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https://www.readbyqxmd.com/read/27913993/antifreeze-glycopeptides-from-structure-and-activity-studies-to-current-approaches-in-chemical-synthesis
#1
REVIEW
Małgorzata Urbańczyk, Jerzy Góra, Rafał Latajka, Norbert Sewald
Antifreeze glycopeptides (AFGPs) are a class of biological antifreeze agents found predominantly in Arctic and Antarctic species of fish. They possess the ability to regulate ice nucleation and ice crystal growth, thus creating viable life conditions at temperatures below the freezing point of body fluids. AFGPs usually consist of 4-55 repetitions of the tripeptide unit Ala-Ala-Thr that is O-glycosylated at the threonine side chains with β-D-galactosyl-(1 → 3)-α-N-acetyl-D-galactosamine. Due to their interesting properties and high antifreeze activity, they have many potential applications, e...
December 2, 2016: Amino Acids
https://www.readbyqxmd.com/read/27905605/an-efficient-2d-11-b-11-b-solid-state-nmr-spectroscopy-strategy-for-monitoring-covalent-self-assembly-of-boronic-acid-derived-compounds-the-transformation-and-unique-architecture-of-bortezomib-molecules-in-the-solid-state
#2
J Brus, J Czernek, M Urbanova, L Kobera, A Jegorov
The difficulty in the prediction of the complicated solid-state structure of boronic acid derivatives, resulting from the complex pathway of reversible covalent interactions, represents a significant obstacle to the development of a new generation of advanced supramolecular systems such as covalent organic frameworks of efficient anticancer drugs. In this contribution, various 2D (11)B-(11)B solid-state NMR correlation techniques supported by DFT calculations were explored to formulate a reliable tool for monitoring the covalent assembly of boronic acid residues in the solid state...
December 1, 2016: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/27905602/achieving-enhanced-ionic-mobility-in-nanoporous-silica-by-controlled-surface-interactions
#3
Mounesha Nagendrachar Garaga, Luis Aguilera, Negin Yaghini, Aleksandar Matic, Michael Persson, Anna Martinelli
We report a strategy to enhance the ionic mobility in an emerging class of gels, based on robust nanoporous silica micro-particles, by chemical functionalization of the silica surface. Two very different ionic liquids are used to fill the nano-pores of silica at varying pore filling factors, namely one aprotic imidazolium based (1-methyl-3-hexylimidazolium bis(trifluoromethanesulfonyl)imide, C6C1ImTFSI), and one protic ammonium based (diethylmethylammonium methanesulfonate, DEMAOMs) ionic liquid. Both these ionic liquids display higher ionic mobility when confined in functionalized silica as compared to untreated silica nano-pores, an improvement that is more pronounced at low pore filling factors (i...
December 1, 2016: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/27901101/structural-basis-for-the-dissociation-of-%C3%AE-synuclein-fibrils-triggered-by-pressure-perturbation-of-the-hydrophobic-core
#4
Guilherme A P de Oliveira, Mayra de A Marques, Carolina Cruzeiro-Silva, Yraima Cordeiro, Caroline Schuabb, Adolfo H Moraes, Roland Winter, Hartmut Oschkinat, Debora Foguel, Mônica S Freitas, Jerson L Silva
Parkinson's disease is a neurological disease in which aggregated forms of the α-synuclein (α-syn) protein are found. We used high hydrostatic pressure (HHP) coupled with NMR spectroscopy to study the dissociation of α-syn fibril into monomers and evaluate their structural and dynamic properties. Different dynamic properties in the non-amyloid-β component (NAC), which constitutes the Greek-key hydrophobic core, and in the acidic C-terminal region of the protein were identified by HHP NMR spectroscopy. In addition, solid-state NMR revealed subtle differences in the HHP-disturbed fibril core, providing clues to how these species contribute to seeding α-syn aggregation...
November 30, 2016: Scientific Reports
https://www.readbyqxmd.com/read/27900841/the-role-of-the-prod1-membrane-anchor-in-newt-limb-regeneration
#5
Kaoru Nomura, Yasushi Tanimoto, Fumio Hayashi, Erisa Harada, Xiao-Yuan Shan, Masafumi Shionyu, Atsushi Hijikata, Tsuyoshi Shirai, Kenichi Morigaki, Keiko Shimamoto
Prod1 is a protein that regulates limb regeneration in salamanders by determining the direction of limb growth. Prod1 is attached to the membrane by a glycosylphosphatidylinositol (GPI) anchor, but the role of membrane anchoring in the limb regeneration process is poorly understood. In this study, we investigated the functional role of the anchoring of Prod1 to the membrane by using its synthetic mimics in combination with solid-state NMR spectroscopy and fluorescent microscopy techniques. Anchoring did not affect the three-dimensional structure of Prod1 but did induce aggregation by aligning the molecules and drastically reducing the molecular motion on the two-dimensional membrane surface...
November 30, 2016: Angewandte Chemie
https://www.readbyqxmd.com/read/27897351/co-existence-of-distinct-supramolecular-assemblies-in-solution-and-in-the-solid-state
#6
Manjunatha Reddy, Aida Huqi, Dinu Iuga, Satoshi Sakurai, Andrew Marsh, Jeffery T Davis, Stefano Masiero, Steven P Brown
The formation of distinct supramolecular assemblies, including a metastable species, is revealed for a lipophilic guanosine (G) derivative in solution and in the solid state. Structurally different G-quartet based assemblies are formed in chloroform depending on the nature of the cation, anion and salt concentration, as characterized by circular dichroism and time course diffusion-ordered NMR spectroscopy data. Intriguingly, even the presence of potassium ions that stabilize G-quartets in chloroform was insufficient to exclusively retain such assemblies in the solid state, leading to the formation of mixed quartet and ribbon-like assemblies as revealed by fast magic-angle spinning (MAS) NMR spectroscopy...
November 29, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27897294/synthesis-of-a-lithium-cyclopentadienide-complex-by-addition-of-lintf2-to-a-zwitterionic-fulvalene
#7
Dominic Schmid, Alexander Seyboldt, Klaus Eichele, Doris Kunz
The synthesis of a η(5)-coordinated LiCp complex by simple addition of a Li-salt in benzene is presented. A strongly zwitterionic fulvalene serves as the Cp-precursor. Evidence for the coordination of Li(+) was obtained by the characterisitic (7)Li NMR chemical shifts, variable temperature experiments in solution and by X-ray structure analysis in the solid state.
November 29, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/27895259/arene-guest-selectivity-and-pore-flexibility-in-a-metal-organic-framework-with-semi-fluorinated-channel-walls
#8
Rebecca Smith, Iñigo J Vitórica-Yrezábal, Adrian Hill, Lee Brammer
A metal-organic framework (MOF) with one-dimensional channels of approximately hexagonal cross-section [Ag2(O2CCF2CF2CO2)(TMP)] 1: (TMP =2,3,5,6-tetramethylpyrazine) has been synthesized with MeOH filling the channels in its as-synthesized form as [Ag2(O2CCF2CF2CO2)(TMP)]·n(MeOH) 1-MEOH: (n = 1.625 by X-ray crystallography). The two types of ligand connect columns of Ag(I) centres in an alternating manner, both around the channels and along their length, leading to an alternating arrangement of hydrocarbon (C-H) and fluorocarbon (C-F) groups lining the channel walls, with the former groups projecting further into the channel than the latter...
January 13, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/27894779/chrysin-cocrystals-characterization-and-evaluation
#9
Renu Chadha, Yashika Bhalla, Avdesh Nandan, Kunal Chadha, Maninder Karan
Solvent free mechanochemical approach is utilized to synthesise new cocrystals of chrysin using supramolecular chemistry based upon reliable synthons. Chrysin, a flavone nutraceutical with wide range of beneficial effects has critically low bioavailability on account of its poor aqueous solubility and consequently poor absorption from the gastrointestinal tract. The present study focuses on this critical aspect and has exploited non covalent interactions to prepare its cocrystals with cytosine and thiamine hydrochloride...
November 3, 2016: Journal of Pharmaceutical and Biomedical Analysis
https://www.readbyqxmd.com/read/27891541/dft-calculations-in-the-assignment-of-solid-state-nmr-and-crystal-structure-elucidation-of-a-lanthanum-iii-complex-with-dithiocarbamate-and-phenanthroline
#10
Vasantha Gowda, Risto S Laitinen, Ville-Veikko Telkki, Anna-Carin Larsson, Oleg N Antzutkin, Perttu Lantto
The molecular, crystal, and electronic structures as well as spectroscopic properties of a mononuclear heteroleptic lanthanum(iii) complex with diethyldithiocarbamate and 1,10-phenanthroline ligands (3 : 1) were studied by solid-state (13)C and (15)N cross-polarisation (CP) magic-angle-spinning (MAS) NMR, X-ray diffraction (XRD), and first principles density functional theory (DFT) calculations. A substantially different powder XRD pattern and (13)C and (15)N CP-MAS NMR spectra indicated that the title compound is not isostructural to the previously reported analogous rare earth complexes with the space group P21/n...
November 28, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/27888838/five-decades-of-homonuclear-dipolar-decoupling-in-solid-state-nmr-status-and-outlook
#11
REVIEW
Kaustubh R Mote, Vipin Agarwal, P K Madhu
It has been slightly more than fifty years since the first homonuclear spin decoupling scheme, Lee-Goldburg decoupling, was proposed for removing homonuclear dipolar interactions in solid-state nuclear magnetic resonance. A family of such schemes has made observation of high-resolution NMR spectra of abundant spins possible in various applications in solid state. This review outlines the strategies used in this field and the future prospects of homonuclear spin decoupling in solid-state NMR.
November 2016: Progress in Nuclear Magnetic Resonance Spectroscopy
https://www.readbyqxmd.com/read/27881902/temperature-dependent-oxygen-effect-on-nmr-d-formula-see-text-relaxation-diffusion-correlation-of-n-alkanes
#12
Igor Shikhov, Christoph H Arns
Nuclear magnetic resonance (NMR) diffusion-relaxation correlation experiments (D-[Formula: see text]) are widely used for the petrophysical characterisation of rocks saturated with petroleum fluids both in situ and for laboratory analyses. The encoding for both diffusion and relaxation offers increased fluid typing contrast by discriminating fluids based on their self-diffusion coefficients, while relaxation times provide information about the interaction of solid and fluid phases and associated confinement geometry (if NMR responses of pure fluids at particular temperature and pressure are known)...
2016: Applied Magnetic Resonance
https://www.readbyqxmd.com/read/27879035/dynamic-nuclear-polarization-provides-new-insights-into-chromophore-structure-in-phytochrome-photoreceptors
#13
Daniel Stöppler, Chen Song, Barth-Jan van Rossum, Michel-Andreas Geiger, Christina Lang, Maria-Andrea Mroginski, Anil Pandurang Jagtap, Snorri Th Sigurdsson, Jörg Matysik, Jon Hughes, Hartmut Oschkinat
Phytochromes are red/far-red photochromic photoreceptors acting as master regulators of development in higher plants, thereby controlling transcription of about 20 % of their genes. Light-induced isomerization of the bilin chromophore leads to large rearrangements in protein structure, whereby the role of protonation dynamics and charge distribution is of particular interest. To help unravel the inherent mechanisms, we present two-dimensional dynamic nuclear polarization (DNP) enhanced solid-state magic-angle spinning (MAS) NMR spectra of the functional sensory module of the cyanobacterial phytochrome Cph1...
November 23, 2016: Angewandte Chemie
https://www.readbyqxmd.com/read/27879018/structural-tuning-of-anion-templated-motifs-with-external-stimuli-through-crystal-to-crystal-transformation
#14
Vadapalli Chandrasekhar, Ashutosh Singh, Ranjay Tiwari, Mandy Lee, Shih Sun, Jogendra Behera
Protonation of trans-1,2-bis(4-pyridyl)ethylene (4,4'-bpe) with dilute sulfuric acid (33%) afforded a protonated adduct [{4,4'-bpe*2H+}2{HSO4}-2{SO4}-2{H2O}2] (1). The neighbouring olefinic bond in molecular structure of 1 was in suitable range (3.931-4.064 Å) to undergo photochemical [2+2] cycloaddition reaction according to Schmidt's postulation. However, 1 upon irradiation with UV light (365 nm) undergoes a molecular sliding involving the 4,4'-bpe*2H+ units, affording 2. The formation of 2 is believed to be stabilized through OSO4***π interactions...
November 23, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27873363/iron-ii-cobalt-ii-nickel-ii-and-zinc-ii-silylene-complexes-reaction-of-the-silylene-iprnc-nipr2-nipr-2-si-with-febr2-cobr2-nibr2-%C3%A2-meoch2-ch2-ome-zncl2-and-znbr2
#15
Johannes A Baus, Felix M Mück, Heidi Schneider, Reinhold Tacke
Reaction of the donor-stabilized silylene [iPrNC(NiPr2 )NiPr]2 Si (1) with FeBr2 , CoBr2 , NiBr2 ⋅MeOCH2 CH2 OMe, ZnCl2 , and ZnBr2 afforded the respective transition-metal silylene complexes 4-8, the formation of which can be described in terms of a Lewis acid/base reaction (4, 5, 7, 8) or a nucleophilic substitution reaction (6). However, the reactivity profile of silylene 1 is not only based on its strong Lewis base character; the different coordination modes of the two guanidinato ligands (4-6 vs. 7 and 8) add an additional reactivity facet...
November 22, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27865050/nmr-spectroscopic-assignment-of-backbone-and-side-chain-protons-in-fully-protonated-proteins-microcrystals-sedimented-assemblies-and-amyloid-fibrils
#16
Jan Stanek, Loren B Andreas, Kristaps Jaudzems, Diane Cala, Daniela Lalli, Andrea Bertarello, Tobias Schubeis, Inara Akopjana, Svetlana Kotelovica, Kaspars Tars, Andrea Pica, Serena Leone, Delia Picone, Zhi-Qiang Xu, Nicholas E Dixon, Denis Martinez, Mélanie Berbon, Nadia El Mammeri, Abdelmajid Noubhani, Sven Saupe, Birgit Habenstein, Antoine Loquet, Guido Pintacuda
We demonstrate sensitive detection of alpha protons of fully protonated proteins by solid-state NMR spectroscopy with 100-111 kHz magic-angle spinning (MAS). The excellent resolution in the Cα-Hα plane is demonstrated for 5 proteins, including microcrystals, a sedimented complex, a capsid and amyloid fibrils. A set of 3D spectra based on a Cα-Hα detection block was developed and applied for the sequence-specific backbone and aliphatic side-chain resonance assignment using only 500 μg of sample. These developments accelerate structural studies of biomolecular assemblies available in submilligram quantities without the need of protein deuteration...
November 16, 2016: Angewandte Chemie
https://www.readbyqxmd.com/read/27862240/solid-state-nmr-study-on-changes-of-phosphate-and-proton-species-in-metal-pyrophosphate-composite-mp2-o7-mo2-ceramics
#17
Masakazu Nishida, Tomoko Tanaka, Wataru Kanematsu
In order to investigate the effects of composite production and the role of the counter cation for metal phosphate conductors, changes in the solid state NMR spectra and magnetic relaxation times caused by the removal of volatile products and water washing were examined for various metal pyrophosphate (MP2 O7 -MO2 ; M = Sn, Si, Ti, Zr). Acidic species could be detected by (1) H MAS NMR spectra for all the composites except ZrP2 O7 -ZrO2 which had the lowest conductivity. The (31) P DD-MAS NMR spectra for MP2 O7 -MO2 composites showed different signal patterns depending on the counter cations participating in the ion exchange as a result of different microstructures...
November 12, 2016: Magnetic Resonance in Chemistry: MRC
https://www.readbyqxmd.com/read/27860464/vertebral-development-and-ossification-in-the-siberian-sturgeon-acipenser-baerii-with-new-insights-on-bone-histology-and-ultrastructure-of-vertebral-elements-and-scutes
#18
Amandine Leprévost, Thierry Azaïs, Michael Trichet, Jean-Yves Sire
In order to improve our knowledge on the vertebral development, structure and mineralization in Acipenseriformes, we undertook a study in a growth series of reared Siberian sturgeons (Acipenser baerii) using in toto clear and stain specimens, histological and ultrastructural observations, X-ray micro-tomography, and solid state NMR analyses. Scutes were also studied to compare the tissue structure and mineralization of endoskeletal and dermal skeletal elements. This study completes and clarifies previous investigations on vertebral development and architecture in sturgeons, and brings original data on the structure of (i) the perichondral bone that is progressively deposited around the vertebral elements during ontogeny, (ii) the typical cartilage composing these elements, and (iii) the scutes...
November 14, 2016: Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology
https://www.readbyqxmd.com/read/27860097/binuclear-c-c-cyclometalated-platinum-ii-nhc-complexes-with-bridging-amidinate-ligands
#19
Hendrik Leopold, Mario Tenne, Alexander Tronnier, Stefan Metz, Ingo Münster, Gerhard Wagenblast, Thomas Strassner
Binuclear C^C* cyclometalated NHC platinum(II) compounds with bridging amidinate ligands were synthesized to evaluate their photophysical properties. Their three-dimensional structures were determined by a combination of 2D NMR experiments, mass spectrometry, DFT calculations, and solid-state structure analysis. The bridging amidinate ligands enforce short distances between the platinum centers of the two cyclometalated structures, which gives rise to extraordinary photophysical properties.
November 18, 2016: Angewandte Chemie
https://www.readbyqxmd.com/read/27860033/synergic-effect-of-active-sites-in-zinc-modified-zsm-5-zeolites-as-revealed-by-high-field-solid-state-nmr-spectroscopy
#20
Guodong Qi, Qiang Wang, Jun Xu, Julien Trébosc, Olivier Lafon, Chao Wang, Jean-Paul Amoureux, Feng Deng
Understanding the nature of active sites in metal-supported catalysts is of great importance towards establishing their structure-property relationships. The outstanding catalytic performance of metal-supported catalysts is frequently ascribed to the synergic effect of different active sites, which is however not well spectroscopically characterized. Herein, we report the direct detection of surface Zn species and (1) H-(67) Zn internuclear interaction between Zn(2+) ions and Brønsted acid sites on Zn-modified ZSM-5 zeolites by high-field solid-state NMR spectroscopy...
November 17, 2016: Angewandte Chemie
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