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Updated: Jun 24, 2026

Measuring G-protein-coupled Receptor Signaling via Radio-labeled GTP Binding
Published on: June 9, 2017
[35S]GTP gamma S binding studies of amphiphilic drugs-activated Gi proteins: a caveat
Dina Manetti1, Lorenzo Di Cesare Mannelli, Silvia Dei
1Dipartimento di Scienze Farmaceutiche, Laboratorio di Progettazione, Sintesi e Studio di Eterocicli Biologicamente Attivi (HeteroBioLab), Università di Firenze, Sesto Fiorentino, FI, Italy.
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.
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