Neutrophils use selective autophagy receptor Sqstm1/p62 to target Staphylococcus aureus for degradation in vivo in zebrafish

Macroautophagy/autophagy functions to degrade cellular components and intracellular pathogens. Autophagy receptors, including SQSTM1/p62, target intracellular pathogens. Staphylococcus aureus is a significant pathogen of humans, especially in immunocompromise. S. aureus may use neutrophils as a proliferative niche, but their intracellular fate following phagocytosis has not been analyzed in vivo. In vitro, SQSTM1 can colocalize with intracellular Staphylococcus aureus, but whether SQSTM1 is beneficial or detrimental in host defense against S. aureus in vivo is unknown. Here we determine the fate and location of S. aureus within neutrophils throughout zebrafish infection. We show Lc3 and Sqstm1 recruitment to phagocytosed S. aureus is altered depending on the bacterial location within the neutrophil and that Lc3 marking of bacterial phagosomes within neutrophils may precede bacterial degradation. Finally, we show Sqstm1 is important for controlling cytosolic bacteria, demonstrating for the first time a key role of Sqstm1 in autophagic control of S. aureus in neutrophils

Kinetic and electron spin resonance analysis of RAFT polymerization of styrene [2]

The kinetic and electron spin resonance analysis of reversible addition-fragmentation chain-transfer (RAFT) polymerization of styrene was discussed. It was found that the time dependence of the intermediate radical concentration varies significantly with the type of RAFT agent. It was also found that the RAFT process is not particularly sensitive to oxygen.Lette

Electron spin resonance studies of reversible addition-fragmentation transfer polymerisation

The polymerisation of styrene in the presence of cumyl dithiobenzoate (RAFT agent) was studied. Electron spin resonance spectroscopy was used to determine the time-dependence of the concentrations of the intermediate radical species, as a function of temperature and relative initial amounts of reactants. The intermediate radical concentration was found to be much lower than predicted by the studies of Barner-Kowollik et al. [Barner-Kowollik, C.; Quinn, J. F.; Morsley, D. R.; Davis, T. P. J. Polym. Sci. Part A: Polym. Chem. 2001, 39, 1353], but consistent with that observed by Hawthorne et al. [Hawthorne, D. G.; Moad, G.; Rizzardo, E.; Thang, S. H. Macromolecules 1999, 32, 5457] and Kwak et al. [Kwak, Y.; Goto, A.; Tsuji.; Murata, Y.; Komatsu, K.; Fukuda, T. Macromolecules 2002, 35, 3026] Several observations that are not consistent with the current RAFT model were made. Intermediate radical signals were observed long after a significant amount of initiator remained and an extra signal appeared in the ESR spectrum at longer reaction times.Conference Pape

Electron spin resonance studies of reversible addition-fragmentation transfer polymerisation

The polymerisation of styrene in the presence of cumyl dithiobenzoate (RAFT agent) was studied. Electron spin resonance spectroscopy was used to determine the time-dependence of the concentrations of the intermediate radical species, as a function of temperature and relative initial amounts of reactants. The intermediate radical concentration was found to be much lower than predicted by the studies of Barner-Kowollik et al. [Barner-Kowollik, C.; Quinn, J. F.; Morsley, D. R.; Davis, T. P. J. Polym. Sci. Part A: Polym. Chem. 2001, 39, 1353], but consistent with that observed by Hawthorne et al. [Hawthorne, D. G.; Moad, G.; Rizzardo, E.; Thang, S. H. Macromolecules 1999, 32, 5457] and Kwak et al. [Kwak, Y.; Goto, A.; Tsuji.; Murata, Y.; Komatsu, K.; Fukuda, T. Macromolecules 2002, 35, 3026] Several observations that are not consistent with the current RAFT model were made. Intermediate radical signals were observed long after a significant amount of initiator remained and an extra signal appeared in the ESR spectrum at longer reaction times.Conference Pape

Synthesis and characterization of polystyrene-graphite nanocomposites via surface RAFT-mediated miniemulsion polymerization

Graphite oxide (GO) was prepared and immobilized with dodecyl isobutyric acid trithiocarbonate (DIBTC) reversible addition-fragmentation chain transfer (RAFT) agent. The hydroxyl groups of GO were attached to the DIBTC RAFT agent through an esterification process. The resultant modified GO was used for the preparation of polystyrene (PS)/graphite nanocomposites in miniemulsion polymerization. The RAFT-grafted GO (GO-DIBTC) at various loadings was dispersed in styrene monomer, and the resultant mixtures were sonicated in the presence of a surfactant (sodium dodecylbenzene sulfonate) and a hydrophobe (hexadecane) to form miniemulsions. The stable miniemulsions thus obtained were polymerized using azobisisobutyronitrile as the initiator to yield encapsulated PS-GO nanocomposites. The molar mass and polydispersity index of PS in the nanocomposites depended on the amount of RAFT-grafted GO in the system, in accordance with the features of the RAFT polymerization method. The PS-GO nanocomposites were of exfoliated morphology, as confirmed by X-ray diffraction and transmission electron microscopy measurements. The thermal stability and mechanical properties of the PS-GO nanocomposites were better than those of the neat PS polymer. Furthermore, the mechanical properties were dependent on the modified GO content (i.e., the amount of RAFT-grafted GO). © 2011 Wiley Periodicals, Inc.Articl

Magnetite nanoparticles for the preparation of ultrapure RAFT polymers

Magnetic nanoparticles (MNP) and the application of a strong external magnetic fields were used to separate living chains from dead chains prepared by the reversible addition-fragmentation chain transfer (RAFT) process, by using Z-functional RAFT agents that are strongly attracted to the MNP surface. The MNP dispersion was mixed with a 32% HCL solution and the organic phase containing the oleic acid and the polymer was extracted and dried to give the extracted polymer. The RAFT functional chains in the unextracted polymer result from the ligand exchange process in the extraction step, which does not attach all RAFT functional chains to the MNP surface. The results also show that the extension data for the unextracted polymer show a significant fraction of high M polymer that apparently contains some RAFT groups.Articl

Reversible addition fragmentation polymerization in heterogeneous media

Reversible addn. fragmentation polymn. is acknowledged as the most versatile of the controlled radical polymn. techniques currently available. The use of this technique in heterogenous media has, however, required and continues to require extra attention. This is due to the changes in mechanism and development of mol. wt. distribution with time when compared to traditional free radical heterogeneous systems. A no. of problems occur that interfere with the formation of stable latexes, including droplet polymn. and phase sepn. The typical approach to improved particle stabilization in the literature was the use of a cosurfactant in predispersed systems and the use of seeded emulsions. Ab initio systems have continued to require starved feed conditions to provide interval III emulsion polymn. This study considers both approaches and examines the possibility of using interval II through the use of a proto-seed in the form of P-NIPAM. [on SciFinder (R)

DePakeing of dipolar chemical-shift NMR spectra

NRC publication: Ye

RAFT polymerisation in water-borne organic dispersions

Two different approaches to achieving controlled reversible addition-fragmentation chain transfer polymerisation in water-borne dispersions have been attempted, both giving reasonable control over molar mass evolution. Molar mass increased linearly with conversion, and the colloidal instability that has sometimes been observed in similar systems (e.g. [de Brouwer, H.; Monteiro, M. J.; Tsavalas, J. G.; Schork, F. J. Macromolecules 2000, 33, 9239]) was avoided. The similarity of results for the two quite different approaches can largely be reconciled utilising the theory of Luo et al. [Luo, Y.; Tsavalas, J.; Schork, F. J. Macromolecules 2001, 34, 5501] The average number of radicals per particle, in terms of both propagating and RAFT intermediate radicals were compared, using two current models in the literature for the ratio of propagating to intermediate species. [Barner-Kowollik, C.; Quinn, J. F.; Morsley, D. R.; Davis, T. P. J. Polym. Sci. Part A: Polym. Chem. 2001, 39, 1353; Monteiro, M. J.; de Brouwer, H. Macromolecules 2001, 34, 349; Kwak, Y.; Goto, A.; Tsujii, Y.; Murata, Y.; Komatsu, K.; Fukuda, T. Macromolecules 2002, 35, 3026] Possible implications for water-borne dispersions under such conditions are that the maximum value of the average number of propagating radicals per particle may be significantly lower than 0.5, depending on the dominant mechanism for radical loss.Conference Pape

Initialisation in RAFT-mediated polymerisation of methyl acrylate

Inhibition in Reversible Addition-Fragmentation chain Transfer (RAFT)-mediated polymerisations is currently a controversial issue; here we provide evidence that the slow "propagation" of the initiating and leaving group radicals during the early part (the period of consumption of the initial RAFT agent) of methyl acrylate RAFT-mediated polymerisation has characteristics similar to inhibition.Articl