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Andrea D Merg, Jennifer C Boatz, Abhishek Mandal, Gongpu Zhao, Soumitra Mokashi-Punekar, Chong Liu, Xianting Wang, Peijun Zhang, Patrick C A van der Wel, Nathaniel L Rosi
Chiral nanoparticle assemblies are an interesting class of materials whose chiroptical properties make them attractive for a variety of applications. Here, C18-(PEPAu(M-ox))2 (PEPAu(M-ox) = AYSSGAPPM(ox)PPF) is shown to direct the assembly of single-helical gold nanoparticle superstructures that exhibit exceptionally strong chiroptical activity at the plasmon frequency with absolute g-factor values up to 0.04. Transmission electron microscopy (TEM) and cryogenic electron tomography (cryo-ET) results indicate that the single helices have a periodic pitch of approximately 100 nm and consist of oblong gold nanoparticles...
October 11, 2016: Journal of the American Chemical Society
Tobias Schubeis, Madhu Nagaraj, Christiane Ritter
Solid-state NMR spectroscopy (ssNMR) is uniquely suited for atomic-resolution structural investigations of large protein assemblies, which are notoriously difficult to study due to their insoluble and non-crystalline nature. However, assignment ambiguities because of limited resolution and spectral crowding are currently major hurdles that quickly increase with the length of the polypeptide chain. The line widths of ssNMR signals are independent of proteins size, making segmental isotope labeling a powerful approach to overcome this limitation...
2017: Methods in Molecular Biology
David A Hirsh, Aaron J Rossini, Lyndon Emsley, Robert W Schurko
In this work, we show how to obtain efficient dynamic nuclear polarization (DNP) enhanced (35)Cl solid-state NMR (SSNMR) spectra at 9.4 T and demonstrate how they can be used to characterize the molecular-level structure of hydrochloride salts of active pharmaceutical ingredients (APIs) in both bulk and low wt% API dosage forms. (35)Cl SSNMR central-transition powder patterns of chloride ions are typically tens to hundreds of kHz in breadth, and most cannot be excited uniformly with high-power rectangular pulses or acquired under conditions of magic-angle spinning (MAS)...
September 21, 2016: Physical Chemistry Chemical Physics: PCCP
Paolo Cerreia Vioglio, Luca Catalano, Vera Vasylyeva, Carlo Nervi, Michele R Chierotti, Giuseppe Resnati, Roberto Gobetto, Pierangelo Metrangolo
Solid-state nuclear magnetic resonance (SSNMR) spectroscopy is a versatile characterization technique that can provide a plethora of information complementary to single crystal X-ray diffraction (SCXRD) analysis. Herein, we present an experimental and computational investigation of the relationship between the geometry of a halogen bond (XB) and the SSNMR chemical shifts of the non-quadrupolar nuclei either directly involved in the interaction ((15) N) or covalently bonded to the halogen atom ((13) C). We have prepared two series of X-bonded co-crystals based upon two different dipyridyl modules, and several halobenzenes and diiodoalkanes, as XB-donors...
October 6, 2016: Chemistry: a European Journal
Alysha Dicke, Tata Gopinath, Yingjie Wang, Gianluigi Veglia
Water plays a central role in membrane protein folding and function. It not only catalyzes lipid membrane self-assembly, but it is also affects the structural integrity and conformational dynamics of membrane proteins. Magic angle spinning (MAS) solid-state NMR is the technique of choice for measuring water accessibility of membrane proteins in a site-specific manner, providing a ruler for membrane protein topology and insertion within lipid bilayers. However, sensitivity and resolution of membrane protein samples for MAS experiments is often dictated by hydration levels, which affect membrane proteins structural dynamics...
October 5, 2016: Journal of Physical Chemistry. B
Keisuke Kishida, Yoshikuni Okumura, Yoshihiro Watanabe, Megumi Mukoyoshi, Silvia Bracco, Angiolina Comotti, Piero Sozzani, Satoshi Horike, Susumu Kitagawa
The separation of 1,3-butadiene from C4 hydrocarbon mixtures is imperative for the production of synthetic rubbers, and there is a need for a more economical separation method, such as a pressure swing adsorption process. With regard to adsorbents that enable C4 gas separation, [Zn(NO2 ip)(dpe)]n (SD-65; NO2 ip=5-nitroisophthalate, dpe=1,2-di(4-pyridyl)ethylene) is a promising porous material because of its structural flexibility and restricted voids, which provide unique guest-responsive accommodation. The 1,3-butadiene-selective sorption profile of SD-65 was elucidated by adsorption isotherms, in situ PXRD, and SSNMR studies and was further investigated by multigas separation and adsorption-desorption-cycle experiments for its application to separation technology...
October 24, 2016: Angewandte Chemie
Daniel Saliba, Mazen Al-Ghoul
We report the synthesis of magnesium-aluminium layered double hydroxide (LDH) using a reaction-diffusion framework (RDF) that exploits the multiscale coupling of molecular diffusion with chemical reactions, nucleation and growth of crystals. In an RDF, the hydroxide anions are allowed to diffuse into an organic gel matrix containing the salt mixture needed for the precipitation of the LDH. The chemical structure and composition of the synthesized magnesium-aluminium LDHs are determined using powder X-ray diffraction (PXRD), thermo-gravimetric analysis, differential scanning calorimetry, solid-state nuclear magnetic resonance (SSNMR), Fourier transform infrared and energy dispersive X-ray spectroscopy...
November 13, 2016: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
João Medeiros-Silva, Deni Mance, Mark Daniëls, Shehrazade Jekhmane, Klaartje Houben, Marc Baldus, Markus Weingarth
(1) H detection can significantly improve solid-state NMR spectral sensitivity and thereby allows studying more complex proteins. However, the common prerequisite for (1) H detection is the introduction of exchangeable protons in otherwise deuterated proteins, which has thus far significantly hampered studies of partly water-inaccessible proteins, such as membrane proteins. Herein, we present an approach that enables high-resolution (1) H-detected solid-state NMR (ssNMR) studies of water-inaccessible proteins, and that even works in highly complex environments such as cellular surfaces...
October 17, 2016: Angewandte Chemie
Dariusz Maciej Pisklak, Monika Zielińska-Pisklak, Łukasz Szeleszczuk
Solid-state nuclear magnetic resonance (ssNMR) is a powerful and unique method for analyzing solid forms of the active pharmaceutical ingredients (APIs) directly in their original formulations. Unfortunately, despite their wide range of application, the ssNMR experiments often suffer from low sensitivity and peaks overlapping between API and excipients. To overcome these limitations, the crosspolarization inversion recovery method was successfully used. The differences in the spin-lattice relaxation time constants for hydrogen atoms T1(H) between API and excipients were employed in order to separate and discriminate their peaks in ssNMR spectra as well as to increase the intensity of API signals in low-dose formulations...
September 22, 2016: International Journal of Pharmaceutics
Stanislav Leonidovich Veinberg, Zachary W Friedl, Austin W Lindquist, Brianna Kispal, Kristopher J Harris, Luke A O'Dell, Robert Schurko
¹⁴N ultra-wideline solid-state NMR (SSNMR) spectra were obtained for sixteen naturally occurring amino acids and four related derivatives using the WURST-CPMG pulse sequence and frequency-stepped techniques. The ¹⁴N quadrupolar parameters were measured for the sp³ nitrogen moieties (CQ ranges from 0.8 to 1.5 MHz). With the aid of plane-wave DFT calculations of the ¹⁴N EFG tensor parameters and orientations, the moieties are grouped into three categories according to the values of the quadrupolar asymmetry parameter, ηQ: low (≤ 0...
September 19, 2016: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Marvin J Bayro, Barbie K Ganser-Pornillos, Kaneil K Zadrozny, Mark Yeager, Robert Tycko
Maturation of HIV-1 requires disassembly of the Gag polyprotein lattice, which lines the viral membrane in the immature state, and subsequent assembly of the mature capsid protein lattice, which encloses viral RNA in the mature state. Metastability of the immature lattice has been proposed to depend on the existence of a structurally ordered, α-helical segment spanning the junction between capsid (CA) and spacer peptide 1 (SP1) subunits of Gag, a segment that is dynamically disordered in the mature capsid lattice...
September 21, 2016: Journal of the American Chemical Society
Sorout Shalini, Vishal M Dhavale, Kavalakal M Eldho, Sreekumar Kurungot, Thallaseril G Ajithkumar, Ramanathan Vaidhyanathan
Pyridinol, a coordinating zwitter-ionic species serves as stoichiometrically loadable and non-leachable proton carrier. The partial replacement of the pyridinol by stronger hydrogen bonding, coordinating guest, ethylene glycol (EG), offers 1000-fold enhancement in conductivity (10(-6) to 10(-3) Scm(-1)) with record low activation energy (0.11 eV). Atomic modeling coupled with (13)C-SSNMR provides insights into the potential proton conduction pathway functionalized with post-synthetically anchored dynamic proton transporting EG moieties...
2016: Scientific Reports
Tuo Wang, Pyae Phyo, Mei Hong
Plant biomass has become an important source of bio-renewable energy in modern society. The molecular structure of plant cell walls is difficult to characterize by most atomic-resolution techniques due to the insoluble and disordered nature of the cell wall. Solid-state NMR (SSNMR) spectroscopy is uniquely suited for studying native hydrated plant cell walls at the molecular level with chemical resolution. Significant progress has been made in the last five years to elucidate the molecular structures and interactions of cellulose and matrix polysaccharides in plant cell walls...
September 2016: Solid State Nuclear Magnetic Resonance
Andrew F Craig, Emily E Clark, Indra D Sahu, Rongfu Zhang, Nick D Frantz, M Sameer Al-Abdul-Wahid, Carole Dabney-Smith, Dominik Konkolewicz, Gary A Lorigan
Characterization of membrane proteins is challenging due to the difficulty in mimicking the native lipid bilayer with properly folded and functional membrane proteins. Recently, styrene-maleic acid (StMA) copolymers have been shown to facilitate the formation of disc-like lipid bilayer mimetics that maintain the structural and dynamic integrity of membrane proteins. Here we report the controlled synthesis and characterization of StMA containing block copolymers. StMA polymers with different compositions and molecular weights were synthesized and characterized by size exclusion chromatography (SEC)...
August 15, 2016: Biochimica et Biophysica Acta
Zackary Falls, Eva Zurek, Jochen Autschbach
Calculations of NMR shielding tensors and nuclear quadrupole coupling (NQC) tensors at the Kohn-Sham density functional level are used to simulate (27)Al magic-angle spinning (MAS) NMR spectra of the important olefin polymerization co-catalyst methylaluminoxane (MAO) at 77, 298, 398, and 498 K and spectrometer magnetic field inductions B ranging from 14.1 to 23.5 T. The calculations utilize the temperature (T) dependent distribution of species present in MAO determined recently by Zurek and coworkers from first-principles theory [Macromolecules, 2014, 47, 8556]...
September 14, 2016: Physical Chemistry Chemical Physics: PCCP
Emanuel D Costa, Josefina Priotti, Silvina Orlandi, Darío Leonardi, María C Lamas, Teresa G Nunes, Hermínio P Diogo, Claudio J Salomon, M João Ferreira
The saturation solubility of PVP:PZQ physical mixtures (PMs) and solid dispersions (SDs) prepared from ethanol (E/E) or ethanol/water (E/W) by the solvent evaporation method at 1:1, 2:1 and 3:1 ratio (w/w) was determined. The presence of PVP improves the solubility of PZQ (0.31±0.01mg/mL). A maximum of 1.29±0.03mg/mL of PZQ in solution was achieved for the 3:1 SD (E/E). The amount of PZQ in solution depends on the amount of polymer and on the preparation method. Solid-state NMR (ssNMR) and DSC were used to understand this behavior...
September 25, 2016: International Journal of Pharmaceutics
Sangita Kumari, Om P Sharma, Om P Khatri
Hexagonal boron nitride nanoplatelets (h-BNNPs), which are structurally analogous to graphene, were prepared via the ultrasound-assisted exfoliation of h-BN powder using N-methyl pyrrolidone as the solvent. The alkylamines with variable alkyl chains and electron-rich nitrogen atoms were grafted onto the boron sites of the h-BNNPs based on Lewis acid-base chemistry. The grafting of the alkylamines onto the h-BNNPs was confirmed using FTIR, XPS, TGA and (13)C SSNMR analyses. The crystalline and structural features of the alkylamine-functionalized h-BNNPs were studied using XRD and HRTEM analyses...
August 17, 2016: Physical Chemistry Chemical Physics: PCCP
Luis Alves, Bruno Medronho, Filipe E Antunes, Daniel Topgaard, Björn Lindman
Cellulose is insoluble in water but can be dissolved in strong acidic or alkaline conditions. How well dissolved cellulose is in solution and how it organizes are key questions often neglected in literature. The typical low pH required for dissolving cellulose in acidic solvents limits the use of typical characterization techniques. In this respect, Polarization Transfer Solid State NMR (PT ssNMR) emerges as a reliable alternative. In this work, combining PT ssNMR, microscopic techniques and X-ray diffraction, a set of different acidic systems (phosphoric acid/water, sulfuric acid/glycerol and zinc chloride/water) is investigated...
October 20, 2016: Carbohydrate Polymers
Yusuke Nishiyama
In spite of tremendous progress made in pulse sequence designs and sophisticated hardware developments, methods to improve sensitivity and resolution in solid-state NMR (ssNMR) are still emerging. The rate at which sample is spun at magic angle determines the extent to which sensitivity and resolution of NMR spectra are improved. To this end, the prime objective of this article is to give a comprehensive theoretical and experimental framework of fast magic angle spinning (MAS) technique. The engineering design of fast MAS rotors based on spinning rate, sample volume, and sensitivity is presented in detail...
September 2016: Solid State Nuclear Magnetic Resonance
Hong-Jin Tang, Li-Jun Ruan, Hai-Yan Tian, Guang-Ping Liang, Wen-Cai Ye, Eleri Hughes, Mikael Esmann, Natalya U Fedosova, Tse-Yu Chung, Jason T C Tzen, Ren-Wang Jiang, David A Middleton
Cardiotonic steroids (CTS) are clinically important drugs for the treatment of heart failure owing to their potent inhibition of cardiac Na(+), K(+)-ATPase (NKA). Bufadienolides constitute one of the two major classes of CTS, but little is known about how they interact with NKA. We report a remarkable stereoselectivity of NKA inhibition by native 3β-hydroxy bufalin over the 3α-isomer, yet replacing the 3β-hydroxy group with larger polar groups in the same configuration enhances inhibitory potency. Binding of the two (13)C-labelled glycosyl diastereomers to NKA were studied by solid-state NMR (SSNMR), which revealed interactions of the glucose group of the 3β- derivative with the inhibitory site, but much weaker interactions of the 3α- derivative with the enzyme...
2016: Scientific Reports
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