Synergetic effect of the epoxide functional groups in the photocatalyzed atom transfer radical copolymerization of glycidyl methacrylate

International audienceMethyl methacrylate (MMA) and glycidyl methacrylate (GMA) were copolymerized by photocatalyzed atom transfer radical polymerization under the visible light irradiation of a compact blue LED lamp, using bis(1,10-phenanthroline)copper(I) as the photocatalyst. The polymerization was found to be all the more fast that the molar fraction of GMA was high. The same effect was observed when GMA was replaced by cyclohexene oxide (CHO) as a non-copolymerizable epoxide-containing compound. These results suggested that the epoxide functional group acted as a reducing agent in both cases, contributing to a faster regeneration of the activator form of the catalyst. This assumption was confirmed by UV-visible spectroscopy measurements, which evidenced a faster conversion of Cu(II) to Cu(I) in the presence of epoxide functional groups. Due to their large excess compared to the catalyst, no degradation of the epoxides was detected during the copolymerization of MMA and GMA, which thus provided well-defined poly(MMA-stat-GMA) copolymers as precursors for further functionalization. The statistical distribution of the epoxide side groups could also be controlled through sequenced additions of the comonomers, in a direct “one-pot” approach

Photocatalyzed Cu-based ATRP involving an oxidative quenching mechanism under visible light

International audienceA new type of photocatalyzed Cu-based atom transfer radical polymerization (ATRP) is described, involving directly the light absorption of the activator form of the copper complex Cu(I). The selected catalyst was bis(1,10-phenanthroline)copper(I), Cu(phen)2+, due to its intense absorption in the visible domain, which permitted to use very soft irradiation conditions, consisting of a simple household blue LED at 0.9 W. An excellent control over the polymerization of methyl methacrylate (MMA) in dimethylformamide (DMF) was observed under irradiation in these conditions, using ethyl α-bromophenylacetate (EBPA) as the initiator, with polydispersity indexes (PDI) as low as 1.10 while using low catalyst content (80 ppm). The proposed mechanism implies first the formation under irradiation of the excited state of the activator form of the complex Cu(I)*. It can then rapidly undergo the oxidative quenching of the alkyl bromide, which results in its conversion into the deactivator form of the complex Cu(II)–Br along with the generation of a propagating radical. The setting up of the ATRP equilibrium ensues. Additionally, it was possible to complete the catalysis mechanism by adding triethylamine (TEA), which permitted a faster polymerization, thanks to a faster regeneration of the activator Cu(I). An excellent control over the polymerization was also observed in the presence of TEA, with PDI as low as 1.06. The addition of TEA allowed also to use a catalyst loading as low as 20 ppm, while maintaining a good controllability

Recrudescent Campylobacter jejuni Infection in an Immunocompetent Adult following Experimental Infection with a Well-Characterized Organism▿ †

The recrudescence of infection with Campylobacter jejuni after appropriate antibiotic treatment has not been previously reported in an immunocompetent adult. We present the complete clinical, microbiologic, and immunologic evaluation of a closely monitored healthy male with recrudescent C. jejuni infection occurring in the absence of immunodeficiency following experimental infection with a well-characterized strain. After antibiotic treatment, the initial infection was clinically cleared and microbiologically undetectable. Subsequently, two episodes of recrudescence occurred, with no change in in vitro antibiotic sensitivity being detected. The immune responses of the individual were compared to those of other participants in the experimental infection study: innate immune responses, including fecal cytokines and C-reactive protein, were intact; however, measures of Campylobacter-specific adaptive immune responses were absent, including serum antibodies, antibody-secreting cells, and in vitro gamma interferon responses. No primary or secondary immunodeficiency was identified. Recrudescent Campylobacter infections after treatment may be more common than has previously been appreciated. This work adds to our understanding of the human immune response to natural Campylobacter infection and reiterates the importance of pathogen-specific adaptive immune responses to this globally important pathogen

Genome-Wide Prediction of SH2 Domain Targets Using Structural Information and the FoldX Algorithm

Current experiments likely cover only a fraction of all protein-protein interactions. Here, we developed a method to predict SH2-mediated protein-protein interactions using the structure of SH2-phosphopeptide complexes and the FoldX algorithm. We show that our approach performs similarly to experimentally derived consensus sequences and substitution matrices at predicting known in vitro and in vivo targets of SH2 domains. We use our method to provide a set of high-confidence interactions for human SH2 domains with known structure filtered on secondary structure and phosphorylation state. We validated the predictions using literature-derived SH2 interactions and a probabilistic score obtained from a naive Bayes integration of information on coexpression, conservation of the interaction in other species, shared interaction partners, and functions. We show how our predictions lead to a new hypothesis for the role of SH2 domains in signaling