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141.
Simultaneous determination of the magnitude and the sign of multiple heteronuclear coupling constants in 19 F or 31P‐containing compounds 下载免费PDF全文
The presence of a highly abundant passive nucleus (Z = 19 F or 31P) allows the simultaneous determination of the magnitude and the sign of up to three different heteronuclear coupling constants from each individual cross‐peak observed in a 2D 1H‐X selHSQMBC spectrum. Whereas J(HZ) and J(XZ) coupling constants are measured from E.COSY multiplet patterns, J(XH) is independently extracted from the complementary IPAP pattern generated along the detected F2 dimension. The incorporation of an extended TOCSY transfer allows the extraction of a complete set of all these heteronuclear coupling constants and their signs for an entire 1H subspin system. 1H‐X/1H‐Y time‐shared versions are also proposed for the simultaneous measurement of five different couplings (J(XH), J(YH), J(XZ), J(YZ), and J(ZH)) for multiple signals in a single NMR experiment. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
142.
Ruiz-Sanchis P Savina SA Albericio F Álvarez M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(5):1388-1408
Research on natural products containing hexahydropyrrolo[2,3-b]indole (HPI) has dramatically increased during the past few years. Newly discovered natural products with complex structures and important biological activities have recently been isolated and synthesized. This review summarizes the structures, biological activities, and synthetic routes for natural compounds containing HPI, emphasizing the different strategies for assembling this motif. It covers a broad range of molecules, from small alkaloids to complex peptides. 相似文献
143.
144.
Dr. Pau Nolis Kumar Motiram-Corral Dr. Míriam Pérez-Trujillo Dr. Teodor Parella 《Chemphyschem》2019,20(3):356-360
A dual NMR data acquisition strategy to handle and detect two active equivalent transfer pathways is presented and discussed. We illustrate the power of this time-efficient approach by collecting two different 2D spectra simultaneously in a single experiment: i) TOCSY or HSQC-TOCSY spectra with different mixing times, ii) F2-13C-coupled and decoupled HSQC spectra, iii) conventional and pure-shift HSQC spectra, or iv) complementary HSQC and HSQC-TOCSY spectra. 相似文献
145.
Guowei Wu Dingling Zhuang Kit Wayne Chew Tau Chuan Ling Kuan Shiong Khoo Dong Van Quyen Shuying Feng Pau Loke Show 《Molecules (Basel, Switzerland)》2022,27(19)
With the rapid development of the economy and productivity, an increasing number of citizens are not only concerned about the nutritional value of algae as a potential new food resource but are also, in particular, paying more attention to the safety of its consumption. Many studies and reports pointed out that analyzing and solving seaweed food safety issues requires holistic and systematic consideration. The three main factors that have been found to affect the food safety of algal are physical, chemical, and microbiological hazards. At the same time, although food safety awareness among food producers and consumers has increased, foodborne diseases caused by algal food safety incidents occur frequently. It threatens the health and lives of consumers and may cause irreversible harm if treatment is not done promptly. A series of studies have also proved the idea that microbial contamination of algae is the main cause of this problem. Therefore, the rapid and efficient detection of toxic and pathogenic microbial contamination in algal products is an urgent issue that needs to be addressed. At the same time, two other factors, such as physical and chemical hazards, cannot be ignored. Nowadays, the detection techniques are mainly focused on three major hazards in traditional methods. However, especially for food microorganisms, the use of traditional microbiological control techniques is time-consuming and has limitations in terms of accuracy. In recent years, these two evaluations of microbial foodborne pathogens monitoring in the farm-to-table chain have shown more importance, especially during the COVID-19 pandemic. Meanwhile, there are also many new developments in the monitoring of heavy metals, algal toxins, and other pollutants. In the future, algal food safety risk assessment will not only focus on convenient, rapid, low-cost and high-accuracy detection but also be connected with some novel technologies, such as the Internet of Things (artificial intelligence, machine learning), biosensor, and molecular biology, to reach the purpose of simultaneous detection. 相似文献
146.
Pablo Martín‐Gago Dr. Marc Gomez‐Caminals Dr. Rosario Ramón Prof. Xavier Verdaguer Pau Martin‐Malpartida Eric Aragón Dr. Jimena Fernández‐Carneado Dr. Berta Ponsati Prof. Pilar López‐Ruiz Maria Alicia Cortes Prof. Begoña Colás Prof. Maria J. Macias Prof. Antoni Riera 《Angewandte Chemie (International ed. in English)》2012,51(8):1977-1977
147.
Wasinger EC Davis MI Pau MY Orville AM Zaleski JM Hedman B Lipscomb JD Hodgson KO Solomon EI 《Inorganic chemistry》2003,42(2):365-376
The geometric and electronic structure of NO bound to reduced protocatechuate 3,4-dioxygenase and its substrate (3,4-dihydroxybenzoate, PCA) complex have been examined by X-ray absorption (XAS), UV-vis absorption (Abs), magnetic circular dichroism (MCD), and variable temperature variable field (VTVH) MCD spectroscopies. The results are compared to those previously published on model complexes described as [FeNO]7 systems in which an S = 5/2 ferric center is antiferromagnetically coupled to an S = 1 NO-. XAS pre-edge analysis indicates that the Fe-NO units in FeIIIPCD[NO-] and FeIIIPCD[PCA,NO-] lack the greatly increased pre-edge intensity representative of most [FeNO]7 model sites. Furthermore, from extended X-ray absorption fine structure (EXAFS) analysis, the FeIIIPCD[NO-] and FeIIIPCD[PCA,NO-] active sites are shown to have an Fe-NO distance of at least 1.91 A, approximately 0.2 A greater than those found in the model complexes. The weakened Fe-NO bond is consistent with the overall lengthening of the bond lengths and the fact that VTVH MCD data show that NO(-)-->FeIII CT transitions are no longer polarized along the z-axis of the zero-field splitting tensor. The weaker Fe-NO bond derives from the strong donor interaction of the endogenous phenolate and substrate catecholate ligands, which is observed from the increased intensity in the CT region relative to that of [FeNO]7 model complexes, and from the shift in XAS edge position to lower energy. As NO is an analogue of O2, the effect of endogenous ligand donor strength on the Fe-NO bond has important implications with respect to O2 activation by non-heme iron enzymes. 相似文献
148.
J. Pedrs F. Calle J. Grajal R.J. Jimnez Riobo C. Prieto J.L. Pau J. Pereiro M. Hermann M. Eickhoff Z. Bougrioua 《Superlattices and Microstructures》2004,36(4-6):815
The anisotropic propagation of surface acoustic modes in GaN and AlN induced by the c-sapphire substrate is presented. In the GaN case, the slow acoustic propagation velocity of GaN compared with sapphire leads to guided modes in the overlayer, which propagate at higher velocities but are more attenuated than the Rayleigh mode. Above the transonic state, pseudo-SAW modes are observed, some of them with low insertion losses. In contrast, only the Rayleigh mode is observed in AlN filters due to its higher acoustic propagation velocity with respect to sapphire. The difference in the crystal structure of the sapphire and the nitrides induces a dependence of the sound velocity of all the modes, and hence their frequency, on the propagation direction. The simulations show very good agreement with the experimental data for both nitride/sapphire structures when the anisotropy induced by the substrate is taken into account. 相似文献
149.
Bayón P Marjanet G Toribio G Alibés R de March P Figueredo M Font J 《The Journal of organic chemistry》2008,73(9):3486-3491
Starting from very accessible raw materials such as p-methoxyphenol, ethylene glycol, and thiophenol, a protocol has been developed to prepare multigram quantities of the polyfunctionalized cyclohexane (+/-)- 7. A highly efficient resolution of (+/-)- 7 has been achieved through enantioselective acetylation catalyzed by Candida antarctica lipase B. Straightforward and enantioselective syntheses of 4-hydroxy-2-cyclohexenone, 1, trans-cyclohex-2-ene-1,4-diol, 2, and their O-protected derivatives 18 and 19 have been readily accomplished from 7. 相似文献
150.
Maiti D Lee DH Narducci Sarjeant AA Pau MY Solomon EI Gaoutchenova K Sundermeyer J Karlin KD 《Journal of the American Chemical Society》2008,130(21):6700-6701
A discrete peroxynitrite-copper(II) complex, [(TMG3tren)CuII(-OONO)]+ (3), has been generated in solution (ESI-MS, m/z = 565.15; tetragonal EPR) by reacting *NO(g) with superoxo complex [(TMG3tren)CuII(O2*-)]+ (2). Complex 3 undergoes a thermal transformation to give CuII-nitrite complex [(TMG3tren)CuII(-ONO)]+ (4) (X-ray) along with ca. 0.5 molar equiv dioxygen. A DFT calculation derived structure with cyclic bidentate k2-O,O'-OONO bound peroxynitrite moiety and dx2-y2 ground state is proposed. Experiments using 18O2 suggest that the adjacent peroxo oxygen atoms in 3 are derived from molecular oxygen. Further, 18O2 containing 3 undergoes O-O bond cleavage to form singly 18-O-labeled 4. The results suggest the viability of biological CuI/O2/(*NO) peroxynitrite formation and chemistry, that is, not coming from free superoxide plus *NO reaction. 相似文献