Entropy-driven binding of octyl gallate in albumin: Failure in the application of temperature effect to distinguish dynamic and static fluorescence quenching

Autor(es)

de Carvalho Bertozo, Luiza ^[1] ; Fernandes, Ana J. F. C. ^[1] ; Yoguim, Mauricio I. ^[1] ; Bolean, Mayte ^[2] ; Ciancaglini, Pietro ^[2] ; Ximenes, Valdecir F. ^[1]

Afiliação do(s) autor(es)

^[1] UNESP Sao Paulo State Univ, Dept Chem, Fac Sci, Sao Paulo - Brazil

^[2] Univ Sao Paulo, Fac Philosophy Sci & Letters Ribeirao Preto, Dept Chem, Ribeirao Preto, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: JOURNAL OF MOLECULAR RECOGNITION; v. 33, n. 7 MAR 2020.
• Citações Web of Science: 0

Resumo

Fluorescence quenching is widely used to obtain association constants between proteins and ligands. This methodology is based on assumption that ground-state complex between protein and ligand is responsible for quenching. Here, we call the attention about the risk of using the temperature criterion for decision of applying or not fluorescence quenching data to measure association constants. We demonstrated that hydrophobic effect can be the major force involved in the interaction and, as such, superposes the well-established rationalization that host/guest complexation is weakened at higher temperatures due to loss of translational and rotational degrees of freedom. To do so, the complexation of bovine serum albumin with octyl gallate was studied by steady-state, time-resolved fluorescence spectroscopy and isothermal titration calorimetry. The results clearly demonstrated the complexation, even though the Stern-Volmer constant increased at higher temperatures (1.6 x 10(4) and 4.1 x 10(5) mol(-1) L at 20 degrees C and 40 degrees C), which could suggest a simple dynamic process and not complexation. The entropy-driven feature of the interaction was demonstrated by the unfavorable enthalpy ( increment H degrees = 104.4 kJmol(-1)) but favorable entropy ( increment S degrees = 447.5 Jmol(-1) K-1). The relevance of the ligand hydrophobicity was also evaluated by comparing ascorbic acid and its ester ascorbyl palmitate. Docking simulations showed a higher number of hydrophobic contacts and lower energy poses for the esters, confirming the experimental results. In conclusion, the well-established rationalization that host/guest complexation is weakened at higher temperatures is not straightforward for protein-ligand interactions. Hence, the temperature effect for a decision between static and dynamic quenching and its use to decide if a complexation at ground state is taking place between ligand and protein should not be used. (AU)

• Processo FAPESP: 14/50926-0 - INCT 2014: biodiversidade e produtos naturais
• Beneficiário: Vanderlan da Silva Bolzani
• Modalidade de apoio: Auxílio à Pesquisa - Programa BIOTA - Temático
• Processo FAPESP: 16/20549-5 - Desenvolvimento e aplicação de sondas fluorescentes e baseadas em dicroísmo circular para estudos de interação de ligantes com proteínas, caracterização de proteínas amiloides e determinação de atividade enzimática
• Beneficiário: Valdecir Farias Ximenes
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 16/22014-1 - Desenvolvimento de Sondas Fluorescentes para Determinação de Sítios de Ligação em Albumina: Estudo da Relação entre Estrutura Molecular, Constante de Associação e Especificidade
• Beneficiário: Luiza de Carvalho Bertozo
• Modalidade de apoio: Bolsas no Brasil - Doutorado