Photophysical and molecular docking approach on the interaction of water-soluble simple keto sugar with acridinedione dyes

Abstract

Photophysical studies in association with molecular docking (MD) methods were employed in the determination of various molecular interactions existing between d-Fructose in the presence of a photoinduced electron transfer (PET) and non-PET based acridinedione (AD) dyes in water. Addition of fructose to AD dyes resulted in a decrease in the absorbance at the longest wavelength absorption maxima accompanied with the formation of an isosbestic point signifying a ground state complex formation. The ground state interaction between fructose and dye is presumably attributed to hydrogen-bonding (HB) and was authenticated by MD studies. Interestingly, the excited state characteristics of PET dye (ADR1) is found to be entirely different from that of non-PET dye (ADR2) on the introduction of fructose. A fluorescence quenching phenomenon is observed in PET dye, whereas an enhancement results in that of a non-PET dye. Fructose promotes electron transfer (ET) through space resulting in a decrease in the fluorescence intensity of ADR1 dye. On the contrary, it suppresses the PET process in ADR2 dye resulting in an increase in the quantum yield. Fluorescence lifetime studies of fructose with AD dyes results in a multi exponential lifetime with varying proportions. The presence of biexponential lifetime components justifies the existence of more than one distinguishable micro heterogenous environment in the aqueous phase containing unequal proportion of distribution of fructose and water molecules around the close vicinity of AD dyes. The local excited (LE) state of the fluorophore experiences a large variation in the excited state such that the emission intensity and fluorescence lifetime are governed by solute induced and solvent mediated HB interactions. MD studies further establish the existence of HB interaction of dye-fructose, wherein the dye acts as the HB donor and sugar as the acceptor. Docking techniques establishes clear and authentic information on the HB donor and acceptor sites in dye and sugar molecule resulting in a most stable conformer. The nature of interaction of a simple sugar molecule with water soluble fluorophores are explored in depth by fluorescence techniques in coordination with MD methods is imparted in the present study.