Synthesis and Characterization of Novel Adsorbents Based on Functionalization of Graphene Oxide with Schiff Base and Reduced Schiff Base for Pesticide Removal.

Graphene oxide (GO) nanosheets were functionalized with Schiff base and reduced Schiff base. Covalent and non-covalent functionalized GO nanostructures have been tested for the removal of pesticides with different chemical structures and properties (e.g.

Prion Amyloid Polymorphs - The Tag Might Change It All.

Sup35p is a protein from . It can propagate using a prion-like mechanism, which means that it can recruit non-prion soluble Sup35p into insoluble fibrils. Sup35p is a large protein showing three distinct domains, N, M and an extended globular domain.

Box C/D snoRNPs: solid-state NMR fingerprint of an early-stage 50 kDa assembly intermediate.

Many cellular functions rely on stable protein-only or protein-RNA complexes. Deciphering their assembly mechanism is a key question in cell biology. We here focus on box C/D small nucleolar ribonucleoproteins involved in ribosome biogenesis.

Sample Preparation for Membrane Protein Structural Studies by Solid-State NMR.

Conformational studies of membrane proteins remain a challenge in the field of structural biology, and in particular the investigation of the proteins in a native-like lipid environment. Solid-state NMR presents a valuable opportunity for this, and we present here three critical steps in the solid-state NMR sample preparation, i.e.

Monitoring ssDNA Binding to the DnaB Helicase from Helicobacter pylori by Solid-State NMR Spectroscopy.

DnaB helicases are bacterial, ATP-driven enzymes that unwind double-stranded DNA during DNA replication. Herein, we study the sequential binding of the "non-hydrolysable" ATP analogue AMP-PNP and of single-stranded (ss) DNA to the dodecameric DnaB helicase from Helicobacter pylori using solid-state NMR. Phosphorus cross-polarization experiments monitor the binding of AMP-PNP and DNA to the helicase.

Variability and conservation of structural domains in divide-and-conquer approaches.

The use of protein building blocks for the structure determination of multidomain proteins and protein-protein complexes, also known as the "divide and conquer" approach, is an important strategy for obtaining protein structures. Atomic-resolution X-ray or NMR data of the individual domains are combined with lower-resolution electron microscopy maps or X-ray data of the full-length protein or the protein complex. Doing so, it is often assumed that the individual domain structures remain invariant in the context of the superstructure.

Solid-state NMR chemical-shift perturbations indicate domain reorientation of the DnaG primase in the primosome of Helicobacter pylori.

We here investigate the interactions between the DnaB helicase and the C-terminal domain of the corresponding DnaG primase of Helicobacter pylori using solid-state NMR. The difficult crystallization of this 387 kDa complex, where the two proteins interact in a six to three ratio, is circumvented by simple co-sedimentation of the two proteins directly into the MAS-NMR rotor. While the amount of information that can be extracted from such a large protein is still limited, we can assign a number of amino-acid residues experiencing significant chemical-shift perturbations upon helicase-primase complex formation.

Solid-state NMR sequential assignments of the N-terminal domain of HpDnaB helicase.

We present solid-state NMR assignments of the N-terminal domain of the DnaB helicase from Helicobacter pylori (153 residues) in its microcrystalline form. We use a sequential resonance assignment strategy based on three-dimensional NMR experiments. The resonance assignments obtained are compared with automated resonance assignments computed with the ssFLYA algorithm.

Efficient and stable reconstitution of the ABC transporter BmrA for solid-state NMR studies.

We present solid-state NMR sample preparation and first 2D spectra of the Bacillus subtilis ATP-binding cassette (ABC) transporter BmrA, a membrane protein involved in multidrug resistance. The homodimeric 130-kDa protein is a challenge for structural characterization due to its membrane-bound nature, size, inherent flexibility and insolubility. We show that reconstitution of this protein in lipids from Bacillus subtilis at a lipid-protein ratio of 0.

A sedimented sample of a 59 kDa dodecameric helicase yields high-resolution solid-state NMR spectra.

Crystal clear: Preparing solid-state NMR samples that yield high-resolution spectra displaying high sensitivity is time-consuming and complicated. A sample of the 59 kDa protein DnaB, prepared simply by preparative centrifugation, provides spectra that are as good as the ones from carefully grown microcrystals.

Characterization of different water pools in solid-state NMR protein samples.

We observed and characterized two distinct signals originating from different pools of water protons in solid-state NMR protein samples, namely from crystal water which exchanges polarization with the protein (on the NMR timescale) and is located in the protein-rich fraction at the periphery of the magic-angle spinning (MAS) sample container, and supernatant water located close to the axis of the sample container. The polarization transfer between the water and the protein can be probed by two-dimensional exchange spectroscopy, and we show that the supernatant water does not interact with protein on the timescale of the experiments. The two water pools have different spectroscopic properties, including resonance frequency, longitudinal, transverse and rotating frame relaxation times.

Prion fibrils of Ure2p assembled under physiological conditions contain highly ordered, natively folded modules.

The difference between the prion and the non-prion form of a protein is given solely by its three-dimensional structure, according to the prion hypothesis. It has been shown that solid-state NMR can unravel the atomic-resolution three-dimensional structure of prion fragments but, in the case of Ure2p, no highly resolved spectra are obtained from the isolated prion domain. Here, we demonstrate that the spectra of full-length fibrils of Ure2p interestingly lead to highly resolved solid-state NMR spectra.

Methyl proton contacts obtained using heteronuclear through-bond transfers in solid-state NMR spectroscopy.

A two-dimensional proton-mediated carbon-carbon correlation experiment that relies on through-bond heteronuclear magnetization transfers is demonstrated in the context of solid-state NMR of proteins. This new experiment, dubbed J-CHHC by analogy to the previously developed dipolar CHHC techniques, is shown to provide selective and sensitive correlations in the methyl region of 2D spectra of crystalline organic compounds. The method is then demonstrated on a microcrystalline sample of the dimeric protein Crh (2 x 10.

Structural constraints for the Crh protein from solid-state NMR experiments.

We demonstrate that short, medium and long-range constraints can be extracted from proton mediated, rare-spin detected correlation solid-state NMR experiments for the microcrystalline 10.4 x 2 kDa dimeric model protein Crh. Magnetization build-up curves from cross signals in NHHC and CHHC spectra deliver detailed information on side chain conformers and secondary structure for interactions between spin pairs.

3D structure determination of the Crh protein from highly ambiguous solid-state NMR restraints.

In a wide variety of proteins, insolubility presents a challenge to structural biology, as X-ray crystallography and liquid-state NMR are unsuitable. Indeed, no general approach is available as of today for studying the three-dimensional structures of membrane proteins and protein fibrils. We here demonstrate, at the example of the microcrystalline model protein Crh, how high-resolution 3D structures can be derived from magic-angle spinning solid-state NMR distance restraints for fully labeled protein samples.

Determining the geometry of strongly hydrogen-bonded silanols in a layered hydrous silicate by solid-state nuclear magnetic resonance.

High-resolution solid-state NMR spectroscopy is exploited to obtain structural constraints involving strongly hydrogen-bonded silanols in octosilicate, a prominent member of the layered hydrous sodium silicates. Proton-silicon cross-polarization dynamics reveals that octosilicate contains two types of Q(3) silicons present in hydrogen-bonded -Si-O-Hcdots, three dots, centeredO-Si- and -Si-O(-)-type sites which can only be distinguished by their different abilities to cross polarize and the different mobilities of neighboring hydrous species. The theoretical analysis of the oscillating components of the polarization transfer buildup curves suggests that the model of heteronuclear pairs is an adequate description of the quantum spin system within hydrogen-bonded -Si-O-Hcdots, three dots, centeredO-Si- fragments.

Straightforward detection of the secondary ionisation of the phosphate group and pK determinations by high-resolution solid-state 31P NMR.

The suitability of high-resolution solid-state 31P NMR for a straightforward determination of the protonation state of phosphate groups as well as of their pK2 values extracted from solid state mono : dianionic ratios has been demonstrated.

An experimental and theoretical study of the 13C and 31P chemical shielding tensors in solid O-phosphorylated amino acids.

A series of l and dl forms of O-phosphorylated amino acids (serine, threonine, tyrosine) have been studied by using solid-state multinuclear NMR spectroscopy and ab initio calculations. Principal elements of the (13)C and (31)P chemical shielding tensors have been measured and discussed in relation to zwitterionic structures and intermolecular contacts. DFT calculations have been compared with experimental data showing their ability to reproduce experimentally obtained tensor values in this challenging class of compounds.