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991.
Structural Revision and Elucidation of the Biosynthesis of Hypodoratoxide by 13C,13C COSY NMR Spectroscopy 下载免费PDF全文
Lena Barra Dr. Kerstin Ibrom Prof. Dr. Jeroen S. Dickschat 《Angewandte Chemie (International ed. in English)》2015,54(22):6637-6640
Feeding of (2,3,4,5,6‐13C5)mevalonolactone to the fungus Hypomyces odoratus resulted in a completely labeled sesquiterpene ether. The connectivity of the carbon atoms was easily deduced from a 13C,13C COSY spectrum, revealing a structure that was different from the previously reported structure of hypodoratoxide, even though the reported 13C NMR data matched. A structural revision of hypodoratoxide is thus presented. Its absolute configuration was tentatively assigned from its co‐metabolite cis‐dihydroagarofuran. Its biosynthesis was investigated by feeding of (3‐13C)‐ and (4,6‐13C2)mevalonolactone, which gave insights into the complex rearrangement of the carbon skeleton during terpene cyclization by analysis of the 13C,13C couplings. 相似文献
992.
Dr. Harindranath Kadavath Dr. Mariusz Jaremko Dr. Łukasz Jaremko Dr. Jacek Biernat Prof. Dr. Eckhard Mandelkow Prof. Dr. Markus Zweckstetter 《Angewandte Chemie (International ed. in English)》2015,54(35):10347-10351
Microtubules are regulated by microtubule‐associated proteins. However, little is known about the structure of microtubule‐associated proteins in complex with microtubules. Herein we show that the microtubule‐associated protein Tau, which is intrinsically disordered in solution, locally folds into a stable structure upon binding to microtubules. While Tau is highly flexible in solution and adopts a β‐sheet structure in amyloid fibrils, in complex with microtubules the conserved hexapeptides at the beginning of the Tau repeats two and three convert into a hairpin conformation. Thus, binding to microtubules stabilizes a unique conformation in Tau. 相似文献
993.
Extraordinary Changes in the Electronic Structure and Properties of CdS and ZnS by Anionic Substitution: Cosubstitution of P and Cl in Place of S 下载免费PDF全文
Summayya Kouser S. R. Lingampalli Dr. P. Chithaiah Anand Roy Sujoy Saha Prof. Umesh V. Waghmare Prof. C. N. R. Rao 《Angewandte Chemie (International ed. in English)》2015,54(28):8149-8153
Unlike cation substitution, anion substitution in inorganic materials such as metal oxides and sulfides would be expected to bring about major changes in the electronic structure and properties. In order to explore this important aspect, we have carried out first‐principles DFT calculations to determine the effects of substitution of P and Cl on the properties of CdS and ZnS in hexagonal and cubic structures and show that a sub‐band of the trivalent phosphorus with strong bonding with the cation appears in the gap just above the valence band, causing a reduction in the gap and enhancement of dielectric properties. Experimentally, it has been possible to substitute P and Cl in hexagonal CdS and ZnS. The doping reduces the band gap significantly as predicted by theory. A similar decrease in the band gap is observed in N and F co‐substituted in cubic ZnS. Such anionic substitution helps to improve hydrogen evolution from CdS semiconductor structures and may give rise to other applications as well. 相似文献
994.
Nicholas P. Calta Dr. Jino Im Alexandra P. Rodriguez Dr. Lei Fang Dr. Daniel E. Bugaris Dr. Thomas C. Chasapis Prof. Arthur J. Freeman Prof. Mercouri G. Kanatzidis 《Angewandte Chemie (International ed. in English)》2015,54(32):9186-9191
EuIr4In2Ge4 is a new intermetallic semiconductor that adopts a non‐centrosymmetric structure in the tetragonal ${I\bar 42m}$ space group with unit cell parameters a=6.9016(5) Å and c=8.7153(9) Å. The compound features an indirect optical band gap Eg=0.26(2) eV, and electronic‐structure calculations show that the energy gap originates primarily from hybridization of the Ir 5d orbitals, with small contributions from the Ge 4p and In 5p orbitals. The strong spin–orbit coupling arising from the Ir atoms, and the lack of inversion symmetry leads to significant spin splitting, which is described by the Dresselhaus term, at both the conduction‐ and valence‐band edges. The magnetic Eu2+ ions present in the structure, which do not play a role in gap formation, order antiferromagnetically at 2.5 K. 相似文献
995.
Corrigendum: Crystallographic Snapshot of an Arrested Intermediate in the Biomimetic Activation of CO2 下载免费PDF全文
996.
A Family of Molecular Sieves Containing Framework‐Bound Organic Structure‐Directing Agents 下载免费PDF全文
Jun Kyu Lee Dr. Jiho Shin Nak Ho Ahn Alessandro Turrina Dr. Min Bum Park Dr. Youngchul Byun Prof. Sung June Cho Prof. Paul A. Wright Prof. Suk Bong Hong 《Angewandte Chemie (International ed. in English)》2015,54(38):11097-11101
Organic structure‐directing agents (OSDAs), such as quaternary ammonium cations and amines, used in the synthesis of zeolites and related crystalline microporous oxides usually end up entrapped inside the void spaces of the crystallized inorganic host lattice. But none of them is known to form direct chemical bonds to the framework of these industrially important catalysts and adsorbents. We demonstrate that ECR‐40, currently regarded as a typical silicoaluminophosphate molecular sieve, constitutes instead a new family of inorganic‐organic hybrid networks in which the OSDAs are covalently bonded to the inorganic framework. ECR‐40 crystallization begins with the formation of an Al–OSDA complex in the liquid phase in which the Al is octahedrally coordinated. This unit is incorporated in the crystallizing ECR‐40. Subsequent removal of framework‐bound OSDAs generates Al‐O‐Al linkages in a fully tetrahedrally coordinated framework. 相似文献
997.
Shaohua Guo Dr. Pan Liu Dr. Yang Sun Kai Zhu Dr. Jin Yi Prof. Mingwei Chen Prof. Masayoshi Ishida Prof. Haoshen Zhou 《Angewandte Chemie (International ed. in English)》2015,54(40):11701-11705
Recently, there has been great interest in developing advanced sodium‐ion batteries for large‐scale application. Most efforts have concentrated on the search for high‐performance electrode materials only in sodium half‐cells. Research on sodium full cells for practical application has encountered many problems, such as insufficient cycles with rapid capacity decay, low safety, and low operating voltage. Herein, we present a layered P2‐Na0.66Ni0.17Co0.17Ti0.66O2, as both an anode (ca. 0.69 V versus Na+/Na) and as a high‐voltage cathode (ca. 3.74 V versus Na+/Na). The full cell based on this bipolar electrode exhibits well‐defined voltage plateaus near 3.10 V, which is the highest average voltage in the symmetric cells. It also shows the longest cycle life (75.9 % capacity retention after 1000 cycles) in all sodium full cells, a usable capacity of 92 mAh g?1, and superior rate capability (65 mAh g?1 at a high rate of 2C). 相似文献
998.
Isomerization of Secondary Phosphirane into Terminal Phosphinidene Complexes: An Analogy between Monovalent Phosphorus and Transition Metals 下载免费PDF全文
Jonathan Wong Yongxin Li Yanwei Hao Rongqiang Tian François Mathey 《Angewandte Chemie (International ed. in English)》2015,54(44):12891-12893
Secondary phosphirane complexes isomerize above 100 °C to give the corresponding terminal phosphinidene complexes, which can be trapped by alkenes and alkynes. This reaction is a rare instance of the isomerization of a PIII derivative into a PI derivative. It appears to mimic the reductive elimination of alkanes from transition‐alkylmetal hydrides. 相似文献
999.
Dr. Chun Zhang Zhen Wang Liangxiao Tan Tian‐Long Zhai Dr. Sheng Wang Prof. Bien Tan Prof. Yan‐Song Zheng Prof. Xiang‐Liang Yang Prof. Hui‐Bi Xu 《Angewandte Chemie (International ed. in English)》2015,54(32):9244-9248
A quadrangular prismatic tricyclooxacalixarene cage 1 based on tetraphenylethylene (TPE) was efficiently synthesized by a one‐pot SNAr condensation reaction. As a result of the porous internal structure in the solid state, cage 1 exhibited a good CO2 uptake capacity of 12.5 wt % and a high selectivity for CO2 over N2 adsorption of 80 (273 K, 1 bar) with a BET surface area of 432 m2 g?1. Formation of cage 1 led to the fluorescence of TPE being switched on in solution. The system was employed as a single‐molecule platform to study the mechanism of aggregation‐induced emission (AIE) by examining the restriction of intramolecular rotation (RIR). 相似文献
1000.
A Triphenylamine with Two Phenoxy Radicals Having Unusual Bonding Patterns and a Closed‐Shell Electronic State 下载免费PDF全文
Dr. Daisuke Sakamaki Soichiro Yano Toshiyuki Kobashi Prof. Dr. Shu Seki Dr. Takuya Kurahashi Prof. Dr. Seijiro Matsubara Dr. Akihiro Ito Prof. Dr. Kazuyoshi Tanaka 《Angewandte Chemie (International ed. in English)》2015,54(28):8267-8270
Reported herein is the structure and the electronic properties of a novel triphenylamine derivative having two phenoxy radicals appended to the amino nitrogen atom. X‐ray single crystal analysis and the magnetic resonance measurements demonstrates the unexpected closed‐shell electronic structure, even at room temperature, of the molecule and two unusual C? N bonds with multiple‐bond character. The theoretical calculations support the experimentally determined molecular geometry with the closed‐shell electronic structure, and predicted a small HOMO–LUMO gap originating from the nonbonding character of the HOMO. The optical and electrochemical measurements show that the molecule has a remarkably small HOMO–LUMO gap compared with its triphenylamine precursor. 相似文献