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191.
Ting R Harwig C auf dem Keller U McCormick S Austin P Overall CM Adam MJ Ruth TJ Perrin DM 《Journal of the American Chemical Society》2008,130(36):12045-12055
The use of a boronic ester as a captor of aqueous [(18)F]-fluoride has been previously suggested as a means of labeling biomolecules in one step for positron emission tomography (PET) imaging. For this approach to be seriously considered, the [(18)F]-labeled trifluoroborate should be humorally stable such that it neither leaches free [(18)F]-fluoride to the bone nor accumulates therein. Herein, we have synthesized a biotinylated boronic ester that is converted to the corresponding trifluoroborate salt in the presence of aqueous [(18)F]-fluoride. In keeping with its in vitro aqueous kinetic stability at pH 7.5, the trifluoroborate appears to clear in vivo quite rapidly to the bladder as the stable trifluoroborate salt with no detectable leaching of free [(18)F]-fluoride to the bone. When this labeled biotin is preincubated with avidin, the pharmacokinetic clearance of the resulting complex is visibly altered. This work validates initial claims that boronic esters are potentially useful as readily labeled precursors to [(18)F]-PET reagents. 相似文献
192.
A total dominating set in a graph G is a set S of vertices of G such that every vertex in G is adjacent to a vertex of S. We study graphs whose vertex set can be partitioned into two total dominating sets. In particular, we develop several sufficient conditions for a graph to have a vertex partition into two total dominating sets. We also show that with the exception of the cycle on five vertices, every selfcomplementary graph with minimum degree at least two has such a partition. 相似文献
193.
Pamela Moyo Tawanda Mugadza Gift Mehlana Upenyu Guyo 《Research on Chemical Intermediates》2016,42(8):6511-6529
We report on the synthesis and characterization of activated carbon–ethylenediamine–cobalt(II) tetracarboxyphthalocyanine conjugate (AC–CONHCH2CH2NH2–CoPc) and its electrocatalytic behavior for oxidation of ascorbic acid. Ultraviolet–visible (UV–Vis), Fourier-transform infrared (FTIR), and electrochemical impedance spectroscopies, and cyclic and square-wave voltammetry were used to characterize the electrode modifiers and modified glassy carbon electrode. The limit of detection was found to be 0.26 µm using 3δ notation. The linear dynamic range was from 1.5 × 10?4 to 1 × 10?2 M with electrode sensitivity of 0.01 A mol?1 L cm?2. A Tafel slope of 200.8 mV decade?1 was found. The concentration of ascorbic acid in the tablet was 0.034 M. Oxalic acid showed no interference in ascorbic acid determination. 相似文献
194.
Christiane Auray-Blais Pamela Lavoie Shunji Tomatsu Vassili Valayannopoulos John J. Mitchell Julian Raiman Maxime Beaudoin Bruno Maranda Joe T.R. Clarke 《Analytica chimica acta》2016
Mucopolysaccharidoses (MPSs) are a group of disorders resulting from primary defects in lysosomal enzymes involved in the degradation of glycosaminoglycans (GAGs). Depending on the specific enzyme defect, the catabolism of one or more GAGs is blocked leading to accumulation in tissues and biological fluids. GAG measurements are important for high-risk screening, diagnosis, monitoring treatment efficacy, and patient follow up. The dimethylmethylene blue (DMB) spectrophotometric method commonly used in most biochemical genetics laboratories relies on a non-specific total GAG analysis which has led to false positive results, and even false negative results (mainly for MPS III and IV patients). The main objective of our project was to devise and validate a reliable tandem mass spectrometry multiplex analysis for the urine quantitation of four GAGs (dermatan sulfate (DS), heparan sulfate (HS), keratan sulfate (KS), and chondroitin sulfate (CS)) for an eventual technological transfer to the clinic. The developed methodology is rapid (7 min) and our results showed good intraday and interday precision (RSDs ≤ 8.7%) and accuracy (Biases range: −12.0%–18.4%). Linearity was good (r2 > 0.995) for DS, HS, CS, and KS calibration curves. In comparison with the DMB spectrophotometric method, this multiplex tandem mass spectrometry method allows GAG fractionation, thus a differentiation of MPS types, except for MPS I and II which are characterized by the same GAG profile. The devised method is a useful and reliable tool for diagnosis of MPS patients, as well as their monitoring and follow up, as shown by longitudinal studies. 相似文献
195.
Dr. Allison M. Latshaw Dr. W. Michael Chance Dr. Gregory Morrison Karl D. zur Loye Branford O. Wilkins Mark D. Smith Dr. Pamela S. Whitfield Dr. Melanie J. Kirkham Dr. Sebastian A. Stoian Prof. Dr. Hans‐Conrad zur Loye 《Angewandte Chemie (International ed. in English)》2016,55(42):13195-13199
Crystals of the first sodalite‐type zeolite containing an all‐iron framework, a ferrolite, Ba8(Fe12O24)Nay(OH)6?x H2O, were synthesized using the hydroflux method in nearly quantitative yield. Ba8(Fe12O24)Nay(OH)6?x H2O crystallizes in the cubic space group with a=10.0476(1) Å. Slightly distorted FeO4 tetrahedra are linked to form Fe4O4 and Fe6O6 rings, which in turn yield channels and internal cavities that are characteristic of the sodalite structure. Barium, sodium, and hydroxide ions and water molecules are found in the channels and provide charge balance. Magnetic measurements indicate that the ferrolite exhibits magnetic order up to at least 700 K, with the field‐cooled and zero‐field‐cooled curves diverging. Analysis of the 57Fe Mössbauer spectra revealed two spectral components that have equal spectral areas, indicating the presence of two subsets of iron centers in the structure. Dehydrated versions of the ferrolite were also prepared by heating the sample. 相似文献
196.
Xingwei Han Xiaofei Zeng Jiexin Wang Dejia Kong N. R. Foster Jianfeng Chen 《中国科学:化学(英文版)》2016,59(8):1010-1017
Functional organic-inorganic nanocomposites with high transparency show significant potential application in many fields. However, it is still a great challenge to prepare flexible transparent nanocomposites due to the intrinsic stiffness of the nanoparticles and the poor interaction between nanoparticles and organic matrices. In this work, a transparent ternary nanocomposite film with enhanced mechanical performance is fabricated by two-steps. First, the transparent ternary ZnO/MWCNTs/n-butyl methacrylate (BMA) nanodispersion is prepared by mixing the ZnO/BMA and MWCNTs/BMA dispersions directly. Then, the ternary nanocoposites film is fabricated via in-situ bulk polymerization of the above nanodispersions. As a result, the tensile strength of the ZnO/MWCNTs/poly-n-butyl methacrylate (PBMA) ternary film is enhanced by 42% and the elongation at break is three times that of ZnO/PBMA nanocomposite. The hardness of the film increases from 5B to 1H with 40 wt% ZnO. These results indicate that ZnO and MWCNTs can improve the mechanical properties of the composite significantly. Importantly, the ternary nanocomposite film still remains high transparency and exhibit excellent UV-shielding performance. The as-prepared transparent multifunctional nanocomposite films have promising applications in optical materials and devices, such as optical filters, contact lenses and protection packing. 相似文献
197.
198.
199.
Cordova JM Noack PL Hilcove SA Lear JD Ghirlanda G 《Journal of the American Chemical Society》2007,129(3):512-518
We have designed a functional model membrane protein by engineering a bis-Histidine heme-binding site into a natural membrane protein, glycophorin A (GpA), structurally characterized by the dimerization of a single transmembrane helix. Out of the 32 residues comprising the transmembrane helix of GpA, five amino acids were mutated; the resulting protein, ME1, has been characterized in dodecyl phosphocholin (DPC) micelles by UV-vis, CD spectroscopy, gel electrophoresis, and analytical ultracentrifugation. ME1 binds heme with sub-micromolar affinity and maintains the highly helical secondary structure and dimeric oligomerization state of GpA. The ME1-Heme complex exhibits a redox potential of -128 +/- 2 mV vs SHE, indicating that the heme resides in a hydrophobic environment and is well shielded from the aqueous phase. Moreover, ME1 catalyzes the hydrogen peroxide dependent oxidation of organic substrates such as TMB (2,2',5,5'-tetramethyl-benzidine). This protein may provide a useful framework to investigate how the protein matrix tunes the cofactor properties in membrane proteins. 相似文献
200.
Foster SL Handa S Krafft M Rowling D 《Chemical communications (Cambridge, England)》2007,(45):4791-4793
The first reported intramolecular pinacol coupling of cyclopropyl ketones has been achieved, demonstrating that cyclisation competes favourably with ring-opening of the cyclopropyl ketyl radical. 相似文献