Amorphous Silicon Oxynitride-Based Powders Produced by Spray Pyrolysis from Liquid Organosilicon Compounds

Silicon oxynitrides (SiO_xN_y) have many advantageous properties for modern ceramic applications that justify a development of their new and efficient preparation methods. In the paper, we show the possibility of preparing amorphous SiO_xN_y-based materials from selected liquid organosilicon compounds, methyltrimethoxysilane CH₃Si(OCH₃)₃ and methyltriethoxysilane CH₃Si(OC₂H₅)₃, by a convenient spray pyrolysis method. The precursor mist is transported with an inert gas or a mixture of reactive gases through a preheated tube reactor to undergo complex decomposition changes, and the resulting powders are collected in the exhaust filter. The powders are produced in the tube at temperatures of 1200, 1400, and 1600 °C under various gas atmosphere conditions. In the first option, argon Ar gas is used for mist transportation and ammonia NH₃ gas serves as a reactive medium, while in the second option nitrogen N₂ is exclusively applied. Powder X-Ray Diffraction (XRD) results confirm the highly amorphous nature of all products except those made at 1600 °C in nitrogen. SEM examination shows the spheroidal particle morphology of powders, which is typical for this method. Fourier Transform Infrared (FT-IR) spectroscopy reveals the presence of Si–N and Si–O bonds in the powders prepared under Ar/NH₃, whereas those produced under N₂ additionally contain Si–C bonds. Raman spectroscopy measurements also support some turbostratic free carbon C in the products prepared under nitrogen. The directly determined O- and N-contents provide additional data linking the process conditions with specific powder composition, especially from the point of view of oxygen replacement in the Si–O moieties formed upon initial precursor decomposition reactions by nitrogen (from NH₃ or N₂) or carbon (from the carbonization of the organic groups).     

CpG underrepresentation and the bacterial CpG-specific DNA methyltransferase M.MpeI

Cytosine methylation promotes deamination. In eukaryotes, CpG methylation is thought to account for CpG underrepresentation. Whether scarcity of CpGs in prokaryotic genomes is diagnostic for methylation is not clear. Here, we report that Mycoplasms tend to be CpG depleted and to harbor a family of constitutively expressed or phase variable CpG-specific DNA methyltransferases. The very CpG poor Mycoplasma penetrans and its constitutively active CpG-specific methyltransferase M.MpeI were chosen for further characterization. Genome-wide sequencing of bisulfite-converted DNA indicated that M.MpeI methylated CpG target sites both in vivo and in vitro in a locus-nonselective manner. A crystal structure of M.MpeI with DNA at 2.15-Å resolution showed that the substrate base was flipped and that its place in the DNA stack was taken by a glutamine residue. A phenylalanine residue was intercalated into the “weak” CpG step of the nonsubstrate strand, indicating mechanistic similarities in the recognition of the short CpG target sequence by prokaryotic and eukaryotic DNA methyltransferases.     

Importance of single molecular determinants in the fidelity of expanded genetic codes

The site-selective encoding of noncanonical amino acids (NAAs) is a powerful technique for the installation of novel chemical functional groups in proteins. This is often achieved by recoding a stop codon and requires two additional components: an evolved aminoacyl tRNA synthetase (AARS) and a cognate tRNA. Analysis of the most successful AARSs reveals common characteristics. The highest fidelity NAA systems derived from the Methanocaldococcus jannaschii tyrosyl AARS feature specific mutations to two residues reported to interact with the hydroxyl group of the substrate tyrosine. We demonstrate that the restoration of just one of these determinants for amino acid specificity results in the loss of fidelity as the evolved AARSs become noticeably promiscuous. These results offer a partial explanation of a recently retracted strategy for the synthesis of glycoproteins. Similarly, we reinvestigated a tryptophanyl AARS reported to allow the site-selective incorporation of 5-hydroxy tryptophan within mammalian cells. In multiple experiments, the enzyme displayed elements of promiscuity despite its previous characterization as a high fidelity enzyme. Given the many similarities of the TyrRSs and TrpRSs reevaluated here, our findings can be largely combined, and in doing so they reinforce the long-established central dogma regarding the molecular basis by which these enzymes contribute to the fidelity of translation. Thus, our view is that the central claims of fidelity reported in several NAA systems remain unproven and unprecedented.     

IL6 −174G>C polymorphism is associated with an increased risk of psoriasis but not response to treatment

Interleukin‐6 (IL‐6) is implicated in the pathogenesis of psoriasis as well as in its treatment efficacy. The aim of this study of 406 patients with psoriasis and 203 healthy controls was to evaluate the association between the IL6 ?174G>C (rs1800795) polymorphism and psoriasis susceptibility, as well as treatment efficacy. The frequency of genotype GG (33.7% vs 20.7%; P = 0.00022; OR = 0.51, 95% confidence interval 0.34–0.76) and of allele G (56.2% vs 46.8%; P = 0.0023) was significantly higher in the psoriasis group compared with controls. No polymorphism variants were associated with better response to topical or combined topical/narrow‐band ultraviolet B (NB‐UVB) treatment. We conclude that the IL6 ?174G>C polymorphism can be a marker of susceptibility to psoriasis, with an almost twofold increased risk of the disease in individuals carrying the GG genotype; however, it was not associated with treatment response to topical and/or NB‐UVB therapy.     

Identification of a BTV-Strain-Specific Single Gene That Increases Culicoides Vector Infection Rate

Since the 2000s, the distribution of bluetongue virus (BTV) has changed, leading to numerous epidemics and economic losses in Europe. Previously, we found a BTV-4 field strain with a higher infection rate of a Culicoides vector than a BTV-1 field strain has. We reverse-engineered parental BTV-1 and BTV-4 strains and created BTV-1/BTV-4 reassortants to elucidate the influence of individual BTV segments on BTV replication in both C. sonorensis midges and in KC cells. Substitution of segment 2 (Seg-2) with Seg-2 from the rBTV-4 significantly increased vector infection rate in reassortant BTV-1_4S2 (30.4%) in comparison to reverse-engineered rBTV-1 (1.0%). Replacement of Seg-2, Seg-6 and Seg-7 with those from rBTV-1 in reassortant BTV-4_1S2S6S7 (2.9%) decreased vector infection rate in comparison to rBTV-4 (30.2%). However, triple-reassorted BTV-1_4S2S6S7 only replicated to comparatively low levels (3.0%), despite containing Seg-2, Seg-6 and Seg-7 from rBTV-4, indicating that vector infection rate is influenced by interactions of multiple segments and/or host-mediated amino acid substitutions within segments. Overall, these results demonstrated that we could utilize reverse-engineered viruses to identify the genetic basis influencing BTV replication within Culicoides vectors. However, BTV replication dynamics in KC cells were not suitable for predicting the replication ability of these virus strains in Culicoides midges.     

Osteitis as a symptom of SAPHO syndrome

SAPHO syndrome is an acronym given to a spectrum of diseases with the following features: synovitis, acne, pustulosis, hyperostosis and osteitis. The main problem of the differential diagnosis in 3 cases presented in our paper was the aseptic osteitis.     

The interaction of glass-ionomer cements containing vinylphosphonic acid with water and aqueous lactic acid

A glass-ionomer cement containing an acrylic acid/vinyl phosphonic acid copolymer, has been investigated for its interaction with water and with aqueous lactic acid and the results compared with those from conventional glass-ionomers based on polyacrylic acid. Cylindrical specimens (12 mm high x 6 mm diameter) were placed in 8 cm3 of aqueous lactic acid (20 mmol dm(-3); pH 2.7) for 1 week, at the end of which the pH was determined. Each specimen was then placed in a fresh 8 cm3 volume of lactic acid and the pH determined after a further week. This procedure was continued for a total of 13 weeks for each specimen. Experiments were also carried out on similar specimens exposed to 8 cm3 of water for 1 week only. Further experiments were carried out in which discs of cement were exposed to thin films (0.15 mm) of lactic acid at pH 4.5, with pH values determined at 30 s, 1, 2, 5 and 10 min. After 1 week, cements had changed the pH of the lactic acid to a mean value of 3.63 (SD 0.08) while in weeks 2-13 they changed it to a mean value of 3.31 (SD 0.11). After 1 week in aqueous lactic acid the cements had gained mass by a mean of 1.26% (SD 0.59%) compared with 1.22% (SD 0.14%) in water. After 13 weeks in lactic acid, cements had lost a mean of 2.83% (SD 0.74%) in mass. Thin films of aqueous lactic acid changed from pH 4.5-5.1 at 30 s and to a steady value of 5.6 (SD 0.3) between 2 and 10 min. These results were similar to those for conventional glass-ionomer cements based on carboxylic acid polymers. Hence, it was concluded that the presence of the vinylphosphonic acid units made no significant difference to the interaction of cements with aqueous solutions.     

A preliminary study of the effect of glass-ionomer and related dental cements on the pH of lactic acid storage solutions

Glass-ionomer cements, both self-hardening and resin-modified, have been shown to increase the pH of lactic acid solutions in which they are stored. Similar results have been obtained for a zinc phosphate and a zinc polycarboxylate cement. The pH was increased over a period of 7 days by between 1.54 and 2.65 pH units from an initial value of pH of 2.60, depending on the cement. It is concluded that, as a result of this ability to neutralize surrounding aqueous solutions, these materials may have the beneficial effect in vivo of inhibiting caries development. In the case of glass-ionomers, this mechanism might complement that of fluoride release.