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Abathodharanan Narayanan, Ravishankar Kartik, Elanchezhian Sangeetha, Raghavachari Dhamodharan
A new superabsorbent with maximum water absorption capacity of ∼1250 g/g is prepared by hydrothermal synthesis from sustainable and biodegradable resources such as chitosan, citric acid and urea (denoted as 'CHCAUR'). CHCAUR is characterized extensively by various analytical techniques such as PXRD, SSNMR, FTIR, and TGA. Pure and saline water absorption study showed that CHCAUR could be a better adsorbent compared to the super absorbent polymer (SAP) used in commercial diaper material. The mechanism of water absorption is shown to arise out of a combination of electrostatic attraction of water to the ionic crosslinks and the presence of macropores as well as undulated surface due to the formation of nanofibrous bundles...
July 1, 2018: Carbohydrate Polymers
Alexander Marchanka, Christoph Kreutz, Teresa Carlomagno
Nucleic acids play key roles in most biological processes, either in isolation or in complex with proteins. Often they are difficult targets for structural studies, due to their dynamic behavior and high molecular weight. Solid-state nuclear magnetic resonance spectroscopy (ssNMR) provides a unique opportunity to study large biomolecules in a non-crystalline state at atomic resolution. Application of ssNMR to RNA, however, is still at an early stage of development and presents considerable challenges due to broad resonances and poor dispersion...
April 12, 2018: Journal of Biomolecular NMR
Antoine Loquet, Nadia El Mammeri, Jan Stanek, Mélanie Berbon, Benjamin Bardiaux, Guido Pintacuda, Birgit Habenstein
The amyloid fold is structurally characterized by a typical cross-β architecture, which is under debate to represent an energy-favourable folding state that many globular or natively unfolded proteins can adopt. Being initially solely associated with amyloid fibrils observed in the propagation of several neurodegenerative disorders, the discovery of non-pathological (or "functional") amyloids in many native biological processes has recently further intensified the general interest invested in those cross-β supramolecular assemblies...
April 5, 2018: Methods: a Companion to Methods in Enzymology
Erika L Buckle, June S Lum, Adrienne Roehrich, Robert Edward Stote, Branden Vandermoon, Martin Dracinsky, Shaun F Filocamo, Gary P Drobny
: A biomimetic approach to the formation of titania (TiO2) nanostructures is desirable due to the mild conditions required in this form of production. We have identified a series of serine-lysine peptides as candidates for the biomimetic production of TiO¬2 nanostructures. We have assayed these peptides for TiO2-precipitating activity upon exposure to titanium bis(ammonium lactato) dihydroxide and have characterized the resulting co-precipitates using scanning electron microscopy. A subset of these assayed peptides efficiently facilitates the production of TiO2 nanospheres...
March 29, 2018: Journal of Physical Chemistry. B
Yue Zhang, Bryan Lucier, Michael Fischer, Zhehong Gan, Paul Boyle, Bligh Desveaux, Yining Huang
Methane is a promising clean and inexpensive energy alternative to traditional fossil fuels, however, its low volumetric energy density at ambient conditions has made devising viable, efficient methane storage systems very challenging. Metal-organic frameworks (MOFs) are promising candidates for methane storage. In order to improve the methane storage capacity of MOFs, a better understanding of methane adsorption, mobility, and host-guest interactions within MOFs must be realized. In this study, methane adsorption within α-Mg3(HCO2)6, α-Zn3(HCO2)6, SIFSIX-3-Zn, and M-MOF-74 (M = Mg, Zn, Ni, Co) has been comprehensively examined...
March 25, 2018: Chemistry: a European Journal
M E Ward, M A Daniëls, E C van Kappel, M M Maurice, M Baldus
We report solid-state Nuclear Magnetic Resonance (ssNMR) studies on amyloid-like protein complexes formed by DIX domains that mediate key protein interactions in the Wnt signalling pathway. Our results provide insight into the 3D fold of the self-associated Axin-DIX domain and identify a potential lipid cofactor.
March 21, 2018: Chemical Communications: Chem Comm
Regiamara Ribeiro Almeida, Elisa Tatiana Silva Damasceno, Stephanne Yonara Barbosa de Carvalho, Gustavo Senra Gonçalves de Carvalho, Leiriana Aparecida Pinto Gontijo, Luiz Gustavo de Lima Guimarães
In order to enable the applicability of the essential oil of Lippia origanoides Kunth, increasing its stability and dispersion in aqueous base, were prepared nanogels of chitosan modified with ferulic acid to be used in their encapsulation. The results obtained by FTIR and13 C SSNMR revealed the formation of CS-FA link in the different synthesized nanogels, while the studied by DLS showed particles with varied sizes and positive charge. A satisfactory encapsulation capacity of the essential oil was obtained for the nanogels...
May 15, 2018: Carbohydrate Polymers
Manoj Kumar, Laxmi Mishra, Paul Carr, Michael Pilling, Peter Gardner, Shawn D Mansfield, Simon R Turner
Cellulose microfibrils are the basic units of cellulose in plants. The structure of these microfibrils is at least partly determined by the structure of the cellulose synthase complex. In higher plants, this complex is composed of 18 to 24 catalytic subunits known as CELLULOSE SYNTHASE A (CESA) proteins. Three different classes of CESA proteins are required for cellulose synthesis and for secondary cell wall cellulose biosynthesis, which include CESA4, CESA7, and CESA8. To probe the relationship between CESA proteins and microfibril structure, we created mutant cesa proteins that lack catalytic activity but retain sufficient structural integrity to allow assembly of the cellulose synthase complex...
March 9, 2018: Plant Physiology
Venkata S Mandala, Jonathan K Williams, Mei Hong
Solid-state nuclear magnetic resonance (SSNMR) spectroscopy elucidates membrane protein structures and dynamics in atomic detail to yield mechanistic insights. By interrogating membrane proteins in phospholipid bilayers that closely resemble the biological membrane, SSNMR spectroscopists have revealed ion conduction mechanisms, substrate transport dynamics, and oligomeric interfaces of seven-transmembrane helix proteins. Research has also identified conformational plasticity underlying virus-cell membrane fusions by complex protein machineries, and β-sheet folding and assembly by amyloidogenic proteins bound to lipid membranes...
March 2, 2018: Annual Review of Biophysics
Sten O Nilsson Lill, Cory M Widdifield, Anna Pettersen, Anna Svensk Ankarberg, Maria Lindkvist, Peter Aldred, Sandra Gracin, Norman Shankland, Kenneth Shankland, Staffan Schantz, Lyndon Emsley
By the combined use of powder and single crystal X-ray diffraction, solid-state NMR, and molecular modelling, the crystal structures of two systems containing the unusually large tenapanor drug molecule have been determined: the free form, ANHY and a dihydrochloride salt form, 2HCl. Dynamic nuclear polarization (DNP) assisted solid-state NMR (SSNMR) crystallography investigations were found essential for the final assignment, and were used to validate the crystal structure of ANHY. From the structural informatics analysis of ANHY and 2HCl, conformational ring differences in one part of the molecule were observed which influences the relative orientation of a methyl group on a ring nitrogen and thereby impacts the crystallizability of the dihydrochloride salt...
February 28, 2018: Molecular Pharmaceutics
Jeffrey Camacho-Bunquin, Magali S Ferrandon, Hyuntae Sohn, Dali Yang, Cong Liu, Patricia Ignacio-de Leon, Frédéric A Perras, Marek Pruski, Peter C Stair, Massimiliano Delferro
Well-defined organoplatinum(IV) sites were grafted on a Zn(II)-modified SiO2 support via surface organometallic chemistry in toluene at room temperature. Solid-state spectroscopies including XAS, DRIFTS, DRUV-Vis, and solid-state (SS)NMR enhanced by dynamic nuclear polarization (DNP), as well as TPR-H2 and TEM techniques revealed highly dispersed (methylcyclopentadienyl)methylplatinum(IV) sites on the surface ((MeCp)PtMe/Zn/SiO2, 1). In addition, computational modelling suggests that the surface reaction of (MeCp)PtMe3 with Zn(II)-modified SiO2 support is thermodynamically favorable (∆G = -12...
February 27, 2018: Journal of the American Chemical Society
Sebastien Alphonse, Boris Itin, Reza Khayat, Ranajeet Ghose
While solid-state NMR (ssNMR) has emerged as a powerful technique to study viral capsids, current studies are limited to capsids formed from single proteins or single polyproteins. The ability to selectively label individual protein components within multi-protein viral capsids and the resulting spectral simplification will facilitate the extension of ssNMR techniques to complex viruses. In vitro capsid assembly by combining individually purified, labeled and unlabeled components in NMR quantities is not a viable option for most viruses...
February 21, 2018: Biochemistry
Chaowei Shi, Yao He, Kitty Hendriks, Bert L de Groot, Xiaoying Cai, Changlin Tian, Adam Lange, Han Sun
NaK and other non-selective channels are able to conduct both sodium (Na+ ) and potassium (K+ ) with equally high efficiency. In contrast to previous crystallographic results, we show that the selectivity filter (SF) of NaK in native-like lipid membranes adopts two distinct conformations that are stabilized by either Na+ or K+ ions. The atomic differences of these conformations are resolved by solid-state NMR (ssNMR) spectroscopy and molecular dynamics (MD) simulations. Besides the canonical K+ permeation pathway, we identify a side entry ion-conduction pathway for Na+ permeation unique to NaK...
February 19, 2018: Nature Communications
Brian K Yoo, Yiling Xiao, Dan McElheny, Yoshitaka Ishii
Cross-seeding of misfolded amyloid proteins is believed to induce cross-species infection of prion diseases. In sporadic Alzheimer's disease (AD), misfolding of 42-residue β-amyloid (Aβ) is widely considered to trigger amyloid plaque deposition. Despite increasing evidence that misfolded Aβ mimics prions, interactions of misfolded 42-residue Aβ42 with more abundant 40-residue Aβ40 in AD are elusive. This study presents in-vitro evidence that a heterozygous E22G pathogenic ("Arctic") mutation of Aβ40 can enhance misfolding of Aβ via cross-seeding from wild-type (WT) Aβ42 fibril...
February 9, 2018: Journal of the American Chemical Society
Conor M Haney, E James Petersson
The neuronal protein α-synuclein (αS) plays a key role in Parkinson's disease, forming inclusions termed Lewy bodies and Lewy neurites. Recent improvements in cryo-electron diffraction and solid state NMR (ssNMR) have led to the elucidation of the structures of peptides derived from the αS fibril core and full-length human αS in fibrils. Despite the valuable insight offered by these methods, there are still several questions about the structures' relevance to pathological aggregates. Herein, we present fluorescence data collected in vitro under the conditions which fibrils are typically assembled...
January 18, 2018: Chemical Communications: Chem Comm
Silvina Orlandi, Josefina Priotti, Hermínio P Diogo, Dario Leonardi, Claudio J Salomon, Teresa G Nunes
Praziquantel (PZQ) is the recommended, effective, and safe treatment against all forms of schistosomiasis. Solid dispersions (SDs) in water-soluble polymers have been reported to increase solubility and bioavailability of poorly water-soluble drugs like PZQ, generally due to the amorphous form stabilization. In this work, poloxamer (PLX) 237 and poly(vinylpyrrolidone) (PVP) K30 were evaluated as potential carriers to revert PZQ crystallization. Binary and ternary SDs were prepared by the solvent evaporation method...
April 2018: AAPS PharmSciTech
Yufei Yang, Shenlin Wang
The structures of RNAs, which play critical roles in various biological processes, provide important clues and insights into the biological functions of these molecules. However, RNA structure determination remains a challenging topic. In recent years, magic-angle-spinning solid-state NMR (MAS SSNMR) has emerged as an alternative technique for structural and dynamic characterization of RNA. MAS SSNMR has been successfully applied to provide atomic-level structural information about several RNA molecules and RNA-protein complexes...
December 25, 2017: Chemistry: a European Journal
Songlin Wang, T Gopinath, Gianluigi Veglia
Oriented sample solid-state NMR (OS-ssNMR) spectroscopy is uniquely suited to determine membrane protein topology at the atomic resolution in liquid crystalline bilayers under physiological temperature. However, the inherent low sensitivity of this technique has hindered the throughput of multidimensional experiments necessary for resonance assignments and structure determination. In this work, we show that doping membrane protein bicelle preparations with paramagnetic ion chelated lipids and exploiting paramagnetic relaxation effects it is possible to accelerate the acquisition of both 2D and 3D multidimensional experiments with significant saving in time...
December 22, 2017: Methods: a Companion to Methods in Enzymology
Tetyana I Levchenko, Bryan E G Lucier, John F Corrigan, Yining Huang
Systematic111 Cd solid-state (SS) NMR experiments were performed to correlate X-ray crystallographic data with SSNMR parameters for a set of CdS-based materials, varying from molecular crystals of small complexes [Cd(SPh)4 ]2- and [Cd4 (SPh)10 ]2- to superlattices of large monodisperse clusters [Cd54 S32 (SPh)48 (dmf)4 ]4- and 1.9 nm CdS. Methodical data analysis allowed for assigning individual resonances or resonance groups to particular types of cadmium sites residing in different chemical and/or crystallographic environments...
January 2, 2018: Inorganic Chemistry
Yoshitaka Ishii, Ayesha Wickramasinghe, Isamu Matsuda, Yuki Endo, Yuji Ishii, Yusuke Nishiyama, Takahiro Nemoto, Takayuki Kamihara
Proton-detected solid-state NMR (SSNMR) spectroscopy has attracted much attention due to its excellent sensitivity and effectiveness in the analysis of trace amounts of amyloid proteins and other important biological systems. In this perspective article, we present the recent sensitivity limit of1 H-detected SSNMR using "ultra-fast" magic-angle spinning (MAS) at a spinning rate (νR ) of 80-100 kHz. It was demonstrated that the high sensitivity of1 H-detected SSNMR at νR of 100 kHz and fast recycling using the paramagnetic-assisted condensed data collection (PACC) approach permitted "super-fast" collection of1 H-detected 2D protein SSNMR...
January 2018: Journal of Magnetic Resonance
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