Peptide sequencing using a patchwork approach and surface-induced dissociation in sector-TOF and dual quadrupole mass spectrometers

Surface-induced ion activation in combination with a database search strategy based on the Patchwork concept is applied to the determination of peptide sequences. Surface-induced dissociation (SID) is performed in a tandem quadrupole mass spectrometer and in a hybrid sector/time-of-flight mass spectrometer in order to evaluate the importance of accurate mass analysis of the SID fragment ions for peptide identification. The modified Patchwork approach is based on piecing together the peptide blocks in a bidirectional way, simultaneously using low-mass fragments originating from the C-terminus and N-terminus of the molecule, and relying on the measurement of the peptide's molecular weight with moderate mass accuracy. The results from this analysis are used as search filters in MASCOT's (http://www.matrixscience.com) Sequence Query search engine, with the simultaneous addition of the full MS/MS peak list. SID is performed with collision targets coated with pure and mixed composition self-assembled monolayers produced by fluorocarbon and hydrocarbon alkanethiolate solutions of varying chemical composition. The resulting MS/MS spectra produced on pure and mixed hydrocarbon SAMs are submitted to the modified version of Patchwork sequencing. It is found that hydrocarbon surfaces improve the relative abundance of larger fragments. Under the moderate mass accuracy conditions (±0.3 u) offered by our linear-TOF-SID instrument, it is found that increasing the abundance of larger fragments dramatically improves the sequencing scores.     

Ru(II)-Catalyzed Amidation of 2-Arylpyridines with Isocyanates via C-H Activation

An efficient Ru(II)-catalyzed amidation of 2-arylpyridines with isocyanates via C-H bond activation is described.     

Quantification of Major Bioactive Withanolides in Withania somnifera (Ashwagandha) Roots by HPTLC for Rapid Validation of Ayurvedic Products

JPC – Journal of Planar Chromatography – Modern TLC - The high-performance thin-layer chromatography (HPTLC) method has been developed for the simultaneous quantification of withaferine...     

The phosphate–carboxylate mixed-anhydride method: a mild,efficient process for ester and amide bond construction

A highly efficient carboxylate–phosphate anhydride pathway is described for the direct, economical synthesis of esters and amides from carboxylic acids and alcohols or amines. The reaction proceeds with retention of configuration with both chiral secondary alcohols and α-amino acid derivatives allowing access to useful chiral auxiliaries, ligands, and organocatalysts. Ester and amide products can be isolated directly in high yield due to the water soluble nature of the side products.     

Determination of thorium concentrations in soil and sand samples using instrumental neutron activation analysis

Thorium along with its daughter products present in the soil is one of the major contributors to the external gamma dose in the environment. To establish the dose levels, quantification of thorium contents in soil samples is very important. As a part of pre-operational environmental radiological surveillance, a total of 23 soil and six sand samples were collected from different locations around the proposed nuclear power plant site of Jaitapur, Maharashtra. Thorium concentrations in these samples were determined by instrumental neutron activation analysis (INAA). Samples were irradiated with neutrons in Apsara reactor at a neutron flux of?~5?×?10¹¹ cm^?2 s^?1 and radioactive assay was carried out using high resolution gamma ray spectrometry. Relative method of INAA was used for quantification of thorium utilizing 311.9?keV gamma ray of ²³³Pa, the daughter product of ²³³Th. The concentrations of thorium in the soil and sand samples were in the ranges of 4.0?C18.8 and 1.2?C6.2?mg?kg^?1 respectively.     

Separation of uranium from iron in ground water samples using ion exchange resins

Uranium determination in environmental samples is faced with problems due to presence of iron and other major elements. Iron is also used many a times for pre-concentration of uranium and actinides. Separation of milligram quantity of Fe from microgram quantity of uranium becomes essential during the estimation step. A simple two step procedure has been standardized for separating uranium and iron using anion exchange in 0.025 M H₂SO₄. Quantitative recovery of uranium was obtained as well as good separation from iron. This method was applied for estimation of uranium in water samples.     

Antibacterial Mechanisms of Zinc Oxide Nanoparticle against Bacterial Food Pathogens Resistant to Beta-Lactam Antibiotics

The increase in β-lactam-resistant Gram-negative bacteria is a severe recurrent problem in the food industry for both producers and consumers. The development of nanotechnology and nanomaterial applications has transformed many features in food science. The antibacterial activity of zinc oxide nanoparticles (ZnO NPs) and their mechanism of action on β-lactam-resistant Gram-negative food pathogens, such as Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi, Serratia marcescens, Klebsiella pneumoniae, and Proteus mirabilis, are investigated in the present paper. The study results demonstrate that ZnO NPs possesses broad-spectrum action against these β-lactamase-producing strains. The minimal inhibitory and minimal bactericidal concentrations vary from 0.04 to 0.08 and 0.12 to 0.24 mg/mL, respectively. The ZnO NPs elevate the level of reactive oxygen species (ROS) and malondialdehyde in the bacterial cells as membrane lipid peroxidation. It has been confirmed from the transmission electron microscopy image of the treated bacterial cells that ZnO NPs diminish the permeable membrane, denature the intracellular proteins, cause DNA damage, and cause membrane leakage. Based on these findings, the action of ZnO NPs has been attributed to the fact that broad-spectrum antibacterial action against β-lactam-resistant Gram-negative food pathogens is mediated by Zn²⁺ ion-induced oxidative stress, actions via lipid peroxidation and membrane damage, subsequently resulting in depletion, leading to β-lactamase enzyme inhibition, intracellular protein inactivation, DNA damage, and eventually cell death. Based on the findings of the present study, ZnO NPs can be recommended as potent broad-spectrum antibacterial agents against β-lactam-resistant Gram-negative pathogenic strains.     

Cost-effective bio-derived mesoporous carbon nanoparticles-supported palladium catalyst for nitroarene reduction and Suzuki–Miyaura coupling by microwave approach

A new heterogeneous catalyst was synthesized by immobilizing Pd on areca nut kernel-derived carbon nanospheres (CNSs). The CNSs, without any further activation processes, accommodated 3% of Pd on their surface. The new Pd/CNS material was used for the reduction of nitroarenes and Suzuki–Miyaura coupling of bromoarenes with aryl boronic acids. The reactions were conducted under microwave irradiation at 160 °C using 12 mol% of Pd/CNS (0.36% actual Pd content). The reduction of nitroarenes into their respective amino compounds was achieved in 10–20 min (conversion up to 100%); by contrast, the Suzuki–Miyaura reactions yielded up to 98% at 150 °C with 10 mol% of Pd/CNS catalyst. The products were identified using gas chromatography and nuclear magnetic resonance spectroscopy. The catalyst was isolated from reaction mixture and reused without any significant loss in the activity. Thus, the present work introduces one-pot-derived porous CNSs as efficient catalytic support to Pd, establishing an alternative to existing Pd/C in terms of cost and efficiency.     

XPS and XAES studies of surface segregation and oxidation of Cu-Ge alloy

Surface segregation of Ge is seen in the Cu-5at%Ge alloy with an activation enthalpy equal to 17 kJ/mol. Oxidation of the alloy in the temperature range 400 to 600 K shows the formation of Cu₂O and GeO which on further heating in vacuum at 650 K converts to GeO₂ with the reduction of Cu₂O to Cu.