Nanopore Sequencing Accurately Identifies the Mutagenic DNA Lesion O6‐Carboxymethyl Guanine and Reveals Its Behavior in Replication

O⁶‐carboxymethylguanine (O⁶‐CMG) is a highly mutagenic alkylation product of DNA, triggering transition mutations relevant to gastrointestinal cancer. However, precise localization of a single O⁶‐CMG with conventional sequencing platforms is challenging. Here nanopore sequencing (NPS), which directly senses single DNA bases according to their physiochemical properties, was employed to detect O⁶‐CMG. A unique O⁶‐CMG signal was observed during NPS and a single‐event call accuracy of >95 % was achieved. Moreover, O⁶‐CMG was found to be a replication obstacle for Phi29 DNA polymerase (Phi29 DNAP), suggesting this lesion could cause DNA sequencing biases in next generation sequencing (NGS) approaches.     

Stability-Indicating HPLC Method for the Determination of Metadoxine as Bulk Drug and in Pharmaceutical Dosage Form

A sensitive and reproducible method is described for the quantitative determination of metadoxine in the presence of its degradation products. The method was based on high performance liquid chromatographic separation of the drug from its degradation products on the reversed phase, kromasil column [C₁₈ (5-micron, 25 cm × 4.6 mm, i.d.)] at ambient temperature using a mobile phase consisting of methanol and water (50: 50, v/v). Flow rate was 1.0 mL min^?1 with an average operating pressure of 180 kg cm^?2 and t _R was found to be 2.85 ± 0.05 min. Quantitation was achieved with UV detection at 286 nm based on peak area with linear calibration curves at concentration range 10–100 μg mL^?1. This method has been successively applied to pharmaceutical formulation. No chromatographic interference from the tablet excipients was found. The method was validated in terms of precision, robustness, recovery and limits of detection and quantitation. Drug was subjected to acid, alkali and neutral hydrolysis, oxidation, dry heat, wet heat treatment and photo and UV degradation. As the proposed method could effectively separate the drug from its degradation products, it can be employed as stability indicating one. Moreover, the proposed HPLC method was utilized to investigate the kinetics of the acidic, alkaline and oxidative degradation processes at different temperatures and their respective apparent pseudo first order rare constant, half-life and activation energy was calculated with the help of Arrhenius plot. In addition the pH-rate profile of degradation of metadoxine in constant ionic strength buffer solutions with in the pH range 2–11 was studied.     

Synthesis and characterization of processable polyamides containing polar quinoxaline unit in the main chain and evaluation of its hydrophilicity

Here we report a new five polyamides prepared via solution-phase polycondensation under Yamazaki-Higashi conditions to prove the suitability of this method. The synthesized polyamides were characterized by FTIR, ¹H-NMR, differential scanning calorimetry, thermogravimetric analysis, inherent viscosity, solubility and wettability tests. These polyamides were amorphous in nature and they are completely soluble in many organic solvents and they could easily be solution-cast into transparent, flexible films. The as-prepaired polymers showed excellent thermal properties. The glass transition temperatures of these polymers are in the range of 251–274?°C under nitrogen atmosphere. The decomposition temperature in nitrogen for a 10% weight-loss temperature is more than 744?°C, and char yield at 900?°C ranged from 43 to 56% in nitrogen. Water contact angles were also tested to know the hydrophilicity of the polyamide films. As-synthesized polyamides showed smallest quantact angles indicating hydrophilic surface.     

Synthesis of 3′-fluoro-4′-amino-hexitol nucleosides with a pyrimidine nucleobase as building blocks for oligonucleotides

The synthesis of 3′-fluoro-4′-amino-hexitol nucleosides with a uracil and cytosine nucleobase was performed. The synthesis started from 1,5:2,3-dianhydro-4,6-benzylidene-allitol and afforded the target compounds in 15 steps. These protected hexitol nucleosides are valuable building blocks for the preparation of a new class of oligonucleotides.     

FTIR and thermal studies on gel grown neodymium tartrate crystals

The growth of neodymium tartrate crystals was achieved in silica gel by single diffusion method. Optimum conditions were established for the growth of good quality crystals. Fourier transform infrared (FT-IR) spectroscopic study indicates the presence of water molecules and tartrate ligands and suggests that tartrate ions are doubly ionised. The thermal behaviour of the material was studied using thermogravimetry (TG), differential thermal analysis (DTA), derivative thermogravimetry (DTG) and differential scanning calorimetry (DSC). Thermogravimetric analysis support the suggested chemical formula of the grown crystal to be Nd₂(C₄H₄O₆)₃·7H₂O, and the presence of seven water molecules as water of hydration. It is shown that the material is thermally stable up 45 °C beyond which it decomposes through many stages till the formation of neodymium oxide (Nd₂O₃) at 995 °C. The decomposition pattern is reported to be typical of a hydrated metal tartrate.     

Synthesis and Characterization of Four-Arm Star Poly(ϵ-caprolactone)-Block-Poly(cyclic-carbonate methacrylate) Copolymers by Combining Ring-Opening Polymerization With Atom Transfer Radical Polymerization

Well-defined four-arm star poly(?-caprolactone)-block-poly(cyclic carbonate methacrylate) (PCL-b-PCCMA) copolymers were synthesized by combining ring-opening polymerization (ROP) with atom transfer radical polymerization (ATRP). First, a four-arm poly(?-caprolactone) (PCL) macroinitiator [(PCL-Br)₄] was prepared by the ROP of ?-CL catalyzed by stannous octoate at 110°C in the presence of pentaerythritol as the tetrafunctional initiator followed by esterification with 2-bromoisobutyryl bromide. The sequential ATRP of CCMA monomer was carried out by using the (PCL-Br)₄ tetrafunctional macroinitiator (MI) and in the presence of CuBr/2, 2′-bipyridyl system in DMF at 80°C with [(MI)]:[CuBr]:[bipyridyl] = 1:1:3 to yield block polymers with controlled molecular weights (M_n (NMR) = 10700 to 27300 g/mol) by varying block lengths and with moderately narrow polydispersities (M_w/M_n = 1.2–1.4). Block copolymers with different PCL: PCCMA copolymer composition such as 50:50, 70:30 and 74:26 were prepared with good yields (48-74%). All these block copolymers were well characterized by NMR, FTIR and GPC and tested their thermal properties by DSC and TGA.     

New Cu-based catalysts supported on TiO2 films for Ullmann S(N)Ar-type C-O coupling reactions

New routes for the preparation of highly active TiO(2)-supported Cu and CuZn catalysts have been developed for C-O coupling reactions. Slurries of a titania precursor were dip-coated onto glass beads to obtain either structured mesoporous or non-porous titania thin films. The Cu and CuZn nanoparticles, synthesized using a reduction by solvent method, were deposited onto calcined films to obtain a Cu loading of 2 wt%. The catalysts were characterized by inductively coupled plasma (ICP) spectroscopy, temperature-programmed oxidation/reduction (TPO/TPR) techniques, (63)Cu nuclear magnetic resonance (NMR) spectroscopy, X-ray diffraction (XRD), scanning and transmission electron microscopy (S/TEM-EDX) and X-ray photo-electron spectroscopy (XPS). The activity and stability of the catalysts obtained have been studied in the C-O Ullmann coupling of 4-chloropyridine and potassium phenolate. The titania-supported nanoparticles retained catalyst activity for up to 12 h. However, catalyst deactivation was observed for longer operation times due to oxidation of the Cu nanoparticles. The oxidation rate could be significantly reduced over the CuZn/TiO(2) catalytic films due to the presence of Zn. The 4-phenoxypyridine yield was 64% on the Cu/nonporous TiO(2) at 120 °C. The highest product yield of 84% was obtained on the Cu/mesoporous TiO(2) at 140 °C, corresponding to an initial reaction rate of 104 mmol g(cat) (-1) s(-1). The activation energy on the Cu/mesoporous TiO(2) catalyst was found to be (144±5) kJ mol(-1), which is close to the value obtained for the reaction over unsupported CuZn nanoparticles (123±3 kJ mol(-1)) and almost twice the value observed over the catalysts deposited onto the non-porous TiO(2) support (75±2 kJ mol(-1)).     

Synthesis and Antimicrobial Screening of Some Novel Chromones and Pyrazoles with Incorporated Isoxazole Moieties

The title compounds 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h and 6a , 6b , 6c , 6d , 6e , 6f , 6g , 6h have been synthesized from β‐diketones and chromones, respectively, having 5‐methyl‐3‐phenylisoxazole moiety. Substituted 2‐acetylphenyl 5‐methyl‐3‐phenylisoxazole‐4‐carboxylate 3a , 3b , 3c , 3d , 3e , 3f , 3g , 3h were converted into 1‐(2‐hydroxyphenyl)‐3‐(5‐methyl‐3‐phenylisoxazole‐4‐yl)propane‐1,3‐dione 4a , 4b , 4c , 4d , 4e , 4f , 4g , 4h by Baker–Venketaraman transformation. Further, the cyclodehydration of diketone 4a , 4b , 4c , 4d , 4e , 4f , 4g , 4h with glacial acetic acid in conc. HCl at reflux gave corresponding substituted 2‐(5‐methyl‐3‐phenylisoxazole‐4‐yl)‐4H‐chromen‐4‐one 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h . The corresponding 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h react with hydrazine hydrate in presence of glacial acetic acid in ethanol at reflux to furnish 2‐(5‐5(5‐methyl‐3‐phenylisoxazole‐4‐yl)‐1H‐pyrazole‐3‐yl)phenol 6a , 6b , 6c , 6d , 6e , 6f , 6g , 6h . The structures of all newly synthesized compounds have been confirmed by IR, ¹H NMR, mass spectral data, as well as elemental analysis. The synthesized compounds have been screened for their antimicrobial activity. Some of the compounds show better antimicrobial activity as compared with the reference drugs Streptomycin, Ampicillin, Gentamycin, Cefixime, and Ketoconazole.     

Chemoselective Synthesis of 1,1-Diacetates from Aldehydes Using Anhydrous Cobalt(II) Bromide Under Solvent-Free Conditions

A mild and efficient method has been developed for the chemoselective preparation of 1,1-diacetates (acylals) from aldehydes catalyzed in the presence of a catalytic amount (0.1 mmol) of anhydrous cobalt(II) bromide under solvent-free conditions. The remarkable selectivity under mild and neutral conditions, excellent yields, short reaction time, and easily available and inexpensive catalyst are important features of this method.