Binding of ibuprofen to human hemoglobin: elucidation of their molecular recognition by spectroscopy, calorimetry, and molecular modeling techniques

Insight into the effect of ibuprofen on the permeability of the membrane: a molecular dynamic simulation study

Studying interactions between drugs and cell membranes is of great interest to designing novel drugs, optimizing drug delivery, and discerning drug mechanism action. In this study, we investigated the physical properties of the bilayer membrane model of POPC upon interaction with ibuprofen (IBU) using molecular dynamics simulations. The area per lipid (APL) was calculated to describe the effect of ibuprofen on the packing properties of the lipid bilayer. The APL was 0.58 nm2 and 0.63 nm2 for the membrane in low and high IBU respectively, and 0.57 nm2 for the membrane without IBU. Our finding showed that the mean square deviation (MSD) increased with increased ibuprofen content. In addition, the order parameter for the hydrocarbon chain of lipids increased with increased ibuprofen content. There was an increment in the transfer free energy after the head group region while it was maximum in the hydrophobic core for hydrogen peroxide (H2O2) (∼6.2 kcal.mol-1) and H2O (∼3.4 kcal.mol-1) which then decreased to respective values of (∼4.6 kcal.mol-1), and (∼2.3 kcal.mol-1) at the center of the bilayer in the presence of IBU. It seems that in the presence of ibuprofen, the free energy profile of the permeability of water and H2O2 significantly decreased. These findings show that ibuprofen significantly influences the physical properties of the bilayer by decreasing the packing and intermolecular interaction in the hydrocarbon chain region and increasing the water permeability of the bilayer. These results may provide insights into the local cytotoxic side effects of ibuprofen and its underlying molecular mechanisms.Communicated by Ramaswamy H. Sarma.

Molecular Interaction of Functionalized Nanoplastics with Human Hemoglobin

Humans are exposed to excessive nanoplastics (NPs) which have ample affinity for globular proteins. We investigated the interaction of functionalized polystyrene nanoplastics (plain: PS, carboxy: PS-COOH, and amine: PS-NH2) with human hemoglobin (Hb) utilizing multi-spectroscopic and docking approaches to acquire insights into molecular aspects of binding mechanism, which will be helpful in assessing the toxicokinetics or toxicodynamics of nanoplastics NPs. Hypsochromicity and hypochromicity were observed invariably in all the spectra (steady-state fluorescence emission, synchronous and three-dimensional) for all complexes, among which PS-NH2 binds effectively and changes the Hb's conformation by enhancing hydrophobicity around aromatic residues, notably tryptophan. All the NPs bind with the hydrophobic pocket of B-chain in Hb, where PS and PS-NH2 bind via hydrophobic force while PS-COOH binds via hydrogen bonding (predominantly) and van der Waals force, consistent validated with docking results. The minimal shift in absorbance peak also indicates enhanced hydrophobicity by PS-NH2 with larger aggregation as demonstrated in resonance light scattering. The amide band's shift, secondary structural analysis, and presence of characteristic functional group peaks in complexes in Infra-Red spectra confirm the structural changes in the protein. As seen in field emission scanning microscopy images, NPs penetrate the surface of proteins. These findings conclude that polystyrene NPs interact with Hb, causing structural alterations that may affect functional characteristics as well, with the greatest effect being in the order: PS-NH2>PS-COOH>PS.

Biochemical aspects of hemoglobin-xenobiotic interactions and their implications in drug discovery

Hemoglobin, a homodimeric globular protein, is found predominantly in red blood cells and in a small amount in blood plasma. Along with binding to certain native molecules, it also interacts with various xenobiotics. The present review aims at studying these interactions and the resultant tangible impact on the structure and function of the protein if any. The review also encompasses various analytical and computational approaches which are routinely used to study these interactions. A detailed discussion on types of interaction exhibited by individual xenobiotics has been included herein. Additionally, the effects of xenobiotic binding on the oxygen carrying capacity of hemoglobin have been reviewed. These insights would be of great value in drug design and discovery. Envisaging probable interactions of designed ligands with hemoglobin would help improvise the process of drug development. This would also open up new avenues for studying hemoglobin-mediated drug delivery.

Interaction of human hemoglobin (HHb) and cytochrome c (Cyt c) with biogenic chloroxine-conjugated silver nanoflowers: spectroscopic and molecular docking approaches

In this research, the biological activity of the antibacterial drug Chloroxine-conjugated biogenic AgNPs (COX-AgNPs) was investigated in simulated physiological conditions (pH = 7.40). Different spectroscopic methods such as UV-visible, fluorescence, and circular dichroism spectroscopic and docking simulation were employed to evaluate the structural changes in the most important blood proteins (human hemoglobin (HHb) and Cytochrome c (Cyt c)) in the presence of COX-AgNPs. The results showed that the COX-AgNPs can bind to HHb and Cyt c and the secondary structure of these proteins remains unchanged, which is crucial in providing insights into the side effects of newly synthesized drugs on their carriers.Communicated by Ramaswamy H. Sarma.

Potential of isoquercitrin as antisickling agent: a multi-spectroscopic, thermophoresis and molecular modeling approach

Sickle cell disease is an inherited disease caused by point mutation in hemoglobin (β-globin gene). Under oxygen saturation, sickle hemoglobin form polymers, leading to rigid erythrocytes. The transition of the blood vessels is altered and initiated by the adhesion of erythrocytes, neutrophils and endothelial cells. Sickle Hemoglobin (HbS) polymerization is a major cause in red blood cells (RBC), promoting sickling and destruction of RBCs. Isoquercitrin, a medicinal bioactive compound found in various medicinal plants, has multiple health benefits. The present study examines the potential of isoquercitrin as an anti-sickle agent, showing a significant decrease in the rate of polymerization as well as sickling of RBCs. Isoquercitrin-induced graded alteration in absorbance and fluorescence of HbS, confirmed their interaction. A negative value of ΔG° strongly suggests that it is a spontaneous exothermic reaction induced by entropy. Negative ΔH° and positive ΔS° predicted that hydrogen and hydrophobic binding forces interfered with a hydrophobic microenvironment of β6Val leading to polymerization inhibition of HbS. HbS-Isoquercitrin complex exhibits helical structural changes leading to destabilization of the HbS polymer as confirmed by CD spectroscopy. MST and DSC results indicate greater changes in thermophoretic mobility and thermal stability of sickle hemoglobin in the presence of isoquercitrin, respectively. These findings were also supported by molecular simulation studies using DOCK6 and GROMACS. Hence, we can conclude that isoquercitrin interacts with HbS through hydrogen bonding, which leads to polymerization inhibition. Consequently, isoquercitrin could potentially be used as a medication for the treatment of sickle cell disease.Communicated by Ramaswamy H. Sarma.

New insights into the binding behavior of lomefloxacin and human hemoglobin using biophysical techniques: binary and ternary approaches

Demonstrates the overlap that had been induced between the fluorescence emission spectrum of Hb and the absorption spectrum of drugs, which has proved that there is a high probability to the occurrence of energy transfer from Hb and LMF in the absence and presence of NRF.

Molecular recognition of bio-active flavonoids quercetin and rutin by bovine hemoglobin: an overview of the binding mechanism, thermodynamics and structural aspects through multi-spectroscopic and molecular dynamics simulation studies

The binding of two bio-active flavonoids, quercetin and rutin, with bovine hemoglobin (BHb) was investigated by multi-spectroscopic and computational (molecular docking and molecular dynamics simulation) studies. The two flavonoids were found to quench the intrinsic fluorescence of BHb through a static quenching mechanism. The binding constants at 288 K were observed to be (14.023 ± 0.73) × 104 M-1 and (7.848 ± 0.20) × 104 M-1, respectively for quercetin and rutin binding with BHb. Both rutin and quercetin were observed to increase the polarity around the Trp residues of BHb as indicated by synchronous and 3D spectral studies. No significant alterations in the secondary structural components of the protein were caused during the binding of the flavonoids as studied by CD and FTIR studies. The negative molar Gibbs free energies indicated the spontaneity of the interaction processes while the binding processes were characterized by a negative enthalpy change (ΔH) and a positive entropy change (ΔS). The possibility of energy transfer from the donor (BHb) to the acceptor molecules (flavonoids) was indicated by the FRET studies. According to the fluorescence studies, the flavonoids interact near to the β2-Trp37 residue of BHb. Excellent correlations with the experimental studies were observed from the molecular docking and molecular dynamics (MD) simulation studies. Further investigations established that these flavonoids are efficient in the inhibition of glucose mediated glycation of BHb.