4.6 Article

Fluorescence and Docking Studies of the Interaction between Human Serum Albumin and Pheophytin

Journal

MOLECULES
Volume 20, Issue 10, Pages 19526-19539

Publisher

MDPI
DOI: 10.3390/molecules201019526

Keywords

Talinum triangulare; pheophytin; human serum albumin; fluorescence spectroscopy; docking

Funding

  1. CAPES (Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior)
  2. CNPq (Conselho Nacional de Desenvolvimento Cientifico e Tecnologico)
  3. FAPERJ (Fundacao de Amparo a pesquisa do Estado do Rio de Janeiro)
  4. CAPES (Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior)
  5. CNPq (Conselho Nacional de Desenvolvimento Cientifico e Tecnologico)
  6. FAPERJ (Fundacao de Amparo a pesquisa do Estado do Rio de Janeiro)

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In the North of Brazil (Para and Amazonas states) the leaves of the plant Talinum triangulare (popular: cariru) replace spinach as food. From a phytochemical point of view, they are rich in compounds of the group of pheophytins. These substances, related to chlorophyll, have photophysical properties that give them potential application in photodynamic therapy. Human serum albumin (HSA) is one of the main endogenous vehicles for biodistribution of molecules by blood plasma. Association constants and thermodynamic parameters for the interaction of HSA with pheophytin from Talinum triangulare were studied by UV-Vis absorption, fluorescence techniques, and molecular modeling (docking). Fluorescence quenching of the HSA's internal fluorophore (tryptophan) at temperatures 296 K, 303 K, and 310 K, resulted in values for the association constants of the order of 10(4) L.mol(-1), indicating a moderate interaction between the compound and the albumin. The negative values of G degrees indicate a spontaneous process; H degrees = 15.5 kJ.mol(-1) indicates an endothermic process of association and S degrees = 0.145 kJ.mol(-1).K-1 shows that the interaction between HSA and pheophytin occurs mainly by hydrophobic factors. The observed Trp fluorescence quenching is static: there is initial non-fluorescent association, in the ground state, HSA:Pheophytin. Possible solution obtained by a molecular docking study suggests that pheophytin is able to interact with HSA by means of hydrogen bonds with three lysine and one arginine residues, whereas the phytyl group is inserted in a hydrophobic pocket, close to Trp-214.

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