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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

Compound 5 binding is an excited state phenomenon. a The changes in compound 5 fluorescence excitation spectra upon addition of BSA. b Normalized absorption (blue) and fluorescence excitation (yellow) spectra of compound 5 overlapped with fluorescence excitation spectrum (green) in presence of BSA
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Fig4: Compound 5 binding is an excited state phenomenon. a The changes in compound 5 fluorescence excitation spectra upon addition of BSA. b Normalized absorption (blue) and fluorescence excitation (yellow) spectra of compound 5 overlapped with fluorescence excitation spectrum (green) in presence of BSA

Mentions: Fluorophore binding to a protein often results in an altered ground state electronic property, which can be visualized by a change in the absorption spectrum. However, the absorption spectrum of compound 5 does not change due to its binding with the serum albumins (Additional file 1: Figure S2). It indicates that the ground state geometry of compound 5 inside the hydrophobic groove of serum albumins remains the same as in the solution. Interestingly, when we recorded the excitation spectrum of compound 5 in presence of serum albumins (Fig. 4, Additional file 1: Figure S3), we observed ~8 nm red shift in the wavelength of excitation maximum (330–338 nm). It indicates that the excited state geometry of compound 5 within the binding site of serum albumin gets altered with the possible formation of an exciplex.Fig. 4


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)

Compound 5 binding is an excited state phenomenon. a The changes in compound 5 fluorescence excitation spectra upon addition of BSA. b Normalized absorption (blue) and fluorescence excitation (yellow) spectra of compound 5 overlapped with fluorescence excitation spectrum (green) in presence of BSA
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig4: Compound 5 binding is an excited state phenomenon. a The changes in compound 5 fluorescence excitation spectra upon addition of BSA. b Normalized absorption (blue) and fluorescence excitation (yellow) spectra of compound 5 overlapped with fluorescence excitation spectrum (green) in presence of BSA
Mentions: Fluorophore binding to a protein often results in an altered ground state electronic property, which can be visualized by a change in the absorption spectrum. However, the absorption spectrum of compound 5 does not change due to its binding with the serum albumins (Additional file 1: Figure S2). It indicates that the ground state geometry of compound 5 inside the hydrophobic groove of serum albumins remains the same as in the solution. Interestingly, when we recorded the excitation spectrum of compound 5 in presence of serum albumins (Fig. 4, Additional file 1: Figure S3), we observed ~8 nm red shift in the wavelength of excitation maximum (330–338 nm). It indicates that the excited state geometry of compound 5 within the binding site of serum albumin gets altered with the possible formation of an exciplex.Fig. 4

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