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chemical shift

Kaspar Valgepea, Renato de Souza Pinto Lemgruber, Kieran Meaghan, Robin William Palfreyman, Tanus Abdalla, Björn Daniel Heijstra, James Bruce Behrendorff, Ryan Tappel, Michael Köpke, Séan Dennis Simpson, Lars Keld Nielsen, Esteban Marcellin
Acetogens are promising cell factories for producing fuels and chemicals from waste feedstocks via gas fermentation, but quantitative characterization of carbon, energy, and redox metabolism is required to guide their rational metabolic engineering. Here, we explore acetogen gas fermentation using physiological, metabolomics, and transcriptomics data for Clostridium autoethanogenum steady-state chemostat cultures grown on syngas at various gas-liquid mass transfer rates. We observe that C. autoethanogenum shifts from acetate to ethanol production to maintain ATP homeostasis at higher biomass concentrations but reaches a limit at a molar acetate/ethanol ratio of ∼1...
May 16, 2017: Cell Systems
Akhnef A Fatykhov, Elvira A Sedova, Aleksander Е Egorov, Sergey N Salazkin, Vladimir A Kraikin
All (1) H and (13) C NMR signals of the four poly(phenylenephthalides): polydiphenylenephthalide (P(DPh)-1), polyterphenylenephthalide (P(TPh)-2) and two sequentially ordered polymers with different ratios of alternating diphenylenephthalide and terphenylenephthalide units (P(DTPh)-3, P(DDTPh)-4) were assigned unequivocally with two-dimensional NMR techniques ((1) H-(1) H COSY and NOESY; (1) H-(13) C HSQC and HMBC). There are four types of polyphenylene fragments: not symmetrical end, symmetrical inner, symmetrical pre-end, and formally symmetric pre-end...
May 18, 2017: Magnetic Resonance in Chemistry: MRC
Carolin Reischauer, Andreas Hock, Orpheus Kolokythas, Christoph A Binkert, Andreas Gutzeit
PURPOSE: To demonstrate that fully navigated magnetic resonance spectroscopy (MRS) with inner-volume saturation (IVS) at 3 T results in high-quality spectra that permit evaluating metabolic changes in hepatic metastases without the need for patient compliance. METHODS: Nine patients with untreated, biopsy-proven large hepatic metastases (minimum diameter of 3 cm) were included. In each patient, localized proton MRS was performed in the metastatic lesion and in uninvolved liver parenchyma...
May 18, 2017: Abdominal Radiology
Nandakumar Rajasekaran, Athi N Naganathan
Elucidating the extent of energetic coupling between residues in single-domain proteins, a fundamental determinant of allostery, information transfer and folding cooperativity, has remained a grand challenge. While several sequence- and structure-based approaches have been proposed, a self-consistent description that is simultaneously compatible with unfolding thermodynamics is lacking. We had recently developed a simple structural perturbation protocol that captures the changes in thermodynamic stabilities induced by point mutations within the protein interior...
May 18, 2017: Biochemical Journal
M L Mei, F Nudelman, B Marzec, J M Walker, E C M Lo, A W Walls, C H Chu
Silver diamine fluoride (SDF) is found to promote remineralization and harden the carious lesion. Hydroxyapatite crystallization is a crucial process in remineralization; however, the role of SDF in crystal formation is unknown. We designed an in vitro experiment with calcium phosphate with different SDF concentrations (0.38, 1.52, 2.66, 3.80 mg/mL) to investigate the effect of this additive on the nucleation and growth of apatite crystals. Two control groups were also prepared-calcium phosphate (CaCl2·2H2O + K2HPO4 in buffer solution) and SDF (Ag[NH3]2F in buffer solution)...
May 1, 2017: Journal of Dental Research
Antonietta Cerulli, Gianluigi Lauro, Milena Masullo, Vincenza Cantone, Beata Olas, Bogdan Kontek, Filomena Nazzaro, Giuseppe Bifulco, Sonia Piacente
The methanol extract of the leafy covers of Corylus avellana, source of the Italian PGI (protected geographical indication) product "Nocciola di Giffoni", afforded two new cyclic diarylheptanoids, giffonins T and U (2 and 3), along with two known cyclic diarylheptanoids, a quinic acid, flavonoid-, and citric acid derivatives. The structures of giffonins T and U were determined as highly hydroxylated cyclic diarylheptanoids by 1D and 2D NMR experiments. Their relative configurations were assigned by a combined quantum mechanical/NMR approach, comparing the experimental (13)C/(1)H NMR chemical shift data and the related predicted values...
May 18, 2017: Journal of Natural Products
Weidong Hu, Allen Mao, Patty Wong, Adrien Larsen, Paul J Yazaki, Jeffrey Y C Wong, John E Shively
Polyethyleneglycol (PEG) lipid nanoparticles (LNPs) spontaneously assemble in water forming uniform sized nanoparticles incorporating drugs with prolonged blood clearance over drugs alone. Previously, DSPE-PEG2000 and several drug adducts, including doxorubicin, were analyzed by a combination of physical and molecular dynamic (MD) studies. In this study a complete chemical shift assignment of DSPE-PEG2000 plus or minus doxorubicin was achieved using NMR 1D-selNOESY, NOESY, COSY, TOCSY, HSQC and HSQC-TOCSY. Chemical shift perturbation, titration, relaxation enhancement and NOESY analysis combined with MD reveal detailed structural information at the atomic level including location of doxorubicin in the micelle, its binding constant, the hydrophilic shell organization and the mobility of PEG2000 tail, demonstrating NMR spectroscopy can characterize drug-DSPE-PEG2000 micelles with molecular weights above 180kDa...
May 18, 2017: Bioconjugate Chemistry
Ting-Zheng Hou, Wen-Tao Xu, Xiang Chen, Hong-Jie Peng, Jia-Qi Huang, Qiang Zhang
Lithium-sulfur (Li-S) battery is a promising high-energy-density energy storage system. The strong anchoring of intermediates is widely accepted to retard the shuttle of polysulfides in a working battery. However, the understanding of the intrinsic chemistry is still deficient. Inspired by the concept of hydrogen bond, herein we focus on the Li bond chemistry in Li-S batteries through sophisticated quantum chemical calculations, in combination with 7Li nuclear magnetic resonance (NMR). Identified as Li bond, the strong dipole-dipole interaction between Li polysulfides and Li-S cathode materials originates from the electron-rich donors (e...
May 18, 2017: Angewandte Chemie
Ching-Hwa Ho, Zhan-Zhi Liu, Min-Han Lin
ReS2 and ReSe2 have recently been enthusiastically studied owing to the specific in-plane electrical, optical and structural anisotropy caused by their distorted one-layer trigonal (1 T) phase, whereas other traditional transition-metal dichalcogenides (TMDCs, e.g. MoS2 and WSe2) have a hexagonal structure. Because of this special property, more and versatile nano-electronics and nano-optoelectronics devices can be developed. In this work, 2D materials in the series ReS2-x Se x (0 ≤ x ≤ 2) have been successfully grown by the method of chemical vapor transport...
June 9, 2017: Nanotechnology
Kenneth T Bogen
Kelch-like ECH-associated protein 1 (Keap1), nuclear factor erythroid 2-like factor 2-related factor 2 (Nrf2), and the antioxidant response element (ARE) are interacting components of a master regulatory signaling pathway that coordinates redox homeostasis, cytoprotective responses, and shifts in stem cell state. This study reexamined detailed dose-response (DR) data reported for in vitro Nrf2-ARE activation in human hepatoblastoma HepG2 cell lines containing either a ARE-bla or ARE-luc reporter at 12 different concentrations of each of 15 chemicals...
April 2017: Dose-response: a Publication of International Hormesis Society
Ol'ha O Brovarets', Ivan S Voiteshenko, Horacio Pérez-Sánchez, Dmytro M Hovorun
This work is devoted to the careful QM/QTAIM analysis of the evolution of the basic physico-chemical parameters along the intrinsic reaction coordinate (IRC) of the biologically important 2AP∙T(WC)↔2AP∙T*(w) and 2AP·C*(WC)↔2AP·C(w) Watson-Crick(WC)↔wobble(w) tautomeric transformations obtained at each point of the IRC using original authors' methodology. Established profiles reflect the high similarity between the courses of these processes. Basing on the scrupulous analysis of the profiles of their geometric and electron-topological parameters it was established that the dipole-active WC↔w tautomerisations of the Watson-Crick-like 2AP∙T(WC) / 2AP·C*(WC) mispairs, stabilized by the two classical N3H···N1, N2H···O2 and one weak C6H···O4/N4 H-bonds, into the wobble 2AP∙T*(w)/ 2AP·C(w) base pairs, respectively, joined by the two classical N2H···N3 and O4/N4H···N1 H-bonds, proceed via the concerted stepwise mechanism through the sequential intrapair proton transfer and subsequent large-scale shifting of the bases relative each other, through the planar, highly stable, zwitterionic transition states stabilized by the participation of the four H-bonds - N1(+)H···O4(-)/N4(-), N1(+)H···N3(-), N2(+)H···N3(-) and N2(+)H···O2(-)...
May 18, 2017: Journal of Biomolecular Structure & Dynamics
Michael J Gladys, Jeong Woo Han, Therese S Pedersen, Anton Tadich, Kane M O'Donnell, Lars Thomsen
Chiral separation using heterogeneous methods has long been sought after. Chiral metal surfaces have the potential to make it possible to model these systems using small amino acids, the building blocks for proteins. A comparison of submonolayer concentrations of alanine enantiomers adsorbed onto Cu{421}(R) has revealed a large geometrical differences between the two molecules as compared to the saturated coverage. Large differences were observed in HR-XPS and NEXAFS and complemented by theoretical DFT calculations...
May 17, 2017: Physical Chemistry Chemical Physics: PCCP
Michael G Siskos, M Iqbal Choudhary, Ioannis P Gerothanassis
Numerous gas phase electron diffraction, ultra-fast electron diffraction, X-ray and neutron diffraction experiments on β-dicarbonyl compounds exhibiting enol-enol tautomeric equilibrium, with emphasis on acetylacetone and dibenzoylmethane, have so far been reported with conflicting results on the structural details of the O-HO intramolecular hydrogen bond and resulted in alternative hypotheses on the intramolecular hydrogen bond potential function either a double minimum potential corresponding to two tautomeric forms in equilibrium or a single symmetrical one...
May 17, 2017: Organic & Biomolecular Chemistry
Xiaopeng Fan, Weihao Zheng, Hongjun Liu, Xiujuan Zhuang, Peng Fan, Yanfang Gong, Honglai Li, Xueping Wu, Ying Jiang, Xiaoli Zhu, Qinglin Zhang, Hong Zhou, Wei Hu, Xiao Wang, Xiangfeng Duan, Anlian Pan
Recombination dynamics during photoluminescence (PL) in two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDs) are complicated and can be easily affected by the surroundings because of their atomically thin structures. Herein, we studied the excitation power and temperature dependence of the recombination dynamics on the chemical vapor deposition-grown monolayer WS2via a combination of Raman, PL, and time-resolved PL spectroscopies. We found a red shift and parabolic intensity increase in the PL emission of the monolayer WS2 with the increasing excitation power and the decay time constants corresponding to the recombination of trions and excitons from transient PL dynamics...
May 17, 2017: Nanoscale
Shogo Toda, Shinsuke Shigeto
Water confined on a nanometer scale plays an essential role in various chemical and biological processes. Confined water molecules are often exposed to electric fields as manifested by those that occur on protein surfaces or in electrical double layers, but the electric field effects on confined water are not fully understood. We used IR electroabsorption (EA) spectroscopy with unprecedented sensitivity to observe electric-field-induced changes in the OH stretching absorption of water (H2O) molecules dissolved in 1,4-dioxane, which constitute a simple model system for confined water...
May 17, 2017: Journal of Physical Chemistry. B
R Viswanath, H S Bhojya Naik, G Arun Kumar, I K Suresh Gowda, S Yallappa
Luminescence technology has been improved with the help of semiconductor nanoparticles that possess novel optical and electrical properties compared with their bulk counterpart. The aim of this study was to design semiconductor nanocrystals in their pure (ZnS) or doped form (ZnS:Mn) with different concentrations of Mn(2+) ions by a wet chemical route stabilized by ethylenediamine tetra-acetic acid (EDTA) and to evaluate their luminescence properties. The nanocrystals were characterized by physicochemical techniques such as X-ray diffraction (XRD), High-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SEAD), EDS, and ultraviolet (UV)-visible light and photoluminescence (PL) studies...
May 16, 2017: Luminescence: the Journal of Biological and Chemical Luminescence
Jinxing Liang, Jing Zhang, Wenxiang Zhou, Toshitsugu Ueda
When the quartz crystal microbalance (QCM) is used in liquid for adsorption or desorption monitoring based bio- or chemical sensing applications, the frequency shift is not only determined by the surface mass change, but also by the change of liquid characteristics, such as density and viscosity, which are greatly affected by the liquid environmental temperature. A monolithic dual-channel QCM is designed and fabricated by arranging two QCM resonators on one single chip for cancelling the fluctuation induced by environmental factors...
May 16, 2017: Sensors
Alexandra Fumasoli, Helmut Buergmann, David G Weissbrodt, George F Wells, Karin Beck, Joachim Mohn, Eberhard Morgenroth, Kai M Udert
Ammonia oxidation decreases the pH in wastewaters where the alkalinity is limited relative to the total ammonia. The activity of ammonia oxidizing bacteria (AOB), however, typically decreases with pH and often ceases completely in slightly acidic wastewaters. Nevertheless, low pH nitrification has been reported in reactors treating human urine, but it is not clear which organisms are involved. In this study, we followed the population dynamics of ammonia oxidizing organisms and reactor performance in synthetic, synthetic fully hydrolysed urine as the pH decreased over time in response to a decrease in the loading rate...
May 16, 2017: Environmental Science & Technology
Daniel M Kroupa, Márton Vörös, Nicholas P Brawand, Brett W McNichols, Elisa M Miller, Jing Gu, Arthur J Nozik, Alan Sellinger, Giulia Galli, Matthew C Beard
Band edge positions of semiconductors determine their functionality in many optoelectronic applications such as photovoltaics, photoelectrochemical cells and light emitting diodes. Here we show that band edge positions of lead sulfide (PbS) colloidal semiconductor nanocrystals, specifically quantum dots (QDs), can be tuned over 2.0 eV through surface chemistry modification. We achieved this remarkable control through the development of simple, robust and scalable solution-phase ligand exchange methods, which completely replace native ligands with functionalized cinnamate ligands, allowing for well-defined, highly tunable chemical systems...
May 16, 2017: Nature Communications
Kannan Natarajan, Andrew C McShan, Jiansheng Jiang, Vlad K Kumirov, Rui Wang, Huaying Zhao, Peter Schuck, Mulualem E Tilahun, Lisa F Boyd, Jinfa Ying, Ad Bax, David H Margulies, Nikolaos G Sgourakis
The molecular mechanism through which the interaction of a clonotypic αβ T-cell receptor (TCR) with a peptide-loaded major histocompatibility complex (p/MHC) leads to T-cell activation is not yet fully understood. Here we exploit a high-affinity TCR (B4.2.3) to examine the structural changes that accompany binding to its p/MHC ligand (P18-I10/H2-D(d)). In addition to conformational changes in complementarity-determining regions (CDRs) of the TCR seen in comparison of unliganded and bound X-ray structures, NMR characterization of the TCR β-chain dynamics reveals significant chemical shift effects in sites removed from the MHC-binding site...
May 16, 2017: Nature Communications
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