Probing the Binding of the Flavonoid Diosmetin to Human Serum Albumin by Multispectroscopic Techniques

Abstract

The binding mechanism of molecular interaction between diosmetin and human serum albumin (HSA) in a pH 7.4 phosphate buffer was studied using atomic force microscopy (AFM) and various spectroscopic techniques including fluorescence, resonance light scattering (RLS), UV-vis absorption, circular dichroism (CD), and Fourier transform infrared (FT-IR) spectroscopy. Fluorescence data revealed that the fluorescence quenching of HSA by diosmetin was a static quenching procedure. The binding constants and number of binding sites were evaluated at different temperatures. The RLS spectra and AFM images showed that the dimension of the individual HSA molecules were larger after interaction with diosmetin. The thermodynamic parameters, ΔH° and ΔS° were calculated to be -24.56 kJ mol(-1) and 14.67 J mol(-1) K(-1), respectively, suggesting that the binding of diosmtin to HSA was driven mainly by hydrophobic interactions and hydrogen bonds. The displacement studies and denaturation experiments in the presence of urea indicated site I as the main binding site for diosmetin on HSA. The binding distance between diosmetin and HSA was determined to be 3.54 nm based on the Förster theory. Analysis of CD and FT-IR spectra demonstrated that HSA conformation was slightly altered in the presence of diosmetin.

Interactions of Three Chalcones with Human Serum Albumin Revealed by Spectroscopic Techniques

“…The red shifts of the emission bands for the chalcones suggested that the combinations of drug and protein resulted in the structural changes of the chalcones. 25 These were consistent with the above conclusions that drug-HSA complexes have formed. In addition, 2′,4′,4-triHC, 2′,4′-diHC and 4-HC all showed single fluorescence emission bands along with the fluorescence intensity increasing obviously after interacting with HSA, which may be due to the excited state intramolecular proton transfer (ESPT).…”

“…(1) are listed in These results indicated that the fluorescence quenching process of HSA by three chalcones was mainly a static quenching. 25 Furthermore, these drugs and HSA formed complexes.…”

Probing the binding mechanisms of α-tocopherol to trypsin and pepsin using isothermal titration calorimetry, spectroscopic, and molecular modeling methods

“…For dynamic quenching, higher temperatures result in faster diffusion and greater quenching. The quenching constant increases with increasing temperature, but the reverse effect will be observed for static quenching [32]. The results show that the K SV values decrease with increasing temperature, and the values of k q are greater (Table 2), which suggests that the mechanism is static quenching [29].…”

Inhibitory kinetics and mechanism of kaempferol on α-glucosidase

“…This phenomenon suggested that kaempferol interacted with the C@O and CAN groups in the protein structure subunits, resulting in the rearrangement of polypeptide carbonyl hydrogen bonding pattern and finally altering the secondary structure of a-glucosidase (Naik, Chimatadar, & Nandibewoor, 2010). To further characterize the secondary structure change of a-glucosidase, the curve-fitted spectra of a-glucosidase infrared amide I bands in the presence and absence of kaempferol were analyzed (Zhang, Wang, & Pan, 2012) The contents of a-helix (1660-1650 cm À1 ), random coil (1648-1638 cm À1 ), b-turn (1680-1660 cm À1 ), b-sheet (1637-1610 cm À1 ) and b-antiparallel (1692-1680 cm À1 ) of free a-glucosidase were 30.6%, 27.5%, 24.1%, 11.6% and 6.2%, respectively (Fig. 2C).…”