Calorimetry and thermal analysis studies on the binding of 13-phenylalkyl and 13-diphenylalkyl berberine analogs to tRNAphe
The interaction of 13- monophenylalkyl and diphenylalkyl berberine analogs with tRNAphe has been investigated using various thermochemical techniques like thermal melting, isothermal titration calorimetry, and differential scanning calorimetry experiments. Thermal melting studies revealed that all the analogs stabilized the tRNAphe better than berberine. The binding affinity for the analogs was of the order of 105 M−1. Calorimetry results suggested that the binding of these analogs was predominantly entropy driven with small negative enthalpy contribution to the standard molar Gibbs energy. The temperature dependence of the standard molar enthalpy changes yielded negative values of standard molar heat capacity changes for the complexation revealing substantial hydrophobic contribution in the RNA binding of these analogs. An enthalpy–entropy compensation behavior was also seen in all the systems. The diphenylalkyl analogs were found to be more effective tRNAphe binders compared to the monophenylalkyl analogs. The utility of the present work lies in understanding the structural and energetic aspects of the interaction of these berberine analogs with tRNA, which may be useful in the development of RNA-targeted drugs.
Keywords13-substituted berberine analogs tRNAphe Binding Interaction Calorimetry Thermodynamics
This work was supported by grants from the Council of Scientific and Industrial Research (CSIR) network project GenCODE (BSC0123). D. Bhowmik is a NET-Senior Research Fellow of the University Grants Commission, Government of India. The authors thank all the colleagues of the Biophysical Chemistry Laboratory for help and cooperation at every stage of this work. Naxopharma srl, Italy acknowledges financial supports by the Italian Ministry of Economic Development, Grant No. 01705, awarded within sixth call of the EuroTransBio initiative, and by Regione Lombardia, Italy, Grant No. 13810040, awarded within Bando ATP2009.
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