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Cryogenics

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https://www.readbyqxmd.com/read/28644014/three-dimensional-localization-of-an-individual-fluorescent-molecule-with-angstrom-precision
#1
Taku Furubayashi, Kazuya Motohashi, Keisuke Wakao, Tsuyoshi Matsuda, Isao Kii, Takamitsu Hosoya, Nobuhiro Hayashi, Mahito Sadaie, Fuyuki Ishikawa, Michio Matsushita, Satoru Fujiyoshi
Among imaging techniques, fluorescence microscopy is a unique method to noninvasively image individual molecules in whole cells. If the three-dimensional spatial precision is improved to the angstrom level, various molecular arrangements in the cell can be visualized on an individual basis. We have developed a cryogenic reflecting microscope with a numerical aperture of 0.99 and an imaging stability of 0.05 nm in standard deviation at a temperature of 1.8 K. The key optics to realize the cryogenic performances is the reflecting objective developed by our laboratory...
June 23, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28643896/the-cope-rearrangement-of-1-5-dimethylsemibullvalene-2-4-d1-experimental-evidence-for-heavy-atom-tunneling
#2
Tim Schleif, Joel Mierez-Perez, Stefan Henkel, Melanie Ertelt, Weston Thatcher Borden, Wolfram Sander
As an experimental test of the theoretical prediction that heavy-atom tunneling is involved in the degenerate Cope rearrangement of semibullvalenes at cryogenic temperatures, mono-deuterated 1,5-dimethyl¬semibullvalene isotopomers were prepared and investigated by IR spectroscopy, using the matrix isolation technique. As predicted, the less thermodynamically stable isotopomer rearranges at cryogenic temperatures in the dark to the more stable one, while broadband IR irradiation above 2000 cm-1 results in an equilibration of the isotopomeric ratio...
June 23, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28643189/cryogenic-vibrational-spectroscopy-provides-unique-fingerprints-for-glycan-identification
#3
Chiara Masellis, Neelam Khanal, Michael Z Kamrath, David E Clemmer, Thomas R Rizzo
The structural characterization of glycans by mass spectrometry is particularly challenging. This is because of the high degree of isomerism in which glycans of the same mass can differ in their stereochemistry, attachment points, and degree of branching. Here we show that the addition of cryogenic vibrational spectroscopy to mass and mobility measurements allows one to uniquely identify and characterize these complex biopolymers. We investigate six disaccharide isomers that differ in their stereochemistry, attachment point of the glycosidic bond, and monosaccharide content, and demonstrate that we can identify each one unambiguously...
June 22, 2017: Journal of the American Society for Mass Spectrometry
https://www.readbyqxmd.com/read/28636333/glycosaminoglycan-analysis-by-cryogenic-messenger-tagging-ir-spectroscopy-combined-with-ims-ms
#4
Neelam Khanal, Chiara Masellis, Michael Z Kamrath, David E Clemmer, Thomas R Rizzo
We combine ion mobility spectrometry with cryogenic, messenger-tagging, infrared spectroscopy and mass spectrometry to identify different isomeric disaccharides of chondroitin sulfate (CS) and heparan sulfate (HS), which are representatives of two major subclasses of glycosaminoglycans. Our analysis shows that while CS and HS disaccharide isomers have similar drift times, they can be uniquely distinguished by their vibrational spectrum between ~3200-3700 cm-1 due to their different OH hydrogen-bonding patterns...
June 21, 2017: Analytical Chemistry
https://www.readbyqxmd.com/read/28635268/isotope-controlled-selectivity-by-quantum-tunneling-hydrogen-migration-versus-ring-expansion-in-cyclopropylmethylcarbenes
#5
Ashim Nandi, Dennis Gerbig, Peter R Schreiner, Weston Thatcher Borden, Sebastian Kozuch
Using the tunneling-controlled reactivity of cyclopropylmethylcar-bene, we demonstrate the viability of isotope-controlled selectivity (ICS), a novel non-classical control element of chemical reactivity where a molecular system with two conceivable products of tunneling exclusively produces one or the other, depending only on isotopic composition. Our multidimensional small-curvature tunneling (SCT) computations indicate that under cryogenic conditions, 1-methoxycyclopropylmethylcarbene shows rapid H-migration to 1-methoxy-1-vinylcyclopropane, whereas deuterium-substituted 1-methoxycyclopropyl-d3-methylcarbene undergoes ring expansion to 1-d3-methylcyclobutene...
June 21, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28630924/capturing-the-radical-ion-pair-intermediate-in-dna-guanine-oxidation
#6
Jialong Jie, Kunhui Liu, Lidan Wu, Hongmei Zhao, Di Song, Hongmei Su
Although the radical ion pair has been frequently invoked as a key intermediate in DNA oxidative damage reactions and photoinduced electron transfer processes, the unambiguous detection and characterization of this species remain formidable and unresolved due to its extremely unstable nature and low concentration. We use the strategy that, at cryogenic temperatures, the transient species could be sufficiently stabilized to be detectable spectroscopically. By coupling the two techniques (the cryogenic stabilization and the time-resolved laser flash photolysis spectroscopy) together, we are able to capture the ion-pair transient G(+•)⋯Cl(-) in the chlorine radical-initiated DNA guanine (G) oxidation reaction, and provide direct evidence to ascertain the intricate type of addition/charge separation mechanism underlying guanine oxidation...
June 2017: Science Advances
https://www.readbyqxmd.com/read/28628252/microstructural-engineering-and-architectural-design-of-metal-organic-framework-membranes
#7
REVIEW
Yi Liu, Yujie Ban, Weishen Yang
In the past decade, a huge development in rational design, synthesis, and application of molecular sieve membranes, which typically included zeolites, metal-organic frameworks (MOFs), and graphene oxides, has been witnessed. Owing to high flexibility in both pore apertures and functionality, MOFs in the form of membranes have offered unprecedented opportunities for energy-efficient gas separations. Reports on the fabrication of well-intergrown MOF membranes first appeared in 2009. Since then there has been tremendous growth in this area along with an exponential increase of MOF-membrane-related publications...
June 19, 2017: Advanced Materials
https://www.readbyqxmd.com/read/28622656/a-combined-experimental-setup-for-op-and-odnmr
#8
Erika L Sesti, Matthew M Willmering, Zayd L Ma, Dustin D Wheeler, Mark S Conradi, Sophia E Hayes
Instrumentation for optically-pumped and optically-detected nuclear magnetic resonance (OPNMR and ODNMR) has been developed and implemented as a single experimental apparatus to study semiconductors such as GaAs and CdTe. These two measurement schemes use many of the same components for experiments. Here we describe, in two parts, the apparatus that can record such measurements and give examples of representative data. In Part 1, the radio-frequency probe and low-temperature cryostat are described, including single-channel and two-channel static cryogenic probes that both incorporate a modified solenoid coil that permits better optical access...
June 7, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28621378/the-hypothiocyanite-radical-oscn-and-its-isomers
#9
Zhuang Wu, Jian Xu, Qifan Liu, Xuelin Dong, Dingqing Li, Nicole Holzmann, Gernot Frenking, Tarek Trabelsi, Joseph S Francisco, Xiaoqing Zeng
A biologically relevant reactive sulfur species (RSS), the hypothiocyanite radical OSCN, is generated in the gas phase through flash vacuum pyrolysis (FVP) of trifluoromethyl sulfinyl cyanide CF3S(O)CN at ca. 1000 K. Upon UV light irradiation (365 nm), OSCN rearranges to novel isomers OSNC and SOCN, and further visible light irradiation (400 ± 20 nm) leads to reverse isomerization. The identification of OSCN, OSNC, and SOCN in cryogenic matrices (Ar and N2, 2.8 K) with IR spectroscopy is supported by quantum chemical calculations up to the CCSD(T)-F12/VTZ-F12 level...
June 16, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28620354/torpor-the-rise-and-fall-of-3-monoiodothyronamine-from-brain-to-gut-from-gut-to-brain
#10
REVIEW
Hartmut H Glossmann, Oliver M D Lutz
3-Monoiodothyronamine (T1AM), first isolated from rat brain, is reported to be an endogenous, rapidly acting metabolite of thyroxine. One of its numerous effects is the induction of a "torpor-like" state in experimental animals. A critical analysis of T1AM, to serve as an endogenous cryogen, is given. The proposed biosynthetic pathway for formation of T1AM, which includes deiodinases and ornithine decarboxylase in the upper intestinum, is an unusual one. To reach the brain via systemic circulation, enterohepatic recycling and passage through the liver may occur...
2017: Frontiers in Endocrinology
https://www.readbyqxmd.com/read/28619585/sensitivity-enhancement-by-chromatographic-peak-concentration-with-ultra-high-performance-liquid-chromatography-nuclear-magnetic-resonance-spectroscopy-for-minor-impurity-analysis
#11
Takashi Tokunaga, Ken-Ichi Akagi, Masahiko Okamoto
High performance liquid chromatography can be coupled with nuclear magnetic resonance (NMR) spectroscopy to give a powerful analytical method known as liquid chromatography-nuclear magnetic resonance (LC-NMR) spectroscopy, which can be used to determine the chemical structures of the components of complex mixtures. However, intrinsic limitations in the sensitivity of NMR spectroscopy have restricted the scope of this procedure, and resolving these limitations remains a critical problem for analysis. In this study, we coupled ultra-high performance liquid chromatography (UHPLC) with NMR to give a simple and versatile analytical method with higher sensitivity than conventional LC-NMR...
June 9, 2017: Journal of Chromatography. A
https://www.readbyqxmd.com/read/28612869/intrinsic-ferromagnetism-and-quantum-transport-transition-in-individual-fe-doped-bi2se3-topological-insulator-nanowires
#12
Wei Niu, Kai Du, Shuangbao Wang, Minhao Zhang, Ming Gao, Yongda Chen, Hao Liu, Wei Zhou, Fengqi Song, Peng Wang, Yongbing Xu, Xuefeng Wang, Jian Shen, Rong Zhang
Time-reversal symmetry is broken by magnetic doping in topological insulators (TIs). An energy gap at the Dirac point opens and thus, generates numerous surface carriers. TI nanostructures are an ideal platform to investigate exotic surface transport behavior due to their large surface-to-volume ratio, which enhances the contribution of the TI surface states. However, magnetic doping into TI nanostructures has been challenging, and induced magnetic behavior has remained elusive. Herein, we have synthesized Fe-doped Bi2Se3 nanowires using a facile chemical vapor deposition with a doping concentration of ∼1 at%...
June 14, 2017: Nanoscale
https://www.readbyqxmd.com/read/28609610/an-rna-aptamer-capable-of-forming-hydrogel-by-self-assembly
#13
Zhen Huang, Gagan N Kangovi, Wei Wen, Sangwoo Lee, Li Niu
Hydrogels are supramolecular assemblies with both solute transport properties like liquids and mechanical properties like elastomers. To date, every type of biomolecules, except ribonucleic acid (RNA), are capable of forming hydrogel. Here we report an RNA that forms hydrogel by self-assembly. This RNA is originally identified by systematic evolution of ligands by exponential enrichment (SELEX) to enhance the activity of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors as a potential RNA drug for treatment of cognitive disorders...
June 13, 2017: Biomacromolecules
https://www.readbyqxmd.com/read/28604656/cryogenic-strength-improvement-by-utilizing-room-temperature-deformation-twinning-in-a-partially-recrystallized-vcrmnfeconi-high-entropy-alloy
#14
Y H Jo, S Jung, W M Choi, S S Sohn, H S Kim, B J Lee, N J Kim, S Lee
The excellent cryogenic tensile properties of the CrMnFeCoNi alloy are generally caused by deformation twinning, which is difficult to achieve at room temperature because of insufficient stress for twinning. Here, we induced twinning at room temperature to improve the cryogenic tensile properties of the CrMnFeCoNi alloy. Considering grain size effects on the critical stress for twinning, twins were readily formed in the coarse microstructure by cold rolling without grain refinement by hot rolling. These twins were retained by partial recrystallization and played an important role in improving strength, allowing yield strengths approaching 1 GPa...
June 12, 2017: Nature Communications
https://www.readbyqxmd.com/read/28598640/cold-anisotropically-interacting-van-der-waals-molecule-tihe
#15
Nancy Quiros, Naima Tariq, Timur V Tscherbul, Jacek Kłos, Jonathan D Weinstein
We have used laser ablation and helium buffer-gas cooling to produce titanium-helium van der Waals molecules at cryogenic temperatures. The molecules were detected through laser-induced fluorescence spectroscopy. Ground-state Ti(a^{3}F_{2})-He binding energies were determined for the ground and first rotationally excited states from studying equilibrium thermodynamic properties, and found to agree well with theoretical calculations based on newly calculated ab initio Ti-He interaction potentials, opening up novel possibilities for studying the formation, dynamics, and nonuniversal chemistry of van der Waals clusters at low temperatures...
May 26, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28598599/generation-spectroscopic-and-chemical-characterization-of-an-octahedral-iron-v-nitrido-species-with-a-neutral-ligand-platform
#16
Gerard Sabenya, Laura Lazaro, Ilaria Gamba, Vlad Martin-Diaconescu, Erik Andris, Thomas Weyhermüller, Frank Neese, Jana Roithova, Eckhard Bill, Julio Lloret-Fillol, Miquel Costas
Iron complex [FeIII(N3)(MePy2tacn)](PF6)2 (1), containing a neutral triazacyclononane-based pentadentate ligand, and a terminally bound azide ligand has been prepared and spectroscopically and structurally characterized. Structural details, magnetic susceptibility data and Mössbauer spectra demonstrate that 1 has a low-spin state (S = 1/2) ferric center. X-Ray diffraction analysis of 1 reveals remarkably short Fe - N (1.859 Å) and long FeN - N2 (1.246 Å) distances, respectively, and the FT-IR spectra showed an unusually low N - N stretching frequency (2019 cm-1), suggesting that the FeN - N2 bond is particularly weak...
June 9, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28598474/anisotropic-longitudinal-electronic-relaxation-affects-dnp-at-cryogenic-temperatures
#17
E M M Weber, H Vezin, J G Kempf, G Bodenhausen, D Abergél, D Kurzbach
We report the observation of anisotropic longitudinal electronic relaxation in nitroxide radicals under typical dynamic nuclear polarization conditions. This anisotropy affects the efficiency of dynamic nuclear polarization at cryogenic temperatures of 4 K and high magnetic fields of 6.7 T. Under our experimental conditions, the electron paramagnetic resonance spectrum of nitroxides such as TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl) is only partly averaged by electronic spectral diffusion, so that the relaxation times T1e(ω) vary across the spectrum...
June 21, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28594561/steering-self-assembly-of-amphiphilic-molecular-nanostructures-via-halogen-exchange
#18
Björn Kriete, Anna S Bondarenko, Varsha R Jumde, Linda E Franken, Adriaan J Minnaard, Thomas L C Jansen, Jasper Knoester, Maxim S Pshenichnikov
In the field of self-assembly, the quest for gaining control over the supramolecular architecture without affecting the functionality of the individual molecular building blocks is intrinsically challenging. By using a combination of synthetic chemistry, cryogenic transmission electron microscopy, optical absorption measurements, and exciton theory, we demonstrate that halogen exchange in carbocyanine dye molecules allows for fine-tuning the diameter of the self-assembled nanotubes formed by these molecules, while hardly affecting the molecular packing determined by hydrophobic/hydrophilic interactions...
June 14, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28593642/assembly-and-performance-of-a-6-4-t-cryogen-free-dynamic-nuclear-polarization-system
#19
Andhika Kiswandhi, Peter Niedbalski, Christopher Parish, Qing Wang, Lloyd Lumata
We report on the assembly and performance evaluation of a 180 GHz/6.4 T dynamic nuclear polarization (DNP) system based on a cryogen-free superconducting magnet. The DNP system utilizes a variable-field superconducting magnet that can be ramped up to 9 T and equipped with cryocoolers that can cool the sample space with the DNP assembly down to 1.8 K via the Joule-Thomson effect. A homebuilt DNP probe insert with top-tuned NMR coil and microwave port was incorporated into the sample space in which the effective sample temperature is approximately 1...
June 7, 2017: Magnetic Resonance in Chemistry: MRC
https://www.readbyqxmd.com/read/28593055/a-surgical-cryoprobe-for-targeted-transcorneal-freezing-and-endothelial-cell-removal
#20
Alina Akhbanbetova, Shinichiro Nakano, Stacy L Littlechild, Robert D Young, Madara Zvirgzdina, Nigel J Fullwood, Ian Weston, Philip Weston, Shigeru Kinoshita, Naoki Okumura, Noriko Koizumi, Andrew J Quantock
PURPOSE: To examine the effects of transcorneal freezing using a new cryoprobe designed for corneal endothelial surgery. METHODS: A freezing console employing nitrous oxide as a cryogen was used to cool a series of different cryoprobe tip designs made of silver for high thermal conductivity. In vitro studies were conducted on 426 porcine corneas, followed by preliminary in vivo investigations on three rabbit corneas. RESULTS: The corneal epithelium was destroyed by transcorneal freezing, as expected; however, the epithelial basement membrane remained intact...
2017: Journal of Ophthalmology
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