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141.
Mary Marshall Zhaoguo Zhu Rachel Harris Prof. Dr. Kit H. Bowen Wei Wang Jie Wang Chu Gong Prof. Dr. Xinxing Zhang 《Chemphyschem》2021,22(1):5-8
Thorium and its compounds have been widely investigated as important nuclear materials. Previous research focused on the potential use of thorium hydrides, such as ThH2, ThH4, and Th4H15, as nuclear fuels. Here, we report studies of the anion, ThH5−, by anion photoelectron spectroscopy and computations. The resulting experimental and theoretical vertical detachment energies (VDE) for ThH5− are 4.09 eV and 4.11 eV, respectively. These values and the agreement between theory and experiment facilitated the characterization of the structure of the ThH5− anion and showed its neutral counterpart, ThH5 to be a superhalogen. ThH5−, which exhibits a C4v structure with five Th−H single bonds, possesses the largest known H/M ratio among the actinide elements, M. The adaptive natural density partitioning (AdNDP) method was used to further analyze the chemical bonding of ThH5− and to confirm the existence of five Th−H single bonds in the ThH5− molecular anion. 相似文献
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Leonard V. Interrante Gary Sigel Mary Garbauskas Carolyn Hejna 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3-4):325-334
Abstract The crystal and molecular structures of the title compounds, [(CH3)2AlNH2]3 1 and [(t-C4H9)2AlNH2]3 2, have been determined in connection with their investigation as possible precursors to aluminum nitride. Both compounds have an (AlN)3 ring-structure with distorted tetrahedral geometries for the ring Al and N atoms. The distortion from tetrahedral geometry is most pronounced for the N atoms where the endocyclic Al-N-Al bond angles average 125.3 for 1 and 134.2 for 2. The (AlN)3 ring in 1 is in a skew-boat conformation with no unusual intra- or intermolecular contacts. Compound 2 on the other hand exhibits an unprecedented planar (AlN)3 ring as required by a crystallographic three-fold symmetry axis. The effects of the Al and N substituents on the (AlN)3 ring size and conformation, as well as on the endocyclic Al-N-Al bond angles, are discussed in the context of the structural results obtained for these and other (AlN)n ring compounds. 相似文献
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Andrew J. Bissette Dr. Stephen P. Fletcher 《Angewandte Chemie (International ed. in English)》2013,52(49):12800-12826
Self‐replication is a fundamental concept. The idea of an entity that can repeatedly create more of itself has captured the imagination of many thinkers from von Neumann to Vonnegut. Beyond the sciences and science fiction, autocatalysis has found currency in economics and language theory, and has raised ethical fears memorably summed up by the “gray goo” trope. Autocatalysis is central to the propagation of life and intrinsic to many other biological processes. This includes the modern conception of evolution, which has radically altered humanity’s image of itself. Organisms can be thought of as imperfect self‐replicators which produce closely‐related species, allowing for selection and evolution. Hence, any consideration of self‐replication raises one of the most profound questions of all: what is life? Minimal self‐replicating systems have been studied with the aim of understanding the principles underlying living systems, allowing us to refine our concepts of biological fitness and chemical stability, self‐organization and emergence, and ultimately to discover how chemistry may become biology. 相似文献
147.
Fuyu Guan Cornelius E. Uboh Lawrence R. Soma Mary Robinson George A. Maylin Xiaoqing Li 《Analytical and bioanalytical chemistry》2013,405(14):4707-4717
Dermorphin is a unique opioid peptide that is 30–40 times more potent than morphine. It was misused and went undetected in horse racing until 2011 when intelligence obtained from a few North American race tracks suggested its use. To prevent such misuse, a reliable analytical method became necessary for detection and identification of dermorphin in post-race horse samples. This paper describes the first liquid chromatography–tandem mass spectrometry (LC–MS/MS) method for such a purpose. Equine plasma and urine samples were pre-treated with ethylenediamine tetra-acetic acid and urea prior to solid-phase extraction (SPE) on Oasis MCX cartridges. Resulting eluates were dried under vacuum and analyzed by LC–MS/MS for dermorphin. The matrix effect, SPE efficiency, intra-day and inter-day accuracy and precision, and stability of the analyte were assessed. The limit of detection was 10 pg/mL in plasma and 20 pg/mL in urine, and the limit of confirmation was 20 pg/mL in plasma and 50 pg/mL in urine. Dermorphin in plasma is stable at ambient temperature, but its diastereomer is unstable. With isotopically labeled dermorphin as an internal standard, the quantification range was 20–10,000 pg/mL in plasma and 50–20,000 pg/mL in urine. The intra-day and inter-day accuracy was from 91 % to 100 % for the low, intermediate, and high concentrations. The intra-day and inter-day coefficients of variation were less than 12 %. The method differentiates dermorphin from its diastereomer. This method is very specific for identification of dermorphin in equine plasma and urine, as assessed by BLAST search and targeted SEQUEST search, and by MS/MS spectrum library search. The method has been successfully applied to analysis of samples collected following dermorphin administration to research horses and of official post-race samples. Figure
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148.
Satoka Aoyagi John S. Fletcher Sadia Sheraz Tomoko Kawashima Irma Berrueta Razo Alex Henderson Nicholas P. Lockyer John C. Vickerman 《Analytical and bioanalytical chemistry》2013,405(21):6621-6628
A novel application of time-of-flight secondary ion mass spectrometry (ToF-SIMS) with continuous Ar cluster beams to peptide analysis was investigated. In order to evaluate peptide structures, it is necessary to detect fragment ions related to multiple neighbouring amino acid residues. It is, however, difficult to detect these using conventional ToF-SIMS primary ion beams such as Bi cluster beams. Recently, C60 and Ar cluster ion beams have been introduced to ToF-SIMS as primary ion beams and are expected to generate larger secondary ions than conventional ones. In this study, two sets of model peptides have been studied: (des-Tyr)-Leu-enkephalin and (des-Tyr)-Met-enkephalin (molecular weights are approximately 400 Da), and [Asn1 Val5]-angiotensin II and [Val5]-angiotensin I (molecular weights are approximately 1,000 Da) in order to evaluate the usefulness of the large cluster ion beams for peptide structural analysis. As a result, by using the Ar cluster beams, peptide molecular ions and large fragment ions, which are not easily detected using conventional ToF-SIMS primary ion beams such as Bi3 +, are clearly detected. Since the large fragment ions indicating amino acid sequences of the peptides are detected by the large cluster beams, it is suggested that the Ar cluster and C60 ion beams are useful for peptide structural analysis. 相似文献
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Eva Alvarez de Eulate Shane O'Sullivan Sharon Fletcher Prof. Dr. Philip Newsholme Prof. Dr. Damien W. M. Arrigan 《化学:亚洲杂志》2013,8(9):2096-2101
The behavior of proteins and polypeptides at electrified aqueous–organic interfaces is of benefit in label‐free detection strategies. In this work, rat amylin (or islet amyloid polypeptide) was studied at the interface formed between aqueous liquid and gelled organic phases. Amylin is a polypeptide that is co‐secreted with insulin from islet beta‐cells and is implicated in fibril formation. In this study, rat amylin was used, which does not undergo aggregation. The polypeptide underwent an interfacial transfer process, from water to the gelled organic phase, under applied potential stimulation. Cyclic voltammetry revealed steady‐state forward and peak‐shaped reverse voltammograms, which were consistent with diffusion‐controlled water‐to‐organic transfer and thin‐film stripping or desorptive back‐transfer. The diffusion‐controlled forward current was greater when amylin was present in an acidic aqueous phase than when it was present in an aqueous phase at physiological pH; this reflects the greater charge on the polypeptide under acidic conditions. The amylin transfer current was concentration dependent over the range 2–10 μM , at both acidic and physiological pH. At physiological pH, amylin was selectively detected in the presence of a protein mixture, which illustrated the bioanalytical possibilities for this electrochemical behavior. 相似文献