Carboxylic Function Research Articles

HYDROBORATION-OXIDATION OF GLYCIRRETHIC ACID’S DERIVATIVES

The hydroboration-oxidation reaction is widely used in the chemistry of terpenoids both for proving the structure of new compounds isolated from natural raw materials and for the directed synthesis of low molecular weight bioregulators. Moreover, most of the known examples affect mono- and sesquiterpenes, a much smaller number - for di- and triterpenoids: most are represented by hydroboration-oxidation of localized double bonds, examples for conjugated dienes are limited only by hydroboration-oxidation of cis-eudesma-6,11-diene, abietic acid and its methyl ester.
 We found that the reduction of the pentacyclic triterpenoid – glycyrrhetate methyl ester – diisobutylaluminium hydride in methylene chloride at -78 ° С and subsequent hydrolysis in the presence of ammonium chloride proceeds with the formation of 3β,30-dihydroxy-18βH-olean-9(11),12(13)-diene with a yield of 90%. It was shown that the hydroboration of the 1,3-diene system in it with a 3.3 molar excess of diborane in tetrahydrofuran is accompanied by the restoration of the carboxyl function, and after oxidation with the hydrogen peroxide-sodium acetate system of the organoboranes formed, three alcohols are mixed (2 : 1 : 1): 3β,11,30-trihydroxy-18βH-olean-12(13)-ene, 3β,12,30-trihydroxy-18βH-olean-9(11)-ene and 3β,9,30-trihydroxy-18βH-olean-12 (13)-ene, respectively. A similar mixture of triols was also obtained by hydroboration-oxidation of 3β-hydroxy-18βH-olean-9(11),12(13)-diene-30-oic acid. The hydroboration-oxidation reactions of 3β,30-dihydroxy-18βH-olean-9(11),12(13)-diene or the corresponding 30th acid proceed as monoprocesses predominantly at 9(11) double bonds.

Chickpea peel waste as sustainable precursor for synthesis of fluorescent carbon nanotubes for bioimaging application

In this study, we report a controlled one-pot green synthesis of multiwalled carbon nanotubes (MWCNTs) via pyrolysis of sustainable agriculture waste (chickpea peel) at 400 °C in aqueous medium. These MWCNTs demonstrated 7.0 nm diameter, 0.28 nm graphitic spacing with carbonyl, hydroxyl, and carboxylic acid functionality. The D band (presence of sp3 defects) and G band (E2g mode of graphite) at 1350 cm−1 and 1580 cm−1 originated in Raman spectrum, respectively. The prepared MWCNTs showed blue fluorescence with 10% fluorescence quantum yield in aqueous medium. The MWCNTs showed triple exponential decay characteristics with an average fluorescence lifetime of 4.7 ns. The synthesized MWCNTs revealed a consistent fluorescence in the cytoplasm of 22RV1 human prostate carcinoma cell line without exerting any sign of cytotoxicity. The MWCNTs also exhibited remarkable cytocompatibility in human immortalized prostate epithelial RWPE1 cells.

Mechanism of photochemical degradation of Fe(III)-EDDS complex

In this work, we investigated the photochemical degradation of the complex Fe(III)-EDDS which is increasingly used in studies of advanced oxidation processes. After irradiation of the aqueous solution, HPLC-HRMS analyses are used to identify the degradation products of EDDS. Six different products are separated and identified with specific chemical formulas. Proposed mechanisms based on the initial photo-redox process can explain the formation of all the products. They correspond to oxidized products with a shorter carbon chain and aldehyde and/or carboxylic acid functions. Among, them the formation of formaldehyde is also proposed in the mechanisms. This study is the first one that identifies degradation products of Fe(III)-EDDS complex and proposes a complete mechanism of degradation that can be applied for other iron complexes.

Modified potentiometric titration method to distinguish and quantify oxygenated functional groups on carbon materials by pKa and chemical reactivity

The presence and form of oxygenated functions on carbons lead to significant differences in material properties that impact surface chemistry, catalysis, electronic, and mechanical properties. Titration methodologies, specifically potentiometric and Boehm titrations, classify the types of acidic functions present on carbon materials into broad categories described as carboxylic, lactonic, and phenolic functions based upon the measured or estimated acid dissociation constants (pKa). The accuracy of these methods depends, however, on the estimates for pKa values and suffers when multiple possible species possess similar pKa values. Here, we improve upon past methods by combining potentiometric and chemical titrations, which involves identifying acidic functions by pKa values but also examining how functional groups react with alkaline titrants. Specifically, Brønsted acids like carboxylic and phenolic groups deprotonate reversibly when contacted with alkaline titrant solutions; however, lactonic functions undergo hydrolysis to form carboxylic acids and hydroxyls during identical treatments. Consequently, comparisons between sequential potentiometric titrations can be used to discriminate between functional groups by examining their pKa values but also their reactivity. Tests on probe compounds and functionalized carbon materials show our method successfully distinguishes lactones from other acidic functions on carbon surfaces and suggests the methodology complements other characterization techniques for carbon materials.

Enhancing the Carboxylation Efficiency of Silk Fibroin through the Disruption of Noncovalent Interactions.

Silk fibroin is a semicrystalline protein used as a renewable polymer source and as a biomaterial platform, but existing methods to synthetically modify fibroin suffer from low efficiencies that can limit the protein's utility. This work reports on a mild synthesis that results in a 2-fold increase in carboxylation through the disruption of noncovalent interactions during the reaction. Importantly, silk fibroin maintains its ability to form β-sheets that are critical for tailoring mechanical and degradation properties, as well as for rendering solid constructs (e.g., films and scaffolds) insoluble in water. Increasing carboxyl functionalization affords control over protein charge, which permits tailoring the loading and release of small molecules using electrostatic interactions. Disruption of noncovalent interactions during aqueous carbodiimide coupling also significantly enhances conjugation efficiency of molecules containing primary amine groups, thus enabling high degrees of functionalization with biological molecules, such as proteins and peptides, for biomaterial applications.

(Invited) Electroactive Redox Polymers, Redox Glyconanoparticles and Supramolecular Assemblies Based on Nanotubes for Bioelectrochemical Applications

For four decades, the development of biointerfaces has been the subject of increasing research efforts in the field of analytical chemistry and energy conversion. In particular, the functionalization of electrodes by biomaterials based on electrogenerated polymers and / or carbon nanotubes, is widely used for the design of biosensors and biofuel cells. Nanotube deposits were successfully functionalized by electropolymerization or π−π stacking interactions with pyrene derivatives exhibiting both affinity or covalent binding interactions towards redox molecules or proteins. Some new approaches for developing nanostructured biomaterials based on functionalized tungsten disulfide nanotubes and self-supporting film of carbon nanotubes (buckypapers) will be illustrated with enzymes as biosensing element [1]. In particular, WS2 nanotubes functionalized with carboxylic acid functions were used for the tyrosinase immobilization in order to form an amperometric biosensor towards catechol and dopamine. Moreover, heteropolyoxometalates (C4H10N)6[P2Mo18O62] and (C6H8NO)4[H2P2W18O62] were immobilized within carbon nanotube matrix and used as mediators for the electron transfer with FAD dependent glucose dehydrogenase [2]. The glucose detection was performed with a sensitivity of 198 mAmolL-1cm-2, and a good reproducibility. A new generation of flexible buckypaper electrodes was produced by using linear polynorbornene polymers containing multiple pyrene groups as crosslinker [3]. In addition, the use of bifunctionalized polymers (pyrene and NHS groups) leads to robust buckypapers with the covalent binding of redox groups or enzymes [4].We have been also interested in the development and characterization of glyconanoparticles (vesicles, micelle aggregates) obtained from the self-assembly of block copolymers composed of polystyrene as a hydrophobic tail and cyclodextrin as a hydrophilic part. These glyconanoparticles, which are stable in suspension in aqueous media, have an outer layer composed of cyclodextrin which allows a post-functionalization of the nanoparticle by hydrophobic molecules through host-guest interactions. These nanoparticles are thus a versatile platform for fixing a wide range of redox mediators. Two types of redox nanoparticles in solution for the electrical connection of enzymes have been developed: nanoparticle modified by 9,10-phenanthrenequinone and nanoparticle modified by ABTS modified by two pyrene groups. This innovative approach will be applied to the electrical wiring of enzymes in solution for the elaboration of solubilized enzymatic fuel cell [5,6]. Acknowledgements The author wishes to acknowledge the support from the Sino-French international research network GDRI 0876 “New nanostructured materials and biomaterials for renewable electrical energy sources” for providing facilities. This work is partly supported by the French National Research Agency (ANR-18-CE09-0022-01).[1]

Anhydride-cured epoxy resin reinforcing with citric acid-modified cellulose

Herein, improvement of the mechanical properties of epoxy resin by compositing with citric acid modified cellulose (CAC) was reported. CAC were prepared from carboxyl functionalization with citric acid to increase the adhesion between cellulose and epoxy resin. The epoxy resin composites were prepared using 2,2-bis (4-glycidyloxyphenyl) propane (BADGE) as component, 4-methylcyclohexane-1,2-dicarboxylic anhydride (MHHPA) as curing agent, and cellulose or CAC as filler. The tensile strength of cellulose/epoxy resin composites were decreased with the content of cellulose increased. On the other hand, the tensile strength of CAC/epoxy resin composites were effectively increased with the content of CAC increased. Moreover, compared with pure epoxy resins and cellulose/epoxy resin composites, the Young's modulus and the toughness of CAC/epoxy resin composites significantly increased with the presence of 10 wt% CAC. SEM images showed that cellulose agglomerated in epoxy resins, in contrast, CAC dispersed uniformly in epoxy resins, determined that the adhesion between CAC and epoxy resins were improved after introduced carboxyl groups to cellulose lead to the mechanical properties improved. CAC was also used to partly replace MHHPA to decrease the usage of toxic curing agent, and the mechanical properties of CAC/epoxy resin composites increased with lower MHHPA content. These results indicated that CAC can partially take place of the conventional curing agent in composite preparation, which may further decrease the production cost and improve the mechanical properties of product.

Amphiphilic Rhenium-Oxo Corroles as a New Class of Sensitizers for Photodynamic Therapy.

A set of rhenium(V)-oxo meso-triarylcorroles bearing ester and carboxylic acid functionalities were synthesized with a view to determining their potential for photodynamic therapy. Toward this end, we measured their near-IR phosphorescence and their ability to sensitize singlet oxygen formation. The two esters studied, ReVO 5,10,15-tris(meta-carbomethoxyphenyl)corrole and ReVO 5,10,15-tris(para-carbomethoxyphenyl)corrole, were found to exhibit phosphorescence quantum yields of around 1% and fairly long phosphorescence lifetimes of about 60 μs in toluene. The corresponding carboxylic acids, which were examined in ethanolic/aqueous media, in contrast, showed much lower phosphorescence quantum yields on the order of 0.01% and somewhat shorter phosphorescent lifetimes. The quantum yields for singlet oxygen formation, on the other hand, turned out to be equally high (0.72 ± 0.02) for the esters and corresponding carboxylic acids. For the two carboxylic acids, we also carried out photocytotoxicity measurements on rat bladder cancer cells (AY27) and human colon carcinoma cells (WiDr). Cell viability measurements (MTT assays) indicated 50% cell death (LD50) for AY27 cells upon 5 min of blue light exposure with the meta carboxylic acid and upon 7 min of exposure with the para carboxylic acid; complete cell death resulted after 20 min for both compounds. The WiDr cells proved less sensitive, and LD50 values were reached after 8 and 12 min illumination with the meta and para carboxylic acids, respectively.

Testing for GW501516 (cardarine) in human hair using LC/MS-MS and confirmation by LC/HRMS.

GW501516, also known as GW-1516 or cardarine and endurobol, is a peroxisome proliferator-activated receptor delta (PPAR-δ) agonist. Activation of the receptor will increase fat-burning capacity and muscle production, as it changes the body's fuel preference from glucose to lipids. GW501516 has no therapeutic use, but can be abused for performance-enhancing purposes using the oral route, at dosages of 10 to 20 mg per day, for 6 to 8 weeks. Both athletes and amateurs can abuse GW501516 as the drug can be easily obtained via the Internet. Since January 2009, the list of prohibited substances and methods of doping as established by the World Anti-Doping Agency includes GW-501516, first as a gene doping substance and now in the S4.5 Metabolic modulators class. It is prohibited at all times. Using LC/MS-MS and confirmation by LC/HRM, after methanol incubation of 20 mg with ultrasound for 1 hour, GW501516 was identified in the hair of a male abuser at 32 and 22 pg/mg in 2 × 2 cm segments. The result is the first evidence that this compound with a carboxylic acid function is incorporated in human hair.

Non-linear adsorption characteristics of modified pine wood sawdust optimised for adsorption of Cd(II) from aqueous systems

Abstract The facile modification of pinewood sawdust, with maleic acid, to produce a sorbent aimed at metal ion adsorption, was tested via the batch adsorption of Cd(II) ions from aqueous solution. The sorbent was characterized for the pH of zero point charge (pHZPC), spectroscopic evaluation of the surface functionalization, structural and morphological features. Factors affecting adsorption behavior, such as adsorbent dose, pH of solution, contact time and Cd(II) ion concentration were investigated. Results obtained show the adsorption rate to be comparatively fast, with equilibrium achieved after ∼35 min. Subsequent analysis, showed Langmuirian behavior and a monolayer adsorption capacity of 180.4 mg g−1, at pH 6; while data derived from two-parameter and three-parameter isotherm models was evaluated using non-linear regression methods, with error analysis, to determine the most appropriate model and allow prediction of optimum parameters. The Sips isotherm model proved the most appropriate in describing the experimental data obtained in the study; with a low level of heterogeneity in the adsorption sites occupied suggesting the interaction of the metal ions is preferential with the added carboxylate moieties only. Additionally, the rate of adsorption was analysed using a range of kinetic models (pseudo-first-order, pseudo-second-order, Bangham and Elovich) in their non-linear forms to provide insight into the adsorption mechanism and showing pseudo-second order behavior is observed, indicating two processes are key in the adsorption process, likely diffusion to the surface and subsequent adsorption on the carboxylate moieties incorporated by chemical modification. In conclusion, the sorbent produced in this study offers high potential for the removal of Cd(II) ions from aqueous solution due to the carboxylic functionalities incorporated into the material, which is optimized by solution pH and adsorbent dose.

Factors influencing the formation of block copolymer-based supramolecular assemblies in bulk and thin films

The factors that control the formation of supramolecular assemblies (SMAs) by hydrogen bonding using polystyrene-block-poly(4-vinyl pyridine) (PS-b-P4VP) and biphenyl systems containing different functionalities were investigated both in bulk as well as in thin films. 4-Hydroxybiphenyl (4HB) (hydroxyl functionalized), biphenyl-4-carboxylic acid (BPCA) (carboxyl functionalized) and 4′-hydroxy-4-biphenylcarboxylic acid (HBCA) (with both hydroxyl and carboxyl functionalities) were chosen as small molecules. Phase behavior of SMAs in bulk was studied by temperature-dependent wide-angle and small-angle X-ray scattering. All the SMAs showed the macrophase separation of small molecules in solvent casted samples. Heating or annealing above the glass transition temperature of block copolymers turned out to be a crucial factor in the effective formation of SMAs in the case of 4HB. On the other hand, SMAs formation is not that effective in the case of the carboxylic group-containing small molecules (BPCA and HBCA). Heating or annealing of as casted films above the melting temperature of small molecules leads to the homogeneous dispersion of BPCA and HBCA in SMAs due to the breakage of hydrogen-bonds. In thin films, SMAs formation by solvent vapor annealing is sensitive to the selectivity of solvents to constituted blocks and small molecules. Breaking of self-association of small molecules by heating above melting temperature of small molecules or annealing in a good solvent for both block copolymers and the small molecules is a key factor in the formation of SMAs in bulk and thin films. The present study provides a guideline for the basic design of effective SMAs using different kinds of small molecules, block copolymers and annealing conditions.

Bio/hydrochar Sorbents for Environmental Remediation

A rising global population and aspirational higher living standards has driven a step change in resource utilization and concomitant anthropogenic pollution across the biosphere. Low‐cost and scalable technologies for environmental remediation are therefore urgently sought, with an emphasis on trash‐to‐treasure strategies that exploit abundant but underutilized waste by‐products of existing sectors. Biochars are carbon‐rich, porous solids produced by biomass pyrolysis under anaerobic or oxygen‐scarce conditions at high temperature (350–700 °C), while hydrochars are produced by hydrothermal biomass carbonization at lower temperature (130–250 °C) and high autogenous pressures (0.3–4.0 MPa). Bio/hydrochars possess unique physicochemical properties, notably high surface areas (100–1500 m2 g−1) and porosity (0.25–2.5 cm3 g−1) and rich surface chemistry featuring carboxylic, phenolic, hydroxyl, and carbonyl functions, amenable to chemical, physical, or biochemical modification, rendering them ideal sorbents for pollutants such as heavy metals (e.g. As and Cr), and toxic organic (e.g., dyes and xenobiotics) and inorganic (e.g., SO2) molecules. Bio/hydrochars are attractive for environmental remediation of pollutant mixtures by surface complexation, redox chemistry, electrostatic interactions/ion exchange, or co‐precipitation. This review discusses recent opportunities and challenges in creating bio/hydrochar sorbents and their nanocomposites through grafting, doping, and chemical/physical activation, for the depollution of aquatic and atmospheric environments.

Combined Peptide and Small-Molecule Approach toward Nonacidic THIQ Inhibitors of the KEAP1/NRF2 Interaction.

The NRF2-ARE pathway is an intrinsic mechanism of defense against oxidative stress. Inhibition of the interaction between NRF2 and its main negative regulator KEAP1 is an attractive strategy toward neuroprotective agents. We report here the identification of nonacidic tetrahydroisoquinolines (THIQs) that inhibit the KEAP1/NRF2 protein-protein interaction. Peptide SAR at one residue is utilized as a tool to probe structural changes within a specific pocket of the KEAP1 binding site. We used structural information from peptide screening at the P2 pocket, noncovalent small-molecules inhibitors, and the outcome from an explorative SAR at position 5 of THIQs to identify a series of neutral THIQ analogs that bind to KEAP1 in the low micromolar range. These analogs establish new H-bond interactions at the P3 and P2 pockets allowing the replacement of the carboxylic acid functionality by a neutral primary carboxamide. X-ray crystallographic studies reveal the novel binding mode of these molecules to KEAP1.

Consecutive Three-Component Synthesis of Donor-Substituted Merocyanines by a One-Pot Suzuki–Knoevenagel Condensation Sequence

The consecutive three-component Suzuki-Knoevenagel condensation (SuKnoCon) synthesis is an efficient, modular one-pot synthetic approach to donor-substituted merocyanines with carboxylic acid functionality. A library of 19 dyes is readily accessible and their electronic properties can be assessed by cyclic voltammetry and absorption and emission spectroscopy. In addition, for illustration of the utility of this concise one-pot concept, several dyes from this library were identified to be well suited as DSSC dyes with relative efficiencies reaching up to 93% of Grätzel's dye N3.

Tunable 3D nanofibrous and bio-functionalised PEDOT network explored as a conducting polymer-based biosensor

Conducting polymers that possess good electrochemical properties, nanostructured morphology and functionality for bioconjugation are essential to realise the concept of all-polymer-based biosensors that do not depend on traditional nanocatalysts such as carbon materials, metal, metal oxides or dyes. In this research, we demonstrated a facile approach for the simultaneous preparation of a bi-functional PEDOT interface with a tunable 3D nanofibrous network and carboxylic acid groups (i.e. Nano-PEDOT-COOH) via controlled co-polymerisation of EDOT and EDOT-COOH monomers, using tetrabutylammonium perchlorate as a soft-template. By tuning the ratio between EDOT and EDOT-COOH monomer, the nanofibrous structure and carboxylic acid functionalisation of Nano-PEDOT-COOH were varied over a fibre diameter range of 15.6 ± 3.7 to 70.0 ± 9.5 nm and a carboxylic acid group density from 0.03 to 0.18 μmol cm−2. The nanofibres assembled into a three-dimensional network with a high specific surface area, which contributed to low charge transfer resistance and high transduction activity towards the co-enzyme NADH, delivering a wide linear range of 20–960 μM and a high sensitivity of 0.224 μA μM−1 cm−2 at the Nano-PEDOT-COOH50% interface. Furthermore, the carboxylic acid groups provide an anchoring site for the stable immobilisation of an NADH-dependent dehydrogenase (i.e. lactate dehydrogenase), via EDC/S–NHS chemistry, for the fabrication of a Bio-Nano-PEDOT-based biosensor for lactate detection which had a response time of less than 10 s over the range of 0.05–1.8 mM. Our developed bio-Nano-PEDOT interface shows future potential for coupling with multi-biorecognition molecules via carboxylic acid groups for the development of a range of advanced all-polymer biosensors.

Influence of Carbohydrate Residues on Antibacterial Activity of Vancomycin

This paper presents synthesis of vancomycin derivatives modified with selected 1- and 2-aminoalditols to carboxylic function and 2,5-anhydro-D-mannose and D-talose to amino function of vancosamine via reductive alkylation. MIC and MBC of these derivatives were determined for reference strains of bacteria: Staphylococcus aureus ATCC 25923, ATCC 6538, ATCC 6538/P, S. epidemidis ATCC 14490, E. faecium PCM 1859, E. faecalis PCM 2673, S. pyogenes PCM 465, and S. pneumonia ATCC 49619 and compared with the activity of vancomycin and its aglycone. Our findings confirm that sugar fragments can play an important role in the mechanism of interaction of vancomycin with bacterial cell wall peptidoglycan.

Thiourea Derivative of 2-[(1R)-1-Aminoethyl]phenol: A Flexible Pocket-like Chiral Solvating Agent (CSA) for the Enantiodifferentiation of Amino Acid Derivatives by NMR Spectroscopy.

Thiourea derivatives of 2-[(1R)-1-aminoethyl]phenol, (1S,2R)-1-amino-2,3-dihydro-1H-inden-2-ol, (1R,2R)-(1S,2R)-1-amino-2,3-dihydro-1H-inden-2-ol, and (R)-1-phenylethanamine have been compared as chiral solvating agents (CSAs) for the enantiodiscrimination of derivatized amino acids using nuclear magnetic resonance (NMR) spectroscopy. Thiourea derivative, prepared by reacting 2-[(1R)-1-aminoethyl]phenol with benzoyl isothiocyanate, constitutes an effective CSA for the enantiodiscrimination of N-3,5-dinitrobenzoyl (DNB) derivatives of amino acids with free or derivatized carboxyl functions. A base additive 1,4-diazabicyclo[2.2.2]octane(DABCO)/N,N-dimethylpyridin-4-amine (DMAP)/NBu4OH) is required both to solubilize amino acid derivatives with free carboxyl groups in CDCl3 and to mediate their interaction with the chiral auxiliary to attain efficient differentiation of the NMR signals of enantiomeric substrates. For ternary systems CSA/substrate/DABCO, the chiral discrimination mechanism has been ascertained through the NMR determination of complexation stoichiometry, association constants, and stereochemical features of the diastereomeric solvates.

Role of the Hydroxo Group in the Coordination of Citric Acid to Trivalent Americium

The molecular characterization based on multi‐technique approach has led to major highlights on revealing the coordination of americium with citric acid. The structure of the different complexes at pH 1 and 3 are described. These characterizations are made possible by the comparison of the americium‐citric acid system with the americium‐tricarballylic acid (one analogue of the citric acid without the alpha‐hydroxo group). The structural analyses (Vis spectrophotometry, NMR, EXAFS, TRLFS and capillary electrophoresis) were carried out after the establishment of the speciation distribution diagrams, allowing to take into account the species repartition for structural analysis data treatment. For the 1:1 complex the hydroxo group is counter intuitively deprotonated and coordinated to the Am(III) at pH 1 as well as two carboxylate functions, whereas at pH 3 the hydroxo is not coordinated and stays protonated allowing the three carboxylate functions to coordinate the metallic cation. Therefore, the hydroxo group affects the Am complexation differently depending on the pHs: by inductive effect at pH 3, and by direct coordination at pH 1.

DFT and Kinetic Evaluation of Chloromethane Removal Using Cost-Effective Activated Carbon

Activated carbon (AC) was first produced from waste rubber tires via pyrolysis and then tested for its ability to adsorb chloromethanes from aqueous solutions. The adsorption activity of the AC was facilitated by the existence of carboxyl and hydroxyl functionalities on its surface. Under optimal conditions (AC dosage of 5 g/L and contact time of 60 min), 86.9% dichloromethane, 98.1% chloroform, and 99.8% carbon tetrachloride (CCl4) were removed from the contaminated water. The adsorption experimental data were fitted to the kinetics and the adsorption isotherms models. The density functional theory approach was adopted to assess the various possibilities of interaction between CCl4 and the functionalized AC. Theoretical modeling predicted the adsorption activity to be predominantly controlled by a hydrogen-bonding-assisted Cl···O=C type of interaction. In addition, the adsorption was found to be facilitated by various types of π···Cl interactions, with the development of an appreciable charge transfer during the process. This theoretical modeling of the interaction between AC and the organic contaminants is an improvement of our previous studies on the adsorption of contaminants using cost-effective AC.

Activation Effects of Carnosine- and Histidine-Containing Dipeptides on Human Carbonic Anhydrases: A Comprehensive Study.

l-Carnosine (β-Ala-l-His) and several other histidine-containing peptides, including two N-methylated forms on the imidazole ring (l-anserine and l-balenine), two derivatives modified on the carboxyl function (carcinine and l-carnosinamide), two analogues differing in the length of the N-terminal residue (l-homocarnosine and Gly-l-His) and the N-acetyl derivatives, were investigated as activators of four isoforms of the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1). The four human isoforms hCA I, II, VA and IX were activated in the low to high micromolar range, with a rather complex structure activity relationship. A performed computational study allowed us to rationalize these results and to propose a binding mode of these activators within the enzyme active site. Similarly to other CA activators, the here studied peptides could find relevant pharmacological applications such as in the management of CA deficiencies, for therapy memory and enhancing cognition or for artificial tissues engineering.