CO2H Groups Research Articles

Chemical Synthesis of Conjugation-Ready Trisaccharides Corresponding to Biological Repeating Units of Pseudomonas aeruginosa Serotype 10 and 19 O-Antigens.

Here we report the chemical synthesis of conjugation-ready trisaccharides, representing biological repeating units of Pseudomonas aeruginosa serotype 10 and 19 O-antigens. The α-d-QuiN3 glycosidic bond was stereoselectively synthesized through TMSI─Ph3P═O mediated 1,2-cis glycosylation. Selective oxidation of the C6-OH group at the disaccharide stage allowed for benzylidene-promoted construction of the α-l-GalN3 glycosidic bond and simplification of the postglycosylation process at the trisaccharide stage. The low reaction temperature and neighboring electron-donating effect facilitated the efficient synthesis of the trisaccharide.

Efficient photocatalytic degradation of chloramphenicol from contaminated water over rGO@MoS2 nanocomposites

Antibiotics-based effluents pose a severe threat to the natural ecosystem by acting as reservoirs for the growth of drug-resistant bacteria if untreated. Herein, a facile and scalable approach was developed to engineer photocatalysts associating reduced graphene oxide (rGO) and molybdenum disulfide (rGO@MoS2) that were used for the degradation of chloramphenicol (CAP) from contaminated water under UV-light. The hydrothermally produced rGO@MoS2 catalysts contain CO, COH, and COC functional groups that contribute to the binding of CAP onto their surface. The rGO surface modification with MoS2 layers offers a high surface area for light absorption. Results show that the rGO@MoS2 catalyst (1:1 w/w) exhibits the highest degradation efficiency (DE) of 86 % within 180 min of light exposure at neutral pH. Further, the kinetic modelling studies for CAP degradation by rGO@MoS2 1:1 showed high linearity with pseudo-first order kinetics (R2 ∼ 0.9). The isotherm modelling studies correspond to Langmuir isotherm (R2 ∼ 0.99), suggesting monolayer-type interaction of CAP with the photocatalyst surface during photodegradation. Furthermore, the mechanism of degradation elucidated using scavenging experiments showed the involvement of both holes (h+) and electrons (e−) that contribute to the degradation of CAP by generating reactive oxygen species (ROS) like OH● and O2●− radicals. The applicability of the rGO@MoS2 photocatalyst towards the degradation of CAP was tested in Ganga water, wherein a similar ∼86 % CAP removal was observed. Furthermore, the photocatalyst was found to be stable and could be reused five times. Overall, these findings demonstrate the usefulness of the rGO@MoS2 1:1 composite as an efficient photocatalyst that can be used for the degradation of harmful organic pollutants from water bodies to provide a safer and cleaner environment.

β-(1 → 4)-Polyglucuronic acids with C2/C3-ketones prepared from regenerated cellulose by catalytic oxidation using solid NaOCl·5H2O

Three commercial regenerated cellulose samples were subjected to TEMPO-catalyzed oxidation using solid NaOCl·5H2O as the primary oxidant for structural analyses of the oxidized products (TEMPO = 2,2,6,6-tetramethylpiperidine-1-oxyl). The regenerated cellulose/water slurries became transparent solutions after oxidation for 60 min. The yields of the oxidized products were almost 100 % when they were isolated as precipitates in ethanol/water mixtures. The solution-state NMR spectra revealed that the oxidized products were almost pure water-soluble β-(1 → 4)-polyglucuronic acids; the reaction conditions described herein ensured the complete oxidation of the C6–OH groups in the regenerated cellulose samples to C6-carboxy groups. However, the solid-state 13C NMR spectra of the oxidized products indicated that C2/C3-ketones (<20 % of the total units) were formed during side reactions, which is characteristic for oxidized products prepared from regenerated cellulose with the C2/C3-glycol structure. These ketones were likely to form intermolecular hemiacetal linkages in the oxidized products. During conductivity titration of the oxidized products, it is necessary to control the sample masses to accurately determine the carboxy contents. The mass-average degree of polymerization decreased from 330 to 890 for the original regenerated cellulose samples to 65–79 for the oxidized products; substantial depolymerization is inevitable during TEMPO-catalyzed oxidation of the regenerated cellulose samples.

Pilot-scale foam and cast-coated nanocellulose filters for water treatment

AbstractA large variety of substances, for instance heavy metal ions from different sources including mining, industry, and agricultural activities, pollute fresh water sources. Bio-based adsorbents, such as cellulose nanofibers (CNF), have recently been introduced in the process of treating water to remove hazardous pollutants primarily owing to their natural abundance, non-toxicity, and renewability. Surface modification of CNF, e.g. by catalytically oxidising the primary C6-OH groups of CNF selectively into carboxylic (COO−) groups with TEMPO, yields materials that are effective in adsorbing positively charged heavy metal ions, e.g. Cu ions. However, to utilise CNF in continuous processes beyond static, batch-wise adsorption, in particular on (pre-)industrial scale, they need to be immobilised on filter substrates in thin layers and an efficient manner. In this work, we report bio-adsorbent-based filters prepared by coating TEMPO-CNF on viscose filters using two different pilot-scale coating approaches, foam and cast coating. The performance of TEMPO-CNF filters was evaluated in terms of their water permeance as well as adsorption of metal ions including Cu(II) and Ca(II). By foam coating thin layers could be fabricated in a time efficient way facilitating high adsorption capacities (52 mg g−1), whilst by cast coating higher amounts of TEMPO-CNF could be deposited allowing for adsorbing higher absolute amounts (280 mg m−2) of heavy metal ions. Graphical abstract

Effect of Position of Donor Units and Alkyl Groups on Dye-Sensitized Solar Cell Device Performance: Indoline-Aniline Donor-Based Visible Light Active Unsymmetrical Squaraine Dyes.

Indoline (In) and aniline (An) donor-based visible light active unsymmetrical squaraine (SQ) dyes were synthesized for dye-sensitized solar cells (DSSCs), where the position of An and In units was changed with respect to the anchoring group (carboxylic acid) to have In-SQ-An-CO2H and An-SQ-In-CO2H sensitizers, AS1-AS5. Linear or branched alkyl groups were functionalized with the N atom of either In or An units to control the aggregation of the dyes on TiO2. AS1-AS5 exhibit an isomeric π-framework where the squaric acid unit is placed in the middle, where AS2 and AS5 dyes possess the anchoring group connected with the An donor, and AS1, AS3, and AS4 dyes having the anchoring group connected with the In donor. Hence, the conjugation between the middle squaric acid acceptor unit and the anchoring -CO2H group is short for AS2, AS5, and AK2 and longer for AS1, AS3, and AS4 dyes. AS dyes showed absorption between 501 and 535 nm with extinction coefficients of 1.46-1.61 × 105 M-1 cm-1. Further, the isomeric π-framework of An-SQ-In-CO2H and In-SQ-An-CO2H exhibited by means of changing the position of In and An units a bathochromic shift in the absorption properties of AS2 and AS5 compared to the AS1, AS3, and AS4 dyes. The DSSC device fabricated with the dyes contains short acceptor-anchoring group distance (AS2 and AS5) showed high photovoltaic performances compared to the dyes having longer distance (AS1, AS3, and AS4) with the iodolyte (I-/I3-) electrolyte. DSSC device efficiencies of 5.49, 6.34, 6.16, and 5.57% have been achieved for AS1, AS2, AS3, and AS4 dyes, respectively; without chenodeoxycholic acid (CDCA), small changes have been observed in the device performance of the AS dyes with CDCA. Significant changes have been noted in the DSSC parameters (open-circuit voltage VOC, short-circuit current JSC, fill factor ff, and efficiency η) for the AS5 dye while sensitized with CDCA and showed highest DSSC efficiency of 8.01% in the AS dye series. This study revealed the potential of shorter SQ acceptor-anchoring group distance over the longer one and the importance of alkyl groups on the overall DSSC device performance for the unsymmetrical squaraine dyes.

A unimolecular artificial cation channel based on cascaded hydrated acid groups.

A cation channel possessing cascaded hydrated acid groups has been successfully constructed using pillar[5]arene integrated with dual cyclodextrins. As a proof-of-concept, the secondary side of cyclodextrin substituted by 24 -CO2H groups presents high coordination sites, which helps hydrated cations to quickly dehydrate and accelerates efficient cation transport (Rb+ > Cs+ > K+ > Na+ > Li+). Notably, benefitted by the protonation and deprotonation of -CO2H groups, ion permeation activity of the channel molecules under acidic condition (pH = 6.0) is 2.8 times higher than that under alkaline conditions (pH = 8.0), exhibiting pH-modulated property and promising potential in building intelligent artificial ion channels with customized features.

A DFT Study of Solvent and Substituent Effects on the Adsorptive and Photovoltaic Properties of Some Selected Porphyrin Derivatives for DSSC Application.

A DFT/TD-DFT method was employed to study the effects of structural modification and solvent variation on the solubility, adsorptive, and photovoltaic properties of six porphyrins (A-F) obtained by structurally modifying two literature porphyrins A and D. The properties of interest were studied in vacuum, acetonitrile (AcCN), dichloromethane (DCM), dimethyl sulphoxide (DMSO), and ethanol (EtOH) for possible application of the molecules as sensitizers in dye-sensitized solar cells (DSSCs). Electronic absorption properties of the molecules were computed via potential energy surface scan, and thermodynamic data were obtained by DFT calculations in the selected media. Solubility properties of the molecules were mostly enhanced with DMSO as the solvent. The adsorptivity of the molecules onto mesoporous titanium (IV) oxide surface were predicted to be enhanced in the presence of DMSO. Most of the molecules were found to exhibit their highest photovoltaic activity measured in terms of the incidentphoton conversion efficiency (IPCE) in AcCN and DCM, rather than in DMSO due to its high viscosity and the ability to use its oxygen to form the catenating O-Ti4+ bond with the Ti4+ of the TiO2, causing inhibition of electron movement on the semiconductor surface. In general, the computed photovoltaic (PV) properties were found to be enhanced with -CO2H group as the substituent, and in AcCN or DCM as the solvent.

Effect of the oil from the fatty tissues of Crocodylus siamensis on gut microbiome diversity and metabolism in mice.

Dietary fat can alter host metabolism and gut microbial composition. Crocodile oil (CO) was extracted from the fatty tissues of Crocodylus siamensis. CO, rich in monounsaturated- and polyunsaturated fatty acids, has been reported to reduce inflammation, counter toxification, and improve energy metabolism. The aim of this study was to investigate the effect of CO on gut microbiota (GM) in laboratory mice as well as the accompanying metabolic changes in the animals. Forty-five C57BL/6 male mice were randomly divided into five groups and orally administrated either sterile water (control [C]); 1 or 3% (v/w) CO (CO-low [CO-L] and CO-high [CO-H], respectively); or 1 or 3% (v/w) palm oil (PO-low and PO-high, respectively) for 11 weeks. Body weight gain, food intake, energy intake, blood glucose levels, and blood lipid profiles were determined. Samples from colon tissue were collected and the 16S rRNA genes were pyrosequenced to clarify GM analyses. The results showed that there were no differences in body weight and blood glucose levels. Food intake by the mice in the CO-L and CO-H groups was statistically significantly less when compared to that by the animals in the C group. However, neither CO treatment had a statistically significant effect on calorie intake when compared to the controls. The CO-H exhibited a significant increase in serum total cholesterol and low-density lipoprotein but showed a downward trend in triglyceride levels compared to the control. The GM analyses revealed that both CO treatments have no significant influence on bacterial diversity and relative abundance at the phylum level, whereas increases of Choa1 and abundance-based coverage estimator indexes, distinct β-diversity, and Proteobacteria abundance were observed in the PO-high group compared with the C group. Furthermore, the abundance of Azospirillum thiophilum and Romboutsia ilealis was significantly higher in the CO-L and CO-H groups which could be associated with energy metabolic activity. Thus, CO may be an alternative fat source for preserving host metabolism and gut flora.

Fabrication of hydroxyl terminated diamond by high-voltage hydroxide ion treatments

Functionalized diamond is promising for biosensing applications due to its attractive properties. Hydroxyl terminated diamond (OH-diamond) surface with chemically functionalizable carboxyl groups is beneficial to silanization, which creating an amine termination is necessary to immobilize proteins and DNA. However, fabrication of high quality OH-diamond surface is still difficult. In this work, OH-diamond is obtained by hydroxide ion treatments in deionized water at high voltages up to 3000 V. The OH-diamond exhibited high intensity of singly oxidized CⅠ carbon bonds (COH and COC) and untraceable doubly oxidized CⅡ carbon bonds (CO or OCO), characterized by X-ray photoelectron spectroscopy measurements. Meanwhile, OH and CO stretching vibration was observed in the Fourier transform infrared spectra. Furthermore, silanizaiton is achieved by 3-aminopropyltriethoxysilane (APTES) on the OH-diamond surface via condensation reaction with surface COH groups. In the end, the stability of OH-diamond surface was investigated by ReaxFF simulations and density function theory (DFT) calculations.

Valorization of Sargassum Biomass as Potential Material for the Remediation of Heavy-Metals-Contaminated Waters.

Sargassum algae has become a major environmental issue due to its abundance in the Pacific Ocean with hundreds of tons reaching the beaches of the Mexican Caribbean every year. This generates large quantities of decomposing organic matter that have a negative impact on the region's economy and ecosystems. Sargassum valorization has turned out to be a fundamental aspect to mitigate its environmental impact. This study proposes the use and application of untreated Sargassum biomass for the decontamination of waters polluted with lead (Pb) and cadmium (Cd) through single and binary adsorption tests. Physicochemical and textural properties examined by SEM, XRD, and FT-IR elucidated that Sargassum biomass is viable to be used as a potential environmental benign adsorbent, exhibiting Cd(II) and Pb(II) adsorption capacities as high as 240 mg g-1 and 350 mg g-1, respectively, outperforming conventionally used adsorbents. This is attributed to its morphology, favorable surface charge distribution, and the presence of -OH and -COH groups. A strong affinity between the biomass and metal pollutants was evidenced by a thermodynamics study, showing a spontaneous and endothermic process. This work sets a practical route for the utilization of the Sargassum biomass, demonstrating its applicability as a potential material for heavy-metal-polluted water remediation, making a substantial contribution to a circular economy system.

Deciphering chloramphenicol biotransformation mechanisms and microbial interactions via integrated multi-omics and cultivation-dependent approaches

BackgroundAs a widely used broad-spectrum antibiotic, chloramphenicol is prone to be released into environments, thus resulting in the disturbance of ecosystem stability as well as the emergence of antibiotic resistance genes. Microbes play a vital role in the decomposition of chloramphenicol in the environment, and the biotransformation processes are especially dependent on synergistic interactions and metabolite exchanges among microbes. Herein, the comprehensive chloramphenicol biotransformation pathway, key metabolic enzymes, and interspecies interactions in an activated sludge-enriched consortium were elucidated using integrated multi-omics and cultivation-based approaches.ResultsThe initial biotransformation steps were the oxidization at the C1-OH and C3-OH groups, the isomerization at C2, and the acetylation at C3-OH of chloramphenicol. Among them, the isomerization is an entirely new biotransformation pathway of chloramphenicol discovered for the first time. Furthermore, we identified a novel glucose-methanol-choline oxidoreductase responsible for the oxidization of the C3-OH group in Sphingomonas sp. and Caballeronia sp. Moreover, the subsequent biotransformation steps, corresponding catalyzing enzymes, and the microbial players responsible for each step were deciphered. Synergistic interactions between Sphingomonas sp. and Caballeronia sp. or Cupriavidus sp. significantly promoted chloramphenicol mineralization, and the substrate exchange interaction network occurred actively among key microbes.ConclusionThis study provides desirable strain and enzyme resources for enhanced bioremediation of chloramphenicol-contaminated hotspot sites such as pharmaceutical wastewater and livestock and poultry wastewater. The in-depth understanding of the chloramphenicol biotransformation mechanisms and microbial interactions will not only guide the bioremediation of organic pollutants but also provide valuable knowledge for environmental microbiology and biotechnological exploitation.ATrkAsjN2DD8FKaZQAS4KPVideo

FTIR spectroscopy of ZrC nanoparticles under the gamma radiation

In the presented work, infrared spectra of nano-ZrC samples were taken in the range of 400–4000 cm−1 of the wavenumbers before and after gamma irradiation (5 Mrad, 15 Mrad, 50 Mrad and 150 Mrad). As a result of the spectral analysis, it is possible to notice that seven IR bands appear in the general approach before irradiation. The peaks explaining the vibration of the ZrC bonds before and after gamma irradiation were explained by the corresponding wavenumbers in the infrared (IR) absorption spectra. Simultaneously, the stretching vibration of the ZrOC bonds are explained by the effect of gamma radiation and the corresponding wavenumbers. Surface activity of ZrC nanoparticles increased as a result of gamma irradiation and this increasing directly affected to the intensity of infrared peaks, which is characterized the COH groups and CO asymmetric stretching vibration. At the relatively high doses, such as 50 Mrad and 150 Mrad, the state of amorphization in nanomaterials is explained by the corresponding spectra.

Anchoring highly distributed Pt species over oxidized graphitic carbon nitride for photocatalytic hydrogen evolution: The effect of reducing agents

Platinum (Pt) as a cocatalyst over graphitic carbon nitride (g-C3N4) is the main active site in the hydrogen evolution reaction (HER). Therefore, controlling the properties of Pt is significant to achieve a high H2 production yield in which the reduction step of the Pt precursor is an important factor. In this study, we prepared Pt-loaded chemically oxidized g-C3N4 photocatalysts for photocatalytic hydrogen evolution using different Pt deposition methods-chemical reduction with hydrazine, hydrogen reduction, and photoreduction. The hydrogen evolution rate of the chemically oxidized Pt/g-C3N4 photocatalysts prepared via hydrogen reduction (1152.8 µmol g-1h−1) was the highest compared to those prepared via chemical reduction (409.9 µmol g-1h−1) and photoreduction (583.7 µmol g-1h−1). The hydrogen reduction method with a fine reducing ability could achieve a uniform distribution of Pt nanoparticles anchored onto the chemically oxidized g-C3N4 nanosheets while maintaining homogeneity between the Pt precursor – reducing agent – g-C3N4. Furthermore, during hydrogen reduction, the greatest ─C═O content and lowest concentrations of ─COOH and ─COH groups on the g-C3N4 surface resulted in an extremely high Pt2+/Pt0 ratio, a strong electronic Pt–g-C3N4 interaction, and the highest charge transfer efficiency, enhancing the hydrogen evolution rate.

Naked-Eye-Detectable Supramolecular Sensing System for Glutaric Acid and Isophthalic Acid

Abstract We report a molecular sensor, comprising a porphyrin core and four 2-aminoquinolyl groups at meso positions, for the naked-eye detection of glutaric acid and isophthalic acid, both featuring a C3 spacer between two CO2H groups. In the presence of the C3 dicarboxylic acids, solutions of the porphyrin sensor underwent significant changes in color and absorption spectra. NMR spectroscopy and X-ray crystallography revealed that the porphyrin derivative bound to two molecules of the C3 dicarboxylic acids selectively to form 1:2 complexes, which dimerized through strong π-stacking interactions. Magnetic circular dichroism (MCD) spectroscopy and density functional theory (DFT) calculations suggested that the red-shifting of the Q-bands in the absorption spectra of the porphyrin derivative arose from tilted quinolyl rings in the dimeric complexes. In addition, we found that a test strip containing the porphyrin sensor could also be used to efficiently detect glutaric acid and isophthalic acid.

Multifunctional Catecholate-Modified 3D TiO2 Nanostructures for Highly Sensitive Photoelectrochemical IL-6 Immunosensors

Protein immunosensors are valuable analytical tools that allow for the detection of proteins with high sensitivity and specificity based on affinity-based interaction between antigen/antibody pairs.1 These devices are increasingly important in clinical settings due to their roles in detecting inflammatory processes, autoimmune disorders, cardiovascular disorders and cancers.1,2 Interleukin-6 (IL-6) is a protein biomarker that plays key roles in immunomodulation, hematopoiesis and inflammatory processes in the human body.3 Elevated levels of IL-6 can be used as evidence for diagnosis of various cancers and autoimmune disorders and even show the progression of COVID-19.3,4 In this work, we developed multifunctional three dimensional (3D) TiO2 nanostructured photoelectrodes as a sensing platform which combine photoelectrochemical (PEC) transduction with a signal-off direct immunoassay to detect IL-6. Surface modification with catecholate ligands was used to modify the properties of TiO2 nanostructures in a three-pronged approach of nanomorphology tuning, photocurrent signal enhancement, and facilitating bioconjugation.3D TiO2 nanostructures were synthesized via acid-hydrothermal process using titanium (IV) butoxide as a precursor. During the synthesis process 3,4-dihydroxybenzaldehyde (DHBA) was added in-situ into the reaction vessel. DHBA is part of the catecholate family of organic ligands which adsorb readily onto TiO2 surfaces. During the synthesis process, DHBA acted as a surfactant with preferential binding affinity for specific crystal facets of TiO2. The addition of DHBA resulted in anisotropic TiO2 crystal growth during synthesis, leading to globular nanorod cluster morphologies with high surface area-to-volume ratios. The 3D TiO2 nanostructures were further modified with extra DHBA after their synthesis. The 3D morphology combined with the extra DHBA resulted in higher UV/visible light absorption and photocurrent density measurements. The synthesized 3D TiO2 nanostructures were used to fabricate photoelectrodes for PEC signal-off immunoassay.The signal-off PEC IL-6 direct immunoassay was constructed by immobilizing a probe layer of anti-IL-6 on the surface 3D TiO2 photoelectrodes. When solutions containing target IL-6 encounter the photoelectrode, IL-6 is immobilized onto the photoelectrode surface through antibody/antigen complexation. Il-6 immobilization on the photoelectrode results in photocurrent signal decrease due to steric hinderance and this signal decrease can be directly correlated to the target concentration. The 3D nanostructure morphology contributed to increased sensitivity for the immunosensor as the higher electroactive surface area can accommodate a higher probe immobilization efficiency. Higher photocurrent generation also resulted in improved limit of detection (LOD) and dynamic range for the sensor. Functionalization by DHBA not only improves photocurrent generation, but also creates an avenue for biofunctionalization through Schiff-base linking between -COH groups of DHBA and -NH2 groups of anti-IL-6. The resultant immunosensor demonstrated excellent performance with an LOD of 3.6 pg mL-1 in plasma and 1.6 pg mL-1 in buffer solution, while having a log-linear dynamic range of 2-2000 pg mL-1. The 3D TiO2 photoelectrodes also demonstrate excellent short-term and long-term stability with little degradation after repeated use.It is evident from our investigations that combining PEC transduction mechanisms with direct signal-off immunoassays can result in high performance biosensors. In particular, the surface modification of 3D TiO2 nanostructure scaffolds with DHBA facilitates the fabrication of materials that are highly nanoporous and generate high photocurrent, resulting in biosensors with large dynamic ranges and low LOD.(1) Zhao, W. W.; Xu, J. J.; Chen, H. Y. Photoelectrochemical Immunoassays. Anal. Chem. 2018, 90 (1), 615–627. https://doi.org/10.1021/acs.analchem.7b04672.(2) Chikkaveeraiah, B. V.; Bhirde, A. A.; Morgan, N. Y.; Eden, H. S.; Chen, X. Electrochemical Immunosensors for Detection of Cancer Protein Biomarkers. ACS Nano 2012, 6 (8), 6546–6561. https://doi.org/10.1021/nn3023969.(3) Khan, M. A.; Mujahid, M. Recent Advances in Electrochemical and Optical Biosensors Designed for Detection of Interleukin 6. Sensors (Switzerland). MDPI AG February 1, 2020. https://doi.org/10.3390/s20030646.(4) Rubin, E. J.; Longo, D. L.; Baden, L. R. Interleukin-6 Receptor Inhibition in Covid-19 — Cooling the Inflammatory Soup. N. Engl. J. Med. 2021, 384 (16), 1564–1565. https://doi.org/10.1056/nejme2103108.

Stability of oxygenated groups on pristine and defective diamond surfaces

The surface functionalization of diamond has been extensively studied through a variety of techniques, such as oxidation. Several oxygen groups have been correspondingly detected on the oxidized diamond, such as COC (ester), CO (ketonic), and COH (hydroxyl). However, the composition and relative concentration of these groups on diamond surfaces can be affected by the type of oxygenation treatment and the diamond surface quality. To investigate the stability of the oxygenated groups at specific diamond surfaces, we evaluated through fully atomistic reactive molecular mechanics (FARMM) simulations, using the ReaxFF force field, the formation energies of CO, COC, and COH groups on pristine and defective diamond surfaces (110), (111), and (311). According to our findings, the COH group has the lowest formation energy on a perfect (110) surface, while the COC is favored on a defective surface. As for the (111) surface, the COC group is the most stable for both pristine and defective surfaces. Similarly, COC group is also the most stable one on the defective/perfect (311) surface. In this way, our results suggest that if in a diamond film the (110) surface is the major exposed facet, the most adsorbed oxygen group could be either COH or COC, in which the COC would depend on the level of surface defects.

Application of aluminum nitride nanotubes as a promising nanocarriers for anticancer drug 5-aminosalicylic acid in drug delivery system

We investigated and discussed the adsorption of the anticancer drug 5-aminosalicylic acid (5-ASA) on the surface of aluminum nitride nano-tubes (AlNNTs) via density functional theory (DFT). The adsorption results using DFT showed the strong interactions of AlNNTs with the carbonyl (–NH2) group of 5-ASA with a higher adsorption energy of approximately − 31.58 kcal.mol−1, while the interaction of AlNNTs with 5-SAS with its –OH and –CO2H groups was weak, which is because of the negative energy of adsorption. Additionally, the values of Gibbs free energy showed the spontaneity of the adsorption of 5-ASA on the surfaces of AlNNTs. In addition, the NBO analysis confirmed the charge transport from the σ orbitals of N and H atoms of 5-ASA to the n* orbitals of N and Al atoms of AlNNTs with high energies. The results demonstrate that 5-ASA tends to interact with AlNNTs in a favorable manner. A significant change was observed in the energy levels of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) during the adsorption of 5-ASA on AlNNTs, thereby decreasing the band gap (Eg) values that enhanced their electrical conductivity. The current work showed that AlNNTs can be considered suitable candidates for delivering 5-ASA in biological systems.

Mechanism of Sugar Ring Contraction and Closure Catalyzed by UDP-d-apiose/UDP-d-xylose Synthase (UAXS)

Uridine diphosphate (UDP)-apiose/UDP-xylose synthase (UAXS) is a member of the short-chain dehydrogenase/reductase superfamily (SDR), which catalyzes the ring contraction and closure of UDP-d-glucuronic acid (UDP-GlcA), affording UDP-apiose and UDP-xylose. UAXS is a special enzyme that integrates ring-opening, decarboxylation, rearrangement, and ring closure/contraction in a single active site. Recently, the ternary complex structure of UAXS was crystallized from Arabidopsis thaliana. In this work, to gain insights into the detailed formation mechanism of UDP-apiose and UDP-xylose, an enzyme-substrate reactant model has been constructed and quantum mechanical/molecular mechanical (QM/MM) calculations have been performed. Our calculation results reveal that the reaction starts from the C4-OH oxidation, which is accompanied by the conformational transformation of the sugar ring from chair type to boat type. The sugar ring-opening is prior to decarboxylation, and the deprotonation of the C2-OH group is the prerequisite for sugar ring-opening. Moreover, the keto-enol tautomerization of the decarboxylated intermediate is a necessary step for ring closure/contraction. Based on our calculation results, more UDP-apiose product was expected, which is in line with the experimental observation. Three titratable residues, Tyr185, Cys100, and Cys140, steer the reaction by proton transfer from or to UDP-GlcA, and Arg182, Glu141, and D337 constitute a proton conduit for sugar C2-OH deprotonation. Although Thr139 and Tyr105 are not directly involved in the enzymatic reaction, they are responsible for promoting the catalysis by forming hydrogen-bonding interactions with GlcA. Our calculations may provide useful information for understanding the catalysis of the SDR family.

Enantioselective Fluorination of α-Substituted β-Diketones Using β,β-Diaryl Serines.

We report the enantioselective fluorination of α-substituted β-diketones using β,β-diaryl serines as a primary amine organocatalyst. The reaction affords the corresponding fluorinated products in yields of 74 to 99% with excellent enantioselectivity (75-95% ee). Moreover, for synthetic applications, the diol, aldols, and the allylic fluoride were synthesized from 2a, maintaining excellent enantioselectivity (94% ee). The control experiment reveals that the CO2H group of the β,β-diaryl serines plays an important role in inducing the high enantioselectivity.

OOCYTE VITRIFICATION FOR FERTILITY PRESERVATION DOES NOT DELAY THE INITIATION OF NEOADJUVANT CHEMOTHERAPY FOR BREAST CANCER

To evaluate whether oocyte vitrification for fertility preservation (FP) delays the initiation of neoadjuvant chemotherapy for breast cancer? We performed a retrospective cohort study including all breast cancer patients eligible for oocyte vitrification following COH or IVM before initiation of neoadjuvant chemotherapy between January 2016 and December 2020. Inclusion criteria were: female patients with confirmed non metastatic breast cancer, 18 to 40 years of age, with indication of neoadjuvant chemotherapy, who have had oocyte retrieval for FP after COH or IVM +/- cryopreservation of ovarian tissue. Various time-points related to cancer diagnosis, FP or chemotherapy were obtained from medical record review. A total of 198 patients with confirmed breast cancer who had oocyte retrieval following COH (n=57) or IVM +/- cryopreservation of ovarian tissue (n=141) for FP prior to neoadjuvant chemotherapy were included. Although women in IVM group were significantly younger as compared to patients who underwent COH (31.7 ± 4.2 vs. 33.3 ± 4.0 years, p=0.019), ovarian reserve parameters, BMI and cancer stage did not differ between the two groups. Overall, the average time from cancer diagnosis to chemotherapy start was similar between patients having undergone COH or IVM before oocyte vitrification (37.3 ± 13.8 vs. 36.9 ±13.5 days in COH and IVM groups respectively; p=0.857). The indication of neoadjuvant chemotherapy for breast cancer should not be considered as an impediment to urgent oocyte vitrification for FP.