Isomer Information from Ion Mobility Separation of High-Mannose Glycan Fragments

Extracted arrival time distributions of negative ion CID-derived fragments produced prior to traveling-wave ion mobility separation were evaluated for their ability to provide structural information on N-linked glycans. Fragmentation of high-mannose glycans released from several glycoproteins, including those from viral sources, provided over 50 fragments, many of which gave unique collisional cross-sections and provided additional information used to assign structural isomers. For example, cross-ring fragments arising from cleavage of the reducing terminal GlcNAc residue on Man₈GlcNAc₂ isomers have unique collision cross-sections enabling isomers to be differentiated in mixtures. Specific fragment collision cross-sections enabled identification of glycans, the antennae of which terminated in the antigenic α-galactose residue, and ions defining the composition of the 6-antenna of several of the glycans were also found to have different cross-sections from isomeric ions produced in the same spectra. Potential mechanisms for the formation of the various ions are discussed and the estimated collisional cross-sections are tabulated.

Open image in new window

Graphical Abstract ?

     

Ultrasound Promoted Step‐Growth Polymerization and Polymer Crosslinking Via Copper Catalyzed Azide–Alkyne “Click” Reaction

Mechano‐activated chemistry is a powerful tool for remodeling of synthetic polymeric materials, however, few reactions are currently available. Here we show that using piezochemical reduction of a Cu^II‐based pre‐catalyst, a step‐growth polymerization occurs via the copper catalyzed azide–alkyne cycloaddition (CuAAC) reaction to form a linear polytriazole. Furthermore, we show that a linear polymer can be crosslinked mechanochemically using the same chemistry to form a solid organogel. We envision that this chemistry can be used to harness mechanical energy for constructive purposes in polymeric materials.     

A Photoactivatable BODIPY Probe for Localization‐Based Super‐Resolution Cellular Imaging

The synthesis and application of a photoactivatable boron‐alkylated BODIPY probe for localization‐based super‐resolution microscopy is reported. Photoactivation and excitation of the probe is achieved by a previously unknown boron‐photodealkylation reaction with a single low‐power visible laser and without requiring the addition of reducing agents or oxygen scavengers in the imaging buffer. These features lead to a versatile probe for localization‐based microscopy of biological systems. The probe can be easily linked to nucleophile‐containing molecules to target specific cellular organelles. By attaching paclitaxel to the photoactivatable BODIPY, in vitro and in vivo super‐resolution imaging of microtubules is demonstrated. This is the first example of single‐molecule localization‐based super‐resolution microscopy using a visible‐light‐activated BODIPY compound as a fluorescent probe.     

Radical cyclisation studies of β-nitroamines from the nitro-Mannich reaction

A range of novel β-nitroacetamides with an alkenyl- or alkynyl tether were synthesized using the deprotonative or conjugate addition nitro-Mannich reaction. They were subjected to radical denitration-cyclisation with a 10 equivalent excess of tributyltin hydride, catalytic AIBN in refluxing benzene to explore the structural and electronic requirements for efficient cyclisation. Cyclisations of the β-nitroacetamides were successful in most cases, undergoing 5-exo-trig cyclisation to give the desired cyclopentyl or indanyl structures. Radical 1,4-translocation of a phenyl group was observed in several cases. Diastereoselectivity was low, with 2 or 3 of 4 possible diastereoisomers observed in most cases. Further purification by crystallisation allowed the isolation of some as single diastereoisomers. It was found that higher yields were obtained by increasing the substitution or reducing the degrees of freedom of the tether between the nitro group and the radical acceptor.     

Quasi-phase-matched modulation instability in birefringent fibers

The phase-sensitive nature of polarization modulation instability has been demonstrated in optical fibers whose birefringence has been manipulated to generate phase mismatches. Quasi-phase-matched modulation instability has been demonstrated, and the gain of the quasi-phase-matched sidebands has been investigated. The results are in good agreement with experiment.     

Monte Carlo simulation of possible conversion processes with respect to soft error generation in a dynamic RAM based neutron detector

The operating principle of a memory based radiation sensor, which is the Soft Error mechanism in silicon integrated circuits was suggested in our research with particular reference to dynamic Random Access Memories (dRAMs), with a view of employing it in neutron detection, imaging and elemental analysis. Thus, having initially proved that dRAMs can be used as heavy charged particle detectors, it was thought that these devices can be made sensitive to neutrons by adding a foil to convert the thermal neutrons to charged particles through the (n,) reaction. In order to further evaluate the feasibility of this approach, a Monte Carlo program has been used to simulate and examine suitable converting materials with respect to soft error generation and to determine methods to increase the sensitivity of dRAMs to neutrons. The aim of this paper is to present results from these calculations and discuss the capabilities of such a neutron detector.     

Gravimetric determination of gold with sodium salt of n-(n-bromo-c-tetradecyl betainyl)-c-tetradecylbetaine

The sodium salt of N-(N-bromo-C-tetradecyl betainyl)-C-tetradecyl betaine is presented as a gravimetrie reagent for the determination of gold. Two complexes have been isolated; one, precipitated from hydrochloric acid solution, containing 22.14% gold; the other, from hydrobromic acid solution, containing 18.01% gold. Both complexes may be dried to constant weight at 85° C, thus giving the advantage of a favorable weight factor. Determinations from hydrobromic acid solutions are more rapid and offer several other advantages. Optimum conditions have been established. The number of interfering ions is small and a method for thie separation of gold from these ions was developed. A procedure for the determination of gold in ore concentrates was applied to several samples with satisfactory results.