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https://www.readbyqxmd.com/read/28548844/two-dynamical-regimes-of-the-substrate-radical-rearrangement-reaction-in-b12-dependent-ethanolamine-ammonia-lyase-resolve-contributions-of-native-protein-configurations-and-collective-configurational-fluctuations-to-catalysis
#1
Meghan Kohne, Chen Zhu, Kurt Warncke
The kinetics of the substrate radical rearrangement reaction step in B12-dependent ethanolamine ammonia-lyase (EAL) from Salmonella typhimurium are measured over a 92 K temperature range. The observed first-order rate constants display a piecewise-continuous Arrhenius dependence, with linear regions over 295→220 K (monoexponential) and 214→203 K (biexponential) that are delineated by a kinetic bifurcation and kinks at 219 and 217 K, respectively. The results are interpreted by using a free energy landscape model and derived microscopic kinetic mechanism...
May 26, 2017: Biochemistry
https://www.readbyqxmd.com/read/28548051/xenon-gas-field-ion-source-from-a-single-atom-tip
#2
Wei-Chiao Lai, Chun-Yueh Lin, Wei-Tse Chang, Po-Chang Li, Tsu-Yi Fu, Chia-Seng Chang, T T Tsong, Ing-Shouh Hwang
Focused ion beam (FIB) systems have become powerful diagnostic and modification tools for nanoscience and nanotechnology. Gas field ion sources (GFISs) built from atomic-size emitters offer the highest brightness among all ion sources and thus can improve the spatial resolution of FIB systems. Here we show that the Ir/W(111) single-atom tip (SAT) can emit high-brightness Xe(+) ion beams with a high current stability. The ion emission current versus extraction voltage was analyzed from 150 K up to 309 K. The optimal emitter temperature for maximum Xe(+) ion emission was ∼150 K and the reduced brightness at the Xe gas pressure of 1 × 10(-4) torr is two to three orders of magnitude higher than that of a Ga liquid metal ion source, and four to five orders of magnitude higher than that of a Xe inductively coupled plasma ion source...
May 26, 2017: Nanotechnology
https://www.readbyqxmd.com/read/28543996/self-assembly-of-perylenediimide-single-strand-dna-conjugates-employing-hydrophobic-interactions-and-dna-base-pairing-to-create-a-diverse-structural-space
#3
Frederick Lewis, Ashutosh Kumar Mishra, Haim Weissman, Elisha Krieg, Kevin A Voltaw, Martin McCullagh, Boris Rybtchiinski
The self-assembly behavior of DNA conjugates possessing a perylenediimide (PDI) head group and a single N-oligonucleotide tail has been investigated using a combination of optical spectroscopy and cryogenic transmission electron microscopy (cryo-TEM) imaging. In order to obtain insight into the interplay between DNA base pairing and PDI hydrophobic interactions we employed systematic variation in the length and composition of the oligo tails. Conjugates with short (TA)n or (CG)n oligo tails (n ≤ 3) form fibers (helical or nonhelical) constructed from -stacked PDI head groups with pendent oligo tails at room temperature in aqueous solution...
May 24, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28534059/cryo-mesh-a-simple-alternative-cryopreservation-protocol
#4
B Funnekotter, E Bunn, R L Mancera
BACKGROUND: The continued development of new cryopreservation protocols has improved post-cryogenic success rates for a wide variety of plant species. Methods like the cryo-plate have proven beneficial in simplifying the cryopreservation procedure. OBJECTIVE: This study assessed the practicality of a stainless steel mesh strip (cryo-mesh) for cryopreserving shoot tips from Anigozanthos viridis. MATERIALS AND METHODS: Shoot tips of A. viridis (Kangaroo Paw) were precultured on 0...
March 2017: Cryo Letters
https://www.readbyqxmd.com/read/28534055/experimental-determination-of-surface-heat-transfer-coefficient-in-a-dry-ice-ethanol-cooling-bath-using-a-numerical-approach
#5
M V Santos, M Sansinena, N Zaritzky, J Chirife
  BACKGROUND: Dry ice-ethanol bath (-78 degree C) have been widely used in low temperature biological research to attain rapid cooling of samples below freezing temperature. The prediction of cooling rates of biological samples immersed in dry ice-ethanol bath is of practical interest in cryopreservation. The cooling rate can be obtained using mathematical models representing the heat conduction equation in transient state. Additionally, at the solid cryogenic-fluid interface, the knowledge of the surface heat transfer coefficient (h) is necessary for the convective boundary condition in order to correctly establish the mathematical problem...
March 2017: Cryo Letters
https://www.readbyqxmd.com/read/28531193/raman-microscopy-investigation-of-vitrification-induced-structural-damages-in-mature-bovine-oocytes
#6
Giulia Rusciano, Carolina De Canditiis, Gianluigi Zito, Marcello Rubessa, Maria Serena Roca, Rosa Carotenuto, Antonio Sasso, Bianca Gasparrini
Although oocyte cryopreservation has great potentials in the field of reproductive technologies, it still is an open challenge in the majority of domestic animals and little is known on the biochemical transformation induced by this process in the different cellular compartments. Raman micro-spectroscopy allows the non-invasive evaluation of the molecular composition of cells, based on the inelastic scattering of laser photons by vibrating molecules. The aim of this work was to assess the biochemical modifications of both the zona pellucida and cytoplasm of vitrified/warmed in vitro matured bovine oocytes at different post-warming times...
2017: PloS One
https://www.readbyqxmd.com/read/28529842/an-environmental-transfer-hub-for-multimodal-atom-probe-tomography
#7
Daniel E Perea, Stephan S A Gerstl, Jackson Chin, Blake Hirschi, James E Evans
Environmental control during transfer between instruments is required for samples sensitive to air or thermal exposure to prevent morphological or chemical changes prior to analysis. Atom probe tomography is a rapidly expanding technique for three-dimensional structural and chemical analysis, but commercial instruments remain limited to loading specimens under ambient conditions. In this study, we describe a multifunctional environmental transfer hub allowing controlled cryogenic or room-temperature transfer of specimens under atmospheric or vacuum pressure conditions between an atom probe and other instruments or reaction chambers...
2017: Advanced Structural and Chemical Imaging
https://www.readbyqxmd.com/read/28528639/matrix-maps-an-intuitive-software-to-acquire-analyze-and-annotate-light-microscopy-data-for-clem
#8
Martin Schorb, Frank Sieckmann
Matrix MAPS provides an intuitive interface for acquiring light microscopy data during a correlative light and electron microscopy experiment either at room or cryogenic temperatures. First, the user graphically defines the geometry of the acquisition region on top of preview images. Multiple independent regions can then be imaged in an automated way, each with individual settings. The same interface allows the user to mark and select points or regions of interest whose coordinates can subsequently be transferred directly to the electron microscope...
2017: Methods in Cell Biology
https://www.readbyqxmd.com/read/28527443/competition-between-weak-oh%C3%A2-%C3%AF-and-ch%C3%A2-o-hydrogen-bonds-thz-spectroscopy-of-the-c2h2-h2o-and-c2h4-h2o-complexes
#9
J Andersen, J Heimdal, B Nelander, R Wugt Larsen
THz absorption spectra have been recorded for the weakly bound molecular complexes of H2O with C2H4 and C2H2 embedded in cryogenic neon matrices at 2.8 K. The observation and assignment of a large-amplitude acceptor OH librational mode of the C2H2-H2O complex at 145.5 cm(-1) confirms an intermolecular CH⋯O hydrogen-bonded configuration of C2v symmetry with the H2O subunit acting as the hydrogen bond acceptor. The observation and assignment of two large-amplitude donor OH librational modes of the C2H4-H2O complex at 255...
May 21, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28524687/observation-of-oscillatory-radial-electric-field-relaxation-in-a-helical-plasma
#10
J A Alonso, E Sánchez, I Calvo, J L Velasco, K J McCarthy, A Chmyga, L G Eliseev, T Estrada, R Kleiber, L I Krupnik, A V Melnikov, P Monreal, F I Parra, S Perfilov, A I Zhezhera
Measurements of the relaxation of a zonal electrostatic potential perturbation in a nonaxisymmetric magnetically confined plasma are presented. A sudden perturbation of the plasma equilibrium is induced by the injection of a cryogenic hydrogen pellet in the TJ-II stellarator, which is observed to be followed by a damped oscillation in the electrostatic potential. The waveform of the relaxation is consistent with theoretical calculations of zonal potential relaxation in a nonaxisymmetric magnetic geometry. The turbulent transport properties of a magnetic confinement configuration are expected to depend on the features of the collisionless damping of zonal flows, of which the present Letter is the first direct observation...
May 5, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28523757/evaluation-of-a-freezer-mill-for-bone-pulverization-prior-to-dna-extraction-an-improved-workflow-for-str-analysis
#11
Emely Morales Colón, Mireya Hernández, Mariel Candelario, María Meléndez, Tracey Dawson Cruz
Traditional methods for bone pulverization typically generate heat, risking stability of DNA sample. SPEX™ has developed cryogenic grinders which introduce liquid nitrogen to cool the sample and aid in the grinding process. In this study, the Freezer Mill 6970 EFM was used with two DNA extraction methods and routine downstream STR analysis procedures. DNA from as little as 0.1 g of bone powder was used to develop full STR profiles after freezer mill pulverization, and the method was reproducible. Further, no contamination was detected upon cleaning/reuse of the sample vials...
May 19, 2017: Journal of Forensic Sciences
https://www.readbyqxmd.com/read/28522842/cryo-electron-microscopy-structure-of-the-macrobrachium-rosenbergii-nodavirus-capsid-at-7-angstroms-resolution
#12
Kok Lian Ho, Chare Li Kueh, Poay Ling Beh, Wen Siang Tan, David Bhella
White tail disease in the giant freshwater prawn Macrobrachium rosenbergii causes significant economic losses in shrimp farms and hatcheries and poses a threat to food-security in many developing countries. Outbreaks of Macrobrachium rosenbergii nodavirus (MrNV), the causative agent of white tail disease (WTD) are associated with up to 100% mortality rates. There are no interventions available to treat or prevent MrNV disease however. Here we show the structure of MrNV virus-like particles (VLPs) produced by recombinant expression of the capsid protein, using cryogenic electron microscopy...
May 18, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28516916/unified-model-for-singlet-fission-within-a-non-conjugated-covalent-pentacene-dimer
#13
Bettina S Basel, Johannes Zirzlmeier, Constantin Hetzer, Brian T Phelan, Matthew D Krzyaniak, S Rajagopala Reddy, Pedro B Coto, Noah E Horwitz, Ryan M Young, Fraser J White, Frank Hampel, Timothy Clark, Michael Thoss, Rik R Tykwinski, Michael R Wasielewski, Dirk M Guldi
When molecular dimers, crystalline films or molecular aggregates absorb a photon to produce a singlet exciton, spin-allowed singlet fission may produce two triplet excitons that can be used to generate two electron-hole pairs, leading to a predicted ∼50% enhancement in maximum solar cell performance. The singlet fission mechanism is still not well understood. Here we report on the use of time-resolved optical and electron paramagnetic resonance spectroscopy to probe singlet fission in a pentacene dimer linked by a non-conjugated spacer...
May 18, 2017: Nature Communications
https://www.readbyqxmd.com/read/28514858/a-cholesterol-based-surface-active-ionic-liquid-that-can-form-microemulsions-and-spontaneous-vesicles
#14
Arghajit Pyne, Jagannath Kuchlyan, Chiranjit Maiti, Dibakar Dhara, Nilmoni Sarkar
In this article, we have reported the synthesis and physicochemical characterization of a novel L-glycine amino acid derived cholesterol based surface active ionic liquid (SAIL). This SAIL has been explored for the preparation of ionic liquid (IL)-in-oil microemulsions and vesicles. The formation of IL-in-oil microemulsion is characterized by construction of a ternary phase diagram, dynamic light scattering (DLS) measurement, proton nuclear magnetic resonance (1H NMR) study, fluorescence measurement using coumarin 480 (C-480) as a molecular probe and also by recording the diffusion behavior of the molecular probe rhodamine 6G (R6G) in microemulsion droplets through Fluorescence correlation spectroscopy (FCS) technique...
May 17, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28513636/modular-synthesis-of-self-assembling-janus-dendrimers-and-facile-preparation-of-drug-loaded-dendrimersomes
#15
Sami Nummelin, Markus Selin, Sacha Legrand, Jarmo Ropponen, Jani Seitsonen, Antti Nykänen, Jari Koivisto, Jouni Hirvonen, Mauri A Kostiainen, Luis M Bimbo
Materials and methods aimed at the next generation of nanoscale carriers for drugs and other therapeutics are currently in great demand. Yet, creating these precise molecular arrangements in a feasible and straightforward manner represents a remarkable challenge. Herein we report a modular synthetic route for amphiphilic Janus-dendrimers via a copper-catalyzed click reaction (CuAAC) and a facile procedure, using simple injection, to obtain highly uniform dendrimersomes with efficient loading of the model drug compound propranolol...
May 17, 2017: Nanoscale
https://www.readbyqxmd.com/read/28512489/effect-of-deep-cryogenic-treatment-on-cyclic-fatigue-of-endodontic-rotary-nickel-titanium-instruments
#16
Mohammad Yazdizadeh, Masoumeh Skini, Seyyed Mohsen Hoseini Goosheh, Mansour Jafarzadeh, Milad Shamohammadi, Vahid Rakhshan
INTRODUCTION: Cyclic fatigue is the common reason for breakage of rotary instruments. This study was conducted to evaluate the effect of cryogenic treatment (CT) in improving the resistance to cyclic fatigue of endodontic rotary instruments. METHODS AND MATERIALS: In this in vitro study, 20 RaCe and 20 Mtwo files were randomly divided into two groups of negative control and CT. CT files were stored in liquid nitrogen at -196(°)C for 24 h, and then were gradually warmed to the room temperature...
2017: Iranian Endodontic Journal
https://www.readbyqxmd.com/read/28507696/highly-chemoselective-ruthenium-ii-catalyzed-direct-arylation-of-cyclic-and-n-n-dialkyl-benzamides-with-aryl-silanes
#17
Pradeep Nareddy, Frank Jordan, Michal Szostak
The ruthenium(ii)-catalyzed oxidative cross-coupling of C(sp(2))-H bonds with organosilanes has been accomplished for the first time. This novel protocol enlists challenging cyclic and N,N-dialkyl benzamides as weakly-coordinating substrates to achieve highly regioselective C(sp(2))-H arylation as a proof-of-concept, taking advantage of the attractive features of organosilanes as coupling partners. This innovative method is characterized by very high chemoselectivity, installing halide functional groups (I, Br, Cl) that are incompatible with Ru(ii)-carboxylate systems employing halides as cross-coupling partners, while obviating the need for sensitive organometallic reagents and cryogenic temperatures typical to the classic directed-ortho-metallation (DoM) techniques, employing benzamides to afford bioactive structural motifs...
April 1, 2017: Chemical Science
https://www.readbyqxmd.com/read/28505763/comparative-study-of-noise-in-low-current-townsend-discharge-in-nitrogen-and-argon
#18
Yu A Astrov, A N Lodygin, L M Portsel, E V Beregulin
Noise in a low-current Townsend discharge in argon and nitrogen is studied. Experiments were performed in a "semiconductor-gas-discharge" structure constituted by a short plane-parallel discharge gap and a high-resistivity photosensitive semiconductor electrode. The noise of optical emission from gas excited by the discharge was investigated with a photomultiplier. Experiments were done at the room temperature of the discharge structure. According to the obtained data, the noise of discharge glow in Ar is astonishingly low-similar to that earlier found for the cryogenic discharge in this gas...
April 2017: Physical Review. E
https://www.readbyqxmd.com/read/28504735/high-sensitivity-narrowband-wavelength-mid-infrared-detection-at-room-temperature
#19
Romain Demur, Arnaud Grisard, Loïc Morvan, Eric Lallier, Nicolas Treps, Claude Fabre
We report an upconversion experiment using an orientation-patterned gallium arsenide (OP-GaAs) crystal to detect small mid-infrared signals on an InGaAs avalanche photodiode. A conversion efficiency up to 20% with a nonpolarized pulsed fiber pump is demonstrated. Our uncooled setup is favorably compared in terms of noise equivalent power, dynamic range, and response time to cryogenically cooled HgCdTe detectors. Its dependence on the polarization of both the pump and signal beams is also investigated.
May 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28504244/mid-infrared-coincidence-measurements-on-twin-photons-at-room-temperature
#20
M Mancinelli, A Trenti, S Piccione, G Fontana, J S Dam, P Tidemand-Lichtenberg, C Pedersen, L Pavesi
Quantum measurements using single-photon detectors are opening interesting new perspectives in diverse fields such as remote sensing, quantum cryptography and quantum computing. A particularly demanding class of applications relies on the simultaneous detection of correlated single photons. In the visible and near infrared wavelength ranges suitable single-photon detectors do exist. However, low detector quantum efficiency or excessive noise has hampered their mid-infrared (MIR) counterpart. Fast and highly efficient single-photon detectors are thus highly sought after for MIR applications...
May 15, 2017: Nature Communications
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