Physico-Chemical nanomaterials science
Study of the Interaction of Bovine Serum Albumin with Gold Nanoparticles

Lesiuk A.I. 1, Kulish M. P.1, Dmytrenko O. P. 1, Busko T. O.1, 
Pavlenko O. L.1, Pundyk I.P.1, Pinchuk-Rugal T.M.1, 
Chegel V.I.2 , Lopatynskyi A.M. 2, Kanyuk M.I.3
1 Department of physics of functional materials, Physics Faculty, National Taras Shevchenko University of Kyiv, Glushkova prosp., 4, Kyiv-03039, Ukraine. 
E-mail: lesyuk.andrey@gmail.com
2 V.Ye. Lashkaryov Institute of Semiconductor Physics of the National Academy of Sciences of Ukraine,Nauki prosp., 41, Kyiv-03028, Ukraine.
3 Palladin Institute of Biochemistry of the National Academy of Sciences of Ukraine, Leontovycha str, 9, Kyiv-01601, Ukraine.

The interaction of bovine serum albumin (BSA) with gold nanoparticles (GNP) was investigated by analyzing the spectrum of fluorescence of tryptophan aminoacid residues in the structure of BSA molecule. 
The quenching of fluorescence intensity with increase of GNP concentration in the water solution was shown. GNPs are covered with citrate, diameter of the particles is . The spectra yield Stern-Volmer quenching constant , binding constant  and number of binding sites . Temperature dependence of the binding constants evidence on the prevailing static mechanism of the quenching. 
Thermodynamic parameters of the interaction were calculated. The negative binding energy of BSA-GNP conjugate  indicates on spontaneous character of the interaction. The positive change of entropy  is attributed to the van der Waals or/and electrostatic forces between BSA and GNP. The negative increment of enthalpy  indicates on the presence of hydrophobic interaction in BSA-GNP conjugates.