Modification Of Functional Groups Research Articles

Straightforward Synthesis of Functionalized 4,5,6,7‐Tetrahydro‐pyrazolo[1,5‐a]pyrazines – Important Building Blocks for Medicinal Chemistry

AbstractA set of building blocks based on the 4,5,6,7‐tetrahydro‐pyrazolo[1,5‐a]pyrazine scaffold is synthesized in a multigram scale in a cost‐efficient manner. The possibility of the introduction of different substituents, neutral or functionalized in different positions of pyrazole and/or piperazine rings, is shown. The efficacy of using NH‐pyrazole carbonic acids as a key intermediate of the process is demonstrated. The regioselectivity for direct insertion of the substituent to the 4,5,6,7‐tetrahydro‐pyrazolo[1,5‐a]pyrazine core is discussed. The synthetic perspectives for using the functionalized 4,5,6,7‐tetrahydro‐pyrazolo[1,5‐a]pyrazine as a bifunctional scaffold is discussed. The utilizing of building blocks obtained for the different region‐ and/or stereoselective synthesis, including sole transformations or modifications of functional groups, is demonstrated. The advantages of the proposed approach are proven compared with the other known methodologies.

Surface Functional Groups Effect on the Absorption Spectrum of Carbon Dots: Initial TD-DFT Study

Carbon dots (CDs) have attracted considerable interest due to their remarkable performance, low cost and ease of preparation, and wide range of potential applications. Surface engineering, including modifying the surface functional group and subsequent chemical modification, is preferable to achieve the requirement of the specific application. Oxygen and Nitrogen-based surface functional groups are two common functionalizations on CDs that are subsequently generated during the synthetic process. In this study, we elucidate the optical properties of oxygen and nitrogen-functionalized CDs using time-dependent density functional theory (TD-DFT). Both considered functional groups, the carbon-oxygen double bond (-C=O) and amino groups (-NH2), are quite favourable to tailor the optical properties of CDs, especially in enhancing its absorption spectrum. Moreover, the carbonyl (-C=O) and amino (-NH2) functional groups effectively serve a new absorption peak in the first near-infrared window (650-900 nm). Our results suggest the potential application of the amino and carbonyl functionalized CDs as a photothermal agent in photothermal cancer therapy.

Crosslinker-free collagen gelation for corneal regeneration

Development of an artificial cornea can potentially fulfil the demand of donor corneas for transplantation as the number of donors is far less than needed to treat corneal blindness. Collagen-based artificial corneas stand out as a regenerative option, having promising clinical outcomes. Collagen crosslinked with chemical crosslinkers which modify the parent functional groups of collagen. However, crosslinkers are usually cytotoxic, so crosslinkers need to be removed from implants completely before application in humans. In addition, crosslinked products are mechanically weak and susceptible to enzymatic degradation. We developed a crosslinker free supramolecular gelation strategy using pyrene conjugated dipeptide amphiphile (PyKC) consisting of lysine and cysteine; in which collagen molecules are intertwined inside the PyKC network without any functional group modification of the collagen. The newly developed collagen implants (Coll-PyKC) are optically transparent and can effectively block UV light, are mechanically and enzymatically stable, and can be sutured. The Coll-PyKC implants support the growth and function of all corneal cells, trigger anti-inflammatory differentiation while suppressing the pro-inflammatory differentiation of human monocytes. Coll-PyKC implants can restrict human adenovirus propagation. Therefore, this crosslinker-free strategy can be used for the repair, healing, and regeneration of the cornea, and potentially other damaged organs of the body.

Unveiling the cooperative roles of pyrrolic-N and carboxyl groups in biomass-derived hierarchical porous carbon nanosheets for high energy-power Zn-ion hybrid supercapacitors

The low energy density of Zn-ion hybrid supercapacitors (ZHSCs) remains to be one of the key challenges against its commercialization due to the lack of cathode materials with high capacity, particularly at high current density. Herein, biomass-derived hierarchical porous carbon nanosheets functionalized with oxygen groups and nitrogen dopants used as the cathode for ZHSCs are synthesized via a consecutive two-step pyrolysis-activation strategy, which manifest a high capacity of 220.1 mAh g−1 at 0.2 A g−1, and maintain 118.2 mAh g−1 when the current density increases 100 times to 20 A g−1. Benefitting from the promising performance of the as-obtained cathode materials, the ZHSC finally demonstrates an ultra-high energy density of 181.6 Wh kg−1 at the power density of 165.0 W kg−1, which surpasses the vast majority of state-of-the-art reported ZHSCs. Accordingly, the experimental results and theoretical calculations reveal that the hierarchically porous ultrathin nanosheet architecture with macro-, meso- and micropores is favorable for boosting the physical adsorption of Zn2+, while the introduction of surface pyrrolic-N and carboxyl (–COOH) groups synergistically boosts the chemical adsorption of Zn2+. The present work provides insights into the synergistic effect of nitrogen doping and oxygen functional groups modification hierarchical porous carbon for Zn-ion storage.

Electrochemical synthesis of Ni doped carbon quantum dots for simultaneous fluorometric determination of Fe3+ and Cu2+ ion facilely

A novel Ni doped carbon quantum dots (Ni-CQDs) fluorescence probe was synthesized by facile electrolysis of monoatomic Ni dispersed porous carbon (Ni–N–C). The obtained Ni-CQDs showed a high quantum yield of 6.3% with the strongest excitation and emission peaks of 360 nm and 460 nm, and maintained over 90% of the maximum fluorescence intensity in a wide pH range of 3–12. The metal ions detectability of Ni-CQDs was enhanced by Ni doping and functional groups modification, and the rapid and selective detection of Fe3+ and Cu2+ ions was achieved with Ni-CQDs through dynamic and static quenching mechanism, respectively. On one hand, the energy band gap of Ni-CQDs was regulated by Ni doping, so that excited electrons in Ni-CQDs were able to transfer to Fe3+ easily. On the other hand, the abundant functional groups promoted the generation of static quenching complexation between Cu2+ and Ni-CQDs. In metal ions detection, the linear quantitation range of Fe3+ and Cu2+ were 100–1000 μM (R2 = 0.9955) and 300–900 μM (R2 = 0.9978), respectively. The limits of detection (LOD) were calculated as 10.17 and 7.88 μM, respectively. Moreover, the fluorescence quenched by Cu2+ could be recovered by EDTA2− due to the destruction of the static quenching complexation. In this way, Ni-CQDs showed the ability to identify the two metal ions to a certain degree under the condition of Fe3+ and Cu2+ coexistent. This work paves the way of facile multiple metal ion detection with high sensitivity.

"VALORIZATION OF RICE STRAW VIA PRODUCTION OF MODIFIED XYLANS AND XYLOOLIGOSACCHARIDES FOR THEIR POTENTIAL APPLICATION IN FOOD INDUSTRY "

The present study attempted to valorise rice straw, one of the most abundant, renewable and economic agricultural wastes, via production of modified xylans and xylooligosaccharides (XOS), which were evaluated for their total antioxidant capacity. The percent contents of extractives, cellulose, hemicelluloses, lignin and ash (silica) in rice straw were found to be 20, 41, 24, 9 and 6, respectively. Hemicellulosic xylan was extracted from straw by reaction with 11% (w/v) sodium hydroxide for about 3 h at 80 °C, so that a yield of about 19.4% was obtained, followed by spectral and thermal analyses. Xylan was then subjected to chemical modifications using acetic anhydride, benzyl chloride and sodium monochloroacetate, and the modifications of functional groups were confirmed by FT-IR and NMR spectral techniques. Controlled acid hydrolysis of xylan was carried out using dilute sulphuric acid (0.1, 0.25, 0.5 and 1.0M) at 121 °C, 15 psi for 10 min to produce XOS-rich hydrolysate. Xylan, modified xylans and XOS exhibited significant concentration dependent AAE values, XOS exhibiting the highest AAE value, followed by xylan, benzylated xylan, carboxymethylated xylan and acetylated xylan. Therefore, rice straw based modified xylans and XOS with potential antioxidant properties may serve as potential candidates for use in food industries as packaging films and functional food ingredients.

Review on covalent organic frameworks and derivatives for electrochemical and photocatalytic CO2 reduction

With increasing potential for environmental volatility in the wake of increasing atmospheric pollutants, the need for sustainable approaches towards renewable energy and pollution reduction is ever-expanding. In recent years, research has geared towards utilizing carbon dioxide, which is seen as the largest threat of climate change, to produce various other useful chemicals while decreasing carbon dioxide levels. Considering this recent research, covalent organic frameworks (COFs) have jumped into the spotlight as promising and exciting new catalysts development to drive efforts towards easing climate change. As a relatively new class of materials, COFs are high surface area crystalline networks with a large degree of fine-tunable chemistry and the capability of metallic hybridization and functional group modifications. This review is a comprehensive and detailed discussion of the recent research accomplishments and goals of both photocatalytic and electrocatalytic carbon dioxide reduction using COFs as catalysts. Recent COF electrochemical catalysis is thoroughly discussed through different metal-based and pristine COFs along with the material design principles necessary to reduce carbon dioxide effectively and selectively. COF photocatalysis is discussed namely on the remarkable ability of irradiation-induced carbon dioxide reduction for pristine metal-free, metalated, and hybrid COFs along with the ability of photocoupled electrocatalytic reduction. Additionally, final conclusions on the state of COF research are provided along with future suggestions towards expanding and improving the investigation and application of COFs for CO2 reduction.

Cl-based functional group modification MIL-53(Fe) as efficient photocatalysts for degradation of tetracycline hydrochloride

MIL-53(Fe) catalyst has been widely used to treat the pollutants in water. However, the limited number of electrons in MIL-53(Fe) catalyst has always affected the rate at which Fe3+ can be reduced to Fe2+. We modulated iron-based metal–organic frameworks (MOFs) using organic ligands modified with chlorine functional groups. The characterization results indicate that the 2Cl-MIL-53(Fe) catalyst exhibited the optimal photoelectric properties while maintaining the original structural characteristics. The experimental analyses and the first-principles study suggest that the introduction of a chlorine functional group not only reduced the band gap width and enhanced the visible-light absorption capacity, but also significantly enhanced the electron cloud density of Fe–O clusters. This could further accelerate the redox cycle of Fe(III)/Fe(II), beneficial for H2O2 activation. The constructed Cl-MIL-53(Fe) catalyst exhibited a 3.8 times higher reaction rate constant than pure MIL-53(Fe) catalyst. The specific TCH degradation pathway and mechanism of 2Cl-MIL-53(Fe) treatment are proposed. This study provides a new strategy for iron-based MOFs as a heterogeneous photo-Fenton catalyst to degrade pollutants in water.

Polydopamine Coating Doped with Graphene Oxide Enhances Enantioseparation of Capillary Column.

How to improve the enantiomer separation efficiency of drugs is a hot topic. In this paper, polydopamine (PDA) coating doped with graphene oxide (GO) by physical adsorption was used to modify the capillary column to enhance the enantioseparation efficiency of the drugs. In the capillary electrochromatography (CEC) system, the novel capillary column with carboxymethyl-β-cyclodextrin (CM-β-CD) as a chiral selector has completed the enantioseparation of four basic drugs (propranolol, metoprolol, amlodipine and chlorpheniramine). The optimum separation conditions were obtained by optimizing the pH of the buffer, the concentration of organic modifier, the concentration of the chiral selector and the voltage, and the resolution and peak shape were significantly improved compared with uncoated bare-fused column. The stability and reproducibility of the new capillary column were satisfactory and the relative standard deviation of intra-day and inter-day was <3.2%, and of column-to-column was <4.8%. The rich functional groups of GO are key factors to improve the enantioseparation efficiency, which also indicates that nanomaterials with easy modification of functional groups and large specific surface area are excellent resources for capillary modification applications.

Computational Screening of Newly Designed Compounds against Coxsackievirus A16 and Enterovirus A71.

Outbreaks of hand, foot, and mouth disease (HFMD) that occur worldwide are mainly caused by the Coxsackievirus-A16 (CV-A16) and Enterovirus-A71 (EV-A71). Unfortunately, neither an anti-HFMD drug nor a vaccine is currently available. Rupintrivir in phase II clinical trial candidate for rhinovirus showed highly potent antiviral activities against enteroviruses as an inhibitor for 3C protease (3Cpro). In the present study, we focused on designing 50 novel rupintrivir analogs against CV-A16 and EV-A71 3Cpro using computational tools. From their predicted binding affinities, the five compounds with functional group modifications at P1′, P2, P3, and P4 sites, namely P1′-1, P2-m3, P3-4, P4-5, and P4-19, could bind with both CV-A16 and EV-A71 3Cpro better than rupintrivir. Subsequently, these five analogs were studied by 500 ns molecular dynamics simulations. Among them, P2-m3, the derivative with meta-aminomethyl-benzyl group at the P2 site, showed the greatest potential to interact with the 3Cpro target by delivering the highest number of intermolecular hydrogen bonds and contact atoms. It formed the hydrogen bonds with L127 and K130 residues at the P2 site stronger than rupintrivir, supported by significantly lower MM/PB(GB)SA binding free energies. Elucidation of designed rupintrivir analogs in our study provides the basis for developing compounds that can be candidate compounds for further HFMD treatment.

Selective adsorption of Ba2+ using chemically modified alginate beads with enhanced Ba2+ affinity and its application to 131Cs production

The 131Cs radioisotope with a short half-life time and high average radiation energy can treat the cancer effectively in prostate brachytherapy. The typical 131Cs production processes have a separation step of the cesium from 131Ba to obtain a high specific radioactivity. Herein, we suggested a novel 131Cs separation method based on the Ba2+ adsorption of alginate beads. It is necessary to reduce the affinity of alginate beads to cesium ions for a high production yield. The carboxyl group of the alginate beads was replaced by a sulfonate group to reduce the cesium affinity while reinforcing their affinity to barium ions. The modified beads exhibited superior Ba2+ adsorption performances to native beads. In the fixed-bed column tests, the saturation time and adsorption capacity could be estimated with the Yoon-Nelson model in various injection flow rates and initial concentrations. In terms of the Cs elution, the modified alginate showed better performance (i.e., an elution over 88%) than the native alginate (i.e., an elution below 10%), indicating that the functional group modification was effective in reducing the affinity to cesium ions. Therefore, the separation of cesium from the barium using the modified alginate is expected to be an additional option to produce 131Cs.

Functional group modified 1D interpenetrated metal-organic frameworks on perfluorooctanoic acid adsorption: Experimental and theoretical calculation study

Functional groups modified metal-organic frameworks (MOFs) was synthesized via a pre-tailor method and served as an adsorbent for perfluorooctanoic acid (PFOA) removal. The material was characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction and N2 sorption-desorption. Monte Carlo simulation and molecular dynamics are derived to predict the possible molecular packing and adsorption mechanism. The Hirshfeld surface with reduced density gradient analysis demonstrates that PFOA is adsorbed on MOF-X mainly affected by van der Waals interactions and steric effects. Adsorption kinetics and isotherms were investigated on the basis of a static experiment. The pseudo-second-order kinetic model and Langmuir isotherm were fitted well to characterize adsorption process. Hereinto, amino-modified MOFs reached the highest adsorption efficiency and the maximum capacity was 185.6 mg/g. Combing the experimental data with theoretical simulation, results indicated that functional group modification is an effective approach to alter the crystal structure and then affect the adsorptive properties of MOFs.

Pretreatment methods to enhance solubilization and anaerobic biodegradability of lignocellulosic biomass (wheat straw): Progress and challenges

Agro-waste (wheat straw) is considered most effective (heating value 16 MJ/kg) for energy recovery through anaerobic digestion (AD). However, the complex lignocellulosic structure obstructs their biotransformation and is a rate-limiting step of the AD process. The pretreatment of agro-waste could remove the physical and chemical barriers and accelerate the downstream AD process. The physical pretreatments (mechanical, thermal, sonication) improve the biodegradation kinetics of wheat straw (>50% and can reach up to 92%) but require more energy. High external or internal heat sources may lead to the formation of recalcitrant compounds, i.e., furan derivatives from cellulose. Chemical pretreatment is effective for rapid reaction rate but is uneconomical due to high chemical cost. It may produce toxic intermediary products, and hinder microbial activities in AD. The ionic liquids are emerging chemical pretreatment and are renewable, recoverable, difficult to oxidize, and bio-based salts. The chemical pretreatment induces cellulose loss up to 59% and lignin up to 69%, while the bio-degradability is as high as 88.3%. In biological pretreatment, bacterial pretreatment is superior to fungal and algal pretreatments, and also helps in the substrate bio-degradation during AD. The FTIR, TGA-DTG, XRD, and SEM technologies can validate the efficiency of the pretreatment method, such as modifications in lignocellulosic functional groups, mass loss, crystal feature, surface topography, and morphology of lignocellulosic biomass. Different mathematical models, especially the modified Gompertz model, are employed to facilitate the insight into the AD research. Energy use and balance are necessary for the pretreatment process to figure out the real synergic effects rather than aiming to achieve enhanced methane production.

A review on experimental chemically modified activated carbon to enhance dye and heavy metals adsorption

Effective and low-cost removal of dye and heavy metals from wastewater still is a great challenge for researchers. Adsorption using activated carbon is widely used in removing these toxic pollutants. Physical, chemical, and biological modifications have been studied for improving activated carbon adsorption performance. Literature suggests that chemical modified activated carbon showed maximum adsorption capacity towards dye and heavy from aqueous solution. Chemical modifications, including acid, base, and impregnation, are studied extensively due to reagent availability, easy modification, and tuning facilities of surface functional groups. However, systematic documentation of chemical modifications on activated carbon is required for dye and heavy metals removal efficiency improvement from wastewater. This review focused on the up to date experimental chemically modified activated carbon that showed improved adsorption capacity towards dye and heavy metals from aqueous solution. The available experimental data recommends that an appropriate treatment strategy of a chemical modification process enhanced dye and heavy metals adsorption capacity of the modified activated carbon. Optimum modification process developed textural or surface functional groups properties of modified activated carbon that improved adsorption or binding capacity toward adsorbate or a particular species. In addition, the adsorption capacity of modified and corresponding activated carbon is compared. • Experimental works of dye and heavy metals adsorption are summarized. • Changed of physiochemical properties of AC after chemical modification are mentioned. • Optimized treatment parameters of chemical modification are focused. • Compared adsorption performance between modified and corresponding AC adsorbents. • Systematic documentation help in tailoring surface functional groups of modified AC.

Changes in functional properties during fermentation of Amorphophallus paeoniifolius (Dennst.) Nicolson yam using Lactobacillus plantarum

The purpose of this study was to see how inoculum loading (2 and 5% v/v) and fermentation period (0–72 h) affected the functional properties of A. paeoniifolius (Dennst.) Nicolson yam flour. L. plantarum fermentation was used to ferment the sliced yam. In general, swelling power of modified flour increased along with the increasing of inoculum and fermentation time but not significant, while the water solubility index reduced significantly by fermentation. The water absorption capacity of flour increased significantly as inoculum concentration and fermentation period were increased, and then decreased with the length of the fermentation process. Bulk density implied that the fermentation process formed an open structure of starch granule with a higher proportion of void spaces. The FTIR analysis showed the modification of functional groups of starch that indicates the change of physicochemical properties along the fermentation process due to the interaction of L. plantarum. The color of the treated flour whiter than control makes its application for various food products will be wider. This result suggested that fermentation by 5% L. plantarum within 48 h could provide a greater extent of flour such as processed cheese, sausage, dough, and baked products.

Influence of Functional Group Modification on the Toxicity of Nanoplastics

Nanoplastics (NPs) are ubiquitous in harvested organisms at various trophic levels, and more concerns on their diverse responses and wide species-dependent sensitivity are continuously increasing. However, systematic study on the toxic effects of NPs with different functional group modifications is still limited. In this review, we gathered and analyzed the toxic effects of NPs with different functional groups on microorganisms, plants, animals, and mammalian/human cells in vitro. The corresponding toxic mechanisms were also described. In general, most up-to-date relevant studies focus on amino (−NH2) or carboxyl (−COOH)-modified polystyrene (PS) NPs, while research on other materials and functional groups is lacking. Positively charged PS-NH2 NPs induced stronger toxicity than negatively charged PS-COOH. Plausible toxicity mechanisms mainly include membrane interaction and disruption, reactive oxygen species generation, and protein corona and eco-corona formations, and they were influenced by surface charges of NPs. The effects of NPs in the long-term exposure and in the real environment world also warrant further study.

Substituent Effects Impact Surface Charge and Aggregation of Thiophenol-Labeled Gold Nanoparticles for SERS Biosensors.

SERS immunoassay biosensors hold immense potential for clinical diagnostics due to their high sensitivity and growing interest in multi-marker panels. However, their development has been hindered by difficulties in designing compatible extrinsic Raman labels. Prior studies have largely focused on spectroscopic characteristics in selecting Raman reporter molecules (RRMs) for multiplexing since the presence of well-differentiated spectra is essential for simultaneous detection. However, these candidates often induce aggregation of the gold nanoparticles used as SERS nanotags despite their similarity to other effective RRMs. Thus, an improved understanding of factors affecting the aggregation of RRM-coated gold nanoparticles is needed. Substituent electronic effects on particle stability were investigated using various para-substituted thiophenols. The inductive and resonant effects of functional group modifications were strongly correlated with nanoparticle surface charge and hence their stability. Treatment with thiophenols diminished the negative surface charge of citrate-stabilized gold nanoparticles, but electron-withdrawing substituents limited the magnitude of this diminishment. It is proposed that this phenomenon arises by affecting the interplay of competing sulfur binding modes. This has wide-reaching implications for the design of biosensors using thiol-modified gold surfaces. A proof-of-concept multiplexed SERS biosensor was designed according to these findings using the two thiophenol compounds with the most electron-withdrawing substitutions: NO2 and CN.

Additive-mediated intercalation and surface modification of MXenes.

2D carbides and nitrides of transition metals, also known as MXenes, are an emerging class of 2D nanomaterials that have shown excellent performances and broad application prospects in the fields of energy storage, catalysis, sensing, electromagnetic shielding, electronics and photonics, and life sciences. This unusual diversity of applications is due to their superior hydrophilicity and conductivity, high carrier concentration, ultra-high volumetric capacitance, rich surface chemistry, and large specific surface area. However, it is difficult to make MXenes with the desired surface functional groups that deliver high reactivity and high stability, because most MXenes are extracted from ceramics (MAX phase) by an etching process, where a large number of metal atoms are inevitably exposed on the surface, with other anions and cations embedded uncontrollably. The exposed metal atoms and implanted ions are thermodynamically unstable and readily react with trace oxygen or oxygen-containing groups to form the corresponding metal oxides or degrade chemically, resulting in a sharp decline in activity and loss of excellent physicochemical properties. The addition of certain synergistic additives during the intercalation and chemical modification of surface functional groups under non-hazardous conditions can result in stable and efficient MXene-based materials with exceptional optical, electrical, and magnetic properties. This review discusses several such methods, mainly additive-mediated intercalation and chemical modification of the surface functional groups of MXene-based materials, followed by their potential applications. Finally, perspectives are given to discuss the future challenges and promising opportunities of this exciting field.

Directional modification of oxygen functional groups by N heteroatoms on soft/hard carbons for sodium storage.

Different oxygen functionalization processes occur for N-doped soft carbon (N-SC) and hard carbon (N-HC), and there may be a competitive relationship between the formation of pyridinic-N and CO groups. For N-SC, abundant CO groups and defects bring excellent Na+ storage performance and cycling stability, especially at high current densities.

A new therapy against MDR bacteria by in silico virtual screening of Pseudomonas aeruginosa LpxC inhibitors

Multidrug-resistant (MDR) bacteria are a significant threat to communities worldwide. MDR Pseudomonas aeruginosa is, a pathogen resistant to most therapies, can cause serious conditions such as endocarditis and pneumonia. The development of an antibiotic is needed before current treatments fail. We targeted LpxC, a key protein for biosynthesizing lipid A of lipopolysaccharide, by in silico virtual screening of current approved therapies. In our first prediction, ZINC000001587011, also known as brequinar, had a low binding energy, high bioavailability, but an unfavorably high calculated octanol-water partition coefficient (cLogP), which signifies poor solubility in water. We performed functional group modification to decrease the high cLogP. Finally, after going through virtual screening of 20,000 candidates and 30 derivatives of ZINC000001587011, we propose that N11 might have the most potential against P. aeruginosa lipid A synthesis, making it a potential treatment for MDR P. aeruginosa.