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Hydrogen Bonding

Kuan-Ju Chen, Hsin-Ling Chen, Chen-Chi Tang, Hsu-Heng Wu, Jeng-Shiung Jan
Biomimetic synthesis of silica/polymer hybrid nanomaterials inspired by silica-condensing microorganisms has gained significant advances in recent years and the as-prepared hybrid materials have been explored for a variety of applications. In this work, silica/polypeptide hybrid nanoparticles (NPs) and coating films can be facilely fabricated by silica mineralization of poly(l-lysine)-block-poly(l-threonine)/poly(l-glutamic acid) (PLL-b-PLT/PGA) fibril complexes assembled in solutions or on substrates at benign conditions...
February 6, 2019: Journal of Colloid and Interface Science
Jin Wu, Zixuan Wu, Xing Lu, Songjia Han, Bo-Ru Yang, Xuchun Gui, Kai Tao, Jianmin Miao, Chuan Liu
Ionic hydrogels, a class of intrinsically stretchable and conductive materials, are widely used in soft electronics. However, the easy freezing and drying of water-based hydrogels significantly limit their long-term stability. Here, a facile solvent-replacement strategy is developed to fabricate ethylene glycol (Eg)/glycerol (Gl)-water binary anti-freezing and anti-drying organohydrogels for ultrastretchable and sensitive strain sensing within a wide temperature range. Due to the ready formation of strong hydrogen bonds between Eg/Gl and water molecules, the organohydrogels gain exceptional freezing and drying tolerance with retained deformability, conductivity and self-healing ability even stay at extreme temperature for a long time...
February 14, 2019: ACS Applied Materials & Interfaces
Martin Brehm, Martin Pulst, Joerg Kressler, Daniel Sebastiani
We present first results on triazolium-based ionic liquids (ILs) as a novel class of non-derivatising solvents for cellulose. Despite their chemical similarity to imidazolium cations, the 1,2,3-triazolium cation lacks the isolated ring proton, leading to reduced formation of N-heterocyclic carbenes (NHCs), and therefore to lower reactivity and less unwanted side reactions. We synthesised six ILs based on 1,2,3-triazolium and 1,2,4-triazolium cations. The acetates are room temperature ionic liquids (RTILs) and dissolve a similar amount of cellulose as the corresponding imidazolium salt...
February 14, 2019: Journal of Physical Chemistry. B
Sheng Xie, Sesha Manuguri, Olof Ramström, Mingdi Yan
The fluorescence properties of AIE-active N-amidinated fluoroquinolones, efficiently obtained by a perfluoroaryl azide-aldehyde-amine reaction, have been studied. The fluorophores were discovered to elicit a highly sensitive fluorescence quenching response towards guest molecules with hydrogen-bond-donating ability. This effect was evaluated in a range of protic/aprotic solvents with different H-bonding capabilities, and also in aqueous media. The influence of acid/base was furthermore addressed. The hydrogen-bonding interactions were studied by IR, NMR, UV-Vis and time-resolved fluorescence decay, revealing their roles in quenching of the fluorescence emission...
February 14, 2019: Chemistry, An Asian Journal
Tomoo Miyahara, Hiroshi Nakatsuji
Bacteriorhodopsin (BR) and Halorhodopsin (HR) are well-known light-driven ion-pumping rhodopsins. BR transfers a proton from the intracellular medium to the extracellular medium. HR takes in chloride-ion from the extracellular medium. A new light-driven sodium-ion-pumping rhodopsin was discovered in 2013 by Inoue, Kandori and co-workers (Nat. Commun. 2013, 4, 1678). The purpose of this article is to elucidate the proton, sodium-ion and chloride-ion transfer mechanisms and the geometrical changes of the intermediates...
February 14, 2019: Journal of Physical Chemistry. A
Yan-Zhen Zheng, Geng Deng, Rui Guo, Da-Fu Chen, Li-Ming Wu
Flavonoids are vital constituents of propolis that are responsible for its medicinal activity. Flavonoid extraction commonly employs ethanol and water as solvents. In the extraction reaction, hydrogen-bonding interactions play a crucial role. In this study, hydrogen-bonding interactions between myricetin-an abundant flavonoid in propolis-and ethanol or water were studied theoretically using density functional theory (DFT) methods. The molecular geometry and charge properties of the myricetin monomer were analyzed first...
February 14, 2019: Journal of Molecular Modeling
Wanqing Wei, Yani Chen, Daiqian Xie, Yanzi Zhou
Chymotrypsin inhibitor 2 (CI2) is a special serine protease inhibitor which can resist hydrolysis for several days with a rapid equilibrium between the Michaelis complex and acyl-enzyme intermediate. The energies and conformational changes for subtilisin-catalyzed proteolysis of CI2 were examined in this paper for the first time by employing pseudo bond ab initio QM/MM MD simulations. In the acylation reaction, a low-barrier hydrogen bond between His64 and Asp32 in the transition state together with the lack of covalent backbone constraints makes the peptide bonds of CI2 break more easily than in other serine protease inhibitors...
February 14, 2019: Physical Chemistry Chemical Physics: PCCP
Zongzhao Sun, Yabin Jiang, Lei Zeng, Limin Huang
Inspired by D-A polymers in organic solar cell and extended conjugate effect, a conceptual design of D-π-A type mesoporous carbon nitride with benzene or thiophene as π-spacer is proposed as an efficient photocatalyst for hydrogen evolution and successfully synthesized in one-pot thermopolymerization based on nucleophilic substitution and Schiff base chemical reaction. On the molecular level, the inserted in-plane benzene as π-spacer by forming covalent bonds C=N (acceptor) and C-N (donor) interrupts the continuity of 3, s-triazine units while it maintains the intrinsic π-π conjugated electronic system...
February 13, 2019: ChemSusChem
Jiaxin Wang, Lixiang Yang, Daixi Li, Ying Xu, Li Yang, Hong Zhao, Zhuangzhi Zhu, Hansen Luan, Qiong Luo
The mechanism of L-Val on how to improve the stability of gabapentin (GBP) was described by the combination of chemical analysis experiments and computer simulations. Scanning electron microscope (SEM), powder X-ray diffraction (PXRD), and differential scanning calorimeter (DSC), coupled with attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), were used to identify β-GBP prepared by rapid solvent removal method. The reaction barriers on crystal planes, β-GBP (100) and β-GBP (10-1), are smaller than α-GBP and γ-GBP, reaching 276...
February 13, 2019: AAPS PharmSciTech
Minhye Shin, Alexandra R Mey, Shelley M Payne
The Feo ferrous iron transporter is widely distributed among bacteria and archaea, but its mechanism of transport has not been fully elucidated. In Vibrio cholerae , the transport system requires three proteins: the small cytosolic proteins FeoA and FeoC and a large cytoplasmic-membrane-associated protein FeoB, which has an N-terminal G-protein domain. We show that, in contrast to Escherichia coli FeoB, which is solely a GTPase, the V. cholerae and Helicobacter pylori FeoB proteins have both GTPase and ATPase activity...
February 13, 2019: Proceedings of the National Academy of Sciences of the United States of America
Yi Jia, Junbai Li
Layer-by-layer (LbL) assembly is a most commonly used method to prepare various microcapsules based on the electrostatic interactions, hydrogen bonding and covalent bonding so on. Among these interactions, Schiff base bond formed in covalent assembly not only has an advantage in stability, but also enables the assembled microcapsules with autofluorescence and pH-sensitivity. In this feature article, we will mainly describe the construction of biomimetic microcapsules through Schiff base mediated LbL assembly...
February 13, 2019: Langmuir: the ACS Journal of Surfaces and Colloids
Aditi Wagle, Su Hui Seong, Srijan Shrestha, Hyun Ah Jung, Jae Sue Choi
In the search for natural products having a dual inhibitory action on diabetes and Alzheimer's disease, this study investigated the activity of different parts of Korean thistle ( Cirsium japonicum var. maackii (Maxim.) Matsum), and its fractional constituents by in vitro enzymatic and in silico molecular docking studies. Cirsium maackii has been used as a traditional medicine for the treatment of several diseases. The ethyl acetate and dichloromethane fractions of a leaf extract showed α-glucosidase and BACE1 inhibitory activity, respectively...
February 12, 2019: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Chi-Tung Yeung, Wesley Ting Kwok Chan, Wai-Sum Lo, Ga-Lai Law, Wing-Tak Wong
The synthesis of a new CF₃-containing stereogenic atropisomeric pair of ortho-disubstituted biphenyl scaffold is presented. The atropisomers are surprisingly conformationally stable for isolation. X-ray structures show that their stability comes from an intramolecular hydrogen bond formation from their two hydroxyl groups and renders the spatial arrangement of their peripheral CF₃ and CH₃ groups very different. The synthesized stereogenic scaffold proved to be effective in catalyzing the asymmetric N -nitroso aldol reaction of enamine and nitrosobenzene...
February 12, 2019: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Kamarza Mulia, Farah Fauzia, Elsa Anisa Krisanti
Mangosteen ( Garcinia mangostana L.) is a fruit that is rich in xanthones, utilized as health supplements or additives in food products due to their high antioxidant activities. Choline chloride (ChCl)-based deep eutectic solvents (DESs) with polyalcohols (ethylene glycol, glycerol, propanediols, and butanediols) as hydrogen bonding donors (HBDs) were used to extract the xanthones from the pericarp of mangosteen. DESs with 1,2-propanediol, 1,3-propanediol, and 1,2-butanediol as HBDs (ChCl to HBD mole ratio of 1:3) afforded the highest extraction yields (2...
February 12, 2019: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Sohag Biswas, Bhabani S Mallik
The extent to which the ions affect the nearby water molecules will decide the structure-making or breaking nature of those ions in aqueous solutions. The effects of a weakly coordinating anion on the structure, dynamics and vibrational properties of water molecules are not so significant as compared to an anion capable of making strong ion-water hydrogen bonds. The present work deals with the first principles molecular dynamics study of an aqueous solution of such a weakly coordinating anion, tetrafluoroborate (BF4-), using dispersion-corrected DFT based first principles molecular dynamics (FPMD) simulations...
February 13, 2019: Journal of Physical Chemistry. B
Tomasz Oniszczuk, Maciej Combrzyński, Arkadiusz Matwijczuk, Anna Oniszczuk, Bożena Gładyszewska, Janusz Podleśny, Grzegorz Czernel, Dariusz Karcz, Agnieszka Niemczynowicz, Agnieszka Wójtowicz
The paper presents the results of studies related to the impact of functional additives in the form of polylactide (PLA), polyvinyl alcohol (PVA), and keratin hydrolysate (K) on the physical characteristics of biopolymer foils. TPS granulate was obtained using a TS-45 single-screw extruder with L/D = 16. Foil was produced with the use of an L/D = 36 extruder with film-blowing section. The impact of the quantity and type of the functional additives on the processing efficiency and energy consumption of granulate extrusion, as well as the physical characteristics of the foil produced: thickness, basis weight, and colour were determined...
2019: PloS One
Jingjing Xu, Franck Merlier, Bérangère Avalle, Vincent Vieillard, Patrice Debré, Karsten Haupt, Bernadette Tse Sum Bui
We describe the preparation and characterization of synthetic antibodies based on molecularly imprinted polymer nanoparticles (MIP-NPs), for the recognition and binding of the highly conserved and specific peptide motif SWSNKS (3S), an epitope of the envelope glycoprotein 41 (gp41) of human immunodeficiency virus type 1 (HIV-1). This motif is implicated in the decline of CD4+ T cells and leads to the deterioration of the immune system during HIV infection. Therefore, the development of MIP-NPs that can target and block the 3S peptide to prevent subsequent cascade interactions directed toward the killing of CD4+ T cells is of prime importance...
February 13, 2019: ACS Applied Materials & Interfaces
Fernan Saiz, Leonardo Bernasconi
We investigate the potential use of Fe(iv)oxo species supported on a metal-organic framework in the catalytic hydroxylation of methane to produce methanol. We use periodic density-functional theory calculations at the 6-31G**/B3LYP level of theory to study the electronic structure and chemical reactivity in the hydrogen abstraction reaction from methane in the presence of Fe(iv)O(oxo) supported on MOF-74. Our results indicate that the Fe(iv)O moiety in MOF-74 is characterised by a highly reactive (quintet) ground-state, with a distance between Fe(iv) and O(oxo) of 1...
February 13, 2019: Physical Chemistry Chemical Physics: PCCP
Xiaolin Jiang, Jiahui Zhang, Dongmei Zhao, Yuehui Li
The presence of different aldehydes is found to have a significant influence on the catalytic performance when using PN(H)P type ligands for dehydrogenation of alcohols. Accordingly, hybrid multi-dentate ligands were discovered based on an oxygen-transfer alkylation of PNP ligands by aldehydes. The relevant Ru-PNN(PO) system provided the desired unsymmetrical esters in good yields via acceptorless dehydrogenation of alcohols. Hydrogen bonding interactions between the phosphine oxide moieties and alcohol substrates likely assisted the observed high chemoselectivity...
February 13, 2019: Chemical Communications: Chem Comm
Yan Xu, Xiaotian Qi, Pengfei Zheng, Carlo C Berti, Peng Liu, Guangbin Dong
Carbon-hydrogen (C-H) and carbon-carbon (C-C) bonds are the main constituents of organic matter. The recent advancement of C-H functionalization technology has vastly expanded our toolbox for organic synthesis1 . In contrast, C-C activation methods that allow editing of the molecular skeleton remain limited2- . So far, a number of methods have appeared for catalytic C-C activation, particularly with ketone substrates, which are typically promoted either by ring-strain release as a thermodynamic driving force4,6 or using directing groups5,7 to control the reaction outcome...
January 30, 2019: Nature
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