Conformational and solution dynamics of hemoglobin (Hb) in presence of a cleavable gemini surfactant: Insights from spectroscopy, atomic force microscopy, molecular docking and density functional theory

Effects of Temperature, Metal Ions and Biosurfactants on Interaction Mechanism between Caffeic Acid Phenethyl Ester and Hemoglobin

Caffeic acid phenylethyl ester (CAPE) is a natural polyphenol extracted from propolis, which is reported to have several pharmacological effects such as antibacterial, antitumor, antioxidant and anti-inflammatory activities. Hemoglobin (Hb) is closely related to the transport of drugs, and some drugs, including CAPE, can lead to a change in Hb concentration. Herein, the effects of temperature, metal ions and biosurfactants on the interaction between CAPE and Hb were studied using ultraviolet-visible spectroscopy (UV-Vis), fluorescence spectroscopy, circular dichroism (CD), dynamic light scattering (DLS) and molecular docking analysis. The results showed that the addition of CAPE led to changes in the microenvironment of Hb amino acid residues as well as the secondary structure of Hb. Hydrogen bonding and van der Waals force were found to be the main driving forces for the interaction between CAPE and Hb through fluorescence spectroscopy and thermodynamic parameter data. The results of fluorescence spectroscopy also showed that lowering the temperature, adding biosurfactants (sodium cholate (NaC) and sodium deoxycholate (NaDC)) and the presence of Cu²⁺ increased the binding force between CAPE and Hb. These results provide useful data for the targeted delivery and absorption of CAPE and other drugs.

Conformational dynamics of myoglobin in the presence of vitamin B12: A spectroscopic and in silico investigation

Myoglobin is an essential transport protein of heart and muscle tissues that acts as a local oxygen reservoir and a marker in different diseased conditions. On the other hand, Vitamin B12 is a vital nutrient that helps synthesize red blood cells, DNA, and proteins. To understand the ability of vitamin B12 to bind to the excess of myoglobin produced in the body under certain conditions (muscle injuries, severe trauma, etc.), it is essential to dig into the interaction between them. Therefore, the present study reports the binding interaction of vitamin B12 and myoglobin employing different spectroscopic and computational methods. The myoglobin's intrinsic fluorescence is quenched by vitamin B12 via static nature as observed from steady-state as well as time-resolved fluorescence measurements. The microenvironment of myoglobin's tryptophan residue gets affected, but there is no change observed in its α-helical content by vitamin B12 as seen from synchronous fluorescence and circular dichroism measurements. The probable binding of vitamin B12 on myoglobin was elucidated through molecular docking, and the interaction stability was studied by molecular dynamics simulation. The determination of vitamin B12's affinity to myoglobin and its effect on the conformational transitions of myoglobin might afford valuable insight for clinical pharmacology.

Spectroscopic and computational insight into the conformational dynamics of hemoglobin in the presence of vitamin B12

Protein-ligand interactions play a significant role in all living organisms, thereby affecting the design and application of drugs and other biomaterials. The current study reports the binding of vitamin B12 to hemoglobin, employing optical spectroscopy and computational methods. It is observed that vitamin B12 quenched the intrinsic fluorescence of hemoglobin. The nature of quenching appears to be static according to the steady-state and time-resolved fluorescence measurements. The conformational changes of hemoglobin caused by vitamin B12 interactions were studied by synchronous fluorescence spectroscopy and protein secondary structure analyses. The synchronous fluorescence spectra indicate the tryptophan residue microenvironment change while no secondary structural change is observed from circular dichroism spectra and molecular dynamics (MD) simulation study. The computational molecular docking elucidated the probable binding of vitamin B12 at the active site of hemoglobin, whereas the stability of the hemoglobin-vitamin B12 complex was studied by MD simulation. The study might be helpful for the treatment of pernicious anemia, hereditary transcobalamin deficiency, and performance enhancement of elite athletes.

Effect of local anesthetic drug procaine hydrochloride on the conformational stability of bovine hemoglobin: Multi-spectroscopic and computational approaches

The interaction between bovine hemoglobin (BHb) and local anesthetic drug procaine hydrochloride (PCH) was examined by spectroscopic and computational studies. Intrinsic fluorescence analysis explored the ground-state complex formation in the binding of PCH with BHb through static quenching mechanism. The binding constants (K_b) are 29.38 × 10³, 22.54 × 10³ and 17.99 × 10³ M^-1 at 288, 298 and 308 K, respectively, and the ratio of BHb:PCH was 1:1 in the interaction mechanism of PCH and BHb. The acquired thermodynamic parameters (ΔH⁰, ΔG⁰ and ΔS⁰) demonstrated that interaction mechanism is spontaneous and enthalpy driven. The van der Waals forces and hydrogen bonding have been played a predominant role in the binding mechanism. The UV-vis spectroscopy validates the ground-state complexation between PCH and BHb and the binding constant (K_b) has been evaluated utilizing Benesi-Hildebrand equation. Fluorescence resonance energy transfer (FRET) results have demonstrated that the distance between donor (BHb) and acceptor (PCH) is very short (2.34 nm) suggesting a significant probability to energy transfer from BHb to PCH. Synchronous fluorescence results revealed that the alteration in the micro-environment of Tyrosine (Tyr) is more than tryptophan (Trp) residues suggesting that PCH molecule is close to Tyr residue. The secondary structure alterations were confirmed by CD, 3-D fluorescence and FT-IR spectroscopic measurements. Moreover, computational analyses further corroborated that PCH molecules are closer to Tyr residues as compared to Trp residues of BHb during the interaction process. The BHb-PCH complexes may contribute to a deeper understanding of the metabolism of drug, blood circulation process and may help to illustrate the relationship between functions and structure of BHb.Communicated by Ramaswamy H. Sarma.

Probing the interaction between levamlodipine and hemoglobin based on spectroscopic and molecular docking methods

In recent years, levamlodipine (LAML) has been widely used as a common drug for the treatment of hypertension. However, no reports exist that focus on the binding process of LAML with the transport proteins present in blood circulation. Here, several spectroscopy techniques, molecular docking and a molecular dynamics simulation were employed to comprehensively analyze the mechanism underlying the interaction between bovine hemoglobin (BHb) and LAML, as well as the effect of other drugs on the BHb-LAML system. The results indicated that a stable BHb-LAML complex was formed and that the binding site for LAML was located at β-37 tryptophan in the central cavity of BHb. Van der Waals force and hydrogen bonds played major roles in this binding process, and the number of binding sites (n) in the binary system was approximately equal to 1. Multiple spectroscopy experiments (FT-IR and three-dimensional fluorescence spectrometry) and a dynamics simulation revealed that LAML could induce a conformational in BHb and that the microenvironment of Trp/Tyr changed. Interestingly, the values of the binding constant between LAML and BHb significantly increased due to the effect of rofecoxib, propranolol and enalapril. Meanwhile, these drugs did not produce synergistic or negative synergistic effects on the LAML binding with BHb. These results provide new insight into the transport mechanisms for LAML in the human body.