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https://www.readbyqxmd.com/read/28542493/the-in-vivo-structure-of-biological-membranes-and-evidence-for-lipid-domains
#1
Jonathan D Nickels, Sneha Chatterjee, Christopher B Stanley, Shuo Qian, Xiaolin Cheng, Dean A A Myles, Robert F Standaert, James G Elkins, John Katsaras
Examining the fundamental structure and processes of living cells at the nanoscale poses a unique analytical challenge, as cells are dynamic, chemically diverse, and fragile. A case in point is the cell membrane, which is too small to be seen directly with optical microscopy and provides little observational contrast for other methods. As a consequence, nanoscale characterization of the membrane has been performed ex vivo or in the presence of exogenous labels used to enhance contrast and impart specificity...
May 2017: PLoS Biology
https://www.readbyqxmd.com/read/28541559/hydraulic-redistribution-under-moderate-drought-among-english-oak-european-beech-and-norway-spruce-determined-by-deuterium-isotope-labeling-in-a-split-root-experiment
#2
Benjamin D Hafner, Martina Tomasella, Karl-Heinz Häberle, Marc Goebel, Rainer Matyssek, Thorsten E E Grams
Hydraulic redistribution (HR) of soil water through plant roots is a crucial phenomenon improving the water balance of plants and ecosystems. It is mostly described under severe drought, and not yet studied under moderate drought. We tested the potential of HR under moderate drought, hypothesizing that (H1) tree species redistribute soil water in their roots even under moderate drought and that (H2) neighboring plants are supported with water provided by redistributing plants. Trees were planted in split-root systems with one individual (i...
May 24, 2017: Tree Physiology
https://www.readbyqxmd.com/read/28541532/constitutive-activation-of-akt2-in-humans-leads-to-hypoglycemia-without-fatty-liver-or-metabolic-dyslipidemia
#3
Marina Minic, Nuno Rocha, Julie Harris, Matthijs P Groeneveld, Sarah Leiter, Nicholas Wareham, Alison Sleigh, Pascale De Lonlay, Khalid Hussain, Stephen O'Rahilly, Robert K Semple
Context: The activating p.Glu17Lys mutation in AKT2, a kinase mediating many of insulin's metabolic actions, causes hypoinsulinemic hypoglycemia and left-sided hemihypertrophy. The wider metabolic profile and longer term natural history of the condition has not yet been reported. Objective: To characterise the metabolic and cellular consequences of the AKT2 p.Glu17Lys mutation in two previously reported males at the age of 17 years. Design/intervention: Body composition analysis using dual energy X ray absorptiometry, overnight profiling of plasma glucose, insulin and fatty acids, oral glucose tolerance testing, and magnetic resonance spectroscopy to determine hepatic triglyceride content were undertaken...
May 23, 2017: Journal of Clinical Endocrinology and Metabolism
https://www.readbyqxmd.com/read/28541050/crystal-structure-of-pr3mgni14dx-studied-by-in-situ-neutron-diffraction
#4
Kenji Iwase, Kazuhiro Mori, Naoyoshi Terashita, Suguru Tashiro, Tetsuya Suzuki
The crystal structure of Pr3MgNi14D18 was determined by neutron diffraction. The determined structure of Pr3MgNi14D18 consisted of 89.0% Gd2Co7-type structure and 11.0% PuNi3-type structure. The lattice parameters of a and c of Gd2Co7-type structure were refined at 0.52903(7) nm and 3.90179(1) nm. The deuterium atoms were distributed among nine deuterium sites in both the CaCu5-type and MgZn2-type cells. The D2 occupancy in the Pr2Ni4 octahedral sites of the CaCu5-type cell was the largest (0.75) when compared with the other deuterium sites (<0...
May 25, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28539365/functional-analysis-of-human-cytochrome-p450-21a2-variants-involved-in-congenital-adrenal-hyperplasia
#5
Chunxue Wang, Pradeep S Pallan, Wei Zhang, Li Lei, Francis K Yoshimoto, Michael R Waterman, Martin Egli, F Peter Guengerich
Cytochrome P450 (P450, CYP) 21A2 is the major steroid 21-hydroxylase, converting progesterone to 11-deoxycorticosterone and 17α-hydroxy(OH)progesterone to 11-deoxycortisol. More than 100 CYP21A2 variants give rise to congenital adrenal hyperplasia (CAH). We previously reported a structure of wild-type (WT) human P450 21A2 with bound progesterone and now present a structure bound to the other substrate (17α-OH progesterone). We found that the 17α-OH progesterone- and progesterone-bound complex structures are highly similar, with only some minor differences in surface loop regions...
May 24, 2017: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/28537076/chemoselective-azidation-of-o-alkynylaldehydes-over-3-2-cycloaddition-and-subsequent-staudinger-reaction-an-access-to-benzonaphthyridines-naphthyridines
#6
Pradeep Kumar, Trapti Aggarwal, Akhilesh K Verma
An efficient tandem approach for the chemoselective synthesis of functionalized azido-pyranoquinolines and azido-iodo-pyranoquinolines via electrophilic cyclization of o-alkynylaldehydes in presence of sodium azide under mild reaction conditions has been described. The Mechanistic studies confirm the formation of azido-pyranoquinolines through nucleophilic attack of azide on pyrilium intermediate over [3+2] cycloaddition of azide on alkyne. The synthesized azido-pyranoquinolines were transformed into benzonaphthyridines via Staudinger reaction...
May 24, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28534637/synthesis-of-cyclic-guanidines-bearing-n-arylsulfonyl-and-n-cyano-protecting-groups-via-pd-catalyzed-alkene-carboamination-reactions
#7
Luke J Peterson, Jingyi Luo, John P Wolfe
Palladium-catalyzed carboamination reactions of N-allylguanidines bearing cleavable N-cyano or N-arylsulfonyl protecting groups are described. The reactions afford cyclic guanidine products in good yield, and transformations of substrates bearing internal alkenes proceed with high diastereoselectivity. Deuterium labeling studies indicate these transformations proceed via anti-aminopalladation pathways.
May 23, 2017: Organic Letters
https://www.readbyqxmd.com/read/28533135/enhanced-local-disorder-in-a-clinically-elusive-von-willebrand-factor-provokes-high-affinity-platelet-clumping
#8
Alexander Tischer, Venkata R Machha, Juan P Frontroth, Maria A Brehm, Tobias Obser, Reinhard Schneppenheim, Leland Mayne, S Walter Englander, Matthew Auton
Mutation of the cysteines forming the disulfide loop of the platelet GPIbα adhesive A1 domain of von Willebrand factor causes quantitative VWF deficiencies in the blood and von Willebrand disease. We report two cases of transient severe thrombocytopenia induced by DDAVP-treatment. Cys1272Trp and Cys1458Tyr mutations identified by genetic sequencing implicate an abnormal gain-of-function phenotype, evidenced by thrombocytopenia, that quickly relapses back to normal platelet counts and deficient plasma VWF. Using surface plasmon resonance, analytical rheology, and hydrogen-deuterium exchange mass spectrometry (HXMS), we decipher mechanisms of A1-GPIbα mediated platelet adhesion and resolve dynamic secondary structure elements that regulate the binding pathway...
May 19, 2017: Journal of Molecular Biology
https://www.readbyqxmd.com/read/28531830/isotope-coded-derivatization-based-lc-esi-ms-ms-methods-using-a-pair-of-novel-reagents-for-quantification-of-hydroxycinnamic-acids-and-hydroxybenzoic-acids-in-fermented-brown-rice-product
#9
Shoujiro Ogawa, Kiriko Takafuji, Sumi Tsubuku, Yukiko Horie, Shigeo Ikegawa, Tatsuya Higashi
Hydroxycinnamic acids (HCAs) and hydroxybenzoic acids (HBAs) are antioxidant phytochemicals found in rice and effective for the prevention of human diseases including cancer. FBRA, which is a functional food manufactured by fermenting brown rice and rice bran with Aspergillus oryzae, has been demonstrated to have chemopreventive effects against carcinogenesis in various organs. In this study, we developed methods for the relative and absolute quantification of ferulic acid, sinapic acid, caffeic acid, protocatechuic acid and syringic acid in the FBRA and raw material (RM; unfermented brown rice and rice bran) samples by LC/ESI-MS/MS combined with derivatization using a newly developed reagent, N-(2-aminoethyl)-4-(diethylamino)benzamide (ADB) and its deuterium-coded analog, d-ADB...
May 2, 2017: Journal of Pharmaceutical and Biomedical Analysis
https://www.readbyqxmd.com/read/28530797/unexpected-biotransformation-of-the-hdac-inhibitor-vorinostat-yields-aniline-containing-fungal-metabolites
#10
Donovon A Adpressa, Kayla J Stalheim, Philip Jerome Proteau, Sandra Loesgen
The diversity of genetically encoded small molecules produced by filamentous fungi remains largely unexplored, which makes these fungi an attractive source for the discovery of new compounds. However, accessing their full chemical repertoire under common laboratory culture conditions is a challenge. Epigenetic manipulation of gene expression has become a well-established tool for overcoming this obstacle. Here we report that perturbation of the endophytic ascomycete Chalara sp. 6661, producer of the isofusidienol class of antibiotics, with the HDAC inhibitor vorinostat resulted in the production of four new modified xanthones...
May 22, 2017: ACS Chemical Biology
https://www.readbyqxmd.com/read/28515318/molecular-mechanism-of-activation-of-class-ia-phosphoinositide-3-kinases-pi3ks-by-membrane-localized-hras
#11
Braden D Siempelkamp, Manoj K Rathinaswamy, Meredith L Jenkins, John E Burke
Class IA PI3Ks are involved in the generation of the key lipid signaling molecule phosphatidylinositol 3,4,5-trisphosphate (PIP3), and inappropriate activation of this pathway is implicated in a multitude of human diseases, including cancer, inflammation, and primary immunodeficiencies. Class IA PI3Ks are activated downstream of the Ras superfamily of GTPases, and Ras-PI3K interaction plays a key role in promoting tumor formation and maintenance in Ras-driven tumors. Investigating the detailed molecular events in the Ras-PI3K interaction has been challenging because it occurs on a membrane surface...
May 17, 2017: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/28514451/structure-of-the-full-length-glucagon-class-b-g-protein-coupled-receptor
#12
Haonan Zhang, Anna Qiao, Dehua Yang, Linlin Yang, Antao Dai, Chris de Graaf, Steffen Reedtz-Runge, Venkatasubramanian Dharmarajan, Hui Zhang, Gye Won Han, Thomas D Grant, Raymond G Sierra, Uwe Weierstall, Garrett Nelson, Wei Liu, Yanhong Wu, Limin Ma, Xiaoqing Cai, Guangyao Lin, Xiaoai Wu, Zhi Geng, Yuhui Dong, Gaojie Song, Patrick R Griffin, Jesper Lau, Vadim Cherezov, Huaiyu Yang, Michael A Hanson, Raymond C Stevens, Qiang Zhao, Hualiang Jiang, Ming-Wei Wang, Beili Wu
The human glucagon receptor, GCGR, belongs to the class B G-protein-coupled receptor family and plays a key role in glucose homeostasis and the pathophysiology of type 2 diabetes. Here we report the 3.0 Å crystal structure of full-length GCGR containing both the extracellular domain and transmembrane domain in an inactive conformation. The two domains are connected by a 12-residue segment termed the stalk, which adopts a β-strand conformation, instead of forming an α-helix as observed in the previously solved structure of the GCGR transmembrane domain...
May 17, 2017: Nature
https://www.readbyqxmd.com/read/28513578/crystal-structure-of-a-multi-domain-human-smoothened-receptor-in-complex-with-a-super-stabilizing-ligand
#13
Xianjun Zhang, Fei Zhao, Yiran Wu, Jun Yang, Gye Won Han, Suwen Zhao, Andrii Ishchenko, Lintao Ye, Xi Lin, Kang Ding, Venkatasubramanian Dharmarajan, Patrick R Griffin, Cornelius Gati, Garrett Nelson, Mark S Hunter, Michael A Hanson, Vadim Cherezov, Raymond C Stevens, Wenfu Tan, Houchao Tao, Fei Xu
The Smoothened receptor (SMO) belongs to the Class Frizzled of the G protein-coupled receptor (GPCR) superfamily, constituting a key component of the Hedgehog signalling pathway. Here we report the crystal structure of the multi-domain human SMO, bound and stabilized by a designed tool ligand TC114, using an X-ray free-electron laser source at 2.9 Å. The structure reveals a precise arrangement of three distinct domains: a seven-transmembrane helices domain (TMD), a hinge domain (HD) and an intact extracellular cysteine-rich domain (CRD)...
May 17, 2017: Nature Communications
https://www.readbyqxmd.com/read/28510987/iridium-catalyzed-formyl-selective-deuteration-of-aldehydes
#14
William John Kerr, Marc Reid, Tell Tuttle
We report the first direct catalytic method for formyl-selective deuterium labeling of aromatic aldehydes under mild conditions, using an iridium-based catalyst designed to favor formyl- over aromatic C-H activation. A good range of aromatic aldehydes is selectively labeled, and a one-pot labeling/olefination protocol is also described. Computational studies support kinetic product control over competing aromatic labeling and decarbonylation pathways.
May 16, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28510287/a-dual-palladium-and-copper-hydride-catalyzed-approach-for-alkyl-aryl-cross-coupling-of-aryl-halides-and-olefins
#15
Stig D Friis, Michael T Pirnot, Lauren N Dupuis, Stephen L Buchwald
We report an efficient means of sp(2) -sp(3) cross coupling for a variety of terminal monosubstituted olefins with aryl electrophiles using Pd and CuH catalysis. In addition to its applicability to a range of aryl bromide substrates, this process was also suitable for electron-deficient aryl chlorides, furnishing higher yields than the corresponding aryl bromides in these cases. The optimized protocol does not require the use of a glovebox and employs air-stable Cu and Pd complexes as precatalysts. A reaction on 10 mmol scale further highlighted the practical utility of this protocol...
May 16, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28505411/quantification-of-endogenous-cholesterol-in-human-serum-on-paper-using-direct-analysis-in-real-time-mass-spectrometry
#16
Hua-Yi Hsieh, Li-Hua Li, Ren-Yu Hsu, Wei-Fong Kao, Ying-Chen Huang, Cheng-Chih Hsu
Blood testing for endogenous small metabolites to determine physiological and biochemical states is routine for laboratory analysis. Here we demonstrate that by combining the commercial direct analysis in real time (DART) ion source with an ion trap mass spectrometer, native cholesterol in its free alcohol form is readily detected from a few hundred nanoliters of human serum loaded onto chromatography paper. Deuterium-labeled cholesterol was used as the internal standard to obtain the absolute quantity of the endogenous cholesterol...
May 23, 2017: Analytical Chemistry
https://www.readbyqxmd.com/read/28505408/ion-mobility-hydrogen-deuterium-exchange-and-isotope-scrambling-tools-to-aid-compound-identification-in-omics-mixtures
#17
Hossein Maleki, Megan M Maurer, Nima Ronaghi, Stephen J Valentine
Liquid chromatography tandem mass spectrometry (LC-MS/MS), a widely used method for comparative 'omics analysis, experiences challenges with compound identification due to matrix effects, difficulty in separating isomer and isobaric ions, and long analysis times. Ion mobility spectrometry (IMS) has proven to be useful in separating isomer and isobar ions, however IMS-MS suffers from decreased peak capacity duet to the correlation in ion size and mass. In proof-of-principle experiments, the use of gas-phase hydrogen/deuterium exchange (HDX) combined with IMS-MS/MS techniques is demonstrated to offer advantages for compound identification...
May 15, 2017: Analytical Chemistry
https://www.readbyqxmd.com/read/28504279/the-structural-impact-of-water-sorption-on-device-quality-melanin-thin-films
#18
Andrew J Clulow, A Bernardus Mostert, Margarita Sheliakina, Andrew Nelson, Norman Booth, Paul L Burn, Ian R Gentle, Paul Meredith
The melanins are a class of pigmentary bio-macromolecules ubiquitous in the biosphere. They possess an intriguing set of physico-chemical properties and have been shown to exhibit hybrid protonic-electronic electrical conductivity, a feature derived from a process termed chemical self-doping driven by the sorption of water. Although the mechanism underlying the electrical conduction has been established, how the sorbed water interacts with the melanin structure at the physical level has not. Herein we use neutron reflectometry to study changes in the structure of synthetic melanin thin films as a function of H2O and D2O vapour pressure...
May 15, 2017: Soft Matter
https://www.readbyqxmd.com/read/28504253/dynamic-diversity-of-synthetic-supramolecular-polymers-in-water-as-revealed-by-hydrogen-deuterium-exchange
#19
Xianwen Lou, René P M Lafleur, Christianus M A Leenders, Sandra M C Schoenmakers, Nicholas M Matsumoto, Matthew B Baker, Joost L J van Dongen, Anja R A Palmans, E W Meijer
Numerous self-assembling molecules have been synthesized aiming at mimicking both the structural and dynamic properties found in living systems. Here we show the application of hydrogen/deuterium exchange (HDX) mass spectrometry (MS) to unravel the nanoscale organization and the structural dynamics of synthetic supramolecular polymers in water. We select benzene-1,3,5-tricarboxamide (BTA) derivatives that self-assemble in H2O to illustrate the strength of this technique for supramolecular polymers. The BTA structure has six exchangeable hydrogen atoms and we follow their exchange as a function of time after diluting the H2O solution with a 100-fold excess of D2O...
May 15, 2017: Nature Communications
https://www.readbyqxmd.com/read/28503999/quantitative-assessment-of-brain-glucose-metabolic-rates-using-in%C3%A2-vivo-deuterium-magnetic-resonance-spectroscopy
#20
Ming Lu, Xiao-Hong Zhu, Yi Zhang, Gheorghe Mateescu, Wei Chen
Quantitative assessment of cerebral glucose consumption rate (CMRglc) and tricarboxylic acid cycle flux (VTCA) is crucial for understanding neuroenergetics under physiopathological conditions. In this study, we report a novel in vivo Deuterium ((2)H) MRS (DMRS) approach for simultaneously measuring and quantifying CMRglc and VTCA in rat brains at 16.4 Tesla. Following a brief infusion of deuterated glucose, dynamic changes of isotope-labeled glucose, glutamate/glutamine (Glx) and water contents in the brain can be robustly monitored from their well-resolved (2)H resonances...
January 1, 2017: Journal of Cerebral Blood Flow and Metabolism
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