Objectives To investigate the clinical implications of vancomycin-resistant Enterococcus faecium (VRE) with VanD phenotype and vanA genotype (VanD-vanA VRE). Methods We tested in vitro and in vivo ...efficacies of teicoplanin against VanD-vanA VRE strains. Change in teicoplanin MICs was monitored during incubation with teicoplanin. In vitro and in vivo time–kill assay and survival analysis using a mouse peritonitis model were performed. Results Teicoplanin MICs of VanD-vanA VRE strains increased to 128 mg/L within 48 h when they were cultured with 120 mg/L teicoplanin. In vitro and in vivo time–kill assay showed that VanD-vanA VRE strains were not eliminated by 120 mg/L teicoplanin in contrast to vancomycin-susceptible E. faecium and VanD-vanB strains. The survival rate of mice infected with VanD-vanA VRE strains treated with teicoplanin was comparable with that of untreated mice. Conclusion Data suggest that teicoplanin would fail in the treatment of VanD type VRE infections if the strains contained the vanA gene, which cannot be detected in the clinical microbiology laboratory.
Thermal stability and barrier performance of reactively sputter deposited Ta–Si–N thin films between Si and Cu were investigated. RF powers of Ta and Si targets were fixed and various N
2/Ar flow ...ratios were adopted to change the amount of nitrogen in Ta–Si–N thin films. The structure of the films are amorphous and the resistivity increases with nitrogen content. After annealing of Si/Ta–Si–N(300 Å)/Cu(1000 Å) structures in Ar–H
2 (10%) ambient, sheet resistance measurement, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and Auger electron spectroscopy (AES) were employed to characterize barrier performance. Cu
3Si and tantalum silicide phase are formed at the same temperature, and the interdiffusion of Si and Cu occurs through the local defect sites. In all characterization techniques, nitrogen in the film appears to play an important role in thermal stability and resistance against Cu diffusion. A 300 Å thick Ta
43Si
4N
53 barrier shows the excellent barrier property to suppress the formation of Cu
3Si phase up to 800°C.
Although it is commonly known as a helix breaker, proline residues have been found in the α‐helical regions of many peptides and proteins. The antimicrobial peptide gaegurin displays α‐helical ...structure and has a central proline residue (P14). The structure and activity of gaegurin and its alanine derivative (P14A) were determined by various spectroscopic methods, restrained molecular dynamics, and biological assays. Both P14 and P14A exhibited cooperative helix formation in solution, but the helical stability of P14 was reduced substantially when compared to that of P14A. Chemical‐shift analysis indicated that both of the peptides formed curved helices and that P14 showed diminished stability in the region around the central proline. However, hydrogen‐exchange data revealed remarkable differences in the location of stable amide protons. P14 showed a stable region in the concave side of the curved helix, while P14A exhibited a stable region in the central turn of the helix. The model structure of P14 exhibited a pronounced kink, in contrast to the uniform helix of P14A. Both peptides showed comparable binding affinities for negatively charged lipids, while P14 had a considerably reduced affinity for a neutral lipid. With its destabilized α‐helix, P14 exhibited greater antibacterial activity than did P14A. Hence, electrostatic interaction between helical peptides and lipid membranes is believed to be the dominant factor for antibacterial activity. Moreover, helical stability can modulate peptide binding to membranes that is driven by electrostatic interactions. The observation that P14 is a more potent antibacterial agent than P14A implies that the helical kink of P14 plays an important role in the disruption of bacterial membranes.
We investigated effects of acetaminophen on LPS-induced hyperalgesia in various pain models. We examined the changes of pain behaviors induced by formalin injected subcutaneously (s.c.) in the hind ...paw, with substance P (SP) and glutamate injected inthrathecally (i.t.). Hyperalgesia was induced by LPS intraperitoneal injection 1 day prior to the pain test. LPS-induced hyperalgesia was exhibited in nociceptive behaviors induced by formalin s.c. (only in the second phase), SP and glutamate i.t. injection. APAP showed a dose-dependent antinociceptive effect on the saline- and LPS-pretreated group in the formalin and SP pain model. However, the analgesic effect of APAP was not observed in the glutamate pain model. To clarify the action site, APAP was administered i.t. or intracerebroventricularly (i.c.v.) 30 min prior to behavioral tests. The 2nd phase of formalin response was not only increased by LPS, but it also significantly attenuated by i.c.v. injections of APAP. However, the effect of APAP was observed only in the LPS-pretreatment, but not in the control group. These results suggest that LPS-induced hyperalgesia in the formalin 2nd phase may be involved in the SP-sensitive neuronal pathways, in which the hyperalgesic response elicited by LPS attenuated by APAP with supraspinal pain modulatory mechanisms.
Agmatine is the product of arginine decarboxylation and can be hydrolyzed by agmatinase to putrescine, the precursor for biosynthesis of higher polyamines, spermidine, and spermine. Besides being an ...intermediate in polyamine metabolism, recent findings indicate that agmatine may play important regulatory roles in mammals. Agmatinase is a binuclear manganese metalloenzyme and belongs to the ureohydrolase superfamily that includes arginase, formiminoglutamase, and proclavaminate amidinohydrolase. Compared with a wealth of structural information available for arginases, no three-dimensional structure of agmatinase has been reported. Agmatinase from Deinococcus radiodurans, a 304-residue protein, shows ∼33% of sequence identity to human mitochondrial agmatinase. Here we report the crystal structure of D. radiodurans agmatinase in Mn2+-free, Mn2+-bound, and Mn2+-inhibitor-bound forms, representing the first structure of agmatinase. It reveals the conservation as well as variation in folding, oligomerization, and the active site of the ureohydrolase superfamily. D. radiodurans agmatinase exists as a compact homohexamer of 32 symmetry. Its binuclear manganese cluster is highly similar but not identical to the clusters of arginase and proclavaminate amidinohydrolase. The structure of the inhibited complex reveals that inhibition by 1,6-diaminohexane arises from the displacement of the metal-bridging water.
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