RESUMEN
Affinity-based chromatography assays encompass the use of solid supports containing immobilized biological targets to monitor binding events in the isolation, identification and/or characterization of bioactive compounds. This powerful bioanalytical technique allows the screening of potential binders through fast analyses that can be directly performed using isolated substances or complex matrices. An overview of the recent researches in frontal and zonal affinity-based chromatography screening assays, which has been used as a tool in the identification and characterization of new anti-cancer agents, is discussed. In addition, a critical evaluation of the recently emerged ligands fishing assays in complex mixtures is also discussed.
Asunto(s)
Antineoplásicos/análisis , Cromatografía de Afinidad , Humanos , LigandosRESUMEN
A bioanalytical platform combining magnetic ligand fishing for α-glucosidase inhibition profiling and HPLC-HRMS-SPE-NMR for structural identification of α-glucosidase inhibitory ligands, both directly from crude plant extracts, is presented. Magnetic beads with N-terminus-coupled α-glucosidase were synthesized and characterized for their inherent catalytic activity. Ligand fishing with the immobilized enzyme was optimized using an artificial test mixture consisting of caffeine, ferulic acid, and luteolin before proof-of-concept with the crude extract of Eugenia catharinae. The combination of ligand fishing and HPLC-HRMS-SPE-NMR identified myricetin 3-O-α-L-rhamnopyranoside, myricetin, quercetin, and kaempferol as α-glucosidase inhibitory ligands in E. catharinae. Furthermore, HPLC-HRMS-SPE-NMR analysis led to identification of six new alkylresorcinol glycosides, i.e., 5-(2-oxopentyl)resorcinol 4-O-ß-D-glucopyranoside, 5-propylresorcinol 4-O-ß-D-glucopyranoside, 5-pentylresorcinol 4-O-[α-D-apiofuranosyl-(1â6)]-ß-D-glucopyranoside, 5-pentylresorcinol 4-O-ß-D-glucopyranoside, 4-hydroxy-3-O-methyl-5-pentylresorcinol 1-O-ß-D-glucopyranoside, and 3-O-methyl-5-pentylresorcinol 1-O-[ß-D-glucopyranosyl-(1â6)]-ß-D-glucopyranoside.
Asunto(s)
Eugenia/química , Inhibidores de Glicósido Hidrolasas/aislamiento & purificación , Inhibidores de Glicósido Hidrolasas/farmacología , Glicósidos/aislamiento & purificación , Glicósidos/farmacología , Resorcinoles/aislamiento & purificación , Resorcinoles/farmacología , alfa-Glucosidasas/efectos de los fármacos , Brasil , Cromatografía Líquida de Alta Presión , Inhibidores de Glicósido Hidrolasas/química , Glicósidos/química , Ligandos , Estructura Molecular , Resonancia Magnética Nuclear Biomolecular , Hojas de la Planta/química , Resorcinoles/químicaRESUMEN
The purinergic receptor signaling system plays an important role in communication between cells in the nervous system and opens new opportunities for screening of potential drugs. Our objective was to explore the pharmacological properties and establish a new methodology for ligand screening for the P2X2 receptor, which has been developed by the combinatorial library approach Systematic Evolution of Ligands by Exponential enrichment (SELEX). To this end, membranes of 1321N1 cells stably transfected with rat P2X2 receptors were resuspended in 2% cholate detergent and subsequently coupled onto an immobilized artificial membrane (IAM). The IAM-cholate-P2X2 mixture was then dialyzed, centrifuged and packed into a FPLC column. Equilibrium binding to the receptor and competition between ATP and the purinergic antagonists suramin and 2'3'-O-(2,4,6-trinitrophenyl) adenosine 5'-triphosphate (TNP-ATP) were analyzed by a chromatographic assay using 32P alpha ATP as a radioligand. Our data indicate that suramin does not compete with ATP for the ligand binding site and TNP-ATP is a competitive antagonist, confirming previous studies [C.A. Trujillo, A.A. Nery, A.H. Martins, P. Majumder, F.A. Gonzalez, H. Ulrich, Biochemistry 45 (2006) 224-233]. In addition, we demonstrate that this assay can be used in in vitro selection procedures for RNA aptamers binding to P2X2 receptors. The results demonstrate that the receptor can be immobilized in a stable format and reused over an extended period of time, facilitating the exploration of ligand-receptor interactions and screening of combinatorial pools for possible ligands.
Asunto(s)
Adenosina Trifosfato/análogos & derivados , Cromatografía de Afinidad/métodos , Receptores Purinérgicos P2/metabolismo , Suramina/farmacología , Adenosina Trifosfato/farmacología , Animales , Astrocitoma/patología , Unión Competitiva , Técnicas de Cultivo de Célula , Línea Celular Tumoral , Evaluación Preclínica de Medicamentos , Colorantes Fluorescentes/metabolismo , Humanos , Ligandos , Modelos Biológicos , Neuronas/efectos de los fármacos , Técnicas de Placa-Clamp , Antagonistas del Receptor Purinérgico P2 , Ratas , Receptores Purinérgicos P2/genética , Receptores Purinérgicos P2X2 , Proteínas Recombinantes/antagonistas & inhibidores , Proteínas Recombinantes/metabolismo , Técnica SELEX de Producción de Aptámeros , TransfecciónRESUMEN
Immobilized enzyme reactors (IMERs) for on-line enzymatic studies are useful tool to select specific inhibitors and may be used for direct determination of drug-receptor binding interactions and for the rapid on-line screening to identify specific inhibitors. This technique has been shown to increase the stability of enzymes. The enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) plays an important role in the life cycle of the Trypanosoma cruzi and it has become a key target in the drug discovery program for Chagas' disease. Crystallographic studies have indicated that there are significant inter-species differences in GAPDH activity and sensitivity. For example the active sites of GAPDH in T. cruzi and humans differ by a substitution of ASP(210) (T. cruzi) by Leu(194) in human. Based on this information we initiated the study to develop optimal conditions for the covalent immobilization of the human GAPDH enzyme on a modified capillary support (400 mm x 0.10 mm). The chromatographic separation of NAD from NADH was achieved using a RP-Spherex-diol-OH (10 cm x 0.46 cm, 10 microm, 100 A) column. By using multidimensional HPLC chromatography system it was possible to investigate the activity and kinetic parameters of the GAPDH-IMER. The values obtained for D-GA3P and NAD were K(m)=3.5+/-0.2 mM and 0.75+/-0.04 mM, respectively, and were compared with values obtained with the free enzyme. The activity of the immobilized GAPDH has been preserved for over 120 days.