Cyanoborohydride Research Articles

Single-Atom Iron Catalysts with Core-Shell Structure for Peroxymonosulfate Oxidation.

The chemical tolerance of ketoenamine covalent organic frameworks (COFs) is excellent; however, the tight crystal structure and low surface area limit their applications in the field of catalysis. In this work, a porous single-atom iron catalyst (FeSAC) with a core-shell structure and high surface area was synthesized by using Schiff base COF nanospheres as the core and ketoenamine COF nanosheets growth on the surfaces. Surface defects were created using sodium cyanoborohydride etching treatment to increase specific surface area. The dye degradation experiments by peroxymonosulfate (PMS) catalyzed by the FeSAC proved that methylene blue can be degraded with a degradation rate constant of 0.125 min-1 under the conditions of 0.1 g L-1 catalyst dosage and 0.05 g L-1 peroxymonosulfate. The FeSAC/PMS system effectively degrades various pollutants in the pH range of 4-10 with over 80% efficiency for four cycles and can be recovered by soaking in iron salt solution. Free radical quenching experiments confirmed that singlet oxygen and superoxide radicals are the main active species for catalysis.

Enhanced ac4C detection in RNA via chemical reduction and cDNA synthesis with modified dNTPs.

The functional analysis of epitranscriptomic modifications in RNA is constrained by a lack of methods that accurately capture their locations and levels. We previously demonstrated that the RNA modification N4-acetylcytidine (ac4C) can be mapped at base resolution through sodium borohydride reduction to tetrahydroacetylcytidine (tetrahydro-ac4C), followed by cDNA synthesis to misincorporate adenosine opposite reduced ac4C sites, culminating in C:T mismatches at acetylated cytidines (RedaC:T). However, this process is relatively inefficient, resulting in <20% C:T mismatches at a fully modified ac4C site in 18S rRNA. Considering that ac4C locations in other substrates including mRNA are unlikely to reach full penetrance, this method is not ideal for comprehensive mapping. Here, we introduce "RetraC:T" (reduction to tetrahydro-ac4C and reverse transcription with amino-dATP to induce C:T mismatches) as a method with enhanced ability to detect ac4C in cellular RNA. In brief, RNA is reduced through NaBH4 or the closely related reagent sodium cyanoborohydride (NaCNBH3) followed by cDNA synthesis in the presence of a modified DNA nucleotide, 2-amino-dATP, that preferentially binds to tetrahydro-ac4C. Incorporation of the modified dNTP substantially improved C:T mismatch rates, reaching stoichiometric detection of ac4C in 18S rRNA. Importantly, 2-amino-dATP did not result in truncated cDNA products nor increase mismatches at other locations. Thus, modified dNTPs are introduced as a new addition to the toolbox for detecting ac4C at base resolution.

Quantitative Peptidomics Using Reductive Methylation of Amines.

A number of different approaches have been used for quantitative peptidomics. In this protocol, we describe the method in which peptides are reacted with formaldehyde and sodium cyanoborohydride, which converts primary and secondary amines into tertiary amines. By using different combinations of regular reagents, deuterated reagents (2H), and reagents containing deuterium and 13C, it is possible to produce five isotopically distinct forms of the methylated peptides, which can be quantified by mass spectrometry. Peptides with free N-termini that are primary amines incorporate two methyl groups using this procedure, which differ by 2Da for each of the five isotopic combinations. Peptides that contain unmodified lysine residues incorporate additional pairs of methyl groups, leading to larger mass differences between isotopic forms. The reagents are commercially available, relatively inexpensive, and chemically stable.

Glycated bovine serum albumin for use in feeding trials with animal models - In vitro methodology and characterization of a glycated substrate for modifying feed pellets.

This study investigated different methods to produce Nε-carboxymethyl-lysine (CML)-enriched bovine serum albumin (BSA) as alternatives to the classical approach using glyoxylic acid (GA) and sodium cyanoborohydride (NaBH3CN) which results in toxic hydrogen cyanide (HCN). The reaction of GA (6mmol/L) and NaBH3CN (21mmol/L) to produce CML remained the most effective with CML yields of 24-35%, followed by 13-24% using 300mmol/L glyoxal (GO). GA promoted specific modification of lysine to CML, and fewer structural modifications of the BSA molecule compared with GO, as evidenced by fluorescence and proteomic analyses. GO promoted greater arginine modification compared with GA (76 vs 23%). Despite structural changes to BSA with GO, murine fecal clearance of CML was similar to literature values. Hence, BSA glycation with 300mmol/L glyoxal is a suitable alternative to GA and NaBH3CN for generating CML-enriched protein free of HCN, but a CML-only fortification model remains to be described.

Mechanism, Kinetics and Simulation of Electrocatalytic Oxidation of Dimethylamine Borane (DMAB) on Electroless Gold

Dimethylamine borane ((CH3)2NHBH3) or DMAB, is broadly used as a reducing agent in electroless autocatalytic platings like gold and nickel-boron, hydrogen storage, and reductive amination. However, the mechanism of its DMAB oxidation procedure remains unclear. This project is based on the hypothesis that a multi-step electron transfer mechanism exists for oxidizing the reducing agent DMAB on gold in alkaline media. According to this mechanism, the active species produced when DMAB is used at high hydroxide content is the BH3OH-. This species is created through a series of irreversible electrochemical oxidation producing the following intermediates BH2(OH)2-, BH(OH)3- and B(OH)4-, which is the final product. Multiple electrochemical methods have been used to uncover the properties of DMAB oxidation progress and verify above-mentioned hypothesis. Electrochemical Impedance Spectroscopy (EIS) was used to test the uncompensated resistance between the working electrode and reference electrode and calibrated in the following experiments: Cyclic voltammetry (CV) showed that DMAB in hydroxide electrolytes have three half-wave potentials with E_(1/2) of -0.778, -0.174 and 0.248 V. Kinetic current values obtained from the Koutecky-Levich plot decreased with temperature with -4.065, -3.62 and -1.45 mA/cm2 at 25°C, 41°C and 52°C, respectively. Rotating Disk Electrode (RDE) and Chronoamperometry (CA) were used to determine the Diffusion Coefficient of BH3(OH)-; BH2(OH)2- and BH(OH)3- 1.38E-05, 3.31E-05 and 1.01E-04, respectively. Tafel analysis was used in obtaining the transfer coefficient, whereas Klingler and Kochi’s method evaluated the constant. These kinetic parameters were used in KISSA-1D software to simulate the CVs. Gas Chromatography with Mass Spectrometry (GC/MS) was used to verify the existence of B(OH)4- and a peak at m/z 78.8 was recorded. All of this provided evidence that the three intermediates are involved in the proposed mechanism. In the future, simulated and experimental approaches will be investigated for other amine boranes compounds such as Sodium cyanoborohydride (NaBH3CN), Sodium triacetoxyborohydride (NaBH(O2CCH3)3), and Sodium borohydride (NaBH4). This work will have far-reaching consequences in enhancing the practical applications of gold and nickel in microelectronics and fuel cells.

Protocols for Efficient Chemical Synthesis of N2 -Modified Guanosine Phosphate Derivatives: Versatile Probes for mRNA Labeling.

A facile, reliable, and efficient method for the synthesis of N2 -modified guanosine nucleotides such as N2 -[benzyl-N-(propyl)carbamate]-guanosine-5'-O-monophosphate, N2 -[benzyl-N-(propyl)carbamate]-guanosine-5'-O-diphosphate, N2 -[benzyl-N-(propyl)carbamate]-guanosine-5'-O-triphosphate, and N2 -[benzyl-N-(propyl)carbamate]-N7 -methyl-guanosine-5'-O-diphosphate, starting from the corresponding nucleotide is described. The general process entails condensation between the exocyclic amine of guanosine nucleotide and 3-[(benzyloxycarbonyl)amino]propionaldehyde in aqueous methanol, followed by reduction using sodium cyanoborohydride to furnish the corresponding N2 -modified guanosine nucleotide in moderate yield with high purity (>99.5%). © 2023 Wiley Periodicals LLC. Basic Protocol: Synthesis of N2 -modified guanosine derivatives.

The conjugation of serotype 31 pneumococcal polysaccharide and CRM197 in N,N-dimethylformamide

Traditionally, PCV (pneumococcal conjugate vaccine) was prepared by the coupling of aldehyde-activated polysaccharide, with a carrier protein via NaCNBH3 (sodium cyanoborohydride) mediated reductive amination in water. However, the reaction is very slow and may take up to several days, which is a significant burden for pharmaceutical companies. Here we report the detailed reaction process of the reductive amination of structurally reassigned serotype 31 polysaccharide and cross reacting material (CRM197) in an organic solvent (N,N-dimethylformamide, DMF) by using STAB (sodium triacetoxyborohydride). The product has been characterized by size exclusion chromatography, nuclear magnetic resonance and transmission electron microscopy. Compared with the traditional method, the reaction can finish within hours and elicited a comparable immune response. The new strategy has the potential of being applied in the preparation of next-generation polysaccharide conjugate vaccines.

Assisted Reductive Amination for Quantitation of Tryptophan, 5-Hydroxytryptophan, and Serotonin by Ultraperformance Liquid Chromatography Coupled with Tandem Mass Spectrometry.

Herein, we used isotopic formaldehyde and sodium cyanoborohydride via reductive amination to label two methyl groups on primary amine to arrange the standards (h2-formaldehyde-modified) and internal standards (ISs, d2-formaldehyde-modified) of tryptophan and its metabolites, such as serotonin (5-hydroxytryptamine) and 5-hydroxytryptophan. These derivatized reactions with a high yield are very satisfactory for manufacturing standards and ISs. This strategy will generate one or two methyl groups on amine to create different mass unit shifts with 14 vs. 16 or 28 vs. 32 in individual compounds for biomolecules with amine groups. In other words, multiples of two mass units shift are created using this derivatized method with isotopic formaldehyde. Serotonin, 5-hydroxytryptophan, and tryptophan were used as examples to demonstrate isotopic formaldehyde-generating standards and ISs. h2-formaldehyde-modified serotonin, 5-hydroxytryptophan, and tryptophan are standards to construct calibration curves, and d2-formaldehyde-modified analogs such as ISs spike into samples to normalize the signal of each detection. We utilized multiple reaction monitoring modes and triple quadrupole mass spectrometry to demonstrate the derivatized method suitable for these three nervous biomolecules. The derivatized method demonstrated a linearity range of the coefficient of determinations between 0.9938 to 0.9969. The limits of detection and quantification ranged from 1.39 to 15.36 ng/mL.

Efficient chemical synthesis of N2 -modified guanosine derivatives: a versatile probes for mRNA labeling

An efficient method for the synthesis of N2 -modified guanosine nucleotides such as N2 -[benzyl-N-(propyl)carbamate]-guanosine-5′-O-monophosphate, N2 -[benzyl-N-(propyl)carbamate]-guanosine-5′-O-diphosphate, N2 -[benzyl-N-(propyl)carbamate]-guanosine-5′-O-triphosphate, and N2 -[benzyl-N-(propyl)carbamate]-N7 -methyl-guanosine-5′-O-diphosphate, starting from the corresponding nucleotide is described. The overall reaction involves the condensation between the exocyclic amine of guanosine nucleotide with 3-[(benzyloxycarbonyl)amino]propionaldehyde in aqueous methanol, followed by reduction using sodium cyanoborohydride to furnish the corresponding N2 -modified guanosine nucleotide in moderate yield with high purity (>99.5%).

The conjugation of serotype 31 pneumococcal polysaccharide and CRM197 in N,N-dimethylformamide

Traditionally, PCV (pneumococcal conjugate vaccine) was prepared by the coupling of aldehyde-activated polysaccharide, with a carrier protein via NaCNBH3 (sodium cyanoborohydride) mediated reductive amination in water. However, the reaction is very slow and may take up to several days, which is a significant burden for pharmaceutical companies. Here we report the detailed reaction process of the reductive amination of structurally reassigned serotype 31 polysaccharide and cross reacting material (CRM197) in an organic solvent (N,N-dimethylformamide, DMF) by using STAB (sodium triacetoxyborohydride). The product has been characterized by size exclusion chromatography, nuclear magnetic resonance and transmission electron microscopy. Compared with the traditional method, the reaction can finish within hours and elicited a comparable immune response. The new strategy has the potential of being applied in the preparation of next-generation polysaccharide conjugate vaccines.

Hydrophilic Aldehyde-Functional Polymer Brushes: Synthesis, Characterization, and Potential Bioapplications.

Surface-initiated activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) is used to polymerize a cis-diol-functional methacrylic monomer (herein denoted GEO5MA) from planar silicon wafers. Ellipsometry studies indicated dry brush thicknesses ranging from 40 to 120 nm. The hydrophilic PGEO5MA brush is then selectively oxidized using sodium periodate to produce an aldehyde-functional hydrophilic PAGEO5MA brush. This post-polymerization modification strategy provides access to significantly thicker brushes compared to those obtained by surface-initiated ARGET ATRP of the corresponding aldehyde-functional methacrylic monomer (AGEO5MA). The much slower brush growth achieved in the latter case is attributed to the relatively low aqueous solubility of the AGEO5MA monomer. X-ray photoelectron spectroscopy (XPS) analysis confirmed that precursor PGEO5MA brushes were essentially fully oxidized to the corresponding PAGEO5MA brushes within 30 min of exposure to a dilute aqueous solution of sodium periodate at 22 °C. PAGEO5MA brushes were then functionalized via Schiff base chemistry using an amino acid (histidine), followed by reductive amination with sodium cyanoborohydride. Subsequent XPS analysis indicated that the mean degree of histidine functionalization achieved under optimized conditions was approximately 81%. Moreover, an XPS depth profiling experiment confirmed that the histidine groups were uniformly distributed throughout the brush layer. Surface ζ potential measurements indicated a significant change in the electrophoretic behavior of the zwitterionic histidine-functionalized brush relative to that of the non-ionic PGEO5MA precursor brush. The former brush exhibited cationic character at low pH and anionic character at high pH, with an isoelectric point being observed at around pH 7. Finally, quartz crystal microbalance studies indicated minimal adsorption of a model globular protein (BSA) on a PGEO5MA brush-coated substrate, whereas strong protein adsorption via Schiff base chemistry occurred on a PAGEO5MA brush-coated substrate.

(Magnetic) Cross-Linked Enzyme Aggregates of Cellulase from T. reesei: A Stable and Efficient Biocatalyst.

Cross-linked enzyme aggregates (CLEAs) represent an effective tool for carrier-free immobilization of enzymes. The present study promotes a successful application of functionalized magnetic nanoparticles (MNPs) for stabilization of cellulase CLEAs. Catalytically active CLEAs and magnetic cross-linked enzyme aggregates (mCLEAs) of cellulase from Trichoderma reesei were prepared using glutaraldehyde (GA) as a cross-linking agent and the catalytic activity and stability of the CLEAs/mCLEAs were investigated. The influence of precipitation agents, cross-linker concentration, concentration of enzyme, addition of bovine serum albumin (BSA), and addition of sodium cyanoborohydride (NaBH3CN) on expressed activity and immobilization yield of CLEAs/mCLEAs was studied. Particularly, reducing the unsaturated Schiff's base to form irreversible linkages is important and improved the activity of CLEAs (86%) and mCLEAs (91%). For increased applicability of CLEAs/mCLEAs, we enhanced the activity and stability at mild biochemical process conditions. The reusability after 10 cycles of both CLEAs and mCLEAs was investigated, which retained 72% and 65% of the initial activity, respectively. The thermal stability of CLEAs and mCLEAs in comparison with the non-immobilized enzyme was obtained at 30 °C (145.65% and 188.7%, respectively) and 50 °C (185.1% and 141.4%, respectively). Kinetic parameters were determined for CLEAs and mCLEAs, and the KM constant was found at 0.055 ± 0.0102 mM and 0.037 ± 0.0012 mM, respectively. The maximum velocity rate (Vmax) was calculated as 1.12 ± 0.0012 µmol/min for CLEA and 1.17 ± 0.0023 µmol/min for mCLEA. Structural characterization was studied using XRD, SEM, and FT-IR. Catalytical properties of immobilized enzyme were improved with the addition of reducent NaBH3CN by enhancing the activity of CLEAs and with addition of functionalized aminosilane MNPs by enhancing the activity of mCLEAs.

A Reductive Aminase Switches to Imine Reductase Mode for a Bulky Amine Substrate.

Imine reductases (IREDs) catalyze the asymmetric reduction of cyclic imines, but also in some cases the coupling of ketones and amines to form secondary amine products in an enzyme-catalyzed reductive amination (RedAm) reaction. Enzymatic RedAm reactions have typically used small hydrophobic amines, but many interesting pharmaceutical targets require that larger amines be used in these coupling reactions. Following the identification of IR77 from Ensifer adhaerens as a promising biocatalyst for the reductive amination of cyclohexanone with pyrrolidine, we have characterized the ability of this enzyme to catalyze couplings with larger bicyclic amines such as isoindoline and octahydrocyclopenta(c)pyrrole. By comparing the activity of IR77 with reductions using sodium cyanoborohydride in water, it was shown that, while the coupling of cyclohexanone and pyrrolidine involved at least some element of reductive amination, the amination with the larger amines likely occurred ex situ, with the imine recruited from solution for enzyme reduction. The structure of IR77 was determined, and using this as a basis, structure-guided mutagenesis, coupled with point mutations selecting improving amino acid sites suggested by other groups, permitted the identification of a mutant A208N with improved activity for amine product formation. Improvements in conversion were attributed to greater enzyme stability as revealed by X-ray crystallography and nano differential scanning fluorimetry. The mutant IR77-A208N was applied to the preparative scale amination of cyclohexanone at 50 mM concentration, with 1.2 equiv of three larger amines, in isolated yields of up to 93%.

Reductive cleavage of annulated 5,6-dihydro-2H-1,2,4-thiadiazine-1,1-dioxides: medium sized ring azasultams.

A novel method for synthesis of medium sized ring azasultams was proposed. It includes reductive cleavage with sodium cyanoborohydride of annulated 5,6-dihydro-2H-1,2,4-thiadiazine-1,1-dioxides that were prepared in bulk quantities by an improved procedure consisting of reacting cyclic imidates with taurine followed by treatment with phosphorus oxychloride in the presence of DIPEA.

Limonin Derivatives via Hydrogenation: Structural Identification and Anti-Inflammatory Activity Evaluation

Limonin is a natural compound which is rich in the fruit of various plants of the Rutaceae family and demonstrated to have a wide range of biological activities. In this work, seven limonin derivatives were successfully synthesized by hydrogenation of limonin, using different reducing agents (sodium cyanoborohydride, lithium aluminum hydride, and sodium borohydride). The chemical structure of the seven derivatives was characterized and identified by a series of techniques, including HR-ESI-MS, 1H-NMR, 13C-NMR, 2D-NMR, and IR. Among the seven limonin derivatives, six limonin derivatives were found to be new compounds which have not been previously reported. Then, the anti-inflammatory activities of the seven synthesized limonin derivatives, as well as the anti-inflammatory activities of eight known natural limonins, were evaluated and compared. Natural limonins, 30-O-Acetylhainangranatumin E and Xylogranatin A, presented significantly better anti-inflammatory activity. Xylogranatin A could inhibit LPS-induced RAW264.7 cell inflammatory factors, with a 90.0% inhibition ratio of TNF-α and 63.77% inhibition ratio of NO release in LPS-induced BV2 cells at 10 μM. Other natural limonins showed poor anti-inflammatory activity. In comparison, all the synthetic limonin derivatives showed decent anti-inflammatory activities, with the highest inhibition ratio of TNF-α of 37.8% and inhibition ratio of NO release of 12.5% in LPS-induced BV2 cells at 10 μM.

Catalyzing benzoxazine polymerization with borohydrides to reduce the cure temperature and coloring

Sodium cyanoborohydride (NaCNBH3) and sodium borohydride (NaBH4) were used as catalysts to lower the ring-opening polymerization (ROP) temperature of 1,3-benzoxazines. According to the dynamic scanning calorimeter (DSC) and Fourier transform infrared (FTIR) studies, the onset ROP temperatures of model benzoxazine were decreased by ca. 80 °C. The activation energies of catalyzed ROP were estimated by Kissinger and Ozawa methods. Moreover, the room temperature behavior of the catalysts in benzoxazine was revealed by 1H NMR and FTIR, and it was found to be dormant at low temperatures and active after 170 °C. Besides catalytic activity, the borohydrides reduced the intense colorization of benzoxazines during curing, and the color changes of catalyzed and uncatalyzed polybenzoxazine samples were measured by colorimetry. Moreover, the thermal stabilities of the catalyzed polybenzoxazines were analyzed and compared to their un-catalyzed counterparts by thermal gravimetric analyses (TGA).

Glucose Scavenging with Pectin Hydrazide: A Step toward Designing Innovative, Functional, All‐Sugar‐Based Polymers

AbstractPolygalacturonic acid hydrazide (PGH) is one of only a few polysaccharide derivatives with pronounced nucleophilic characteristics known today. This water‐soluble and benign material could be reacted with the hydrophilic aldehydes D‐glucose in water, without any catalyst and at room temperature, resulting in a product that is the first example of new family of all‐sugar‐based polysaccharide derivatives. The reaction is reversible, allowing for D‐glucose loading and unloading of the PGH. The D‐glucose binds as the α−, and β anomer of the glucopyranosyl form. The reaction is orthogonal to the reactivity of the hydroxyl groups in the polysaccharide and enables the mild generation of new bio‐inspired polysaccharide derivatives. The glucose attachment could be rendered irreversibly by reducing the hydrazone with sodium cyanoborohydride, leading to the acyclic sugar derivative. A brief hydrodynamic and light scattering study of the polymers showed varying macromolecular properties at consistent molar mass values of the modified polysaccharide derivatives.

Catechol-Based Polymers with High Efficacy in Cytosolic Protein Delivery

Catechol-Based Polymers with High Efficacy in Cytosolic Protein Delivery

On-capillary fluorescent labeling of saccharides for capillary electrophoresis.

The feasibility of on-capillary derivatization of saccharides by aromatic amine-based fluorescent labeling agents was tested. To avoid the problematic evolution of gaseous hydrogen cyanide, the Schiff base reduction by sodium cyanoborohydride, as the second step of the standard reductive amination protocol, was omitted. Glucose was used as a model analyte and 7-amino-1,3-naphthalenedisulfonic acid as the labeling agent. Our experiments showed that the direct reaction of the saccharide with the labeling agent in 2.5-M acetic acid yields a labeled product that is sufficiently stable to be separated from the labeling agent in 20-mM phosphate buffer, pH 3.5, and detected using UV detection. The glucose and label zones were introduced separately into the capillary and mixed using a negative voltage. Mixing voltage, its duration, the concentration of acetic acid in the reaction zone, and the waiting time between mixing and separation were optimized. To show the applicability of the procedure to a broader range of analytes, a mixture of different types of saccharides, that is, xylose (pentose), fucose (hexose), glucose (hexose), N-acetylglucosamine (N-acetylaminosaccharide), and lactose (disaccharide), was subjected to derivatization and analysis under the optimal conditions. The linearity and repeatability of the process were evaluated as critical parameters for its analytical applications. Six-point calibration dependences in the 1-50mM range showed excellent determination coefficients of 0.9992 or higher for all five saccharides tested. The repeatability of the labeled saccharide peak areas was between 2.2% and 4.3%.

A high-specificity aniline-based mass tag for aldehyde detection.

We studied an aldehyde-labeling reagent, N-{2-[(4-aminophenoxy)methyl]benzyl}-N,N-diethylethanaminium bromide (CAX-A), containing an aniline functional group for the detection of aldehydes with high specificity. Six standard aldehydes were labeled by CAX-A and analyzed using LC-ESI-Orbitrap-MS. The aldehydes (each 40 nmol) were derivatized with CAX-A in the presence of sodium cyanoborohydride at room temperature overnight. The labeling reaction was applied to two urine samples for the detection of putative aldehydes. All six standard CAX-aldehyde derivatives were detected as precursor ions by dilution to 830 fmol/injection (signal-to-noise [S/N] ratio 587-1573). A total of 2184 MS1 features were detected overall in urine and blanks, of which 14 were putative aldehydes found only in urine. CAX-A can provide three levels of specificity for aldehyde detection. First is the known labeling specificity of the aniline functional group for aldehydes, which we confirmed here by observing a significant peak only from the aldehyde (S/N = 3388) when a mixture of an aldehyde, a ketone (no peak), and a quinone (S/N = 2.3) was tested. Second is the ease of formation of an analyte-characteristic first product ion (via anchimeric-assisted loss of triethylamine as a neutral) in MS2 from a CAX-labeled analyte. Third is the formation of a characteristic second product ion via loss of CO in MS3. CAX-A enables the specific, convenient detection of putative aldehydes in urine.