Identification of HPr kinase/phosphorylase inhibitors: novel antimicrobials against resistant Enterococcus faecalis

Journal of Computer-Aided Molecular Design - Enterococcus faecalis, a gram-positive bacterium, is among the most common nosocomial pathogens due to its limited susceptibility to antibiotics and its...     

Assessment of labelled products with different radioanalytical methods: study on 18F-fluorination reaction of 4-[18F]fluoro-N-[2-[1-(2-methoxyphenyl)-1-piperazinyl]ethyl-N-2-pyridinyl-benzamide (p-[18F]MPPF)

The serotonin receptor 5-HT_1A ligand 4-[¹⁸F]fluoro-N-[2-[1-(2-methoxyphenyl)-1-piperazinyl]ethyl-N-2-pyridinyl-benzamide (p-[¹⁸F]MPPF) was produced by a simplified method of Le Bars et al. Traditional oil bath heating was compared to microwave heating. Various radioanalytical methods, radio-Thin Layer Chromatography (TLC), High Pressure Liquid Chromatography (HPLC) and Mass Spectrometry (MS), were compared in the evaluation of the labelled product(s). The crude reaction mixture consisted of p-[¹⁸F]MPPF and 2–4 radioactive by-products eluting after the product fraction, and the reverse-phase HPLC method failed occasionally to separate p-[¹⁸F]MPPF from the radioactive by-product with close retention time. The heating method had no significant effect on the composition of labelled by-products. In LC-(ESI)-MS analysis of p-[¹⁸F]MPPF the labelled product was identified with m/z ratio of 435 ([M + H⁺]). The other HPLC fractions were measured to have following m/z ratios: (1) 327; 349; (675) (2) 402; 407/408; (791) and (3) 436, suggesting different kind of decomposition of the labelled product and/or the inactive precursor. The ion trap mass spectrometer was sufficient for the qualitative analysis of p-[¹⁸F]MPPF. However, differentiation of by-products arising from the decomposition of p-[¹⁸F]MPPF or from its precursor p-MPPNO₂ proved to be challenging.     

Redox- and protonation-state driven substrate-protein dynamics in respiratory complex I

Respiratory complex I is a key enzyme in the electron transport chains of mitochondria and bacteria. It transfers two electrons to quinone and couples this redox reaction to proton pumping to electrically charge the membrane it is embedded in. The charge and pH gradient across the membrane drives the synthesis of ATP. The redox reaction and proton pumping in complex I are separated in space and time, which raises the question of how the two reactions are coupled so efficiently. Here, we focus on the unique ～35 Å long tunnel of complex I, which houses the binding site of quinone reduction. We discuss the redox and protonation reactions that occur in this tunnel and how they influence the dynamics of protein and substrate. On the basis of recent structural data and results from molecular simulations, we review how quinone reduction and dynamics may be coupled to proton pumping in complex I.     

Ion permeability of SAMs on nanoparticle surfaces

This article reports on the ion permeability of self-assembled monolayers (SAMs) formed on the surface of charged alkanethiol-protected gold nanoparticles, so-called monolayer-protected clusters (MPCs). The capacitance and thus the charging energy required to add/remove an electron from the metal core are extremely sensitive to ions entering the monolayer, and the extent of ion penetration can be tuned by the charge and size of the ions and the permittivity of the solvent. Experimentally, this effect is comparable to ion association with conventional redox molecules, indicating that MPCs despite their large size and the fundamentally differing nature of the electron transfer process can be treated analogously to redox molecules.     

Gradient-enhanced FAWSETS perfusion measurements

This work describes the use of custom-built gradients to enhance skeletal muscle perfusion measurements acquired with a previously described arterial spin labeling technique known as FAWSETS (flow-driven arterial water stimulation with elimination of tissue signal). Custom-built gradients provide active control of the static magnetic field gradient on which FAWSETS relies for labeling. This allows selective, 180 degrees modulations of the phase of the perfusion component of the signal. Phase cycling can then be implemented to eliminate all extraneous components leaving a signal that exclusively reflects capillary-level perfusion. Gradient-enhancement substantially reduces acquisition time and eliminates the need to acquire an ischemic signal to quantify perfusion. This removes critical obstacles to application of FAWSETS in organs other than skeletal muscle and makes the measurements more desirable for clinical environments. The basic physical principles of gradient-enhancement are demonstrated in flow phantom experiments and in vivo utility is demonstrated in rat hind limb during stimulated exercise.     

Choice behavior of information services when prices are increased and decreased from reference level

The purpose of this study is to estimate the impact of price increases and decreases for three, at least partly, compensatory services. The existence of a reference effect in pricing has been commonly accepted. However, the observations of consumer choices with prices below and above the reference price have produced mixed results. Both symmetric and asymmetric behavior has been observed. The current study differs from the mainstream in the way that the object is a service and instead of scanner panel data, stated preferences measured by choice based conjoint analysis are used. Moreover, instead of dealing with changes in value caused by price changes, we consider changes in demand on the respondent level. The main outcome of the study was that with the traditional service the respondents reacted more strongly to price increases (loss) than to price decreases (gain), whereas in the two more modern services the reactions were more versatile; with the majority of respondents the reactions were stronger to price decreases (gain).     

Characterization of the alnumycin gene cluster reveals unusual gene products for pyran ring formation and dioxan biosynthesis

Alnumycin is closely related to the benzoisochromanequinone (BIQ) polyketides such as actinorhodin. Exceptional structural features include differences in aglycone tailoring that result in the unique alnumycin chromophore and the existence of an unusual 4-hydroxymethyl-5-hydroxy-1,3-dioxan moiety. Cloning and sequencing of the alnumycin gene cluster from Streptomyces sp. CM020 revealed expected biosynthesis genes for polyketide assembly, but several genes encoding subsequent tailoring enzymes were highly atypical. Heterologous expression studies confirmed that all of the genes required for alnumycin biosynthesis resided within the sequenced clone. Inactivation of genes aln4 and aln5 showed that the mechanism of pyran ring formation differs from actinorhodin and granaticin pathways. Further inactivation studies identified two genes, alnA and alnB, involved in the synthesis and attachment of the dioxan moiety, and resulted in the production of the polyketide prealnumycin.     

The neuronal ceroid lipofuscinosis <Emphasis Type="Italic">Cln8</Emphasis> gene expression is developmentally regulated in mouse brain and up-regulated in the hippocampal kindling model of epilepsy

Background  

The neuronal ceroid lipofuscinoses (NCLs) are a group of inherited neurodegenerative disorders characterized by accumulation of autofluorescent material in many tissues, especially in neurons. Mutations in the CLN8 gene, encoding an endoplasmic reticulum (ER) transmembrane protein of unknown function, underlie NCL phenotypes in humans and mice. The human phenotype is characterized by epilepsy, progressive psychomotor deterioration and visual loss, while motor neuron degeneration (mnd) mice with a Cln8 mutation show progressive motor neuron dysfunction and retinal degeneration.     

Global integrability of p-superharmonic functions on metric spaces

We consider a metric space equipped with a doubling measure and a length metric. We prove that p-superharmonic functions are integrable with a small exponent on Hölder domains of the space.     

Liquid chromatography tandem mass spectrometry determination of total budesonide levels in dog plasma after inhalation exposure

A sensitive and selective method to quantify budesonide in dog plasma samples was developed and fully validated. Liquid–liquid extraction was followed by solid-phase extraction and liquid chromatography–tandem mass spectrometry with electrospray ionization. After reconstitution of the analytes in the mobile phase, samples were analysed by reversed-phase liquid chromatography with isocratic elution. d8-Budesonide was used as an internal standard, and characteristic transitions of d8-budesonide and budesonide were used for quantification. The method was validated with respect to selectivity, specificity, linearity, recovery, repeatability, reproducibility and limits of detection and quantification. The validated method was successfully applied to monitor the plasma levels of budesonide in dogs exposed to clinical doses of inhaled and intravenous drug.