A comparison of the inclusion behavior of human serum albumin and holo transferrin with fluoxymesterone in the presence of three different cyclodextrins

A phenanthroline-based erbium (III) complex: molecular docking, DNA/BSA -binding and biological evaluation

With the help of both theoretical as well as experimental research, in vitro binding research with CT-DNA (calf thymus) and BSA (bovine serum albumin) were carefully examined to figure out the chemotherapeutic and pharmacokinetic facets of the Erbium complex, which contains 1,10-phenanthroline (Phen). The binding characteristics and the mechanism of complex's interaction with DNA as well as the protein were determined utilizing fluorescence quenching method. Findings indicated that the complex's interaction with DNA via groove binding into DNA's minor grooves, with their binding constants falling within the 104 M-1 range. Furthermore, thermodynamic characteristics and the fluorescence emission of the tryptophan residues of the protein were obtained through fluorescence quenching studies at different temperatures. According to the results of the binding constants, the protein's interactions with the Er- complex were moderate, demonstrating that the compound may be transported effectively by the protein. Molecular docking results supported that of the experimental research. The HeLa and MCF-7 cancer cell lines, along with the normal human fibroblast cell line, were used in an MTT assay evaluation of the Er-complex cytotoxicity. The Er-complex displayed a selective inhibitory effect on the proliferation of different cancer cells.Communicated by Ramaswamy H. Sarma.

Cyclodextrins and Their Polymers Affect Human Serum Albumin's Interaction with Drugs Used in the Treatment of Pulmonary Infections

Respiratory infectious diseases have challenged medical communities and researchers. Ceftriaxone, meropenem and levofloxacin are widely used for bacterial infection treatment, although they possess severe side effects. To overcome this, we propose cyclodextrin (CD) and CD-based polymers as a drug delivery system for the drugs under consideration. CD polymers demonstrate higher binding affinity for levofloxacin (Ka ≈ 10⁵ M) compared to drug-CD complexes. CDs slightly alter the drugs' affinity for human serum albumin (HSA), whereas CD polymers increase the drugs' binding affinity up to 100 times. The most significant effect was observed for more the hydrophilic drugs ceftriaxone and meropenem. The drug's encapsulation in CD carriers leads to a decrease in the degree of change in the protein's secondary structure. The drug-CD carrier-HSA complexes demonstrate satisfying antibacterial activity in vitro, and even a high binding affinity does not decrease the drug's microbiological properties after 24 h. The proposed carriers are promising for a drug form with a prolonged drug release.

Insights into an α-Glucosidase Inhibitory Profile of 4,4-Dimethylsterols by Multispectral Techniques and Molecular Docking

Inhibition of α-glucosidase activity is closely related to the treatment of type 2 diabetes. However, the potential mechanism by which 4,4-dimethylsterols inhibit α-glucosidase has not been elucidated. In this work, the inhibitory activity and mechanism of 4,4-dimethylsterols against α-glucosidase were studied through kinetic analysis, fluorescence spectroscopy, ultraviolet spectroscopy, circular dichroism, and molecular docking. 4,4-Dimethylsterols showed higher inhibition activity against α-glucosidase than acarbose with an IC₅₀ value of 0.71 mg/mL and a noncompetitive inhibition type. They could bind to α-glucosidase through van der Waals forces and hydrogen bonds and quench its endofluorescence with a static quenching mechanism. Changes in the secondary structure of α-glucosidase were induced by its binding interaction with 4,4-dimethylsterols. Molecular docking further indicated that a hydrogen bond was generated between OH at the C-3 position of 4,4-dimethylsterols and the α-glucosidase residue Arg-442. This study provides new insights into the potential utilization of 4,4-dimethylsterols as antidiabetic phytochemicals in dietary supplements.

Synthesis of two novel pyrazolo[1,5-a]pyrimidine compounds with antibacterial activity and biophysical insights into their interactions with plasma protein

Two novel water-soluble pyrazolo[1,5-a]pyrimidine derivatives, 5-chloro-7-(4-methyl-piperazin -1-yl)-pyrazolo[1,5-a]pyrimidine (CMPS) and N'-(5-chloro-pyrazolo[1,5-a]pyrimidin-7-yl)-N,N-dimethyl -propane-1,3-diamine (NCPS), were synthesized and characterized with antibacterial activity. Then, the interactions of these compounds with bovine serum albumin (BSA) were studied by fluorescence, time-resolved fluorescence, circular dichroism (CD) spectroscopy and molecular docking. The results indicate that both CMPS and NCPS could effectively quench the intrinsic fluorescence of BSA via a static quenching process. The energy transfer from BSA to CMPS and NCPS may occur with high probability. Both CMPS and NCPS bind in the site I of BSA. The hydrophobic force and hydrogen bonds play major roles in the complex formation. Binding constants for both systems show that the affinity of CMPS binding to BSA is stronger than that of NCPS. The results of three-dimensional fluorescence and CD spectra reveal that the binding of CMPS and NCPS to BSA can induce conformational changes of BSA, and the influence of CMPS is slightly stronger than that of NCPS.

Evaluation of the toxicity of 5-fluorouracil on three digestive enzymes from the view of side effects

Among the side effects of 5-fluorouracil (5-FU), the performance of the gastrointestinal reactions is faster and more obvious than others. In this work, the effects of 5-FU on the activities and conformational structures of the important digestive enzymes including α-amylase, pepsin and trypsin were studied to analyze the mechanism of the gastrointestinal adverse effects causing by 5-FU binding. The results showed that the enzymatic activity of pepsin was obviously reduced by the presence of 5-FU that bound directly to the enzyme activity cavity site. The molecular modeling and fluorescence quenching data indicated that the hydrophobic, polar and hydrogen bonding forces were involved in the ground state complex formation between proteases and 5-FU. In addition, 5-FU changed the tertiary structures of α-amylase, pepsin, and trypsin.

Utility of Europium ion characteristic peak for quantitation of Fenoterol hydrobromide and Salmeterol xinafoate in different matrices; application to stability studies

A simple selective luminescent dependent approach was established for quantitation of two selective β₂ agonists namely; Fenoterol hydrobromide (FEN) and Salmeterol xinafoate (SAL). This approach utilizes the capability of the cited drugs to undergo a complexation reaction with Europium ion (Eu³⁺) in the presence of 1,10-phenanthroline as a co-ligand. The resultant complex leads to a hypersensitive transition and enhancement of the Eu³⁺ emission peak at 615nm (279nm excitation). Under the optimized conditions, the rectilinear concentration plots of both drugs were (70-1500ngmL^-1) and (100-2000ngmL^-1) with limit of quantitation 51.3 and 84.4ngmL^-1 for FEN and SAL, respectively. The luminescence properties of the complex and its optimum formation conditions were carefully investigated according to the regulations of ICH and the method was successfully applied in plasma. The good accuracy and selectivity of the suggested method allowed extending the proposed protocol into stability study of the cited drugs.

Streptozocin; a GLUT2 binding drug, interacts with human serum albumin at loci h6DOM3-h7DOM3

Streptozocin (STZ) is a broad range antibiotic, highly genotoxic, antineoplastic and hyperglycemic. HSA is the most abundant protein in physiology and it binds to almost all exogenic and endogenic ligands, including drugs. STZ-induced fluorescence quenching of HSA has been done at pH 7.4, pH 3.5 and at pH 7.4 with 4.5 M urea at temperatures 286 K, 291 K, and 306 K. K_sv found to be 10³ M^-1, binding constant 1.5X10³M^-1 and binding sites ~1. But, K_sv for HSA and glucopyranose interaction was found lesser than that of HSA-STZ binding. Binding of STZ/glucopyranose on HSA seems to result in complex formation as calculated K_q > 10¹⁰ M^-1 s^-1. The number of binding sites, binding constants, and binding energies were increased with temperature. The ΔG⁰, ΔH⁰, and ΔS⁰ for HSA-STZ interaction were found to be -17.7 × 10³ J·mol^-1; 2.34 × 10⁵ J·mol^-1 and 841 JK^-1 mol^-1 respectively at pH 7.4 and 291 K. The comparative bindings of N, F and I states of HSA with STZ and their molecular docking analyses indicate that IIIA-B junction (i.e., inter-helix h6_DOM3-h7_DOM3) is the probable binding site, a locus close to fatty acid binding site-5. These results could be useful for therapeutic and analytical exploitation of STZ, as albumin used as the vehicle for drug delivery.

Titanium oxide nanoparticles fabrication, hemoglobin interaction, white blood cells cytotoxicity, and antibacterial studies

This study is focused on the fabrication and characterization of titanium oxide (TiO₂) NPs. Afterwards; the interaction of TiO₂ NPs with human hemoglobin (Hb) was investigated by FTIR spectroscopy, fluorescence spectroscopy, and molecular docking studies. Also, the cytotoxic effect of fabricated TiO₂ NPs against human white blood cells (WBCs) was considered by MTT assay. The antibacterial effect of synthesized NPs was examined on Pseudomonas aeruginosa (ATCC 27853); Escherichia coli (ATCC 25922) and Staphylococcus aureus (ATCC 25923). TEM and DLS investigations showed that the synthesized TiO₂ NPs have a narrow nano-sized distribution. XRD pattern of the fabricated NPs exhibited that the TiO₂ NPs contain anatase phase. Similarity in amide I and II signal intensities showed that secondary structure of the adsorbed Hb is preserved. The intrinsic fluorescence study revealed that the fluorescence quenching of Hb was done by complex formation between Hb and TiO₂ NPs trough the hydrogen bond and van der Waals interactions. Synchronous fluorescence spectroscopy determined that interaction of TiO₂ NPs with Hb did not unfold the Hb structure in the vicinity of the Tyr and Trp residues. Molecular docking study depicted that Glu-95, Thr-134 and Tyr-140 are involved in the formation of hydrophilic bonds. MTT data and antibacterial assays indicated that TiO₂ NPs endow distinguished antibacterial activities against Gram-negative and Gram positive strains at safe concentrations. This study may reveal that fabricated TiO₂ NP can be used as a safe and potent antibacterial agent. Communicated by Ramaswamy H. Sarma.