Exploring the binding interactions of janus green blue with serum albumins from spectroscopic and calorimetric studies aided by in silico calculations

Photo-Physical Characteristics of Janus Green B in Different Solvents and its Interaction Mechanism with Silver Nanoparticles

This work explores the effects of solvent polarity on Janus Green B (JGB) photophysical properties. The Lippert-Mataga, Billot, and Ravi equations were utilized to calculate the singlet-state excited dipole moments (µe) and ground state dipole moments (µg) using absorption and fluorescence spectra analyses. The results showed an increase in the former, which is suggestive of electronic structural alterations upon excitation. Analysis of fluorescence quantum yield values revealed that JGB's environment had an impact on its emission characteristics; it was particularly sensitive to silver nanoparticles, suggesting possible interactions. While simulations of electron density, electrostatic potential, and energy gap (Eg) helped to understand the electronic structure of JGB, theoretical absorption spectra produced by Time Dependent Density Function Theory (TD-DFT) calculations offered insights into electronic transitions during absorption. To sum up, the present study contributes to our comprehension of the molecular behavior of JGB in various solvents by elucidating the intricate relationship among solvent polarity, molecular environment, and interactions with silver nanoparticles. Additionally, theoretical computations support the interpretation of experimental results.

Interaction of food colorant indigo carmine with human and bovine serum albumins: A multispectroscopic, calorimetric, and theoretical investigation

In this work we have studied the interaction of the food dye Indigo-Carmine (IndC) with the most studied model transport proteins i.e. human and bovine serum albumin (HSA & BSA). A multispectroscopic approach was used to analyze the details of the binding process. The intrinsic fluorescence of both the albumins was significantly quenched by IndC and the quenching was both static and dynamic in nature with the former being dominant. The HSA-lndC and BSA-IndC distance after complexation was determined by Förster resonance energy transfer (FRET) method which suggested efficient energy transfer from the albumins to IndC. Thermodynamics of serum protein-IndC complexation was estimated by isothermal titration calorimetry (ITC) which revealed that the binding was enthalpy driven. Circular dichroism (CD) and FTIR spectroscopy revealed that the binding of IndC induced secondary structural changes in both the serum proteins. Synchronous and 3D fluorescence spectroscopy revealed that the binding interaction caused microenvironmental changes of protein fluorophores. Molecular docking analysis suggested that hydrogen bonding and hydrophobic interactions are the major forces involved in the complexation process.

Comparative study of the interaction mechanism of astilbin, isoastilbin, and neoastilbin with CYP3A4

The interactions of human CYP3A4 with three selected isomer flavonoids, such as astilbin, isoastilbin and neoastilbin, were clarified using spectral analysis, molecular docking, and molecular dynamics simulation. During binding with the three flavonoids, the intrinsic fluorescence of CYP3A4 was statically quenched in static mode with nonradiative energy conversion. The fluorescence and ultraviolet/visible (UV/vis) data revealed that the three flavonoids had a moderate and stronger binding affinity with CYP3A4 due to the order of the Ka1 and Ka2 values ranging from 104 to 105  L·mol-1 . In addition, astilbin had the highest affinity with CYP3A4, then isoastilbin and neoastilbin, at the three experimental temperatures. Multispectral analysis confirmed that binding of the three flavonoids resulted in clear changes in the secondary structure of CYP3A4. It was found from fluorescence, UV/vis and molecular docking analyses that these three flavonoids strongly bound to CYP3A4 by means of hydrogen bonds and van der Waals forces. The key amino acids around the binding site were also elucidated. Furthermore, the stabilities of the three CYP3A4 complexes were evaluated using molecular dynamics simulation.

Interactions between hydroxylated polycyclic aromatic hydrocarbons and serum albumins: Multispectral and molecular docking analyses

Hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs) can bind to serum albumin and influence their distribution and elimination in organisms. Herein, multispectral analysis and molecular docking methods were used to investigate the binding mechanism of two OH-PAHs, 1-hydroxyphenanthrene (1-OHPhe) and 9-hydroxyphenanthrene (9-OHPhe), with two homologous serum albumins, human serum albumin (HSA) and bovine serum albumin (BSA). The quenching constants of HSA with 1-OHPhe and 9-OHPhe were much larger than those for BSA. Energy transfer from the tryptophan (Trp) residues in HSA to 1-OHPhe and 9-OHPhe was more probable than from Trp in BSA. The interactions of 1-OHPhe and 9-OHPhe with Trp in HSA and BSA altered the microenvironment of Trp. Molecular docking results revealed that the binding modes and binding forces of 1-OHPhe and 9-OHPhe with HSA and BSA were different. The two OH-PAHs were used as fluorescent probes to analyze the microenvironmental hydrophobicities of HSA and BSA, which were distinctly different. The structural difference between HSA and BSA induced significant variations in their binding behavior with 1-OHPhe and 9-OHPhe. Moreover, HSA was more susceptible to 1-OHPhe and 9-OHPhe than BSA. This work suggests that the differences between the two serum albumins should be considered in related studies.