Carboxylic Acid Groups Research Articles

Reduced sulfur compounds and carboxylic acid groups in dissolved PFRs of iron-biochar enhance Cr(VI) reduction in anaerobic conditions

In addition to the adsorption and immobilization capacities of iron-modified biochars, these materials produce persistent free radicals (PFRs) that can carry out metal [i.e., Cr(VI)] redox transformations, but the primary forms and active species of PFRs involved are not well understood. Here, we investigated the key species of PFRs of α-Fe2O3-modified biochar (MBC) and their influence on Cr(VI) reduction under anaerobic conditions simulating paddy soil environments. MBC produced bulk phenoxyl PFRs that promoted Cr(VI) reduction due to the catalytic effect of the transition metal Fe. In addition, MBC was more efficient in reducing Cr(VI) under anaerobic conditions than under aerobic conditions due to the more active and accessible dissolved PFRs present in the dissolved organic matter (DOM). The electron transfer capacity of DOM was demonstrated by excitation-emission matrix (EEM) spectrophotometry combined with parallel factor analysis, which showed that the protein-like and humic-like components of DOM were involved in Cr(VI) reduction. Furthermore, Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) analysis indicated that reduced-S compounds (O/S < 4) and carboxylic acid (–COO) groups in the unsaturated aliphatic and lignin-like compounds are potentially the main active species accelerating Cr(VI) reduction under anaerobic conditions. Our results provide new insights into the role of dissolved PFRs from iron-modified biochar in promoting Cr(VI) reduction under anaerobic conditions such as flooded soils.Graphical

Modified exfoliated graphene functionalized with carboxylic acid-group and thionine on a screen-printed carbon electrode as a platform for an electrochemical enzyme immunosensor.

An enzyme immunoassay was developed based on the coulometric measurement of immunoglobulin M (IgM) against Hantaan viruses (HTNV) by using virus-like particles (VLPs) as recognition molecules. The surface functionalization of screen-printed carbon electrodes (SPCEs) was achieved through paste-exfoliated graphene that was modified with a COOH group and a thionine mediator through supramolecular-covalent scaffolds, on SPCEs by using the binder contained in the ink. After the covalent immobilization of the antibody, the sensor was used for the sandwich enzyme immunoassay of IgM against HTNV. By using HTNV VLPs as the second recognization molecules, the resulting sensor efficiently monitored the reaction of IgM against HTNV and anti-IgM antibody with high specificity. By attaching HTNV nucleocapsid protein antibody conjugate with horseradish peroxidase (HRP) onto VLPs, the signal response of the assay was derived from the coulometric measurement of H2O2 reduction mediated by thionine on the electrode surface after the application of a potential (- 0.2V vs. Ag/AgCl). The ratio of charges measured before or after H2O2 addition was used to quantify IgM because these charges could be used as background charges or total charges, respectively. The ratio exhibited good agreement with IgM concentration within a range 0.1 to 1000pgmL-1, and a detection limit of 0.06pgmL-1 was obtained. The assay demonstrated high sensitivity and specificity toward HTNV-specific IgM in serum.

Research on the performances of VPEG macromonomer grafted different functional groups to prepare polycarboxylate superplasticizers

AbstractThe advent of novel polyether macromonomer has garnered significant attention within the industrial domain. In this study, a range of polycarboxylate superplasticizers (PCEs) was produced via free radical polymerization, employing a new polyether monomer, 4‐hydroxybutyl vinyl polyethylene glycol ether (VPEG). This monomer served as the predominant component and was grafted with various functional monomers on its main chain. The molecular configuration of the resultant PCEs was discerned through Fourier infrared spectroscopy and gel permeation chromatography, while the surface tension underwent assessment via a surface tension meter. Both the initial and subsequent fluidity of cement paste and mortar were leveraged to ascertain the dispersion and retention efficacy of the synthetic PCEs. The ramifications of diverse functional group grafts of the new polyether monomer on the cement hydration procedure and strength attributes were elucidated via setting time, hydration heat assays of cement paste, SEM analysis, and compressive strength evaluations of mortar. Observations reveal that the carboxylic acid group significantly reduces surface tension, whereas the sulfonic acid group's effect remains minimal. The incorporation of both the amide and sulfonic acid groups marginally impacts the preliminary dispersion efficacy of PCEs but notably affects dispersion retention. Furthermore, these functional groups facilitate cement hydration, expedite the primary setting time of the cement paste, and bolster the initial compressive strength of the mortar. Specifically, the grafted of sodium methacrylsulfonate (SMAS) yields the most noticeable results. Finally, the working mechanism of PCEs with varying molecular structures has been explained in light both theoretical and experimental results. This research offers valuable insights for subsequent investigations into the fabrication of polycarboxylate superplasticizers using the VPEG macromonomer.

Simultaneous determination of BGT-002 and its acyl glucuronide metabolite ZM326E-M2 in human plasma by liquid chromatography-tandem mass spectrometry and its application to a pharmacokinetic study

BGT-002, a new type of ATP-citrate lyase inhibitor, is a promising therapeutic for treatment of hypercholesterolemia. After an oral administration of BGT-002 to subjects, it underwent extensive metabolism and an acyl monoglucuronide (ZM326E-M2) on 1- carboxylic acid group was the major circulating metabolite. In this study, an LC-MS/MS method was developed and validated for the simultaneous determination of BGT-002 and ZM326E-M2 in plasma and the evaluation of their pharmacokinetic characteristics in humans. After extraction from the plasma by acetonitrile-induced protein precipitation, the analytes were separated on a Waters ACQUITY UPLC® BEH C18 column using acetonitrile and 2 mM ammonium acetate containing 0.1% formic acid as the mobile phase for gradient elution. Negative electrospray ionization was performed using multiple reaction monitoring (MRM) of m/z 501.3→325.4 for ZM326E-M2 and m/z 507.3→331.2 for D6-ZM326E-M2, and pseudo-MRM of m/z 325.3→325.3 for BGT-002 and m/z 331.3→331.3 for D6-ZM326E, respectively. The method was validated with respect to accuracy, precision, linearity, stability, selectivity, matrix effect, and recovery. The analytical range in human plasma was linear over a concentration range of 0.0500–50.0 μg/mL for BGT-002 and 0.0100–10.0 μg/mL for ZM326E-M2. The pharmacokinetic results showed that after a single oral administration of 100 mg BGT-002, the parent drug was rapidly absorbed with a mean time to peak concentration (tmax) of 1.13 h, compared with BGT-002, the tmax (4.00 h) of ZM326E-M2 was significantly delayed. The peak concentration and plasma exposure of ZM326E-M2 were about 14.1% and 19.5% of the parent drug, suggesting that attention should be paid to the safety and efficacy of ZM326E-M2 in clinical research.

Pyrolysis of macroalgae residue from the agar industry for silica‐rich biochar and other sustainable chemicals: Process performances, product applications, and simple business scenario

AbstractThe macroalgae residue from the industrial agar extraction process contains a significant amount of carbon and has potential as a renewable feedstock. Unfortunately, it is often overlooked and is poorly utilized. This study aims to valorize this macroalgae residue through pyrolysis to produce silica‐rich biochar and other value‐added products in the form of biocrude oil (BCO) and biopyrolysis gas. The macroalgae residue was pyrolyzed at 300–700 °C with a heating rate of 20–40 °C/min. Yields of biochar, BCO, and gas of 62%, 25%, and 13% were obtained at a temperature of 700 °C and a heating rate of 20 °C/min. Biochar has a porous structure, a surface area exceeding 15 m2/g, and is dominated by amorphous silica of up to 13%. This silica‐rich biochar also contains Na and K, which hold potential benefits in agriculture, serving as soil ameliorants and playing a crucial role in enhancing soil fertility and promoting plant growth. In the meantime, BCO contains 29.3% carboxylic acid group as the most important chemical component. Other than that, the biopyrolysis gas contains mainly CH4 and H2 (up to 24–32%), which can act as chemical building blocks. Finally, a simple business scenario of silica‐rich biochar production reveals that it has a specific cost of 0.37 US$/kg. It could be economically viable as a soil ameliorant or fertilizer. However, challenges persist in scaling up production to an industrial scale.

Phytoconstituents, Fourier-Transform Infrared Characterization, and Antioxidant Potential of Ethyl Acetate Extract of Corchorus olitorius (Malvaceae)

Oxidative stress is a condition that is characterized by the generation of reactive oxygen species more than the amount endogenous antioxidants can absorb. Several diseases are associated with oxidative stress, notably during disease progression. Thus, the present study aimed to determine the phytoconstituents and antioxidant potential of the ethyl acetate leaf extract of Corchorus olitorius (ELEC). The phytochemicals were qualitatively and quantitatively determined, followed by characterization using Fourier-transform infrared (FTIR) spectroscopy. The antioxidant potential was determined in vitro. Alkaloids, saponins, and flavonoids were detected in concentrations of 8.50 ±2.65, 11.83 ±0.73, and 19.17% ±0.73, respectively. The FTIR spectrum revealed 9 peaks including six at the group frequency region corresponding to alcohols, carboxylic acid, amine salts, alkenes, alkyne, esters, and oxime functional groups. The ELEC exhibited lower total reducing power (11.06 ±1.34 AAE µg/ml) compared to its total antioxidant capacity (49.26 ±2.44 AAE µg/ml) with a higher (60.47% ±2.44) percentage inhibition of peroxidation than AA (37.98% ±1.88). Furthermore, the ELEC exhibited a lower (0.20 ±0.01 nmol/ml) MDA concentration than AA (0.42 ±0.02 nmol/ml). Conclusively, C. olitorius might be applied for the management of oxidative stress-linked ailments and a source of novel therapeutics for these ailments.

Identification of acetic acid levels in ecoenzyme from organic materials of orange peel with acid-base titration method

This study aimed to elucidate the comparison of the levels of acetic acid and the pH of the ecoenzymes from organic matter variations of sweet and sour orange peels. The acetic acid is an organic compound containing a carboxylic acid group which is also widely applied in the health and industrial fields. Preparation of acetic acid from substrate products containing ethanol which can be obtained from fruit ingredients including oranges. One of the uses and management of organic waste, including vegetables and fruit, is by making ecoenzymes from fruit peels with a mixture of water and sugar. Fruit peels that can be used as organic ecoenzyme ingredients vary widely, so the content in ecoenzymes becomes very diverse and tends to be unstable. This type of research is descriptive. This study consisted of three stages, namely the manufacture of ecoenzymes from pasaman orange peel, gunung omeh, kaffir lime and lime in 7 variations (for 100 days), measurement of acetic acid levels and pH in the ecoenyzme samples for 14 days and 100 days. Acetic acid levels were determined using the acid-base titration method. The results of this study showed that the highest levels of acetic acid ecoenzyme in the 100-day fermentation were 5.53% in the sour orange group, while the lowest in the mixed ecoenzyme was 3.32%. The most acidic ecoenzyme pH was at 100 days of fermentation (pH ±3.5).

Bioflocculation of pollutants in wastewater using flocculant derived from Providencia huaxiensis OR794369.1

BackgroundWater pollution has become a major environmental and health concern due to increasing population and industrialisation. Microbial flocculants are promising agents for treatment of contaminated water owing to their effectiveness, eco-friendliness, and high biosafety levels. In this study, culture conditions of Providencia huaxiensis OR794369.1 were optimised and its bioflocculant was extracted, characterised and used to treat wastewater.ResultsThe maximum flocculating activity of 92% and yield of 3.5 g/L were obtained when cultivation conditions were: 3% inoculum size, starch, casein, initial pH of 6, cultivation temperature of 30 oC and 72 h of fermentation. The bioflocculant is an amorphous glycoprotein biomolecule with 37.5% carbohydrates, 27.9% protein, and 34.6% uronic acids. It is composed of hydroxyl, amino, alkanes, carboxylic acid and amines groups as its main functional structures. It was found to be safe to use as it demonstrated non-cytotoxic effects on bovine dermis and African green monkey kidney cells, illustrating median inhibitory concentration (IC50) values of 180 and > 500 µg/mL on both cell lines, respectively. It demonstrated the removal efficiencies of 90% on chemical oxygen demand (COD), 97% on biological oxygen demand (BOD) and 72% on Sulphur on coal mine wastewater. It also revealed the reduction efficacies of 98% (COD) and 92% (BOD) and 70% on Sulphur on domestic wastewater.ConclusionThe bioflocculant was effective in reducing pollutants and thus, illustrated potential to be used in wastewater treatment process as an alternative.

Decoding Polymeric Additive‐Driven Self‐Healing Processes in Perovskite Solar Cells from Chemical and Physical Bonding Perspectives

AbstractThis review addresses the self‐healing effects in perovskite solar cells (PSCs), emphasizing the significance of chemical and physical bonding as core mechanisms. Polymeric additives play a vital role in inducing self‐healing phenomena along with the intrinsic properties of perovskite materials, both of which are discussed herein. As a relatively underexplored area, the self‐healing effect induced by polymeric additives in PSCs is reviewed from a chemical perspective. The chemical bonds involved in self‐healing include isocyanate, disulfide, and carboxylic acid groups. The physical bonds related to self‐healing effects are primarily hydrogen bonding and chelation. Self‐healing in flexible perovskite devices extends their lifespan and improves their mechanical robustness against environmental and mechanical stressors. This discussion delves into the initiation methods for self‐healing, the conditions required, and the recovery‐rate profiles. This review not only catalogs various approaches to self‐healing, but also considers the fundamental limitations and potential of this phenomenon in PSCs. In addition, insights and an outlook on self‐healing in perovskite‐based optoelectronics are provided, offering guidance for future research and applications.

Synergistic mechanism of amidation on corrosion inhibition of laurate triethanolamine for HT300 gray cast iron in NaCl solution

AbstractSarcosine was inserted between fatty chain and carboxylic group of lauric acid to obtain lauroyl sarcosine, and the corrosion inhibition of lauroyl sarcosine triethanolamine (LSTEA) was significantly improved. The synergistic mechanism of amide group and lauric acid was investigated by comparing the corrosion behavior on the surface of HT300 gray cast iron in 330 mg/L NaCl solution. The results showed that both lauryl triethanolamine (LATEA) and LSTEA could prevent corrosion. At 298 K, when 1000 mg/L inhibitor was added, the inhibition rates are 71.93% and 83.89%, respectively. The morphology analysis also verified that LSTEA had better inhibition properties than LATEA. Comparing the adsorption parameters and Density Functional Theory (DFT) calculation results, it was found that LATEA and LSTEA could spontaneously adsorb on the surface of gray cast iron as monolayer to form a stable protective layer. However, the chelation of amide group and the electron absorption effect could make the electron density distributed at the polar end of the whole molecule, covering the active sites at the interface to the maximum extent, so that LSTEA has more excellent corrosion inhibition for gray cast iron.

Hydrogen-bonding interactions in 5-fluorocytosine-urea (2/1), 5-fluorocytosine-5-fluorocytosinium 3,5-dinitrosalicylate-water (2/1/1) and 2-amino-4-chloro-6-methylpyrimidine-6-chloronicotinic acid (1/1).

Three new compounds, namely, 5-fluorocytosine-urea (2/1), 2C4H4FN3O·CH4N2O, (I), 5-fluorocytosine-5-fluorocytosinium 3,5-dinitrosalicylate-water (2/1/1), 2C4H4FN3O·C4H5FN3O+·C7H2N2O7-·H2O, (II), and 2-amino-4-chloro-6-methylpyrimidine-6-chloronicotinic acid (1/1), C6H4ClNO2·C5H6ClN3, (III), have been synthesized and characterized by single-crystal X-ray diffraction. In compound (I), 5-fluorocytosine (5FC) molecules A and B form two different homosynthons [R22(8) ring motif], one formed via N-H...O hydrogen bonds and the second via N-H...N hydrogen bonds. In addition to this interaction, a sequence of fused-ring motifs [R21(6), R33(8), R22(8), R43(10) and R22(8)] are formed, generating a supramolecular ladder-like hydrogen-bonded pattern. In compound (II), 5FC and 5-fluorocytosinium are linked by triple hydrogen bonds, generating two fused-ring motifs [R22(8)]. The neutral 5FC and protonated 5-fluorocytosinum cation form a dimeric synthon [R22(8) ring motif] via N-H...O and N-H...N hydrogen bonds. On either side of the dimeric synthon, the neutral 5FC, 5-fluorocytosinium cation, 3,5-dinitrosalicylate anion and water molecule are hydrogen bonded through N-H...O, N-H...N, N-H...OW and OW-HW...O hydrogen bonds, forming a large ring motif [R1010(56)], leading to a three-dimensional supramolecular network. In compound (III), 2-amino-4-chloro-6-methylpyrimidine (ACP) interacts with the carboxylic acid group of 6-chloronicotinic acid via N-H...O and O-H...O hydrogen bonds, generating an R22(8) primary ring motif. Furthermore, the ACP molecules form a base pair via N-H...N hydrogen bonds. The primary motif and base pair combine to form tetrameric units, which are further connected by Cl...Cl interactions. In addition to this hydrogen-bonding interaction, compounds (I) and (III) are further enriched by π-π stacking interactions.

Expanding the Synthetic Toolbox: Discovery of a Robust Aldehyde Dehydrogenase for Integrated Chemocatalysis and Enzyme Catalysis

AbstractChemobiocatalysis has recently emerged as a promising tool in organic synthesis; nonetheless, chemobiocatalytic transformations remain challenging due to the incompatibility between the two types of catalysts. Many enzymes, especially aldehyde dehydrogenases (ALDHs), are readily inactivated under the chemocatalytic conditions. Herein, we present a robust NADP+‐dependent p‐hydroxybenzaldehyde dehydrogenase from Pseudomonas aeruginosa (PaHBDH) for integrated chemocatalysis and enzyme catalysis. Apart from good activities toward a number of aromatic aldehydes, PaHBDH showed excellent thermal and storage stability in the absence of any stabilizer, but was also highly tolerant toward various organic solvents. The usefulness of PaHBDH in integrated catalysis was demonstrated by the synthesis of a group of aromatic carboxylic acids in good yields by combining with photo‐/electrochemical NADP+ regeneration. The photoenzymatic approach was further extended by integrating with a chemo(bio)catalytic cascade in one pot to allow for the conversion of furfural into value‐added C4 chemicals. The finding of this work may expand the synthetic toolbox for integrated catalysis.

Promoting Ruddlesden-Popper Perovskite Formation by Tailoring Spacer Intramolecular Interaction for Efficient and Stable Solar Cells.

Low-dimensional Ruddlesden-Popper phase (LDRP) perovskites are widely studied in the field of photovoltaics due to their tunable energy-band properties, enhanced photostability, and improved environmental stability compared to the 3D perovskites. However, the insulating spacers with weak intramolecular interaction used in LDRP materials limit the out-of-plane charge transport, leading to poor device performance of LDRP perovskite solar cells (PSCs). Here, a functional ligand, 3-guanidinopropanoic acid (GPA), which is capable of forming strong intramolecular hydrogen bonds through the carboxylic acid group, is employed as an organic spacer for LDRP PSCs. Owing to the strong interaction between GPA molecules, high-quality LDRP (GPA)2(MA)n-1PbnI3n+1 film with promoted formation of n = 5 phase, improved crystallinity, preferential vertical growth orientations, reduced trap-state density, and prolonged carrier lifetime is achieved using GPAI as the dimensionality regulator compared to butylamine hydroiodide (BAI). As a result, GPA-based LDRP PSC exhibits a champion power conversion efficiency of 18.16% that is much superior to the BA-based LDRP PSC (15.43%). Importantly, the optimized GPA-based LDRP PSCs without encapsulation show enhanced illumination, thermal, storage, and humidity stability compared to BA-based ones. This work provides new insights into producing high n value LDRP films and their efficient and stable PSCs.

Preparation and characterization of novel mirabegron salts for sustaining dissolution and improving diffusion/permeability

Overactive bladder (OAB) is a disturbing and distressing condition associated with severe adverse consequences, such as depression, social isolation and participation restriction. Mirabegron (Mira.), used for the treatment of OAB is a BCS class-III drug that displays inconsistent bioavailability upon oral administration depending on dose, gender, and food intake. The present investigation aimed to synthesize sustained release/slow dissolving salts of Mira. to overcome its food intake dependent erratic bioavailability and to improve its permeability. The solvent evaporation method was used to prepare novel slow dissolving salts of Mira. by reacting it with various long-chain fatty acids (stearic acid, palmitic acid, myristic acid, and lauric acid). The differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD) studies suggested the genesis of a new crystalline phase due to a reaction between Mira. and fatty acids. Fourier-transform infrared spectroscopy (FTIR) and 1H Nuclear magnetic resonance (NMR) studies confirmed the transfer of proton between the primary amine group (-NH2) of Mira. and carboxylic acid group (-COOH) of fatty acids and thus the formation of salts. The prepared salts have significantly slower dissolution than Mira. in 6.8 pH phosphate buffer. The equilibrium solubility of prepared salts were lower than Mira in 6.8 pH phosphate buffer and water. The in-vitro diffusion study using the Franz diffusion cell proved better permeability of the prepared salts compared to Mira.

Hematin anhydride (β-hematin): An analogue to malaria pigment hemozoin possesses nonlinearity

Hematin anhydride (β-hematin), the synthetic analogue of the malaria pigment, “hemozoin”, is a heme dimer produced by reciprocal covalent bonds among carboxylic acid groups on the protoporphyrin-IX ring and the iron atom present in the two adjacent heme molecules. Hemozoin is a disposal product formed from the digestion of hemoglobin present in the red blood cells infected with hematophagous malaria parasites. Besides, as the parasites invade red blood cells, hemozoin crystals are eventually released into the bloodstream, where they accumulate over time in tissues. Severe malaria infection leads to significant dysfunction in vital organs such as the liver, spleen, and brain in part due to the autoimmune response to the excessive accumulation of hemozoin in these tissues. Also, the amount of these crystals in the vasculature correlates with disease progression. Thus, hemozoin is a unique indicator of infection used as a malaria biomarker and hence, used as a target for the development of antimalarial drugs. Hence, exploring various properties of hemozoin is extremely useful in the direction of diagnosis and cure. The present study focuses on finding one of the unknown properties of β-hematin in physiological conditions by using the Z-scan technique, which is simple, sensitive, and economical. It is observed that hemozoin possesses one of the unique material properties, i.e., nonlinearity with a detection limit of ∼ 15 µM. The self-defocusing action causes β-hematin to exhibit negative refractive nonlinearity. The observed data is analyzed with a thermal lensing model. We strongly believe that our simple and reliable approach to probing the nonlinearity of β-hematin will provide fresh opportunities for malaria diagnostics & cure in the near future.

A fixed-charge model of the N-protomer of 4-aminobenzoic acid to facilitate the study of the unimolecular and bimolecular chemistry of its "neutral" carboxylic acid group.

There are a growing number of examples of protomers formed via electrospray ionization (ESI) that do not fragment under mobile proton conditions, giving rise to distinct tandem mass spectra. To model the N-protomer of 4-aminobenzoic acid, here we study the gas-phase unimolecular and bimolecular chemistry of the 4-(carboxyphenyl)trimethylammonium ion. 4-(Carboxyphenyl)trimethylammonium iodide was synthesized, purified via recrystallization and transferred to the gas phase via ESI. 4-(Carboxyphenyl)trimethylammonium ion, 7, was mass selected and subjected to collision-induced dissociation and ion-molecule reactions in a linear ion trap mass spectrometer. The major fragmentation channel for the fixed-charge cation 7 is methyl radical loss, whereas loss of trimethylamine and CO2 represents minor pathways. The free carboxylic acid functional group of 7 is unreactive toward a number of neutral reagents (methanol, acetone, acetonitrile, and N,N'-diisopropylcarbodiimide). 7 reacts very slowly with trimethylborate via addition-elimination, consistent with density functional theory (DFT) calculations that show this reaction is slightly endothermic. The deuterated cation 7(D) undergoes slow D/H exchange with ethanol, and DFT calculations reveal that a flip-flop mechanism operates. The free carboxylic group of 7 is not very reactive toward neutral reagents in the gas phase.

Stereospecific Indium(III)‐Catalysed Tandem Cycloisomerization of Functionalized 1,6‐enynes: Scope and Mechanistic Insights

AbstractTandem cycloisomerization reactions of functionalized 1,6‐enynes under indium(III) catalysis are described. This atom‐economic transformation proceeds smoothly with 5‐exo‐dig regioselectivity using commercial In(III) halides and 1,6‐enynes furnished with alcohol, carboxylic acid or amine functional groups to give bicyclic structures in good yields and diastereoselectivities. The reaction with enynals involves a three–step mechanism to give an oxatricycle and a conjugated 1,3‐diene. In the absence of the internal nucleophile the enyne cycloisomerization evolves through a skeletal rearrangement or a cyclopropanation reaction after the regioselective 5‐exo‐dig cyclization. The 1,6‐enyne cycloisomerization is stereospecific and the stereoselectivity appears to be independent of the internal nucleophile. Experimental data support a common reaction mechanism involving an initial alkyne electrophilic π‐coordination of In(III) followed by Markovnikov electrophilic alkene addition and ring‐closure by nucleophilic attack. DFT studies hold up a stepwise mechanism involving the formation of a chiral non‐classical carbocation intermediate that determines the diastereoselectivity of this tandem cycloisomerization reaction.

Mimicking Charged Host-Defense Peptides to Tune the Antifungal Activity and Biocompatibility of Amphiphilic Polymers.

Invasive fungal infections impose a substantial global health burden. They cause more than 1.5 million deaths annually and are insufficiently met by the currently approved antifungal drugs. Antifungal peptides are a promising alternative to existing antifungal drugs; however, they can be challenging to synthesize, and are often susceptible to proteases in vivo. Synthetic polymers which mimic the properties of natural antifungal peptides can circumvent these limitations. In this study, we developed a library of 29 amphiphilic polyacrylamides with different charged units, namely, amines, guanidinium, imidazole, and carboxylic acid groups, representative of the natural amino acids lysine, arginine, histidine, and glutamic acid. Ternary polymers incorporating primary ammonium (lysine-like) or imidazole (histidine-like) groups demonstrated superior activity against Candida albicans and biocompatibility with mammalian cells compared to the polymers containing the other charged groups. Furthermore, a combination of primary ammonium, imidazole, and guanidinium (arginine-like) within the same polymer outperformed the antifungal drug amphotericin B in terms of therapeutic index and exhibited fast C. albicans-killing activity. The most promising polymer compositions showed synergistic effects in combination with caspofungin and fluconazole against C. albicans and additionally demonstrated activity against other clinically relevant fungi. Collectively, these results indicate the strong potential of these easily producible polymers to be used as antifungals.

A zero-waste one step method to produce carboxy nanocellulose from the untreated barley and wheat straws

A zero-waste simple method was developed to produce carboxy nanocellulose directly from the untreated barley and wheat straw by treating with nitric acid (55%) and sodium nitrite at 40 °C for 12 h. This method significantly reduced the need for toxic chemicals such as TEMPO ((2,2,6,6-tetramethylpiperidin-1-yl)-oxyl) and radical generating chemicals. The process also reduced the usage of corrosive bases and acids and energy demand during the pretreatment process for the multi-step acid hydrolysis of biomass. Moreover, the by-product can be easily neutralized with the addition of NaOH, and the neutralized solution can be concentrated to obtain sodium nitrate which can be utilized as a fertilizer. The current method produces rod shaped and spherical particles of carboxy nanocellulose from the barley and wheat straw respectively with lower crystallinity (ca. ⁓30% of crystallinity index) than the barley and wheat straw itself (ca. ⁓60% of crystallinity index) as evidenced from the grazing incidence X-ray diffraction (GIXRD) technique. The conductometric titration revealed a high concentration (ca. ⁓2.6 mmol/g) of surface carboxylic (-COOH) acid groups and this result is supported by the high zeta potential value (ca ⁓-40mV) for the synthesized carboxy nanocellulose.

The dynamic nature of natural and fatty acid modified calcite surfaces.

Calcium carbonate, particularly in the form of calcite, is an abundant mineral widely used in both human-made products and biological systems. The calcite surface possesses a high surface energy, making it susceptible to the adsorption of organic contaminants. Moreover, the surface is also reactive towards a range of chemicals, including water. Consequently, studying and maintaining a clean and stable calcite surface is only possible under ultrahigh vacuum conditions and for limited amounts of time. When exposed to air or solution, the calcite surface undergoes rapid transformations, demanding a comprehensive understanding of the properties of calcite surfaces in different environments. Similarly, attention must also be directed towards the kinetics of changes, whether induced by fluctuating environments or at constant condition. All these aspects are encompassed in the expression "dynamic nature", and are of crucial importance in the context of the diverse applications of calcite. In many instances, the calcite surface is modified by adsorption of fatty acids to impart a desired nonpolar character. Although the binding between carboxylic acid groups and calcite surfaces is strong, the fatty acid layer used for surface modification undergoes significant alterations when exposed to water vapour and liquid water droplets. Therefore, it is also crucial to understand the dynamic nature of the adsorbed layer. This review article provides a comprehensive overview of the current understanding of both the dynamics of the calcite surface as well as when modified by fatty acid surface treatments.