A multi-spectroscopic and computational simulations study to delineate the interaction between antimalarial drug hydroxychloroquine and human serum albumin

The effect of chrysin binding on the conformational dynamics and unfolding pathway of human serum albumin

Studies on the interactions between ligands and proteins provide insights into how a possible medication alters the structures and activities of the target or carrier proteins. The natural flavonoid aglycone Chrysin (CHR) has demonstrated anti-inflammatory, antioxidant, antiapoptotic, neuroprotective, and antineoplastic effects, both in vitro and in vivo. In this work, we investigated the impact of CHR binding on the as-yet-unexplored conformation, dynamics, and unfolding mechanism of human serum albumin (HSA). We determined CHR binding to HSA domain-II with the association constant (Ka) of 2.70 ± 0.21 × 105 M-1. The urea-induced sequential unfolding mechanism of HSA was used to elucidate the debatable binding location of CHR. CHR binding induced both secondary and tertiary structural alterations in the protein as studied by far-UV circular dichroism and intrinsic fluorescence spectroscopy. Red edge excitation shift (REES) indicated a decrease in conformational dynamics of the protein on the complex formation. This suggested an ordered compact and spatial arrangement of the CHR-boundmolecule. The binding of CHR was found to significantly modulate the urea-induced unfolding pathway of HSA. Urea-induced unfolding pathway of HSA became a two-state process (N-U) from a three-state process (N-I-U). The interaction of CHR is found to increase the thermal stability of the protein by ∼4 °C. This study focuses on the fundamental sciences and demonstrates how prospective medication compounds can alter the dynamics and stability of protein structure.

Spectroscopic investigation and structural simulation in human serum albumin with hydroxychloroquine/Silybum marianum and a possible potential COVID-19 drug candidate

In this study, the interaction between human serum albumin (HSA) and the hydroxychloroquine/Silybum marianum (HCQ/SM) mixture was investigated using various techniques. The observed high binding constant (Kb) and Stern-Volmer quenching constant (KSV) indicate a strong binding affinity between the HCQ/SM mixture and HSA. The circular dichroism (CD) analysis revealed that HCQ/SM induced conformational changes in the secondary structure of HSA, leading to a decrease in the α-helical content. UV-Vis analysis exhibited a slight redshift, indicating that the HCQ/SM mixture could adapt to the flexible structure of HSA. The experimental results demonstrated the significant conformational changes in HSA upon binding with HCQ/SM. Theoretical studies were carried out using molecular dynamics simulation via the Gromacs simulation package to explore insights into the drug interaction with HSA-binding sites. Furthermore, molecular docking studies demonstrated that HCQ/SM-HSA exhibited favorable docking scores with the receptor (5FUZ), suggesting a potential therapeutic relevance in combating COVID-19 with a value of -6.24 kcal mol-1. HCQ/SM exhibited stronger interaction with both SARS-CoV-2 virus main proteases compared to favipiravir. Ultimately, the experimental data and molecular docking analysis presented in this research offer valuable insights into the pharmaceutical and biological properties of HCQ/SM mixtures when interacting with serum albumin.

Synergistic antimicrobial activity, MD simulation studies and crystal structure of natural alcohol motif containing novel substituted cinnamates

A series of natural alcohols motif containing novel substituted cinnamates were developed and screened against five bacterial strains namely, Enterococcus faecal (E. faecalis), Escherichia coli (E. coli), Bacillus subtilis (B. subtilis), Pseudomonas aeruginosa (P. aeruginosa) and Klebsiella pneumonieae (K. pneumonieae). Among all cinnamates, YS17 was identified with 100% bacterial growth inhibition across the panel, except in E. faecalis with MIC values of 0.25 mg/mL against B. subtilis and P. aeruginosa whereas 0.125, 0.5 and 1 mg/mL against E. coli, K. pneumonieae and E. faecalis, respectively. The growth inhibitory property of YS17 was further validated by disk diffusion, synergistic study and in vitro toxicity assays. Interestingly, YS17 exhibits synergistic effect in combination with the standard drug Ampicillin (AMP). The single crystal structure analysis of YS4 and YS6 was also performed which reconfirmed their proposed structures. Molecular docking visualized significant non-covalent interactions between E. coli MetAP and YS17 and the structural and conformational changes were further analysed using MD simulation studies. Overall, the study provided a suitable core for further synthetic alterations for their optimization as an antibacterial agent. Communicated by Ramaswamy H. Sarma.

Comparative investigation on interaction between potent antimalarials and human serum albumin using multispectroscopic and computational approaches

This study performed a comparative investigation to explore the interaction mechanisms between two potential antimalarial compounds, JMI 346 and JMI 105, and human serum albumin (HSA), a vital carrier protein responsible for maintaining important biological functions. Our aim was to assess the pharmacological efficiency of these compounds while comprehensively analyzing their impact on the dynamic behavior and overall stability of the protein. A comprehensive array of multispectroscopic techniques, including UV-Vis. spectroscopy, steady-state fluorescence analysis, synchronous fluorescence spectroscopy, three-dimensional fluorescence and circular dichroism spectroscopy, docking studies, and molecular dynamics simulations, were performed to probe the intricate details of the interaction between the compounds and HSA. Our results revealed that both JMI 346 and JMI 105 exhibited promising pharmacological effectiveness within the context of malaria therapy. However, JMI 346 was found to exhibit a significantly higher affinity and only minor altered impact on HSA, suggesting a more favorable interaction with the protein on the dynamic behavior and overall stability of the protein in comparison to JMI 105. Further studies can build on these results to optimize the drug-protein interaction and enable the development of more potent and targeted antimalarial treatments.