tetrahydro-2,6-disubstituted-8-aryldipyrrolo[3,4-b:3′,4′-e]pyridine-3,5-diones (III). These compounds appear to be the first to incorporate the dipyrrolo[3,4-b:3′,4′-e]pyridine ring system. 相似文献
663.
The oxetane ring in taxol 总被引:2,自引:0,他引:2
Wang M Cornett B Nettles J Liotta DC Snyder JP 《The Journal of organic chemistry》2000,65(4):1059-1068
Numerous structure-activity studies combining synthesis and bioassay have been performed for the anti-cancer drug Taxol. The four-membered D-ring, an oxetane, is one of four structural features regarded to be essential for biological activity. This proposition is examined by application of a Taxol-epothilone minireceptor, K(i) estimation for microtubule binding and docking of Taxol analogues into a model of the Taxol-tubulin complex. In this way, we evaluate the two characteristics considered responsible for oxetane function: (1) rigidification of the tetracyclic Taxol core to provide an appropriate framework for presenting the C-2, C-4, C-13 side chains to the microtubule protein and (2) service as a hydrogen-bond acceptor. An energy decomposition analysis for a series of Taxol analogues demonstrates that the oxetane ring clearly operates by both mechanisms. However, a broader analysis of four-membered ring containing compounds, C- and D-seco derivatives, and structures with no oxetane equivalent underscores that the four-membered ring is not necessary for Taxol analogue bioactivity. Other functional groups and ligand-protein binding characteristics are fully capable of delivering Taxol biobehavior as effectively as the oxetane D-ring. This insight may contribute to the design and development of novel anticancer drugs. 相似文献
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666.
Geld TL Neal H Akerlof C Chapman J Errede D Ken MT Kesten P Meyer DI Nitz D Thun R Tschirhart R Abachi S Derrick M Kooijman P Musgrave B Price L Repond J Sugano K Blockus D Brabson BB Brom J Jung C Ogren H Rust DR Snyder A Cork B Baringer P Bylsma BG Debonte R Low EH McIlwain RL Miller DH Ng CR Rangan K Shibata E 《Physical review D: Particles and fields》1992,45(11):3949-3954
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We demonstrate, in both two and three dimensions, how a self-guided beam in a non-Kerr medium is split into two beams on weak illumination. We also provide an elegant physical explanation that predicts the universal character of the observed phenomenon. Possible applications of our findings to guiding light with light are also discussed. 相似文献
670.