Isothermal titration calorimetry and stopped flow circular dichroism investigations of the interaction between lomefloxacin and human serum albumin in the presence of amino acids

Screening and analysis of the targeted compounds in Choerospondias axillaris extract by receptor chromatographic column with immobilized angiotensin II type 1 receptor

As a result of the lack of modern techniques, the study of Tibetan medicine has been hindered in identifying bioactive compounds. Herein, we established a chromatographic approach using an immobilized angiotensin II type 1 receptor (AT1R) via a one-step method triggered by haloalkane dehalogenase. The bioactive compounds from Choerospondias axillaris (Guangzao) were screened and identified using the immobilized AT1R followed by MS. Frontal analysis (FA) and adsorption energy distribution (AED) were used to evaluate the association constants. Molecular docking was used to investigate the binding configurations, and the surface efficiency index, binding efficiency index, and ligand-lipophilicity efficiency (LLE) were calculated to assess the drug-like properties. The results identified naringenin, pinocembrin, and chrysin as the compounds that specifically bind to AT1R in Guangzao. FA and AED confirmed that there is only one type of binding site between these compounds and AT1R. The association constants were (2.40 ± 0.02) × 104 M-1 for naringenin (5.22 ± 0.26) × 104 M-1 for pinocembrin, and (4.27 ± 0.14) × 104 M-1 for chrysin, respectively. These compounds can bind with AT1R through the orthosteric binding pocket. Naringenin exhibited better LLE than pinocembrin and chrysin. These results confirmed the feasibility of using the immobilized AT1R column for screening and analyzing bioactive compounds in Tibetan medicines.

Covalent immobilization of human serum albumin on cellulose acetate membrane for scavenging amyloid beta - A stepping extracorporeal strategy for ameliorating Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by interrupted neurocognitive functions and impaired mental development presumably caused by the accumulation of amyloid beta (Aβ) in the form of plaques. Targeting Aβ has been considered a promising approach for treating AD. In the current study, human serum albumin (HSA), a natural Aβ binder, is covalently immobilized onto the surface of a cellulose acetate (CA) membrane to devise an extracorporeal Aβ sequester. The immobilization of HSA at 3.06 ± 0.22 μg/mm2 of the CA membrane was found to be active functionally, as evidenced by the esterase-like activity converting p-nitrophenyl acetate into p-nitrophenol. The green fluorescent protein-Aβ (GFP-Aβ) fusion protein, recombinantly produced as a model ligand, exhibited characteristics of native Aβ. These features include the propensity to form aggregates or fibrils and an affinity for HSA with a dissociation constant (KD) of 0.91 μM. The HSA on the CA membrane showed concentration-dependent sequestration of GFP-Aβ in the 1-10-μM range. Moreover, it had a greater binding capacity than HSA immobilized on a commercial amine-binding plate. Results suggest that the covalent immobilization of HSA on the CA surface can be used as a potential platform for sequestering Aβ to alleviate AD.

Insights into the binding of half-sandwich phosphino Ir(III) and Ru(II) complexes to deoxyribonucleic acid, albumin and apo-transferrin: Experimental and theoretical investigation

A group of cytotoxic half-sandwich iridium(III) (Ir(η5-Cp*)Cl2PPh2CH2OH (IrPOH)), (Ir(η5-Cp*)Cl2P(p-OCH3Ph)2CH2OH (IrMPOH)), and ruthenium(II) (Ru(η6-p-cymene)Cl2PPh2CH2OH (RuPOH), Ru(η6-p-cymene)Cl2P(p-OCH3Ph)2CH2OH (RuMPOH)) complexes with phosphine ligands exhibit the ability to (i) slow hydrolysis which is reversed by adding a high NaCl concentration; (ii) oxidation of NADH to NAD+; (iii) induction of cytotoxicity towards various cancer cell lines. Furthermore, we found that RuPOH and RuMPOH selectively inhibit the proliferation of skin cancer cells (WM266-4) while Ir(III) complexes were found to be moderate against prostate cancer cells (DU-145). Herein, to elucidate the cytotoxic effects, we investigated the interaction of these complexes with DNA and serum proteins by gel electrophoresis, fluorescence spectroscopy, and molecular docking studies. Fluorescence spectroscopic data (calf thymus DNA: CT-DNA titration), together with analysis of DNA fragmentation (gel electrophoresis) and molecular docking provided evidence for the multimodal interaction of Ir(III) and Ru(III) complexes with DNA with predominance of intercalation and minor groove binding. All examined complexes caused single-stranded cleavage of the sugar-phosphate backbone of plasmid DNA. The affinity of the complexes for apo-transferrin (apo-Tf) and human serum albumin (HSA) was evaluated by fluorescence emission spectroscopy to calculate the binding constants which suggested a tight and reversible binding. Moreover, ruthenium complexes can mimic the binding of iron compounds to specific biomolecules such as albumin and transferrin better than iridium complexes. In silico study indicate that complexes mostly bind to (i) apo-Tf with a preference for a single binding site and/or (ii) to dock within all the four predicted binding sites of HSA with the predominance of site I which include tryptophan residues of HSA. This class of ruthenium(II) and iridium(III) complexes has unusual features worthy of further exploration in the design of novel anticancer drugs.

In Vitro and In Vivo Synergistic Antitumor Activity of Albumin-Coated Oleic Acid-Loaded Liposomes toward Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most lethal and prevalent cancers, closely associated with cirrhosis and fibrosis. This study aimed to assess the antitumor activity of oleic acid-liposomes (uncoated liposomes) upon coating with albumin against HCC. The in vitro studies revealed the high safety of the prepared uncoated and albumin-coated liposomes to normal HFB-4 cells (EC100 of 35.57 ± 0.17 and 79.133 ± 2.92 µM, respectively) with significant anticancer activity against HepG-2 cells with IC50 of 56.29 ± 0.91 and 26.74 ± 0.64 µM, respectively. The albumin-coated liposomes revealed superior apoptosis induction potential (80.7%) with significant upregulation of p53 gene expression (> 7.0-fold), compared to OA. The in vivo study revealed that the administration of uncoated or albumin-coated liposomes (100 mg/kg) for six weeks markedly retarded the DENA-induced HCC in Wistar albino rates through regulating the liver enzymes, total bilirubin level, pro-inflammatory cytokines, and oxidative stress. Accordingly, the current study supports the in vitro and in vivo chemo-preventive feature of albumin-coated liposomes against HCC through modulation of apoptosis, improvement of the immune response, reduction of inflammation, and restoration of impaired oxidative stress, which is the first reported to the best of our knowledge.

Investigation of hexacyanoferrate(II)/(III) charge-dependent interactions with bovine and human serum albumins

In the present paper, the binding interactions of highly negative-charged ions, namely hexacyanoferrates(II/III), i.e. [Fe(CN)₆]^4- and [Fe(CN)₆]^3- with bovine and human serum albumins (BSA and HSA, respectively) have been studied for the first time in an aqueous solution (10 mM cacodylate buffer of pH 7.0) using steady-state fluorescence spectroscopy, isothermal titration calorimetry, and CD spectroscopy supported by molecular dynamics-based computational approaches. The Stern-Volmer equation as well as its modifications suggested that hexacyanoferrates(II/III) effectively quenched the intrinsic fluorescence of the albumins through a static mechanism. The proteins under study possess only one binding site on the surface capable of binding one mole of hexacyanoferrates(II/III) ions per one mole of albumin (HSA or BSA). The formation of albumin complexes is an enthalpy-driven process (|ΔH_ITC| > |TΔS_ITC|). The strength of the interactions depends mainly on the type of albumin, and changes as follows: BSA-K₃[Fe(CN)₆] ∼ BSA-K₄[Fe(CN)₆] > HSA-K₃[Fe(CN)₆] ∼ HSA-K₄[Fe(CN)₆]. Finally, potential binding sites of bovine and human serum albumins have been investigated and discussed based on a competitive fluorescence displacement assay (with warfarin and ibuprofen as site markers) and molecular dynamics simulations.

Probing the behavior and kinetic studies of amphiphilic acrylate copolymers with bovine serum albumin

This article presents that acrylate copolymers are the potential candidate against the adsorption of bovine serum albumin (BSA). A series of copolymers poly(methyl methacrylate) (pMMA), poly(3-sulfopropyl methacrylate-co-methyl methacrylate) p(SPMA-co-MMA), and poly(dimethylaminoethyl methacrylate-co-methyl methacrylate) p(DMAEMA-co-MMA) were synthesized via free radical polymerization. These amphiphilic copolymers are thermally stable with a glass transition temperature (Tg) 50-120 °C and observed the impact of surface charge on amphiphilic copolymers to control interactions with the bovine serum albumin (BSA). These copolymers pMD1 and pMS1 have surface charges, - 56.6 and - 72.6 mV at pH 7.4 in PBS buffer solution that controls the adsorption capacity of bovine serum albumin (BSA) on polymers surface. Atomic force microscopy (AFM) analysis showed minimum roughness of 0.324 nm and 0.474 nm for pMS1 and pMD1. Kinetic studies for BSA adsorption on these amphiphilic copolymers showed the best fitting of the pseudo-first-order model that showed physisorption and attained at 25 °C and pH 7.4 within 24 h.

Comparison of interaction, structure, and cell proliferation of α-lactalbumin-safflower yellow complex induced by microwave heating or conventional heating

BACKGROUND

The protein-polyphenol interaction mechanism has always been a research hotspot, but their interaction is affected by heat treatment, which is widely applied in food processing. Moreover, the effects of microwave or water-bath heating on the protein-polyphenol interaction mechanism have been not clarified. The pasteurization condition (65 °C, 30 min) was selected to compare the effects of microwave or water bath on binding behavior, structure, and cell proliferation between α-lactalbumin (α-LA) and safflower yellow (SY), thus providing a guide for the selection of functional dairy processing conditions.

RESULTS

Microwave heat treatment of α-LA-SY resulted in stronger fluorescence quenching than that of conventional heat treatment. Moreover, the binding constant K_a of all α-LA-SY samples was augmented significantly after microwave or water bath treatment, and microwave-heated α-LA-SY showed the maximum K_a . Fourier transform infrared spectroscopy showed that microwave heating resulted in more ordered structures of α-LA into its disordered structures than water bath heating. However, the ferric reducing antioxidant power and chroma value of α-LA-SY were more reduced by microwave heating than by water bath heating. Moreover, microwave heating facilitated the cell proliferation of α-LA-SY compared with water bath treatment.

CONCLUSION

It was demonstrated that microwave heating promoted interaction between α-LA and SY more than water bath heating did. Microwave heat treatment was a safe and effective way to enhance the binding affinity of α-LA to SY, being a potential application in food industry. © 2022 Society of Chemical Industry.

Colchicine as potential inhibitor targeting MMP-9, NOX2 and TGF-β1 in myocardial infarction: a combination of docking and molecular dynamic simulation study

The global data revealed that myocardial infarction (MI) in coronary heart disease has been the leading cause of mortality worldwide in both developing and developed countries. The remodeling process after MI is essential to be the leading cause of heart failure due to cardiac remodeling. The evidence showed the increment of MMP-9, NOX2 and TGF-β1 expressions are biomarkers that influence cardiac remodeling. Lately, colchicine is widely used in the treatment of cardiovascular diseases. The effects of colchicine on NOX2, MMP-9 and TGF-β1 in the molecular models are still not yet discussed. We proposed a molecular docking and molecular dynamics simulation study to show the interaction between colchicine, NOX2, MMP-9 and TGF-β1. Colchicine has a good binding affinity with MMP-9, NOX2 and TGF-β1 based on the value, which are -8.3 Kcal/mol, -6.7 Kcal/mol and -6.5 Kcal/mol, respectively. Colchicine also binds to some catalytic residues in MMP-9, NOX2 and TGF-β1 that are responsible for inhibitor effects. The RMSD values between colchicine and MMP-9, NOX2 and TGF-β1 are 2.4 Å, 2 Å and 2.1 Å, respectively. The RMSF values of ligand and receptors complex showed relatively similar fluctuations. The SASA analysis showed that colchicine could create a more stable interaction with MMP-9. PCA analysis revealed that colchicine is capable of creating a solid and stable interaction with MMP-9 mainly, also NOX2 and TGF-β1. In conclusion, docking and molecular dynamics analysis showed evidence of colchicine roles in the inhibition of MMP-9, NOX2 and TGF-β1 in order to inhibit the remodeling process after MI.Communicated by Ramaswamy H. Sarma.

Disagreements Between Calorimetric and Van't Hoff Enthalpies of Adsorption II: Effect of pH and pH Buffers on Phenobarbital Adsorption to Activated Carbon

The reported inconsistencies between the van't Hoff equation and calorimetry hinder the utility of thermodynamics in biochemical and pharmaceutical research. A novel thermodynamic approach is developed herein for ligand adsorption with a focus on the interpretation of calorimetric data in the presence of concurrent proton exchange reactions. Such exchange reactions typically result in a pH-dependence of calorimetric measurements that obscures intrinsic binding enthalpies. It is shown that for the adsorption of phenobarbital to activated carbon, the measured calorimetric enthalpy is a result of three linked acid/base equilibria. A model was established to predict the intrinsic binding enthalpy using 1) the adsorbate's pKa and 2) the adsorbate's enthalpy of protonation. The observed calorimetric enthalpy of binding exhibited both pH and buffer-dependence and was between -5 and -42 kJ/mol. Meanwhile, the predicted intrinsic enthalpy (-25.1 kJ/mol) of binding was in excellent agreement with the measured intrinsic enthalpy (-25.6 kJ/mol). Corrections to the observed calorimetric enthalpies allowed comparisons with enthalpies obtained from the van't Hoff method. It is shown that the predicted intrinsic calorimetric enthalpy agrees well with the van't Hoff enthalpies in instances where observed enthalpies significantly deviated. This treatment is general and is not specific to phenobarbital or activated carbon.

Disagreements Between Calorimetric and Van't Hoff Enthalpies of Adsorption: A New Langmuir-like Model to Account for the Effect of Solvent Displacement Stoichiometry

The reported inconsistencies between calorimetry and the van't Hoff equation hinder the utility of thermodynamics in pharmaceutical research. In ligand binding or adsorption assays, it is believed that the van't Hoff equation falls short because of the lack of stoichiometric treatment in the equilibrium constant. A new modified Langmuir-Like equation that accounts for the stoichiometry of solute adsorption and solvent displacement is proposed in this work. The performance of the model was evaluated by studying the adsorption of phenobarbital from aqueous solutions by commercial activated carbon. The amount of water occupying the adsorption sites was estimated by graphical analysis of the 'knee point' of water-vapor adsorption isotherms and was found to correlate well with the relative percentage of hydroxyl and carbonyl surface groups. It was found that one phenobarbital molecule displaces 2-6 water molecules from the adsorption site. It is shown that adsorption enthalpy was not affected by the adjustment for stoichiometry, supporting the notion that the van't Hoff enthalpy is intrinsic and is independent of the stoichiometry of solvent displacement in Langmuir-based binding. The widely reported disparities between the van't Hoff and calorimetric enthalpies are unlikely to be from a stoichiometric origin.

The influence of several nutritional supplements on the rational use of cabozantinib

To promote the rational use of cabozantinib (CBZ), this paper studied the influence of several nutritional supplements on the interaction between CBZ and bovine serum albumin (BSA), an appropriate alternative model for human serum albumin (HSA) that is one of the important transporter proteins in plasma, by fluorescence spectroscopy and UV-vis spectroscopy. The results showed that CBZ could quench the fluorescence of BSA via a dynamic-static quenching process, and the six nutritional supplements did not change the quenching mode of BSA by CBZ. However, all of them could reduce the binding constant of the CBZ-BSA system at 293 K and increase the polarity around tryptophan residues. Among them, nicotinamide and vitamin B₁₂ (VB₁₂ ) had a greater effect on the binding constants of the CBZ-BSA system. In the meantime, the thermodynamic parameters of the CBZ-BSA system were examined, indicating that the interaction of CBZ with BSA was spontaneous and dominated by hydrophobic forces. Further research discovered that the combining of CBZ with BSA was primarily located within Site I of BSA, and the binding distance r was 2.48 nm. Consequently, while taking CBZ, patients should use VB₁₂ and nicotinamide carefully, which may interfere with the transport of drugs.

In silico Study of the Proteins Involved in the Persistence of Brucella spp

BACKGROUND

One of the major problems with Brucella infections is its tendency to become chronic and recurrent, providing a hindrance to the management of this infection. It has been proposed that chronicity is greatly affected by a phenomenon called persistence in bacteria. Several mechanisms are involved in bacterial persistence, including the type II toxin-antitoxin system, the SOS and oxidative and stringent responses.

METHODS

In this in silico study, these persistence mechanisms in Brucella spp. were investigated.

RESULTS

The structure and the interactions between modules involved in these systems were designed, and novel peptides that can interfere with some of these important mechanisms were developed.

CONCLUSION

Since peptide-based therapeutics are a new and evolving field due to their ease of production, we hope that peptides developed in this study, as well as the information about the structure and interactions of modules of persistence mechanisms, can further be used to design drugs against Brucella persister cells in the hope of restraining the chronic nature of Brucellosis.

pH-sensitive O-carboxymethyl chitosan/sodium alginate nanohydrogel for enhanced oral delivery of insulin

Oral drug delivery is considered the most preferred mode of treatment because of its high patient compliance and minimal invasiveness. However, the oral delivery of protein drug has been a difficult problem which restricts its application due to the unstable and inefficient penetration of protein in the gastrointestinal tract. In this study, a novel OCMC/SA nanohydrogel was prepared by using of O-carboxymethyl chitosan (OCMC) and sodium alginate (SA) to solve the problem. The OCMC/SA had a typical nanostructure, which was helpful to increase the specific surface area and enhanced the bioavailability of the drugs. OCMC/SA had a high drug loading capacity and realized passive drug targeting function by responding to the different pH value of the microenvironment. It could have a certain protective effect on drugs in strong acid circumstances, while its structure got loosed and effectively released drugs in intestinal circumstances. OCMC/SA could release the drug for >12 h, and the released insulin could maintain high activity. OCMC/SA nanohydrogel showed promising results in type 1 diabetic rats, and its pharmacological bioavailability was 6.57 %. In conclusion, this study constructed a novel OCMC/SA nanohydrogel, which had a lot of exciting characteristics and provided a new strategy for oral drug delivery.

New Synthetic Quinoline (Qui) Derivatives as Novel Antioxidants and Potential HSA's Antioxidant Activity Modulators-Spectroscopic Studies

The antioxidant activity of drugs, as well as the influence of drugs on the activity of endogenous antioxidant mechanisms in the human body is of great importance for the course of the disease and the treatment process. Due to the need to search for new therapeutic methods, the study of newly synthesized substances with potential therapeutic activity is necessary. This study aimed to designate some properties and characteristic parameters of new, synthetic quinoline three derivatives-1-methyl-3-allylthio-4-(4'-methylphenylamino)quinolinium bromide (Qui1), 1-methyl-3-allylthio-4-(3'-hydroxyphenylamino)quinolinium bromide (Qui2) as well as 1-methyl-3-allylthio-4-(4'-hydroxyphenylamino)quinolinium bromide (Qui3), including their antioxidant properties, as well as to analyse their activity as the potential modulators of Human Serum Albumin (HSA) antioxidant activity. In order to achieve the goal of the study, spectroscopic methods such as UV-Vis and circular dichroism (CD) spectroscopy have been used and based on the obtained data only slight and probably some surface interaction of quinoline derivatives (Qui1-Qui3) with HSA have been observed. The effect of Qui1-Qui3 on the HSA secondary structure was also insignificant. All analysed quinine derivatives have antioxidant activity against ABTS cation radical, in turn against DPPH radical, only Qui3 has noticeable antioxidant potential. The highest reduction potential by Qui3 as well as (Qui3 + HSA)_complex has been shown. Qui3 mixed with HSA has mostly the synergistic effect against DPPH, ABTS and FRAP, while Qui1 and Qui2 in the presence of HSA mostly have a synergistic and additive effect towards ABTS, respectively. Based on the obtained results it can be concluded that Qui2 and Qui3 can be considered potential modulators of HSA antioxidant activity.

Development of 1,3-diynyl derivatives of noscapine as potent tubulin binding anticancer agents for the management of breast cancer

We developed 1,3-diynyl derivatives of noscapine (an opium alkaloid) through in silico combinatorial approach and screened out a panel of promising derivatives that bind tubulin and display anticancer activity. The selected derivatives such as 9-4-^tBu-Ph-Diyne (20p), 9-3,4-Di-Cl-Diyne (20k) and 9-3,4-Di-F-Diyne (22s) noscapinoids revealed improved predicted binding energy of -6.676 kcal/mol for 20p, -7.294 kcal/mol for 20k and -7.750 kcal/mol for 20s respectively in comparison to noscapine (-5.246 kcal/mol). These 1,3-diynyl derivatives (20p, 29k and 20s) were strategically synthesized in high yields by regioselective modification of noscapine scaffold and HPLC purified (purity is >96%). The decrease in intrinsic fluorescence of purified tubulin to 8.39%, 17.39% and 25.47% by 20p, 20k and 20s respectively, compared to control suggests their binding capability to tubulin. Their cytotoxicity activity was validated based on cellular studies using two human breast adenocarcinoma (MCF-7 and MDA-MB-231), a panel of primary breast tumor cells and one normal human embryonic kidney cell (293 T). The 1,3-diynyl noscapinoids, 20p, 20k and 20s inhibited cellular proliferation in all the cancer cells that ranged between 6.2 and 38.9 µM, without affecting the normal healthy cells (cytotoxicity is <5% at 100 µM). Further, these novel derivatives arrest cell cycle in the G2/M-phase, followed by induction of apoptosis to cancer cells. Thus, we conclude that 1,3-diynyl-noscapinoids have great potential to be a novel therapeutic agent for breast cancers.Communicated by Ramaswamy H. Sarma.

Investigations on the binding specificity of β-galactoside analogues with human galectin-1 using molecular dynamics simulations

Galectin-1 (Gal-1) is the first member of galectin family, which has a carbohydrate recognition domain, specifically binds towards β-galactoside containing oligosaccharides. Owing its association with carbohydrates, Gal-1 is involved in many biological processes such as cell signaling, adhesion and pathological pathways such as metastasis, apoptosis and increased tumour cell survival. The development of β-galactoside based inhibitors would help to control the Gal-1 expression. In the current study, we carried out molecular dynamics (MD) simulations to examine the structural and dynamic behaviour Gal-1-thiodigalactoside (TDG), Gal-1-lactobionic acid (LBA) and Gal-1-beta-(1→6)-galactobiose (G16G) complexes. The analysis of glycosidic torsional angles revealed that β-galactoside analogues TDG and LBA have a single binding mode (BM1) whereas G16G has two binding modes (BM1 and BM2) for interacting with Gal-1 protein. We have computed the binding free energies for the complexes Gal-1-TDG, Gal-1-LBA and Gal-1-G16G using MM/PBSA and are -6.45, -6.22 and -3.08 kcal/mol, respectively. This trend agrees well with experiments that the binding of Gal-1 with TDG is stronger than LBA. Further analysis revealed that the interactions due to direct and water-mediated hydrogen bonds play a significant role to the structural stability of the complexes. The result obtained from this study is useful to formulate a set of rules and derive pharmacophore-based features for designing inhibitors against galectin-1.Communicated by Ramaswamy H. Sarma.

Integrating transcriptomics and network analysis-based multiplexed drug repurposing to screen drug candidates for M2 macrophage-associated castration-resistant prostate cancer bone metastases

Metastatic castration-resistant prostate cancer (CRPC) has long been considered to be associated with patient mortality. Among metastatic organs, bone is the most common metastatic site, with more than 90% of advanced patients developing bone metastases (BMs) before 24 months of death. Although patients were recommended to use bone-targeted drugs represented by bisphosphonates to treat BMs of CRPC, there was no significant improvement in patient survival. In addition, the use of immunotherapy and androgen deprivation therapy is limited due to the immunosuppressed state and resistance to antiandrogen agents in patients with bone metastases. Therefore, it is still essential to develop a safe and effective therapeutic schedule for CRPC patients with BMs. To this end, we propose a multiplex drug repurposing scheme targeting differences in patient immune cell composition. The identified drug candidates were ranked from the perspective of M2 macrophages by integrating transcriptome and network-based analysis. Meanwhile, computational chemistry and clinical trials were used to generate a comprehensive drug candidate list for the BMs of CRPC by drug redundancy structure filtering. In addition to docetaxel, which has been approved for clinical trials, the list includes norethindrone, testosterone, menthol and foretinib. This study provides a new scheme for BMs of CRPC from the perspective of M2 macrophages. It is undeniable that this multiplex drug repurposing scheme specifically for immune cell-related bone metastases can be used for drug screening of any immune-related disease, helping clinicians find promising therapeutic schedules more quickly, and providing reference information for drug R&D and clinical trials.

Zein enhanced the digestive stability of five citrus flavonoids via different binding interaction

BACKGROUND

Zein is commonly used to construct food flavonoid delivery systems. This study investigated the effect and mechanism of zein on the digestive stability of five citrus flavonoids, namely hesperetin (HET), hesperidin (HED), neohesperidin (NHD), naringenin (NEN), and naringin (NIN).

RESULTS

Zein enhanced the digestive stability of the five citrus flavonoids, especially that of HET and NEN, during digestion in the stomach and small intestine. Fluorescence spectroscopy results suggested that citrus flavonoids spontaneously quenched the endogenous fluorescence of zein in static quenching mode. The binding of HET, HED and NHD to zein was driven respectively by electrostatic, hydrophobic and electrostatic interaction. However, Van der Waals' force and hydrogen (H)-bond interaction represented the primary driving force for binding NEN, and NIN to zein to form complexes. The binding of the five citrus flavonoids to zein also caused a diverse bathochromic shift in ultraviolet absorbance. Analysis using Fourier-transform infrared and Raman spectroscopy revealed that the binding behavior of the five citrus flavonoids had different effects on changes in the secondary structures, disulfide bonds, and tyrosine exposure of zein. The results were also partially verified by molecular dynamic simulation.

CONCLUSIONS

Zein enhanced the digestive stability of the five citrus flavonoids via different binding interactions that was due to the difference in molecular structure of citrus flavonoids. © 2022 Society of Chemical Industry.

Starch and chitosan-based antibacterial dressing for infected wound treatment via self-activated NO release strategy

In this work, a positively charged chitosan-grafted-polyarginine (CS-N-PArg) as the macro-molecular NO donor, and a negatively charged acetalated starch (AcSt-O-PAsp) as a glucose donor, have been synthesized. To achieve the multi-enzymatic cascade system for local generation of self-supply glucose to increase the H₂O₂ concentration for the subsequent oxidization of L-Arg into NO, the designed positively charged CS-N-PArg, negatively charged AcSt-O-PAsp, glucoamylase (GA) and glucose oxidase (GOx) are absorbed and assembled in the pore of the gelatin sponge via electrostatic interaction to establish a smart antibacterial dressings (CS/St + GOx/GA). Once stimulated by Escherichia coli (E. coli)-infected wounds (a slightly acidic environment), the cascade reaction system can sequentially induce to generate glucose, H₂O₂ and NO, which exhibits a meaningful alternative idea for a high-performance antibacterial therapy.

Imperative persistent interaction analysis of anticancer noscapine-ionic liquid with calf thymus DNA

In this study, we have shown the interaction between opium poppy alkaloid noscapine-based ionic liquid [Pip-Nos]OTf and ct-DNA using UV-visible absorption spectroscopy, fluorescence spectroscopy, CD, and computational studies. The absorption spectra showed a hypochromic shift with no shift in the absorption maxima suggesting groove or electrostatic binding. Fluorescence spectra showed an enhancement in fluorescence emission suggesting that the probable mode of binding should be groove binding. Ethidium bromide (EB) competitive and Ionic strength study showed the absence of intercalative and electrostatic modes of interaction. Further, CD analysis of ct-DNA suggested a groove binding mode of interaction of [Pip-Nos]OTf with ct-DNA. [Pip-Nos]OTf displayed a strong binding with the target ct-DNA with a molecular docking score of -41.47 kJ/mol with all 3D coordinates and full conformation. Also, molecular binding contact analyses depicted the stable binding of drug and ct-DNA with potential hydrogen bonds and hydrophobic interactions. The structural superimposition dynamics analysis showed the stable binding of [Pip-Nos]OTf with the ct-DNA model through RMSD statistics. Moreover, the ligand interaction calculations revealed the involvement of large binding energy along with a high static number of molecular forces including the hydrogen bonds and hydrophobic interactions in their complexation. These significant results report the potency of [Pip-Nos]OTf and its important futuristic role in cancer therapeutics.

Exposure to ambient air pollution and osteoarthritis; an animal study

Exposure to air pollution has been associated with many adverse health effects. However, the evidence on the effects on osteoarthritis (OA) is scarce and the potential mechanism is unclear yet. Therefore, this study assessed the effect of exposure to air pollution (gaseous and particulate matter) and OA based on an animal model. We used four groups of female rats, including i) exposure to PMs and gaseous pollutants, ii) exposure only to gaseous pollutants, iii) exposure only to PMs, and iv) control (unexposed) group. The OA biomarkers, i.e., osteocalcin, cartilage oligomeric protein (COMP), and N-Telopeptides of Type I Collagen (NTX-I) and cytokines were measured in the plasma to detect the effect of exposure to ambient air pollution on OA in this animal model. The forced jogging exercises for 1 h and 5 days per week were used to record the physical activities. The median (interquartile range) concentrations of PM_2.5 and PM₁₀ were 35.9 (15.4) and 47.5 (22.5) μg/m³, respectively. The median (interquartile range (IQR)) of PM_2.5, PM₁₀, CO, NO₂, SO₂ and O₃ in the inlet ambient air were 36.9 (16.9), 51.7 (23.6) μg/m³, 16.1 (12.5) ppm, 413.7 (177.1), 334.2 (218.8) and 208.9 (113.1) ppb, respectively. The osteocalcin was significantly lower in PM as well as PM-gaseous exposure groups compared to control. Moreover, expressions of COMP were increased significantly in the PMs and exposure group compared to the control. For the PMs-gaseous exposure group, the COMP expressions were the highest compared to the control group. Similar results were observed for NTX-I. Exposure to PM and gaseous pollutants significantly increased plasma cytokine levels compared to control. Overall, our study showed a significant effect of exposure to PMs and PMs-gaseous exposure with OA in rats. Moreover, we observed a synergistic effect of mixed gaseous-PMs exposure compared to PMs and gaseous pollutants separately.

Functionalized SPION immobilized on graphene-oxide: Anticancer and antiviral study

The progressive and fatal outbreak of some diseases such as cancer and coronavirus necessitates using advanced materials to bring such devastating illnesses under control. In this study, graphene oxide (GO) is decorated by superparamagnetic iron oxide nanoparticles (SPION) (GO/SPION) as well as polyethylene glycol functionalized SPION (GO/SPION@PEG), and chitosan functionalized SPION (GO/SPION@CS). Field emission scanning electron microscopic (FESEM) images show the formation of high density uniformly distributed SPION nanoparticles on the surface of GO sheets. The structural and chemical composition of nanostructures is confirmed by X-ray diffraction and Fourier transform infrared spectroscopy. The saturation magnetization of GO/SPION, GO/SPION@PEG and GO- SPION@CS are found to be 20, 19 and 8 emu/g using vibrating sample magnetometer. Specific absorption rate (SAR) values of 305, 283, and 199 W/g and corresponding intrinsic loss power (ILP) values of 9.4, 8.7, and 6.2 nHm²kg^-1 are achieved for GO/SPION, GO/SPION@PEG and GO/SPION@CS, respectively. The In vitro cytotoxicity assay indicates higher than 70% cell viability for all nanostructures at 100, 300, and 500 ppm after 24 and 72 h. Additionally, cancerous cell (EJ138 human bladder carcinoma) ablation is observed using functionalized GO/SPION under applied magnetic field. More than 50% cancerous cell death has been achieved for GO/SPION@PEG at 300 ppm concentration. Furthermore, Surrogate virus neutralization test is applied to investigate neutralizing property of the synthesized nanostructures through analysis of SARS-CoV-2 receptor-binding domain and human angiotensin-converting enzyme 2 binding. The highest level of SARS-CoV-2 virus inhibition is related to GO/SPION@CS (86%) due to the synergistic exploitation of GO and chitosan. Thus, GO/SPION and GO/SPION@PEG with higher SAR and ILP values could be beneficial for cancer treatment, while GO/SPION@CS with higher virus suppression has potential to use against coronaviruses. Thus, the developed nanocomposites have a potential in the efficient treatment of cancer and coronavirus.

The Molecular Mechanism of Traditional Chinese Medicine Prescription: Gu-tong Formula in Relieving Osteolytic Bone Destruction

Bone metastasis is a common complication in patients with advanced tumors, causing pain and bone destruction and affecting their quality of life. Typically, complementary and alternative medicine (CAM), with unique theoretical guidance, has played key roles in the treatment of tumor-related diseases. Gu-tong formula (GTF), as a representative prescription of traditional Chinese medicine, has been demonstrated to be an effective clinical medication for the relief of cancer pain. However, the molecular mechanism of GTF in the treatment of osteolytic metastasis is still unclear. Herein, we employ network pharmacology and molecular dynamics methods to uncover the potential treatment mechanism, indicating that GTF can reduce the levels of serum IL6 and TGFB1 and thus limit the scope of bone cortical damage. Among the active compounds, sesamin and deltoin can bind stably with IL6 and TGFB1, respectively, and have the potential to become anti-inflammatory and anticancer drugs. Although the reasons for the therapeutic effect of GTF are complex and comprehensive, this work provides biological plausibility in the treatment of osteolytic metastases, which has a guiding significance for the treatment of cancer pain with CAM.

Exploring the binding mechanism of ferulic acid and ovalbumin: insights from spectroscopy, molecular docking and dynamics simulation

BACKGROUND

Ferulic acid (FA), a phenolic acid widely occurring in nature, has attracted extensive attention because of its biological activity. Ovalbumin (OVA) is a commonly used carrier protein. The mechanism of FA binding with OVA was investigated by utilizing a variety of spectral analyses, accompanied by computer simulation.

RESULTS

It was discovered that the fluorescence quenching mechanism of OVA by FA was a static mode as a result of the formation of an FA-OVA complex, which was verified by the concentration distributions and pure spectrum of the constituents decomposed from the high overlap spectrum signals using multivariate curve resolution-alternate least squares algorithm. Hydrogen bonds and Van der Waals forces drove the formation of FA-OVA complex with a binding constant of 1.69 × 10⁴  L mol^-1 . The presence of FA induced the loose structure of OVA with an attenuation of α-helix content and improved the thermal stability of OVA. Computer docking indicated that FA interacted with the amino acid residues Arg84, Asn88, Leu101 and Ser103 of OVA through hydrogen bonds. Molecular dynamics simulation proved that the combination of FA with OVA boosted the conformational stability of OVA and hydrogen bonds brought a crucial part in stabilizing the structure of the complex.

CONCLUSIONS

The study may supply the theoretical basis for the design of FA transport system using OVA as carrier protein to improve the instability and low bioavailability of FA. © 2021 Society of Chemical Industry.

Albumin Glycation Affects the Delivery of C-Peptide to the Red Blood Cells

Serum albumin is a prominent plasma protein that becomes modified in hyperglycemic conditions. In a process known as glycation, these modifications can change the structure and function of proteins, which decrease ligand binding capabilities and alter the bioavailability of ligands. C-peptide is a molecule that binds to the red blood cell (RBC) and stimulates the release of adenosine triphosphate (ATP), which is known to participate in the regulation of blood flow. C-peptide binding to the RBC only occurs in the presence of albumin, and downstream signaling cascades only occur when the albumin and C-peptide complex contains Zn²⁺. Here, we measure the binding of glycated bovine serum albumin (gBSA) to the RBC in conditions with or without C-peptide and Zn²⁺. Key to these studies is the analytical sample preparation involving separation of BSA fractions with boronate affinity chromatography and characterization of the varying glycation levels with mass spectrometry. Results from this study show an increase in binding for higher % glycation of gBSA to the RBCs, but a decrease in ability to deliver C-peptide (0.75 ± 0.11 nM for 22% gBSA) compared to samples with less glycation (1.22 ± 0.16 nM for 13% gBSA). A similar trend was measured for Zn²⁺ delivery to the RBC as a function of glycation percentage. When 15% gBSA or 18% gBSA was combined with C-peptide/Zn²⁺, the derived ATP release from the RBCs significantly increased to 113% or 36%, respectively. However, 26% gBSA with C-peptide/Zn²⁺ had no significant increase in ATP release from RBCs. These results indicate that glycation of BSA interferes in C-peptide and Zn²⁺ binding to the RBC and subsequent RBC ATP release, which may have implications in C-peptide therapy for people with type 1 diabetes.

Exploring the interaction between Cry1Ac protein and Zn2+, Cd2+ metal ions by fluorescence quenching and molecular docking approaches

Bacillus Thuringiensis (Bt) protein has a strong ability to complex with metal ions, which may increase the transport of metal ions in the soil multi-media system. In this study, the interactions between Cry1Ac protein and metal ions (Zn²⁺ and Cd²⁺) were investigated through spectroscopies and molecular docking methods. The spectra results showed that both Zn²⁺ and Cd²⁺ quenched the fluorescence intensity of Cry1Ac protein through the static quenching. The binding constants with 4-5 orders of magnitude also indicated the interactions between the ions and the Cry1Ac protein. The thermodynamic analysis showed that hydrogen bonds and van der Waals forces were predominant during the processes. In terms of the Förster non-radiation energy transfer theory, the binding distances between metal ions and Cry1Ac protein were approximately 0.21-0.24 nm, indicating the existence of a non-radiative energy transfer between them. Furthermore, molecular docking revealed that the metal ions participated in ligand binding with the Cry1Ac at the locations Asp569, Thr560, Asn564 and Gln566. The present work provided reasonable models helping us further understand the transport effect of heavy metals in the presence of Cry1Ac. The results could provide mechanistic insights into the nature of metal ions-Cry1Ac interactions and offer important information on the toxicity risk of metal ions-Cry1Ac binding interactions.

Interaction mechanism between ZnO nanoparticles-whey protein and its effect on toxicity in GES-1 cells

The interaction between zinc oxide nanoparticles (ZnO NPs) and whey protein (WP) was studied. The gastric epithelial cell line (GES-1) was used to evaluate the toxicity intensity of ZnO NPs. The interaction mechanism of ZnO NPs and WP was studied by spectroscopic techniques. The results showed that the inhibitory effect of ZnO NPs on cells activity could be reduced when added to ZnO NPs at a concentration of 50 µg/ml. The fluorescence quenching mechanism of ZnO NPs on WP is a combination of dynamic and static quenching. The interaction force between ZnO NPs and WP can be considered as H-bond and VdW force, and they have two binding sites. The interaction between WP and ZnO NPs leads to the loosening of the structural skeleton of WP and the extension of peptide chain, which exposes the tyrosine (Tyr) and tryptophan (Trp) hydrophobic groups in the hydrophobic region of protein molecules and reduces the hydrophobicity of the microenvironment. The ZnO NPs might form a complex with WP through H-bond, hydrophobic interactions, and so on, leading to peptide chain rearrangement, and finally causing changes in the secondary structure of α-helix. Practical Application This study provides a theoretical basis for future research on the interaction between food ingredients and nanomaterials, the evaluation of toxicity of nanomaterials and the application scope of nanomaterials in food field.

Multispectroscopic studies on the molecular interactions between bovine gamma-globulin and borohydride-capped silver nanoparticles

Interactions between bovine gamma-globulin (BGG) and borohydride-capped silver nanoparticles (BAgNPs) were studied using dynamic light scattering and spectroscopic techniques like UV-Vis, fluorescence and circular dichroism. The results were compared with earlier reported^[1] interactions between γ-globulin and citrate-coated AgNPs (CAgNPs). BAgNPs were synthesized and characterized. Irrespective of the coating on AgNPs, nanoparticles had formed ground state complexes with the protein. CAgNPs as well as BAgNPS had caused static quenching of tryptophan (Trp) fluorescence of the protein. The change in the capping agent from citrate to borohydride weakened the binding of nanoparticles with the protein. But the same change in capping agent had increased the- fluorescence quenching efficiency of AgNPs. Hydrogen bonding and van der Waals interactions were involved in BGG-BAgNPs complex similar to the CAgNPs complex with γ-globulin. Polarity of the Trp microenvironment in BGG was not altered by BAgNPs contrary to CAgNPs as supported by synchronous and three-dimensional fluorescence. Resonance light scattering experiment also suggested nano-bio conjugation. Far-UV and near-UV CD spectra respectively pointed towards changes in the secondary and tertiary structure of BGG by BAgNPs, which was not observed in case of CAgNPs.

Molecular recognition between bacterial phosphorothioate DNA and sulfur-binding domain (SBD): competition between the water cage and chalcogen-hydrophobic packet

Bacterial DNA phosphorothioation (PT) physiologically and stereo-specifically replaces a non-bridging oxygen in a phosphate link with a sulfur atom, which can be recognized by a highly conserved sulfur-binding domain (SBD). Here we conducted thermodynamic integration (TI), molecular dynamics simulation, and quantum chemical calculations to decipher the specific molecular interactions between PT-DNA and SBD in Streptomyces coelicolor type IV restriction enzyme ScoMcrA. The TI-calculated binding affinity of (5'-CCG_Rp-PSGCCGG-3')₂ is larger than that of (5'-CCGGCCGG-3')₂ by about 7.4-7.7 kcal mol^-1. The binding difference dominantly stems from hydration energy of non-phosphorothioate DNA (9.8-10.6 kcal mol^-1) in aqueous solution, despite the persistent preference of 2.6-3.2 kcal mol^-1 in the DNA-SBD MD simulations. Furthermore, the quantum chemical calculations reveal an unusual non-covalent interaction in the phosphorothioate-binding scenario, where the ^PS⋯N^P165 chalcogen bond prevails the ^PS⋯HC_β vdW interactions from the adjacent residues H116-R117-Y164-P165-A168. Thus, the chalcogen-hydrophobic interaction pulls PT-DNA into the SBD binding pocket while the water cage pulls a normal DNA molecule out. The synergetic mechanism suggests the special roles of the proline pyrrolidine group in the SBD proteins, consistent with the experimental observations in the X-ray crystallography and structural bioinformatics analysis.

Binding of the B-Raf Inhibitors Dabrafenib and Vemurafenib to Human Serum Albumin: A Biophysical and Molecular Simulation Study

Drug binding to human serum albumin (HSA) significantly affects in vivo drug transport and biological activity. To gain insight into the binding mechanism of the two B-Raf tyrosine kinase inhibitors dabrafenib and vemurafenib to HSA, in this work, we adopted a combined strategy based on fluorescence spectroscopy, isothermal titration calorimetry (ITC), circular dichroism (CD), and molecular simulations. Both anticancer drugs are found to bind spontaneously and with a 1:1 stoichiometry within the same binding pocket, located in Sudlow's site II (subdomain IIIA) of the protein with comparable affinity and without substantially perturbing the protein secondary structure. However, the nature of each drug-protein interactions is distinct: whereas the formation of the dabrafenib/HSA complex is more entropically driven, the formation of the alternative vemurafenib/HSA assembly is prevalently enthalpic in nature. Kinetic analysis also indicates that the association rate is similar for the two drugs, whereas the residence time of vemurafenib within the HSA binding pocket is somewhat higher than that determined for the alternative B-Raf inhibitor.

Investigation of protective effect of ethanol on the natural structure of protein with infrared spectroscopy

The stability of biological drugs with protein as an active substance depends heavily on the retention of natural protein structure during freeze-drying. Stabilizers have become important substances in the process of protein freeze-drying. In order to further understand the mechanism of the interaction between protein and stabilizers, human serum albumin (HSA) and simple hydroxyl compound ethanol were used as models. Infrared (IR) spectroscopy combined with chemometrics was implemented to investigate the changes of secondary structure and hydration of HSA when different concentrations of ethanol were considered as interference. Through the analysis of the protein secondary structure and hydrated layer, we found that the addition of ethanol-d6 increased the α-helix of HSA and reduced the disordered structure. The hydrogen bond structure around HSA was enhanced and intermolecular aggregation was reduced through the action of the water molecules. The hypothesis was verified by circular dichroism (CD) and transmission electron microscopy (TEM) observation by adding different concentrations of ethanol-d6. It was found that a small amount of ethanol could protect the native conformation of HSA. In conclusion, this study revealed the mechanism of ethanol as a protein protector, provided a new idea for protein purification process and a theoretical basis for biomolecular interaction.

Chebulinic and chebulagic acid binding with serum proteins: biophysical and molecular docking approach

Chebulinic acid (CHN) and chebulagic acid (CHG) have been known for centuries for their anti-cancer, anti-diabetes, HIV and anti-inflammatory properties. In this study, the interaction of these phytochemicals CHN/CHG, with the two major transport proteins for various drugs, human serum albumin (HSA) and α-1-acid glycoprotein (AGP), was unraveled by using several spectroscopic techniques and computational methods. The binding of CHN/CHG quenches the HSA/AGP fluorescence intensities, and also these phytochemicals are bound strongly to HSA/AGP proteins. An apparent decrease in fluorescence intensities of CHN/CHG-HSA and CHN/CHG-AGP complex showed the static mode of fluorescence quenching. Furthermore, the intrinsic fluorescence and using site-specific markers ibuprofen competing with these molecules, thereby replacing it in the binding site of subdomain IIIA. The computational methods substantiated the experimental findings, revealing that CHN interacted with Lys414A, Glu492A, Glu492A and Lys413A residues of subdomain IIIA of HSA and for CHG showed the interaction with Lys545A and Lys413A residues of subdomain IIIA of HSA. Fluorescence and surface plasmon resonance data unveiled a previously unreported binding event between CHN/CHG and HSA; the determined binding affinities of both compounds were slightly higher for HSA than AGP. A change in functionality of protein confirmed the esterase-like activity of HSA in the presence of CHG/CHN upon binding with CHG/CHN. Displacement and circular dichroism (CD) experiments analysis showed that the two CHN/CHG and binding specifically to IIIA subdomain on HSA results in the conformational changes in the HSA. Thus, CD revealed a few conformational changes in HSA due to CHN/CHG. The binding of these two phytochemicals to the plasma proteins would give a path to develop new inspired drug molecules for chronic diseases.Communicated by Ramaswamy H. Sarma.

Solvent Effects on the Photophysical Properties of a Donor-acceptor Based Schiff Base

In this work, a donor-acceptor substituted aromatic system ((E)-N-((E)-3-(4 (dimethylamino)phenyl) allylidene)-4-(trifluoromethyl) benzenamine (DPATB) has been synthesized and its detailed photophysics of intramolecular charge transfer process have been explored on the basis of steady state absorption, fluorescence and time resolved spectroscopy in combination with density functional theory calculations. Large solvent dependency fluorescence spectral shift and the calculated large excited state dipole moment clearly indicate an efficient charge transfer occurring from the donor group to the acceptor moiety in the excited state. Effect on addition of acid and pH on steady state spectral properties further reveals excited state charge transfer character. Quantum chemical calculations were performed in order to study the conformation and polarity of DPATB at their ground as well as excited electronic states. The HOMO and LUMO molecular orbital pictures are obtained at DFT level using B3LYP functional and 6-311 + g(d,p) basis set which clearly support excited state intramolecular charge transfer process. The molecular electrostatic potential maps for the optimized ground state, donor twisted and acceptor twisted geometry shed insight on the electrostatic potential and charge distribution in a system which gives information about the reacting site of the probe and nature of the reaction. In this work, detailed photophysics of excited state intramolecular charge transfer process in donor-acceptor system (DPATB) was evaluated using steady state and time-resolved fluorescence spectroscopy in combination with density functional theory calculations. Large solvent dependency fluorescence spectral shift and the calculated large excited state dipole moment clearly indicate an efficient charge transfer occurring in DPATB. Molecular orbital pictures as obtained from DFT based computational analysis reveals a significant change in the distribution of electron density upon transition from HOMO to LUMO which confirms an ICT process occurring from the donor group to the acceptor moiety in the excited state.

8-Prenylnaringenin tissue distribution and pharmacokinetics in mice and its binding to human serum albumin and cellular uptake in human embryonic kidney cells

8-Prenylnaringenin (8-PN), a hop flavonoid, is a promising food substance with health benefits. Compared with nonprenylated naringenin, 8-PN exhibits stronger estrogenic activity and prevents muscle atrophy. Moreover, 8-PN prevents hot flushes and bone loss. Considering that prenylation reportedly improves the bioavailability of flavonoids, we compared the parameters related to the bioavailability [pharmacokinetics and tissue distribution in C57/BL6 mice, binding affinity to human serum albumin (HSA), and cellular uptake in HEK293 cells] of 8-PN and its mother (non-prenylated) compound naringenin. C57/BL6 mice were fed an 8-PN or naringenin mixed diet for 22 days. The amount of 8-PN (nmol/g tissue) in the kidneys (16.8 ± 9.20), liver (14.8 ± 2.58), muscles (3.33 ± 0.60), lungs (2.07 ± 0.68), pancreas (1.80 ± 0.38), heart (1.71 ± 0.27), spleen (1.36 ± 0.29), and brain (0.31 ± 0.09) was higher than that of naringenin. A pharmacokinetic study in mice demonstrated that the C _max of 8-PN (50 mg/kg body weight) was lower than that of naringenin; however, the plasma concentration of 8-PN 8 h after ingestion was higher than that of naringenin. The binding affinity of 8-PN to HSA and cellular uptake in HEK293 cells were higher than those of naringenin. 8-PN bioavailability features assessed in mouse or human model experiments were obviously different from those of naringenin.

Exciton-Tryptophan Coupling Pulse Behavior Along with Corona Formation, Binding Analysis and Interaction Study of ZnO Nanorod-Serum Albumin Protein Bioconjugate

The bioconjugate of bovine serum albumin (BSA) and zinc oxide nanorods (ZnO NRs) is investigated to explore the behavior of the tryptophan (Trp)-exciton coupling and corona formation. The pulse like nature of the coupled system between Trp of BSA and exciton of ZnO NRs has been observed after analysis of the optical parameters like refractive index, susceptibility, and optical dielectric constant. The time constant for tryptophan, exciton surface binding (t₁ ) and reorganization (t₂ ) are found to be (t₁ ) 8min, 7min and (t₂ ) 150 min, 114.5 min, respectively. The close proximity binding of BSA with ZnO NRs via tryptophan as well as exciton is responsible for bioconjugate formation. The aggregated structure of BSA is observed from small-angle X-ray scattering study in interaction with ZnO NRs. The change in secondary structure and tertiary deformation of the serum protein have been studied from FTIR and emission quenching analysis. The number of binding sites (n) signified to the enhancement of the cooperative binding. The binding has been found to be endothermic and favored by unfavorable positive enthalpy with a favorable entropy change from the result of the isothermal titration calorimetry (ITC).

Interaction Properties of Biosynthesized Cadmium Sulphide Quantum Dots with Human Serum Albumin: Further Investigation of Antibacterial Activities and Sensing Applications

Synthesis of low dimensional quantum dots (QDs) (1-10 nm) via green route has garnered great interest having the prospective use in many biological applications (diagnosis, drug delivery and in vivo sensing), which is difficult to achieve by chemical synthesize methods having larger QDs particles or hazardous reagents required for synthesizing of QDs. Here, we have synthesized biogenic cadmium sulphide (CdS) QDs using green tea extract as reducing agents that were homogeneous and smaller size particles 2-4 nm. We also elucidate the (a) protein binding, (b) antibacterial and (c) sensing applications of biogenic CdS QDs in this present work. The biosynthesized CdS QDs were found to have extensive antibacterial activity against both gram-negative E. coli and gram-positive E. faecalis bacterial strains. Since the introduction of QDs in biological media, they can form protein-QDs complex; hence we investigate the binding interaction of CdS QDs with the carrier protein human serum albumin (HSA) in vitro. The synthesized CdS QDs quenched the intrinsic fluorescence of HSA through static quenching mechanism and binding constant (K_b ) was found in order of 10⁴ M^-1 . It was also observed that presence of biogenic CdS QDs affects the HSA-ligand interactions in vitro. The synthesized CdS showed highly effective sensors for tetracycline, rifampicin and bilirubin with LOD values of 99, 141 and 29 ng/mL respectively.

Molecular interactions of trichoderma β-1,4-glucosidase (ThBglT12) with mycelial cell wall components of phytopathogenic Macrophomina phaseolina

Efficacy of a β-1,4-glucosidase from Trichoderma harzianum T12 (ThBglT12) in disrupting the cell wall of the phytopathogenic fungus M. phaseolina (Macrophomina phaseolina) was studied, as the underlying molecular mechanisms of cell wall recognition remains elusive. In this study, the binding location identified by a consensus of residues predicted by COACH tool, blind docking, and multiple sequence alignment revealed that molecular recognition by ThBglT12 occurred through interactions between the α-1,3-glucan, β-1,3-glucan, β-1,3/1,4-glucan, and chitin components of M. phaseolina, with corresponding binding energies of -7.4, -7.6, -7.5 and -7.8 kcal/mol. The residue consensus verified the participation of Glu172, Tyr304, Trp345, Glu373, Glu430, and Trp431 in the active site pocket of ThBglT12 to bind the ligands, of which Trp345 was the common interacting residue. Root mean square deviation (RMSD), root mean square fluctuation (RMSF), total energy, and minimum distance calculation from molecular dynamics (MD) simulation further confirmed the stability and the closeness of the binding ligands into the ThBglT12 active site pocket. The h-bond occupancy by Glu373 and Trp431 instated the role of the nucleophile for substrate recognition and specificity, crucial for cleaving the β-1,4 linkage. Further investigation showed that the proximity of Glu373 to the anomeric carbon of β-1,3/1,4-glucan (3.5 Å) and chitin (5.5 Å) indicates the nucleophiles' readiness to form enzyme-substrate intermediates. Plus, the neighboring water molecule appeared to be correctly positioned and oriented towards the anomeric carbon to hydrolyze the β-1,3/1,4-glucan and chitin, in less than 4.0 Å. In a nutshell, the study verified that the ThBglT12 is a good alternative fungicide to inhibit the growth of M. phaseolina.Communicated by Ramaswamy H. Sarma.

Benzothiazole Pyrazoline: Acid-Switchable Absorption and Fluorescence of Photoinduced Electron Transfer (PET)

Acid-responsive fluorescent compounds were prepared by introducing an ortho-hydroxyphenyl to pyrazoline with a benzothiazole backbone. These compounds demonstrated normal fluorescence photoinduced electron transfer (PET) under neutral conditions but the addition of trifluoroacetic acid showed an arctic blue fluorescence, we verified that a protonation process of nitrogen in the thiazole ring which weakened the ability of thiazole to donate electrons to the pyrazoline and changed the photoinduced electron transfer led to photoinduced electron transfer (PET), which was the mechanism of the fluorescence quenching phenomenon under strongly acidic conditions. The photophysical properties of Benzothiazole pyrazoline exhibited blue emission at 421 nm in aqueous DMSO. The blue shift in the emission was switched by acid in DMSO, showing the compound's distinct fluorescence peak at 554 nm. To investigate solvatochromism, eight different solvents were used. The red-shift emission observed in enhancing the polarity of solvents and emission in DMSO suggested the conformation of the molecule which led to the intramolecular charge transfer by color and emission changes. Furthermore, the probe was also applied using the High-performance liquid chromatography (HPLC) with a UV detector to determine the trifluoroacetic acid in water samples. Interestingly, the method was found to be linear over the range of 10.0 µg L^-1 to 250.0 µg L^-1 (0.999). Under the optimum condition, the separation of trifluoroacetic acid was achieved in 20 min with the LOD of 1.3 µg L^-1 and LOQ of 5.1 µg L^-1. This proposed method also showed satisfactory results when applied for the analysis of trifluoroacetic acid in a water sample.