Solvent Geometry Regulated J- and H-Type Aggregates of Photoswitchable Organogelator: Phase-Selective Thixotropic Gelation and Oil Spill Recovery

We demonstrate supramolecular polymerization and formation of 1D nanofiber of azobenzene based organogelator (AZO-4) in cyclic hydrocarbon solvents (toluene and methylcyclohexane). The AZO-4 exhibits J- and H-type aggregates in toluene: MCH (9 : 1) and MCH: toluene (9 : 1) respectively. The type of aggregate was governed by the geometry of the solvents used in the self-assembly process. The J-type aggregates with high thermal stability in toluene is due to the enhanced interaction of AZO-4 π- surface with the toluene π-surface, whereas H-aggregate with moderate thermal stability in MCH was due to the interruption of the cyclic hydrocarbon in van der Waals interactions of peripheral chains of AZO-4 molecule. The light induced reversible photoisomerization is observed for both J- and H-aggregates. The macroscopic property revealed spontaneous and strong gelation in toluene preferably due to the strong interactions of the AZO-4 nanofibers with the toluene solvent molecules compared to the MCH. The rheological measurements revealed thixotropic nature of the gels by step-strain experiments at room temperature. The thermodynamic parameter (ΔHm) of gel-to-sol transition was determined for all the gels to get more insight into the gelation property. Furthermore, the phase selective gelation property was extended to the oil spill recovery application using diesel/water and petrol/water mixture.

Comparative study on Antibacterial efficacy of a series of chromone sulfonamide derivatives against drug-resistant and MDR-isolates

Sulfonamide derivatives have numerous pharmaceutical applications having antiviral, antibacterial, antifungal, antimalarial, anticancer, and antidepressant activities. The structural flexibility of sulfonamide derivatives makes them an excellent candidate for the development of new multi-target agents, although long-time exposure to sulfonamide drugs results in many toxic impacts on human health. However, sulfonamides may be functionalized for developing less toxic and more competent drugs. In this work, sulfonamides including Sulfapyridine (a), Sulfathiazole (b), Sulfamethoxazole (c), and Sulfamerazine (d) are used to synthesize Schiff bases of 7-hydroxy-4-methyl-2-oxo-2H-chromene-8-carbalde-hyde (1a-1d). The synthesized compounds were spectroscopically characterized and tested against hospital isolates of three Gram-positive (Methicillin-resistant Staphylococcus aureus PH217, Ampicillin-resistant Coagulase-negative Staphylococcus aureus, multidrug-resistant (MDR) Enterococcus faecalis PH007R) and two Gram-negative bacteria (multidrug-resistant Escherichia coli, and Salmonella enterica serovar Typhi), compared to the quality control strains from ATCC (S. aureus 29213, E. faecalis 25922, E. coli 29212) and MTCC (S. Typhi 734). Two of the four Schiff bases 1a and 1b are found to be more active than their counterpart 1c and 1d; while 1a have showed significant activity by inhibiting MRSA PH217 and MDR isolates of E. coli at the minimum inhibitory concentration (MIC) of 150 μg/mL and 128 μg/mL with MBC of 1024 µg/mL, respectively. On the other hand, the MIC of 1b was 150 μg/mL against both S. aureus ATCC 29213 and Salmonella Typhi MTCC 734, compared to the control antibiotics Ampicillin and Gentamycin. Scanning electron microscopy demonstrated the altered surface structure of bacterial cells as a possible mechanism of action, supported by the in-silico molecular docking analysis.

Entropy-Enthalpy Compensation in Solvent Geometry Regulated Supramolecular Polymerization of Luminescent Napthalimide via a Non-Cooperative, Isodesmic Mechanism

Supramolecular polymers of π-conjugated systems are an important class of materials with fascinating functions and properties originated from the dynamic behavior and highly ordered molecular organizations. Here, a donor-π-acceptor based functionalized luminescent napthalene monoimide (NMI) undergoes J-type self-assembly by non-covalent interactions via a non-cooperative, isodesmic mechanism to form supramolecular 1D nanowire. The fundamental insights into the thermodynamics regulating the supramolecular polymerization were derived through the fitting of the isodesmic model to variable temperature UV/Vis data in linear (dodecane) and nonliner hydrocarbon (decalin) based solvents. This shows a significant role of entropy-enthalpy compensation in solvent geometry-regulated formation and stabilization of supramolecular polymer. Furthermore, we have quantitively estimated the influence of solvent geometry and found that NMI forms stronger self-assembly and spontaneous gel in linear hydrocarbon based solvent compared to nonliner one and thereby substantially increases the degree of polymerization in linear hydrocarbon solvent (dodecane). This is accredited to the effective influence of the linear hydrocarbon solvent molecules in the polymerization process by favourable van der waals interactions with the peripheral alkyl chains of the NMI monomers in contrast to unfavourable interaction of nonliner hydrocarbon solvent due to geometry mismatch.

Urea-Promoted Neat Synthesis of Fused Dihydroisoquinolines and Disubstituted Pyridines: A Mechanistic Observation with Molecular-Sensing Studies

An efficient and short synthesis of fused dihydroisoquinolines, diaryl substituted pyridine derivatives in good to high yields has been established by using an environmentally safe, solvent-metal-oxidant-free tandem approach. In this article, we discuss how the electrocyclic reaction is more pronounced in the solid phase in the presence of urea, whereas the typical aza-Michael addition is more prominent in presence of arylamine in the solution phase for 3-(2-formylcycloalkenyl)acrylic ester derivative substrates. The wide range of substrates and urea-promoted neat synthesis made our approach more significant in medical and also analytical science. Moreover, an isoquinoline alkaloid decumbenine B analogue has been synthesized by using our newly developed neat methodology. We have also investigated the photophysical properties of the synthesized fused dihydroisoquinoline derivatives. One of the synthesized molecules was used as a sensor for the selective detection of toxic picric acid. Therefore, the effective neat synthesis and molecular sensing applications of these compounds made our approach more exciting in the field of heterocyclic chemistry.

Structural modulation of insulin by hydrophobic and hydrophilic molecules

In the bloodstream, insulin interacts with various kinds of molecules, which can alter its structure and modulate its function. In this work, we have synthesized two molecules having extremely hydrophilic and hydrophobic side chains. The effects of hydrophilic and hydrophobic molecules on the binding with insulin have been investigated through a multi-spectroscopic approach. We found that hydrophilic molecules have a slightly higher binding affinity towards insulin. Insulin can bind with the hydrophilic molecules as it binds glucose. The high insulin binding affinity of a hydrophobic molecule indicates its dual nature. The hydrophobic molecule binds at the hydrophobic pocket of the insulin surface, where hydrophilic molecules interact at the polar surface of the insulin. Such binding with the hydrophobic molecule perturbs strongly the secondary structure of the insulin much more in comparison to hydrophilic molecules. Therefore, the stability of insulin decreases in the presence of hydrophobic molecules.

A novel nickel(II) complex with N,S donor Schiff base: Structural characterisation, DFT, TD-DFT study and catalytic investigation

One new mononuclear nickel(II) thiosemicarbazone complex (1), has been synthesised from the Schiff base ligand derived from p-anisaldehyde and thiosemicarbazide. Complex 1 is characterized by using different spectroscopic techniques and single crystal X-ray structure analysis. Time dependent density functional theory (TD-DFT) was performed to simulate the electronic spectra of the complex 1 with the help of Polarizable Continuum Model (PCM) model. Complex 1 acts as functional models. The catalytic property has been evaluated from Lineweaver-Burk plot using the Michaelis-Menten approach of enzyme catalysis with a kcat value of the order of 708 h-1.

Anion-assisted supramolecular polymerization of luminescent organic π-conjugated chromophores in a moderately polar solvent: tunable nanostructures and their corresponding effects on electronic properties

Supramolecular polymers of π-conjugated organic chromophores have emerged as promising candidates in organic electronics because of their dynamic and highly ordered molecular organization. Herein, we demonstrate the formation of luminescent, highly conducting supramolecular polymers of a functionalized naphthalimide π-chromophore-based organic semiconductor in a moderately polar organic solvent (tetrahydrofuran) by overcoming solute-solvent H-bonding via assistance from fluoride anions. The polymerization is exclusively guided by the synergistic effects of cascade H-bonding (F-⋯H-N- of primary amines, followed by -CO⋯H-N- of amides), π-π stacking and hydrophobic interactions. An increasing molar equivalent of anions leads to a morphology transition from 1D nanowires to 2D nanosheets via nanotubes and nanorings, but above a particular threshold of the same anion, depolymerization-mediated disruption of long-range order and formation of non-luminescent spherical particles was observed. Such significant impacts of anions in supramolecular polymerization-depolymerization were utilized in modulating the electronic properties of this naphthalimide-based organic semiconductor.

Small Molecule Interactions with Biomacromolecules: DNA Binding Interactions of a Manganese(III) Schiff Base Complex with Potential Anticancer Activities

A manganese(III) complex, [MnIII(L)(SCN)(enH)](NO3)·H2O (1•H2O) (H2L = 2-((E)-(2-((E)-2-hydroxy-3-methoxybenzylidene-amino)-ethyl-imino)methyl)-6-methoxyphenol), has been synthesized and characterized by single-crystal X-ray diffraction analysis. The interaction of 1•H2O with DNA was studied by monitoring the decrease in absorbance of the complex at λ = 324 nm with the increase in DNA concentration, providing an opportunity to determine the binding constant of the 1•H2O-ct-DNA complex as 5.63 × 103 M-1. Similarly, fluorescence titration was carried out by adding ct-DNA gradually and monitoring the increase in emission intensity at 453 nm on excitation at λex = 324 nm. A linear form of the Benesi-Hildebrand equation yields a binding constant of 4.40 × 103 M-1 at 25 °C, establishing the self-consistency of our results obtained from absorption and fluorescence titrations. The competitive displacement reactions of dyes like ethidium bromide, Hoechst, and DAPI (4',6-diamidine-2'-phenylindole dihydrochloride) from dye-ct-DNA conjugates by 1•H2O were analyzed, and the corresponding KSV values are 1.05 × 104, 1.25 × 104, and 1.35 × 104 M-1 and the Kapp values are 2.16 × 103, 8.34 × 103, and 9.0 × 103 M-1, from which it is difficult to infer the preference of groove binding over intercalation by these DNA trackers. However, the molecular docking experiments and viscosity measurement clearly indicate the preference for minor groove binding over intercalation, involving a change in Gibbs free energy of -8.56 kcal/mol. The 1•H2O complex was then evaluated for its anticancer potential in breast cancer MCF-7 cells, which severely abrogates the growth of the cells in both 2D and 3D mammospheres, indicating its promising application as an anticancer drug through a minor groove binding interaction with ct-DNA.

Live-Cell Mitochondrial Targeted NIR Fluorescent Covalent Labeling of Specific Proteins Using a Dual Localization Effect

Here, our designed water-soluble NIR fluorescent unsymmetrical Cy-5-Mal/TPP+ consists of a lipophilic cationic TPP+ subunit that can selectively target and accumulate in a live-cell inner mitochondrial matrix where a maleimide residue of the probe undergoes faster chemoselective and site-specific covalent attachment with the exposed Cys residue of mitochondrion-specific proteins. On the basis of this dual localization effect, Cy-5-Mal/TPP+ molecules remain for a longer time period even after membrane depolarization, enabling long-term live-cell mitochondrial imaging. Due to the adequate concentration of Cy-5-Mal/TPP+ reached in live-cell mitochondria, it facilitates site-selective NIR fluorescent covalent labeling with Cys-exposed proteins, which are identified by the in-gel fluorescence assay and LC-MS/MS-based proteomics and supported by a computational method. This dual targeting approach with admirable photostability, narrow NIR absorption/emission bands, bright emission, long fluorescence lifetime, and insignificant cytotoxicity has been shown to improve real-time live-cell mitochondrial tracking including dynamics and interorganelle crosstalk with multicolor imaging applications.

Anti-HSV nucleoside and non-nucleoside analogues: spectroscopic characterisation of naphthyl and coumarinyl amides and their mode and mechanism of antiviral action

Nucleoside analogues acyclovir, valaciclovir, and famciclovir are the preferred drugs against human Herpes Simplex Viruses (HSVs). However, the viruses rapidly develop resistance against these analogues which demand safer, more efficient, and nontoxic antiviral agents. We have synthesized two non-nucleoside amide analogues, 2-Oxo-2H-chromene-3-carboxylic acid [2-(pyridin-2-yl methoxy)-phenyl]-amide (HL1) and 2-hydroxy-1-naphthaldehyde-(4-pyridine carboxylic) hydrazone (HL2). The compounds were characterized by different physiochemical methods including elementary analysis, FT-IR, Mass spectra, 1H-NMR; and evaluated for their antiviral efficacy against HSV-1F by Plaque reduction assay. The 50% cytotoxicity (CC50), determined by MTT test, revealed that HL1 (270.4 μg/ml) and HL2 (362.6 μg/ml) are safer, while their antiviral activity (EC50) against HSV-1F was 37.20 μg/ml and 63.4 μg/ml against HL1 and HL2 respectively, compared to the standard antiviral drug Acyclovir (CC50 128.8 ± 3.4; EC50 2.8 ± 0.1). The Selectivity Index (SI) of these two compounds are also promising (4.3 for HL1 and 9.7 for HL2), compared to Acyclovir (49.3). Further study showed that these amide derivatives block the early stage of the HSV-1F life cycle. Additionally, both these amides make the virus inactive, and reduce the number of plaques, when infected Vero cells were exposed to HL1 and HL2 for a short period of time.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03658-0.

Synthesis of Multifused Pyrrolo[1,2-a]quinoline Systems by Tandem Aza-Michael-Aldol Reactions and Their Application to Molecular Sensing Studies

Herein, we have presented a weak acid-promoted tandem aza-Michael-aldol strategy for the synthesis of diversely fused pyrrolo[1,2-a]quinoline (tricyclic to pentacyclic scaffolds) by the construction of both pyrrole and quinoline ring in one pot. The described protocol fabricated two C-N bonds and one C-C bond in the pyrrole-quinoline rings which have been sequentially formed under transition-metal-free conditions by the extrusion of eco-friendly water molecules. A ketorolac drug analogue has been synthesized following the current protocol, and one of the synthesized tricyclic pyrrolo[1,2-a]quinoline fluorophores has been used to detect highly toxic picric acid via the fluorescence quenching effect.

Arylative Methylation of 2,3-Dihydropyrazines and Pyrazinones Using Dimethyl Sulfoxide as a C1 Source

Divergent synthesis of α-C-H methylated pyrazines and pyrazinones using dimethyl sulfoxide as a nonconventional methylating agent under metal-free conditions was reported. Dimethyl sulfoxide-coordinated bromine cation pools generated from the treatment of dimethyl sulfoxide and 1,2-dibromoethane undergo Pummerer-type fragmentation to afford an electrophilic methyl(methylene)sulfonium ion for reaction with a carbon nucleophile followed by aromatization to afford α-methylated pyrazines and pyrazinones.

Unveiling the catecholase activities and DNA binding of heterogeneous mono-, di-, and polymeric Schiff Base Cu(II) complexes

A mononuclear, dinuclear, and a polymeric Cu(II) complexes of the general formula [Cu(L1)Cl2] (1), [Cu2(L2)2(µ1.1-CH3COO-)2] (2), and [Cu2(L3)2(µ-N3)(N3)]n (3) have been synthesized using NNN and NNO tridentate Schiff base ligands...

Identification of 4-acrylamido-N-(pyridazin-3-yl)benzamide as anti-COVID-19 compound: a DFTB, molecular docking, and molecular dynamics study

Omicron is one of the variants of COVID-19 and continuing member of a pandemic. There are several types of vaccines that were developed around the globe to fight against the virus. However, the world is suffering to find suitable drug candidates for the virus. The main protease (Mpro) enzyme of the virus is the best target for finding drug molecules because of its involvement in viral infection and protein synthesis. ZINC-15 is a database of 750 million commercially available compounds. We find 125 compounds having two aromatic rings and amide groups for non-covalent interactions with active site amino acids and functional groups with the capability to bind -SH group of C145 of Mpro through covalent bonding by a nucleophilic addition reaction. The lead compound (Z144) was identified using molecular docking. The non-covalent interactions (NCI) calculations show the interactions between amino acids present in the active site of the protein and the lead molecules are attractive in nature. The density functional-based tight-binding (DFTB) study of the lead compound with amino acids in the active site indicates that Q190 and Q193 play a very critical role in stabilization. The Michael addition of the acrylamide group of the lead molecule at β-position is facile because the low energy lowest unoccupied molecular orbital (LUMO) is concentrated on the group. From molecular dynamics during 100 ns, it has come to light that strong non-covalent interactions are key for the stability of the lead inside the protein and such binding can fold the protein. The free energy for this interaction is -42.72 kcal mol-1 which was obtained from MM-GB/SA calculations.

ß-Sheet Induced Helical Self-Assembly Structure Formation by Dityrosine Dipeptide: Crystallographic Evidence and Other Biophysical Studies

Self-assembled structures derived from short peptides are a versatile class of organic building blocks which have shown great potential in a wide range of domains. In the current study, side-chain protected dityrosine based short peptide (TP) was synthesized, and its conformation accompanied by a self-assembly pattern was investigated through several spectroscopic studies and single crystal X-ray analysis. The single crystal X-ray analysis of TP confirmed that it exhibited a ß-sheet pattern which further self-assembled to form ß-sheet-promoted helical architectures by various noncovalent interactions. To the best of our knowledge, this is the first crystallographic report of a side-chain protected dityrosine based short peptide adopting ß-sheet-promoted helical structures. Morphological analysis of TP also revealed ß-sheet as well as helical conformations. NMR study suggested that both amide hydrogens of TP are involved in intermolecular hydrogen bonding. Moreover, CD spectroscopy established the self-assembly phenomenon of TP in the solution state by showing both corresponding ß-sheet and α-helix bands. Hirshfeld surface analysis and DFT study also concluded similar results. These kinds of small peptide units mimicking important protein secondary structures like helical assembly would be of pivotal significance as they may act as small peptidomimetics, mimicking the protein "Hotspot" area.

Correction: Coumarin derivatives inhibit the aggregation of β-lactoglobulin

Correction for ‘Coumarin derivatives inhibit the aggregation of β-lactoglobulin’ by Hasan Parvej et al., RSC Adv., 2022, 12, 17020–17028, https://doi.org/10.1039/D2RA01029A.

Crystallography-based exploration of non-covalent interactions for the design and synthesis of coumarin for stronger protein binding

Protein molecules are a good target for the inhibition or promotion of biological processes. Different methods like QSAR and molecular docking have been developed to accurately design small binder molecules for target proteins. An alternative model has been developed wherein a statistical method is used to find the propensity of different non-covalent interactions between small molecules and amino acid residues of the protein. The results give hints as to the choice of substituents required at the SM to strongly bind to a protein. In this case, 75 different types of proteins bound with coumarin derivatives have been investigated and the non-covalent interactions observed between the basic coumarin moiety and amino acids have been analyzed. Density functional theory (DFT) calculations were used to identify the electronic features of coumarin to understand the feasibility of the observed non-covalent interactions and to find appropriate groups that can modulate these interactions. The binding affinity towards a protein (β-lactoglobulin (BLG)) and the stability of the protein complex have been investigated through docking and molecular dynamics of 100 ns, respectively. The modeled compounds were synthesized and investigated with regards to their interactions with the model carrier protein. The thermodynamics of the interactions were also investigated and the binding is governed by the Le Chatelier principle.

Identification of natural flavonoids as novel EGFR inhibitors using DFT, molecular docking, and molecular dynamics

The quantum mechanical descriptors from DFT, molecular docking, molecular dynamics, and NCIplot methodology have been utilized to find a potential anti-EGFR flavonoid.

Significant photodegradation of carcinogenic organic dyes by a 1D supramolecular heteroleptic Cu(ii) complex under sunlight irradiation

The crucial role of supramolecular interactions in the self-assembly and architecture of the heteroleptic Cu(II) coordination polymer has been investigated and its ability to degrade organic molecules using sunlight.

Coumarin derivatives inhibit the aggregation of β-lactoglobulin

The binding of a small molecule to a protein through non-covalent interactions mainly depends on its size and electronic environment. Such binding can change the stability of the three dimensional protein structure which sometimes may destabilize it to accelerate or to inhibit protein aggregation. Coumarin is a widely used fluorescent dye with several biological applications. Different substituents (electron-donating and electron-withdrawing) at different positions of the coumarin moiety can influence its molecular volume, physical and chemical properties. Here we investigate the effect of such substituents of coumarin on the aggregation of a model protein, beta-lactoglobulin (β-lg) through a multi spectroscopic approach. It was observed that coumarin methyl ester with an 8-hydroxyl group can inhibit the β-lg aggregation. This compound can bind the hydrophobic site of beta-lactoglobulin and stabilize a particular protein conformation through the formation of hydrogen bond and hydrophobic interactions. Thus a properly designed compound can inhibit protein–protein interactions through protein–small molecule interactions. Other coumarinoid compounds also are effective in the prevention of thermal aggregation of β-lg.

Aggregation of β-lactoglobulin (β-lg) was inhibited through the stabilization of the native structure by various non-covalent interactions of coumarin derivatives. The 8-hydroxy compound was most effective against the self-assembly of β-lg.

Exploring the Noncovalent Interactions of the Dinuclear Cu(II) Schiff Base Complex with Bovine Serum Albumin and Cell Viability against the SiHa Cancer Cell Line

In the present study, a dinuclear bis(μ-acetate) dicopper(II) complex [Cu₂L₂(μ_1.1-CH₃COO^-)₂] has been synthesized from a tridentate NNO Schiff Base ligand L (L = 2,4-dibromo-6-((3-(methylamino)propylimino)methyl)phenol) and characterized by elemental, ultraviolet-visible (UV-vis), Fourier transform infrared (FTIR), ¹H NMR, and electrospray ionization-mass spectrometry (ESI-MS) spectroscopic studies. The single-crystal X-ray structure, different noncovalent interactions, Hirshfeld surface analysis, and density functional theory (DFT) studies of the dinuclear complex were determined by crystallographic computational studies. The structural study exposed that the complex consists of the penta-coordinated double μ_1.1-acetato-bridged dinuclear units of Cu(II), and it is a centrosymmetric dimer in which the center of inversion lies at the midpoint of two Cu(II) ions. Hirshfeld surface and DFT studies pointed out the probable potentiality of the crystal in prospective binding with the protein. This was experimentally verified by carrying out the binding interaction studies against bovine serum albumin (BSA) protein using various spectroscopic methods. It was observed that the copper(II) complex could strongly bind to BSA and could quench the intrinsic fluorescence of BSA. Further, the studied complex was appraised for cell viability studies against SiHa cancer cells. It is observed that cell viability increases with time, demonstrating the biocompatible nature of the complex.

Factors for COVID-19 Infection that Govern the Severity of Illness

Coronaviruses have been posing a serious threat to mammals and birds and a new class of SARS-CoV is creating havoc to the world after its first incidence in Wuhan City in China in December 2019. These viruses are mainly responsible for causing serious respiratory tract infections which generally appear initially as the common cold and can be lethal just like SARS-CoV. The problems seem to vary and worsen from one person to another depending on age, gender, ethnicity, blood groups, host genetics, and associated comorbidities. Complications should also arise as this virus keeps mutating and evolving. This review points out the various underlying causes behind the severity of the illness and the mechanisms associated with it. This review will help society to understand the risks and severities associated with COVID-19. Individuals with health complexities and predispositions listed in this review are the most vulnerable in terms of severity and should take every possible measure to protect themselves from getting infected. As a consequence, this will lead to a decrease in mortality rates arising from COVID-19. Doi: 10.28991/SciMedJ-2021-0302-9 Full Text: PDF

Ligand substituent effect on the cytotoxicity activity of two new copper(ii) complexes bearing 8-hydroxyquinoline derivatives: validated by MTT assay and apoptosis in MCF-7 cancer cell line (human breast cancer)

In this study, we have examined the effect of ligand substituent on the structure-cytotoxicity relationships of the MCF-7 cancer cell line (human breast cancer), by two copper(ii) complexes {[Cu(qmbn)(Hqmba)(q)]·NO3·2H2O} (1) and {[Cu(Hqmba)2(q)]·NO3·2H2O} (2) (where, qmbn = 2-(quinolin-8-yloxy)(methyl) benzonitrile (L1); Hqmba = 2-((quinolin-8-yloxy)methyl)benzoic acid (L2) and q = quinolin-8-olate). The structural analysis reveals that both the complexes exhibit distorted octahedral (CuN3O3) configuration which is further corroborated by density functional theory (DFT) calculations. The cytotoxicity impact of ligands (L1 and L2) and complexes (1 and 2) was screened against the MCF-7 cell line (human breast cancer). The MTT assay uptake indicated that the presence of -COOH functionality in complex 2 leads to higher cytotoxicity (lower IC50) than that observed for complex 1 containing a -CN group. This could be due to the strong H-bonding forming propensity of the carboxylic acids. Incubation of MCF-7 cancer cells with IC50 concentrations of 1 and 2 promoted cellular detachments via nuclear condensation and membrane destabilization followed by apoptosis as a result of metal-assisted generation of reactive oxygen species. Flow cytometry analysis showed that 1 and 2 might prompt early apoptosis in MCF-7 cells as the maximum percentage of cells appeared in the LR quadrant. Furthermore, mRNA expression analysis confirmed that both the complexes induced apoptosis in MCF-7 cells. Comparative mRNA expression analysis of complexes with their respective ligands also confirmed the enhanced apoptotic behavior of complexes. Furthermore, molecular docking studies of the complexes have also been performed with the active site of EGFR kinase receptors (major target for any cancer causing agent) due to similar analogues with FDA-approved EGFR inhibitors in order to rationalize its promising cytotoxicity activity.

A crystallography-based investigation of weak interactions for drug design against COVID-19

Interactions between proteins and small molecules play important roles in the inhibition of protein function. However, a lack of proper knowledge about non-covalent interactions can act as a barrier towards gaining a complete understanding of the factors that control these associations. To find effective molecules for COVID-19 inhibition, we have quantitatively investigated 143 X-ray crystal structures of the SARS-CoV-2 M^pro protein of coronavirus with covalently or non-covalently bound small molecules (SMs). Our present study is able to explain ordinary and perceptive aspects relating to protein inhibition. The active site of the protein consists of 21 amino acid residues, but only nine are actively involved in the ligand binding process. The H41, M49, and C145 residues have highest priority with respect to interactions with small molecules through hydrogen bond, CH-π, and van der Waals interactions. At the active site, this ranking of amino acids is clear, based on different spatial orientations of ligands, and consistent with the electronic properties. SMs with aromatic moieties that bind to the active site of the protein play a distinct role in the determination of the following order of interaction frequency with the amino acids: CH-π > H-bonding > polar interactions. This present study revealed that the G143 and C145 residues play crucial roles in the recognition of the carbonyl functionality of SMs through hydrogen bonding. With this knowledge in mind, an effective inhibitor small-molecule for SARS-CoV-2 M^pro was designed: docking studies showed that the designed molecule has strong binding affinity towards the protein. The non-covalent interactions in the protein-ligand complex are in good agreement with the results obtained from X-ray crystallography. Moreover, the present study focused on weak forces and their influence on protein inhibition, henceforth shedding much light on the essential requirements for moieties that should be present in a good inhibitor and their orientations at the ligand binding site.

Modulation of amyloid fibrillation of bovine β-lactoglobulin by selective methionine oxidation

Deposition of oxidation-modified proteins during normal aging and oxidative stress are directly associated with systemic amyloidoses. Methionine (Met) is believed to be one of the most readily oxidisable amino acid residues of protein. Bovine beta-lactoglobulin (β-lg), a model globular whey protein, has been presented as a subsequent paradigm for studies on protein aggregation and amyloid formation. Herein, we investigated the effect of t-butyl hydroperoxide (tBHP)-induced oxidation on structure, compactness and fibrillation propensity of β-lg at physiological pH. Notably, whey protein modification, specifically Met residues, plays an important role in the dairy industry during milk processing and lowering nutritional value and ultimately affecting their technological properties. Several bio-physical studies revealed enhanced structural flexibility and aggregation propensity of oxidised β-lg in a temperature dependent manner. A molecular docking study is used to predict possible interactions with tBHP and infers selective oxidation of methionine residues at 7, 24 and 107 positions. From our studies, it can be corroborated that specific orientations of Met residues directs the formation of a partially unfolded state susceptible to fibrillation with possible different cytotoxic effects. Our studies have greater implications in deciphering the underlying mechanism of different whey proteins encountering oxidative stress. Our findings are also important to elucidate the understanding of oxidation induced amyloid fibrillation of protein which may constitute a new route to pave the way for a modulatory role of oxidatively stressed proteins in neurological disorders.

Fluxional chloro-pyrrole–Pd(ii) complex to cationic η2-pyrrole–Pd(ii) complex: subtlety in structure-directed bonding mode

The fluxional pyrrole ring of a Pd(ii) complex produces a η²-pyrrole–Pd(ii) complex. It is the first report of a η²-pyrrole complex of Pd(ii).

Bovine serum albumin interactive one dimensional hexanuclear manganese(iii) complex: synthesis, structure, binding and molecular docking studies

A hexanuclear Mn(III) complex was synthesized and structiurally characterized which exhibits fluorescence quenching of BSA probably through site selective binding at the mouth of site I in subdomain IIA.

Mononuclear copper(ii) Schiff base complex: synthesis, structure, electrical analysis and protein binding study

A mononuclear copper(ii)-Schiff base complex has been explored for dual applications – complete electrical analysis and BSA protein binding study.

Anti-COVID-19 terpenoid from marine sources: A docking, admet and molecular dynamics study

Traditional medicines contain natural products (NPs) as main ingredient which always give new direction and paths to develop new advanced medicines. In the COVID-19 pandemic, NPs can be used or can help to find new compound against it. The SARS coronavirus-2 main protease (SARS CoV-2 M^pro) enzyme, arbitrate viral replication and transcription, is target here. The study show that, from the electronic features and binding affinity of all the NPs with the enzyme, the compounds with higher hydrophobicity and lower flexibility can be more favorable inhibitor. More than fifty NPs were screened for the target and one terpenoid (T3) from marine sponge Cacospongia mycofijiensis shows excellent SARS CoV-2 M^pro inhibitory activity in comparison with known peptide based inhibitors. The molecular dynamics simulation studies of the terpenoids with the protein indicates that the complex is stable and hydrogen bonds are involved during the complexation. Considering binding affinity, bioavailability, pharmacokinetics and toxicity of the compounds, it is proposed that the NP T3 can act as a potential drug candidate against COVID-19 virus.

Design and Synthesis of Near-Infrared Mechanically Interlocked Molecules for Specific Targeting of Mitochondria

The entrapment of squaraine (SQ) within a molecular container to form rotaxane has been shown to improve the dye stability and the fluorescence proficiency inside the mitochondria. The macrocycle provides shelter and protects the near-infrared (NIR) SQ chromophore from nucleophilic attacks made by the exposed thiol of Cys-containing mitochondrial proteins and mitochondrial glutathione. Herein a microwave-assisted template-directed clipping reaction on low-loading 2-chlorotrityl chloride resin is used to develop an NIR unsymmetrical squaraine rotaxane in high quantum yield.

Self-assembling behaviour of a modified aromatic amino acid in competitive medium

Aromatic amino acid, specifically phenylalanine (Phe), is one of the most studied building blocks in peptide synthesis due to its importance in biology. It is reported in the literature that Phe-containing peptides have a high tendency to form different self-assembled materials due to efficient aromatic-aromatic interactions. In this article, we have tuned the supramolecular interactions of phenylalanine by making it electron-deficient upon introduction of the nitro group in the ring. The presence of the nitro group has a profound influence on the self-assembly process. It has been observed that 4-nitrophenylalanine (4NP) is a highly efficient gelator compared with the native phenylalanine in DMSO solvent in terms of minimum gelation concentration and it forms hydrogen bonding mediated crystals in water. The change of self-assembling patterns of 4NP in these solvents was studied using X-ray diffraction, UV-Vis spectroscopy, FE-SEM and other techniques. With the help of different experimental data and density functional theory (DFT), we have simulated the theoretical structure of 4NP in DMSO. The theoretical structure of 4NP in DMSO is different compared with that of crystals in water. We then studied the self-assembly process of 4NP in the mixed solvent of DMSO (polar aprotic) and water (polar protic). Different competitive non-covalent interactions of solvents as well as the ratio of the solvent mixture guide the final self-assembly state of 4NP.

Multitargeting Antibacterial Activity of a Synthesized Mn2+ Complex of Curcumin on Gram-Positive and Gram-Negative Bacterial Strains

Curcumin is an important molecule with a plethora of pharmacological activities and therapeutic potentials. Despite its efficacy, it remained a potential drug candidate owing to hydrolytic instability and poor aqueous solubility. To overcome the limitations related to low solubility, low bioavailability, and the fact that curcumin is never present in solution as a "single unit", its complex was prepared with MnII with the idea that binding to a metal ion might help to resolve these issues. The complex was characterized by elemental and spectral analysis. The structure of the complex was determined by density functional theory calculations. The complex was stable at physiological buffer conditions, unlike curcumin. It did not have any detrimental effect on mammalian cells. There was a significant enhancement in the antibacterial activity of the complex compared to curcumin against both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. It showed a strong affinity for deoxyribonucleic acid (DNA) evident from a high binding constant value with calf thymus DNA and also from the retarded electrophoretic mobility of bacterial plasmid DNA. The complex showed "superoxide dismutase-like" activity leading to the generation of reactive oxygen species (ROS). The complex caused bacterial membrane perturbation evident from calcein leakage assay, which was further corroborated by scanning and transmission electron microscopic experiments. Overall, the present study shows improved stability and antibacterial potency of a nontoxic complex over curcumin. Its multitargeting mode of action such as ROS-production, effective binding with DNA, and permeabilization of bacterial membrane together allows it to be an effective antibacterial agent that could be taken further for therapeutic use against bacterial infections.

In silico fight against novel coronavirus by finding chromone derivatives as inhibitor of coronavirus main proteases enzyme

Novel coronavirus, 2019-nCoV is a danger to the world and is spreading rapidly. Very little structural information about 2019-nCoV make this situation more difficult for drug designing. Benzylidenechromanones, naturally occurring oxygen heterocyclic compounds, having capability to inhibit various protein and receptors, have been designed here to block mutant variety of coronavirus main protease enzyme (SARC-CoV-2 M^pro) isolated from 2019-nCoV with the assistance of molecular docking, bioinformatics and molecular electrostatic potential. (Z)-3-(4'-chlorobenzylidene)-thiochroman-4-one showed highest binding affinity to the protein. Binding of a compound to this protein actually inhibits the replication and transcription of the virus and, ultimately, stop the virus multiplication. Incorporation of any functional groups to the basic benzylidenechromanones enhances their binding ability. Chloro and bromo substitutions amplify the binding affinity. ADME studies of all these compounds indicate they are lipophilic, high gastro intestine absorbable and blood-brain barrier permeable. The outcome reveals that the investigated benzylidenechromanones can be examined in the case of 2019-nCoV as potent inhibitory drug of SARC-CoV-2 M^pro, for their strong inhibition ability, high reactivity and effective pharmacological properties.

Structural alteration of myoglobin with two homologous cationic surfactants and effect of β-cyclodextrin: multifaceted insight and molecular docking study

Structural alteration and regeneration of myoglobin.

Simultaneous formation of non-oxidovanadium(iv) and oxidovanadium(v) complexes incorporating phenol-based hydrazone ligands in aerobic conditions

A family of non-oxidovanadium(iv) complexes incorporating multidentate hydrazone ligands were synthesized through a thermodynamically unfavourable process along with oxidovanadium(v) species.

Curious Results in the Prospective Binding Interactions of the Food Additive Tartrazine with β-Lactoglobulin

The detailed characterizations of the binding interactions between food additive tartrazine (TZ) and β-lactoglobulin (β-LG) have been investigated through spectroscopic techniques combined with a molecular modeling study. A series of analyses, such as hyperchromic change in the UV-visible spectra, temperature-dependent quenching constant, time-resolved fluorescence, and Rayleigh scattering measurements, show that quenching of β-LG proceeds by a static quenching mechanism. TZ specifically binds with β-LG in a stoichiometry ratio of 1:1, and the observed binding constants (10⁴, K) are 7.64, 9.13, 9.72, and 10.79 at 293, 298, 303, and 308 K, respectively. However, the curious results of binding constants (K) with temperature, encountered in the static quenching, have been well explained on the basis of Le Chatelier's principle. Thermodynamic data and pH-dependent studies along with the surface hydrophobicity binding displacement assay reveal that the durable mode of binding is chiefly entropy-driven, revealing noteworthy interactions of such ionic molecules with the hydrophobic part of β-LG. The modulation of protein conformation has been investigated through steady-state absorption spectroscopy, synchronous emission spectroscopy, circular dichroism, and dynamic light scattering studies. TZ acts as a potential inhibitor in fibrillogenesis. Furthermore, the molecular docking study offers accurate insights about the binding of TZ with β-LG, in consistence with the experimental results. This study would be helpful in pharmaceutical, food, and industrial engineering chemistry research.