Hydrogen bonding in Alzheimer's amyloid-β fibrils probed by 15N{17O} REAPDOR solid-state NMR spectroscopy

An exclusive label: 15N{17O} REAPDOR NMR was used to validate intermolecular C17O=H-15N hydrogen bonding in Ac-Aβ(16-22)-NH2 (see scheme) and Aβ(11-25) amyloid fibrils, which are associated with Alzheimer's disease, by selectively labeling them with 17O and 15N. This method was effective for confirming the structure of these fibrils, and could be useful for a number of other biological samples. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Exploring the interactions of irbesartan and irbesartan–2-hydroxypropyl-β-cyclodextrin complex with model membranes

The interactions of irbesartan (IRB) and irbesartan–2-hydroxypropyl-β-cyclodextrin (HP-β-CD) complex with Dipalmitoyl Phosphatidylcholine (DPPC) bilayers have been explored utilizing an array of biophysical techniques ranging from Differential Scanning Calorimetry (DSC), Small angle X-ray Scattering (SAXS), ESI Mass-Spectrometry (ESI-MS) and solid state Nuclear Magnetic Resonance (ssNMR). Molecular Dynamics (MD) calculations have been also conducted to complement the experimental results. Irbesartan was found to be embedded in the lipid membrane core and to affect the phase transition properties of the DPPC bilayers. SAXS studies revealed that irbesartan alone does not display perfect solvation since some coexisting irbesartan crystallites are present. In its complexed form IRB gets fully solvated in the membranes showing that encapsulation of IRB in HP-β-CD may have beneficial effects in the ADME properties of this drug. MD experiments revealed the topological and orientational integration of irbesartan into the phospholipid bilayer being placed at about 1 nm from the membrane centre

The Conformational Equilibrium of the Neuropeptide Y2 Receptor in Bilayer Membranes

Dynamic structural transitions within the seven-transmembrane bundle represent the mechanism by which G-protein-coupled receptors convert an extracellular chemical signal into an intracellular biological function. Here, the conformational dynamics of the neuropeptide Y receptor type 2 (Y2R) during activation was investigated. The apo, full agonist-, and arrestin-bound states of Y2R were prepared by cell-free expression, functional refolding, and reconstitution into lipid membranes. To study conformational transitions between these states, all six tryptophans of Y2R were(13)C-labeled. NMR-signal assignment was achieved by dynamic-nuclear-polarization enhancement and the individual functional states of the receptor were characterized by monitoring(13)C NMR chemical shifts. Activation of Y2R is mediated by molecular switches involving the toggle switch residue Trp281(6.48)of the highly conserved SWLP motif and Trp327(7.55)adjacent to the NPxxY motif. Furthermore, a conformationally preserved "cysteine lock"-Trp116(23.50)was identified

High-Resolution 3D Structure Determination of Kaliotoxin by Solid-State NMR Spectroscopy

High-resolution solid-state NMR spectroscopy can provide structural information of proteins that cannot be studied by X-ray crystallography or solution NMR spectroscopy. Here we demonstrate that it is possible to determine a protein structure by solid-state NMR to a resolution comparable to that by solution NMR. Using an iterative assignment and structure calculation protocol, a large number of distance restraints was extracted from 1H/1H mixing experiments recorded on a single uniformly labeled sample under magic angle spinning conditions. The calculated structure has a coordinate precision of 0.6 Å and 1.3 Å for the backbone and side chain heavy atoms, respectively, and deviates from the structure observed in solution. The approach is expected to be applicable to larger systems enabling the determination of high-resolution structures of amyloid or membrane proteins

Effectiveness of a web-based screening and brief intervention with weekly text-message-initiated individualised prompts for reducing risky alcohol use among teenagers: study protocol of a randomised controlled trial within the ProHEAD consortium

Background: Early and excessive alcohol use is a significant threat to healthy development. Evidence supports the effectiveness of electronic alcohol interventions for young drinkers. However, effects are typically small and studies targeting under 18-year-olds are scarce. This trial is the first to evaluate the effectiveness of a single-session, brief, motivational, web-based intervention (ProWISE) plus weekly text-message-initiated individualised prompts (TIPs) in reducing alcohol consumption and alcohol-related harm among children and adolescents aged ≥ 12 years. TIPs are designed to decrease risky alcohol use by reaching youth in the contexts of their everyday lives and by providing individualised feedback on drinking intentions, actual drinking and succession in achieving personal goals for low-risk drinking or abstinence. Methods/Design: The trial is part of the multicentre consortium ProHEAD testing e-interventions for mental health problems in children and adolescents. Participants in grades 6–13 aged ≥ 12 years will be recruited in schools which participate in ProHEAD (target N = 15,000). Main criterion for inclusion in the ProWISE-TIP trial is a positive screening for at-risk alcohol use in the CRAFFT-d questionnaire (target n = 1076). In a multicentre, four-arm, randomised controlled design the following groups will be compared: (A) web-based intervention plus TIPs for 12 weeks; (B) web-based intervention plus text-message-initiated assessment of alcohol consumption for 12 weeks; (C) web-based intervention only; and (D) alcohol-related psychoeducation. TIPs will be delivered shortly before and after high-risk situations for excessive alcohol use and will be tailored to age, gender, drinking motives and alcohol consumption. Study participants will be followed up at three, six and nine months in the ProWISE-TIP trial and at one and two years in the ProHEAD consortium. Primary outcome is alcohol use in the past 30 days at nine months after enrolment. Secondary outcomes are alcohol-related problems, co-occurring substance use, health service utilisation, mental health problems and quality of life. Discussion: Trial results will generate important evidence on how to enhance effectiveness of single-session, web-based alcohol interventions for youth. The ProWISE-TIP intervention, if effective, can be used as a stand-alone alcohol intervention or as an add-on to school-based or community-based alcohol prevention programs. Trial registration German Clinical Trials Register, DRKS00014606. Registered on 20 April 2018

Fractional deuteration applied to biomolecular solid-state NMR spectroscopy

Solid-state Nuclear Magnetic Resonance can provide detailed insight into structural and dynamical aspects of complex biomolecules. With increasing molecular size, advanced approaches for spectral simplification and the detection of medium to long-range contacts become of critical relevance. We have analyzed the protonation pattern of a membrane-embedded ion channel that was obtained from bacterial expression using protonated precursors and D2O medium. We find an overall reduction of 50% in protein protonation. High levels of deuteration at Hα and Hβ positions reduce spectral congestion in (1H,13C,15N) correlation experiments and generate a transfer profile in longitudinal mixing schemes that can be tuned to specific resonance frequencies. At the same time, residual protons are predominantly found at amino-acid side-chain positions enhancing the prospects for obtaining side-chain resonance assignments and for detecting medium to long-range contacts. Fractional deuteration thus provides a powerful means to aid the structural analysis of complex biomolecules by solid-state NMR