title: [35S]GTP gamma S binding studies of amphiphilic drugs-activated Gi proteins: a caveat.
abstract: This paper documents a serious problem met during the testing of Gi protein-activating properties of a new series of synthetic compounds by measuring the induced binding of [(35)S]GTPgammaS to different subtypes of Gi protein. The problem arose from the strong affinity between [(35)S]GTPgammaS and the tested compounds, that are characterized by several (2-4) positive charges and high lipophilicity. Apparently, such affinity yields insoluble, labelled complexes that, also in the absence of Gi protein, are retained on the filters and give rise to false positive results.
authors.affiliation: Dipartimento di Scienze Farmaceutiche, Laboratorio di Progettazione, Sintesi e Studio di Eterocicli Biologicamente Attivi (HeteroBioLab), Università di Firenze, Sesto Fiorentino, FI, Italy.
authors.forename: Dina
authors.initials: D
authors.lastname: Manetti
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Di Cesare Mannelli
authors.forename: Silvia
authors.initials: S
authors.lastname: Dei
authors.forename: Luca
authors.initials: L
authors.lastname: Guandalini
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Martini
authors.forename: Martina
authors.initials: M
authors.lastname: Banchelli
authors.forename: Carla
authors.initials: C
authors.lastname: Ghelardini
mesh_terms: D004353:Drug Evaluation, Preclinical / Q000009:adverse effects; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000737:chemistry / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000737:chemistry / Q000378:metabolism*; D057927:Hydrophobic and Hydrophilic Interactions; D011485:Protein Binding / Q000187:drug effects / Q000502:physiology; D012995:Solubility; D013462:Sulfur Radioisotopes / Q000378:metabolism; D013500:Surface Tension / Q000187:drug effects; D013501:Surface-Active Agents / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology*
chemical_list: D013462:Sulfur Radioisotopes; D013501:Surface-Active Agents; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D019206:GTP-Binding Protein alpha Subunits, Gi-Go