RESUMEN
Galectins are a class of carbohydrate-binding proteins named for their galactose-binding preference and are involved in a host of processes ranging from homeostasis of organisms to immune responses. As a first step towards correlating the carbohydrate-binding preferences of the different galectins with their biological functions, we determined carbohydrate recognition fine-specificities of galectins with the aid of carbohydrate microarrays. A focused set of oligosaccharides considered relevant to galectins was prepared by chemical synthesis. Structure-activity relationships for galectin-sugar interactions were determined, and these helped in the establishment of redundant and specific galectin actions by comparison of binding preferences. Distinct glycosylations on the basic lactosyl motifs proved to be key to galectin binding regulation--and therefore galectin action--as either high-affinity ligands are produced or binding is blocked. High-affinity ligands such as the blood group antigens that presumably mediate particular functions were identified.
Asunto(s)
Carbohidratos/química , Galectinas/metabolismo , Análisis por Micromatrices , Oligosacáridos/metabolismo , Antígenos de Grupos Sanguíneos/metabolismo , Humanos , Oligosacáridos/síntesis química , Unión Proteica , Relación Estructura-ActividadAsunto(s)
Alginatos/síntesis química , Ácidos Hexurónicos/síntesis química , Técnicas de Síntesis en Fase Sólida , Alginatos/química , Automatización , Secuencia de Carbohidratos , Cromatografía de Gases y Espectrometría de Masas , Ácidos Hexurónicos/química , Espectroscopía de Resonancia Magnética , Datos de Secuencia MolecularRESUMEN
A resorcinarene bearing four TEMPO units recognizes small molecules in solutions.
Asunto(s)
Fenilalanina/análogos & derivados , Fenilalanina/química , Marcadores de Spin , Calixarenos , Cristalografía por Rayos X , Óxidos N-Cíclicos , Espectroscopía de Resonancia por Spin del Electrón , Radicales Libres/química , Enlace de Hidrógeno , Modelos Moleculares , Estructura MolecularRESUMEN
For automated oligosaccharide synthesis to impact glycobiology, synthetic access to most carbohydrates has to become efficient and routine. Methods to install "difficult" glycosidic linkages have to be established and incorporated into the overall synthetic concept. Described here is the first automated solid-phase synthesis of oligosaccharides containing the challenging beta-mannosidic linkage. Carboxybenzyl mannoside building blocks proved effective beta-mannosylation agents and resulted in excellent conversion and good to moderate selectivities. [(Triisopropylsilyl)oxy]-methyl ether (Tom), served as an orthogonal, minimally intrusive, and readily cleavable protecting group for the elongation of the C3 position of mannose. The desired oligosaccharide products were readily separated from by-products containing unwanted stereoisomers using reverse-phase HPLC. The methods described here expand the scope of carbohydrates currently accessible by automation as many oligosaccharides of biological interest contain beta-mannosidic linkages.
Asunto(s)
Manosa/química , Oligosacáridos/síntesis química , Cromatografía Líquida de Alta Presión , Estructura Molecular , Oligosacáridos/químicaRESUMEN
The pharmacological exploitation of the galanin receptors as drug targets for treatment of epilepsy, depression, and pain has been hampered by the lack of workable compounds for medicinal chemists from random screening of large chemical libraries. The present work uses the tripeptidomimetic galnon and displays its presumed pharmacophores on a rigid molecular scaffold. The scaffold is related to marine natural products and presents three functional groups near one another in space, in a manner reminiscent of a protein surface. An active compound, Galmic, was identified from a small synthetic library and tested in vitro and in vivo for its affinity and efficacy at galanin receptors. Galmic has micromolar affinity for GalR1 receptors (Ki = 34.2 microM) and virtually no affinity for GalR2 receptors. In vitro, Galmic, like galanin, suppresses long-term potentiation in the dentate gyrus; it blocks status epilepticus when injected intrahippocampally or administered i.p. Galmic applied i.p. shows antidepressant-like effects in the forced-swim test, and it is a potent inhibitor of flinching behavior in the inflammatory pain model induced by formalin injection. These data further implicate brain and spinal cord galanin receptors as drug targets and provide an example of a systemically active compound based on a scaffold that mimics protein surfaces.