Membrane interactions and alignment of structures within the HIV-1 Vpu cytoplasmic domain: effect of phosphorylation of serines 52 and 56

AbstractThe cytoplasmic domain of the HIV-1 accessory protein Vpu is involved in the binding and degradation of the viral receptor CD4. In order to analyze previous structural models in the context of membrane environments, regions of VpuCYTO incorporating particular conformational features have been synthesized and labelled with 15N at selected backbone amides. Well-oriented proton-decoupled 15N solid-state NMR spectra with 15N chemical shifts at the most upfield position indicate that the amphipathic helix within [15N-Leu 45]-Vpu27–57 strongly interacts with mechanically aligned POPC bilayers and adopts an orientation parallel to the membrane surface. No major changes in the topology of this membrane-associated amphipathic helix were observed upon phosphorylation of serine residues 52 and 56, although this modification regulates biological function of Vpu. In contrast, [15N-Ala 62]-Vpu51–81 exhibits a pronounced 15N chemical shift anisotropy

AN AUTOMATIC MEASUREMENT SYSTEM WITH SPREADING RESISTANCE AND PCIV PROFILING FOR CHARACTERIZATION OF SEMICONDUCTORS

This article deals with the design and a control program of an automatic measuring system (AMS). The AMS allows to obtain the carrier concentration profile n(x) from the spreading resistance (SRP, with single point probe) and point contact current voltage (PCIV) measurements on a bevelled structure. The software of the AMS contains the possibility of calibration needed for converting the measured data into a carrier concentration profile and graphical subroutines for conversion of the resistivity to concentration. The software of the AMS further permits monitoring of running measurements by SRP and PCIV by LAN networks. The attained results in designing and creating the control program were verified by measuring and determining the carrier concentration profile on selected structures. The experimental n(x) profile has been compared with that calculated by program SUPREM

Monitoring of phosphorus cross-contamination in ion implantation of arsenic by spreading resistance

Při využívaní iontového implantátora pro různé prvky (bór, fosfor, arzén, antimon) může docházet ke kontaminaci nežádoucím prvkem. Zvláštní pozornost je potřebné věnovat zabránění fosforové kontaminaci při implantaci arzénu a antimonu. Uvedená metoda na monitorování úrovně fosforové kontaminace při arzénové implantaci je alternativou k SIMS (Secondary Ion Mass Spectrometry). Tato metoda kombinuje využití simulace a metody odporu šíření SRP (spreading resistance profiling) k určování fosforové kontaminace při arzénové implantaci po difuzním procesu. Monitorování bylo uskutečněno pro vysokodávkovou implantaci arzénu. Pomocí programu SUPREM byl vytvořen teoretický model, který umožňuje určit vliv různých dávek fosforové kontaminace v arzénové implantaci. Tento model byl následně validován pomocí SIMS a SRP měření. Uveden je vliv různých úrovní fosforové kontaminace (až po 1014 cm-2 dávky fosforu) na profil volných nosičů náboje který byl pozorován při provoze iontového implantátora. Taktéž je uveden konverzní graf, pomocí kterého lze z hloubky p-n přechodu měřeného metodou SRP určit dávku kontaminace fosforem. Experimentální výsledky ukázaly dobrou shodu mezi SIMS daty a navrhovanou SRP metodou. Tato SRP metoda může být použitá pro detekci dávek fosforu až po 1012 cm-2 a představuje levnější metodu na kontrolu fosforové kontaminace v arzénové implantaci než SIMS

Interactions involved in the realignment of membrane-associated helices. An investigation using oriented solid-state NMR and attenuated total reflection Fourier transform infrared spectroscopies.

A series of histidine-containing peptides (LAH4X6) was designed to investigate the membrane interactions of selected side chains. To this purpose, their pH-dependent transitions from in-plane to transmembrane orientations were investigated by attenuated total reflection Fourier transform infrared and oriented solid-state NMR spectroscopies. Peptides of the same family have previously been shown to exhibit antibiotic and DNA transfection activities. Solution NMR spectroscopy indicates that these peptides form amphipathic helical structures in membrane environments, and the technique was also used to characterize the pK values of all histidines in the presence of detergent micelles. Whereas one face of the amphipathic helix is clearly hydrophobic, the opposite side is flanked by four histidines surrounding six leucine, alanine, glycine, tryptophan, or tyrosine residues, respectively. This diversity in peptide composition causes pronounced shifts in the midpoint pH of the in-plane to transmembrane helical transition, which is completely abolished for the peptides carrying the most hydrophilic amino acid residues. These properties open up a conceptually new approach to study in a quantitative manner the hydrophobic as well as specific interactions of amino acids in membranes. Notably, the resulting scale for whole residue transitions from the bilayer interface to the hydrophobic membrane interior is obtained from extended helical sequences in lipid bilayers.Journal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe

Interactions involved in the realignment of membrane-associated helices. An investigation using oriented solid-state NMR and attenuated total reflection Fourier transform infrared spectroscopies.

A series of histidine-containing peptides (LAH4X6) was designed to investigate the membrane interactions of selected side chains. To this purpose, their pH-dependent transitions from in-plane to transmembrane orientations were investigated by attenuated total reflection Fourier transform infrared and oriented solid-state NMR spectroscopies. Peptides of the same family have previously been shown to exhibit antibiotic and DNA transfection activities. Solution NMR spectroscopy indicates that these peptides form amphipathic helical structures in membrane environments, and the technique was also used to characterize the pK values of all histidines in the presence of detergent micelles. Whereas one face of the amphipathic helix is clearly hydrophobic, the opposite side is flanked by four histidines surrounding six leucine, alanine, glycine, tryptophan, or tyrosine residues, respectively. This diversity in peptide composition causes pronounced shifts in the midpoint pH of the in-plane to transmembrane helical transition, which is completely abolished for the peptides carrying the most hydrophilic amino acid residues. These properties open up a conceptually new approach to study in a quantitative manner the hydrophobic as well as specific interactions of amino acids in membranes. Notably, the resulting scale for whole residue transitions from the bilayer interface to the hydrophobic membrane interior is obtained from extended helical sequences in lipid bilayers.Journal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe