Interaction of tetramethylpyrazine with two serum albumins by a hybrid spectroscopic method

Exploring the binding mechanism and adverse toxic effects of chiral phenothrin to human serum albumin: Based on multi-spectroscopy, biochemical and computational approach

To understand the binding mechanism of a mixture of chiral phenothrin with human serum albumin (HSA), we used multi-spectroscopy, including steady-state fluorescence spectroscopic titration, three-dimensional fluorescence spectroscopy, circular dichroism, and FTIR spectra to explore the precise interactions between the complex. Based on the modified Stern-Volmer equation, the binding constant (K_a) was calculated under three temperatures, which revealed that phenothrin interacts with HSA through a static quenching mechanism. The thermodynamic parameters including enthalpy change (ΔH) and entropy change (ΔS) were determined by fitting the experimental data with van't Hoff equation, which indicates that electrostatic force and hydrogen bonds dominate the interplay in the phenothrin-HSA complex. Circular dichroism and FTIR showed the addition of phenothrin changed the secondary structure of proteins, in which the α-helicity decreased from 52.37% in free HSA to 50.02%. The esterase-like activity was reduced with the increase of phenothrin concentration, which may be attributed to the perturbated senior structure of HSA. Competitive displacement experiments confirmed that phenothrin inserted into the subdomain IIA (site I) of HSA. Several computational approaches such as molecular docking, frontier molecular orbital analysis, and electrostatic potential analysis were utilized to probe into the binding mode of the phenothrin-HSA complex. The binding behaviors of the chiral phenothrin mixture differed during the complexation. In conclusion, both the experimental and theoretical investigations provide useful information for better understanding and reducing the potential deleterious effects of the chiral phenothrin mixture on human long-term physio-pathological status.

Tetramethylpyrazine supplementation improves performance, digestion, blood and immune state of broilers exposure to oxidative stress

This study aimed to investigate the effect of dietary tetramethylpyrazine (TMP) on the growth performance, nutrient digestion, blood parameters and immunity of broilers under oxidative stress. Five treatments included negative control, positive control with lipopolysaccharide induction and TMP addition at 50, 100 and 150 mg/kg of diet using 600 male Arbor Acres broiler chicks. Results showed that during 1-14 days of age, body weight gain and feed efficiency in the positive control were worsened (p < .05) compared with the negative control, while with incremental TMP doses from 0 to 150 mg/kg there were linear and quadratic increases (p < .001) in body weight gain and a linear decrease in feed/gain (p = .001). During 12-14 days of age, with incremental TMP doses, crude protein digestibility was linearly increased (p = .001), and gross energy utilization was linearly and quadratically changed (p < .001). At 14 days of age, the TMP beneficially regulated digestive enzymes, blood parameters and immunoglobulins, showing linear and quadratic responses (p ≤ .008) on trypsin, lipase, glutamic pyruvic transaminase, glucose, lipoproteins, albumin, immunoglobulins (M, Y), interleukin 6 and interferon α, and only linear changes (p ≤ .030) on amylase, glutamic oxaloacetic transaminase, immunoglobulin A and interleukin 2. Most parameters in TMP groups reached to the levels of negative control and the effects of TMP at 100 or 150 mg/kg were more pronounced on body weight gain, crude protein digestibility, trypsin and glutamic pyruvic transaminase. It is concluded that TMP can be used as a feed additive capable of improving growth, blood parameter and immunity of broiler chicks under oxidative stress.

Biological activity of bis(pyrazolylpyridine) and terpiridine Os(ii) complexes in the presence of biocompatible ionic liquids

New bis(pyrazolylpyridine) Os(ii) complexes showing possible biological activity with diverse modes of action in the presence of biocompatible ionic liquids as non-toxic cosolvents for sparingly soluble complexes.

Impact of Drug Metabolism/Pharmacokinetics and their Relevance Upon Traditional Medicine-based Cardiovascular Drug Research

BACKGROUND

The representative cardiovascular herbs, i.e. Panax, Ligusticum, Carthamus, and Pueraria plants, are traditionally and globally used in the prevention and treatment of various cardiovascular diseases. Modern phytochemical studies have found many medicinal compounds from these plants, and their unique pharmacological activities are being revealed. However, there are few reviews that systematically summarize the current trends of Drug Metabolism/Pharmacokinetic (DMPK) investigations of cardiovascular herbs.

METHODS

Here, the latest understanding, as well as the knowledge gaps of the DMPK issues in drug development and clinical usage of cardiovascular herbal compounds, was highlighted.

RESULTS

The complicated herb-herb interactions of cardiovascular Traditional Chinese Medicine (TCM) herb pair/formula significantly impact the PK/pharmacodynamic performance of compounds thereof, which may inspire researchers to develop a novel herbal formula for the optimized outcome of different cardiovascular diseases. While the Absorption, Distribution, Metabolism, Excretion and Toxicity (ADME/T) of some compounds has been deciphered, DMPK studies should be extended to more cardiovascular compounds of different medicinal parts, species (including animals), and formulations, and could be streamlined by versatile omics platforms and computational analyses.

CONCLUSION

In the context of systems pharmacology, the DMPK knowledge base is expected to translate bench findings to clinical applications, as well as foster cardiovascular drug discovery and development.

Experimental and quantum chemical study оn the DNA/protein binding and the biological activity of a rhodium(iii) complex with 1,2,4-triazole as an inert ligand

A rhodium(iii) complex with 1,2,4-triazole and a pincer type nitrogen-donor ligand was synthesized, and its interaction with biomolecules was examined.

A multifunctional sensor for selective and sensitive detection of vitamin B12 and tartrazine by Förster resonance energy transfer

We used thiamine nitrate (TN) as single material to fabricate nitrogen and sulfur co-doped carbon quantum dots (N,S-CQDs) with a quantum yield of 10.4% through one-pot hydrothermal method, and its properties were characterized by TEM, XPS, FTIR, fluorescence (FL) and UV-vis spectrophotometer, respectively. The fluorescence of N,S-CQDs was effectively quenched in the presence of vitamin B12 (VB12)/tartrazine due to Förster resonance energy transfer (FRET). Moreover, the rate (K_T) and efficiency (E%) of energy transfer from N,S-CQDs (as a donor) to VB12/tartrazine (as an acceptor) enhanced with increasing the concentrations of acceptor, and the K_T and E% were also varied with the change of excitation wavelengths (from 338 to 408 nm). Based on this principle, a multifunctional fluorescence probe was designed for selective and sensitive detection of VB12/tartrazine with a detection limit (3σ/slope) of 15.6/18.0 nmol/L. Meanwhile, the proposed method was successfully employed to detect VB12/tartrazine in milk and several beverages with a recovery range of 97.5-104.2%/91.0-110.6%.

The magnetic properties, DNA/HSA binding and nuclease activity of manganese N-confused porphyrin

The first oxidative cleavage of DNA by manganese [Formula: see text]-confused porphyrin [chloro(2-aza-2-methyl-5,10,15,20-tetrakis([Formula: see text]-chlorophenyl)-21-carbaporphyrin)manganese(III), 1] using H2O2 as oxidant agent and its magnetic, calf thymus DNA(ct-DNA)- and human serum albumin (HSA) binding properties were investigated. The magnitude of the axial (D) zero-field splitting for the mononuclear Mn(III) center in 1 was determined to be approximately 2.71 cm[Formula: see text] by paramagnetic susceptibility measurements. The DNA- and HSA binding experimental results showed that 1 bound to ct-DNA via an outside groove binding mode and the hydrophobic cavity located in subdomain IIA of HSA with the binding constant of 4.144 × 105 M[Formula: see text] and [Formula: see text] 106 M[Formula: see text], respectively. Thermodynamic parameters revealed that both DNA- and HSA binding were spontaneous process. The main driven forces were the hydrogen bond and van der Waals for the former, but hydrophobic interaction for the latter, which were further confirmed by molecular docking modeling. Manganese [Formula: see text]-confused porphyrin 1 could cleave the supercoiled plasmid DNA efficiently in the presence of hydrogen peroxide. Hydroxyl radical ([Formula: see text]OH) was found the active species for oxidative damage of DNA.

Binding properties of drospirenone with human serum albumin and lysozyme in vitro

The interaction of drospirenone (DP) with human serum albumin (HSA)/lysozyme (LYZ) was investigated using different optical techniques and molecular models. Results from the emission and time resolved fluorescence studies revealed that HSA/LYZ emission quenching with DP was initiated by static quenching mechanism. The LYZ-DP system was more easily influenced by temperature than the HSA-DP system. Displacement experiments demonstrated that the DP binding site was mainly located in site 1 of HSA. Based on the docking methods, DP was mainly bound in the active site hinge region where Trp-62 and Trp-63 are located. Conformation study showed that DP had different effects on the local conformation of HSA and LYZ molecules.

DNA Binding, Photonuclease Activity and Human Serum Albumin Interaction of a Water-Soluble Freebase Carboxyl Corrole

The DNA binding property of 5,10,15-Tris(4-carboxyphenyl) corrole (TCPC) was studied by UV-Visible, fluorescence and circular dichroism (CD) spectroscopic methods. TCPC can bind to ct-DNA via an outside binding mode with the binding constant of K_b = 1.05 × 10⁵ M⁻¹. TCPC also displayed good photonuclease activity, which involves singlet oxygen species (¹O₂). The binding constant between TCPC and human serum albumin (HSA) is K_A = 2.24 × 10⁵ M⁻¹ with a simulated binding distance of 2.06 nm. The fluorescence quenching of HSA by TCPC followed a static quenching process. Site marker competitive displacement experiments indicated that warfarin site I is the main binding site. The secondary structure of HSA was changed upon interaction with TCPC, which was confirmed by UV-Visible and CD spectroscopy.

Studies on the synthesis, characterization, human serum albumin binding and biological activity of single chain surfactant-cobalt(III) complexes

The interaction of surfactant-cobalt(III) complexes [Co(bpy)(dien)TA](ClO4)3 · 3H2O (1) and [Co(dien)(phen)TA](ClO4)3 · 4H2O (2), where bpy = 2,2'-bipyridine, dien = diethylenetriamine, phen = 1,10-phenanthroline and TA = tetradecylamine with human serum albumin (HSA) under physiological conditions was analyzed using steady state, synchronous, 3D fluorescence, UV/visabsorption and circular dichroism spectroscopic techniques. The results show that these complexes cause the fluorescence quenching of HSA through a static mechanism. The binding constant (Kb ) and number of binding-sites (n) were obtained at different temperatures. The corresponding thermodynamic parameters (∆G°, ∆H° and ∆S°) and Ea were also obtained. According to Förster's non-radiation energy transfer theory, the binding distance (r) between the complexes and HSA were calculated. The results of synchronous and 3D fluorescence spectroscopy indicate that the binding process has changed considerably the polarity around the fluorophores, along with changes in the conformation of the protein. The antimicrobial and anticancer activities of the complexes were tested and the results show that the complexes have good activities against pathogenic microorganisms and cancer cells.

Investigation of the interaction between human serum albumin and antitumor palladium(II) complex containing 1,10-phenanthroline and dithiocarbamate ligands

The interaction between [Pd(But-dtc)(phen)]NO3 (where But-dtc = butyldithiocarbamate and phen = 1,10-phenanthroline) with HSA (Human Serum Albumin) was investigated by applying fluorescence, UV-Vis and circular dichroism techniques under physiological conditions. The results of fluorescence spectra indicated that the Pd(II) complex could effectively quench the fluorescence intensity of HSA molecules via static mechanism. The number of binding sites and binding constant of HSA-Pd(II) complex were calculated. Analysis of absorption titration data on the interaction between Pd(II) complex and HSA revealed the formation of HSA-Pd(II) complex with high-binding affinity. Thermodynamic parameters indicated that hydrophobic forces play a major role in this interaction. Furthermore, CD measurements were taken to explore changes in HSA secondary structure induced by the Pd(II) complex.

DNA/HSA interaction and nuclease activity of an iron(III) amphiphilic sulfonated corrole

The DNA binding of amphiphilic iron(III) 2,17-bis(sulfonato)-5,10,15-tris(pentafluorophenyl)corrole complex (Fe-SC) was studied using spectroscopic methods and viscosity measurements. Its nuclease-like activity was examined by using pBR322 DNA as a target. The interaction of Fe-SC with human serum albumin (HSA) in vitro was also examined using multispectroscopic techniques. Experimental results revealed that Fe-SC binds to ct-DNA via an outside binding mode with a binding constant of 1.25 × 10(4) M(-1). This iron corrole also displays good activity during oxidative DNA cleavage by hydrogen peroxide or tert-butyl hydroperoxide oxidants, and high-valent (oxo)iron(V,VI) corrole intermediates may play an important role in DNA cleavage. Fe-SC exhibits much stronger binding affinity to site II than site I of HSA, indicating a selective binding tendency to HSA site II. The HSA conformational change induced by Fe-SC was confirmed by UV/Vis and CD spectroscopy.

Spectroscopic studies on the interaction between tetrandrine and two serum albumins by chemometrics methods

The binding interactions of tetrandrine (TETD) with bovine serum albumin (BSA) and human serum albumin (HSA) have been investigated by spectroscopic methods. These experimental data were further analyzed using multivariate curve resolution-alternating least squares (MCR-ALS) method, and the concentration profiles and pure spectra for three species (BSA/HSA, TETD and TETD-BSA/HSA) existed in the interaction procedure, as well as, the apparent equilibrium constants Kapp were evaluated. The binding sites number n and the binding constants K were obtained at various temperatures. The binding distance between TETD and BSA/HSA was 1.455/1.451nm. The site markers competitive experiments indicated that TETD primarily bound to the tryptophan residue of BSA/HSA within site I. The thermodynamic parameters (ΔG, ΔH and ΔS) calculated on the basis of different temperatures revealed that the binding of TETD-BSA was mainly depended on the hydrophobic interaction strongly and electrostatic interaction, and yet the binding of TETD-HSA was strongly relied on the hydrophobic interaction. The results of synchronous fluorescence, 3D fluorescence and FT-IR spectra show that the conformation of proteins has altered in the presence of TETD. In addition, the effect of some common ions on the binding constants between TETD and proteins were also discussed.