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Binding interaction of a novel fluorophore with serum albumins: steady state fluorescence perturbation and molecular modeling analysis.

Pal U, Pramanik SK, Bhattacharya B, Banerji B, Maiti NC - Springerplus (2015)

Bottom Line: The fluorescence yield of the compound substantially increased inside hydrophobic protein surface and ~30 nm decrease in Stokes' shift, compared to aqueous solution, was observed.Thus, the molecule appears as a new fluorescence probe to report the nature of its binding site in terms of increased fluorescence quantum yield and decreased Stokes' shift.Further it could be useful to detect and study the drug binding site of specific protein of interest.

View Article: PubMed Central - PubMed

Affiliation: Structural Biology and Bioinformatics Division, Council of Scientific and Industrial Research (CSIR)-Indian Institute of Chemical Biology (IICB), Kolkata, West Bengal India.

ABSTRACT
Fluorescence emission and anisotropy are widely used to measure the binding parameters and kinetic behavior of reactions that cause a change in the rotational time of a fluorescent molecule. We report here fluorescence emission and anisotropy behavior of a newly synthesized novel naphthalene base fluorophore (methyl 3-[(6-{[2-(tert-butoxy)-2-oxoethyl] (4-methoxyphenyl)amino}naphthalen-2-yl)formamido]propanoate) in several solution conditions including its binding to human and bovine serum albumin proteins both in their native and denatured states. The fluorescence yield of the compound substantially increased inside hydrophobic protein surface and ~30 nm decrease in Stokes' shift, compared to aqueous solution, was observed. Shift in fluorescence excitation peak position from the absorption peak of the molecule was ~8 nm in protein solution. This indicated possible alteration of excited state geometry of the compound by the globular fold of albumins. In addition, we measured the steady state fluorescence anisotropy of the molecule to evaluate several thermodynamic parameters and the results suggested the binding was energetically favorable. The measured ΔG° was ~-30 kJ mol(-1) and the derived dissociation constant was ~10(-6) M. The molecular docking analysis further highlighted the nonspecific association of the compound with the proteins and hydrophobic forces may have a significant role in the binding processes. Under the denatured condition of the protein, the compound lost its binding efficacy and reduction in fluorescence intensity was observed. Thus, the molecule appears as a new fluorescence probe to report the nature of its binding site in terms of increased fluorescence quantum yield and decreased Stokes' shift. It can also report the changes in the binding site due to global change in protein structure such as unfolding/misfolding often linked to several human disorder. Further it could be useful to detect and study the drug binding site of specific protein of interest.

No MeSH data available.


Related in: MedlinePlus

Determination of thermodynamic parameters of compound 5 binding from van’t Hoff’s plot. a Decrease in the binding equilibrium constant with the decreasing temperature for BSA-compound 5 interaction and the fitted van’t Hoff equation. b Increase in the binding equilibrium constant with the decreasing temperature for HSA-compound 5 interaction and the fitted van’t Hoff equation
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Fig3: Determination of thermodynamic parameters of compound 5 binding from van’t Hoff’s plot. a Decrease in the binding equilibrium constant with the decreasing temperature for BSA-compound 5 interaction and the fitted van’t Hoff equation. b Increase in the binding equilibrium constant with the decreasing temperature for HSA-compound 5 interaction and the fitted van’t Hoff equation

Mentions: Equilibrium constant of a reaction changes with the temperature (Fig. 3). Such a change can be explained by van’t Hoff’s equation, which in turn, gives the standard enthalpy and standard entropy changes for the reaction. The associations of the compound with serum albumins are thermodynamically favorable, which is evident from the decrease in Gibbs free energy (Table 2). Moreover, the binding with HSA is enthalpy driven (negative ΔH°) whereas the binding with BSA is entropy driven (positive ΔS°). It suggests that, despite the structural similarity in the two proteins, the interactions with HSA are thermodynamically different from that of BSA.Fig. 3


Binding interaction of a novel fluorophore with serum albumins: steady state fluorescence perturbation and molecular modeling analysis.

Pal U, Pramanik SK, Bhattacharya B, Banerji B, Maiti NC - Springerplus (2015)

Determination of thermodynamic parameters of compound 5 binding from van’t Hoff’s plot. a Decrease in the binding equilibrium constant with the decreasing temperature for BSA-compound 5 interaction and the fitted van’t Hoff equation. b Increase in the binding equilibrium constant with the decreasing temperature for HSA-compound 5 interaction and the fitted van’t Hoff equation
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4582037&req=5

Fig3: Determination of thermodynamic parameters of compound 5 binding from van’t Hoff’s plot. a Decrease in the binding equilibrium constant with the decreasing temperature for BSA-compound 5 interaction and the fitted van’t Hoff equation. b Increase in the binding equilibrium constant with the decreasing temperature for HSA-compound 5 interaction and the fitted van’t Hoff equation
Mentions: Equilibrium constant of a reaction changes with the temperature (Fig. 3). Such a change can be explained by van’t Hoff’s equation, which in turn, gives the standard enthalpy and standard entropy changes for the reaction. The associations of the compound with serum albumins are thermodynamically favorable, which is evident from the decrease in Gibbs free energy (Table 2). Moreover, the binding with HSA is enthalpy driven (negative ΔH°) whereas the binding with BSA is entropy driven (positive ΔS°). It suggests that, despite the structural similarity in the two proteins, the interactions with HSA are thermodynamically different from that of BSA.Fig. 3

Bottom Line: The fluorescence yield of the compound substantially increased inside hydrophobic protein surface and ~30 nm decrease in Stokes' shift, compared to aqueous solution, was observed.Thus, the molecule appears as a new fluorescence probe to report the nature of its binding site in terms of increased fluorescence quantum yield and decreased Stokes' shift.Further it could be useful to detect and study the drug binding site of specific protein of interest.

View Article: PubMed Central - PubMed

Affiliation: Structural Biology and Bioinformatics Division, Council of Scientific and Industrial Research (CSIR)-Indian Institute of Chemical Biology (IICB), Kolkata, West Bengal India.

ABSTRACT
Fluorescence emission and anisotropy are widely used to measure the binding parameters and kinetic behavior of reactions that cause a change in the rotational time of a fluorescent molecule. We report here fluorescence emission and anisotropy behavior of a newly synthesized novel naphthalene base fluorophore (methyl 3-[(6-{[2-(tert-butoxy)-2-oxoethyl] (4-methoxyphenyl)amino}naphthalen-2-yl)formamido]propanoate) in several solution conditions including its binding to human and bovine serum albumin proteins both in their native and denatured states. The fluorescence yield of the compound substantially increased inside hydrophobic protein surface and ~30 nm decrease in Stokes' shift, compared to aqueous solution, was observed. Shift in fluorescence excitation peak position from the absorption peak of the molecule was ~8 nm in protein solution. This indicated possible alteration of excited state geometry of the compound by the globular fold of albumins. In addition, we measured the steady state fluorescence anisotropy of the molecule to evaluate several thermodynamic parameters and the results suggested the binding was energetically favorable. The measured ΔG° was ~-30 kJ mol(-1) and the derived dissociation constant was ~10(-6) M. The molecular docking analysis further highlighted the nonspecific association of the compound with the proteins and hydrophobic forces may have a significant role in the binding processes. Under the denatured condition of the protein, the compound lost its binding efficacy and reduction in fluorescence intensity was observed. Thus, the molecule appears as a new fluorescence probe to report the nature of its binding site in terms of increased fluorescence quantum yield and decreased Stokes' shift. It can also report the changes in the binding site due to global change in protein structure such as unfolding/misfolding often linked to several human disorder. Further it could be useful to detect and study the drug binding site of specific protein of interest.

No MeSH data available.


Related in: MedlinePlus