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761.
The crystal and molecular structures of two liquid crystalline symmetric dimers containing the mesogenic group α,α′‐dimethylbenzalazine and flexible polymethylenic spacers of different parity (even and odd) are reported. They show nematic phases with strong odd–even effects. The unusual result we have found is that the odd dimer crystallizes adopting a molecular conformation in which the two mesogenic groups are aligned with respect to each other, as for the even dimer. The crystal packing of the two dimers is also analogous. 相似文献
762.
Luis Espinoza Felipe Bulat Danahe Coll Francisco Coll Marcelo D. Preite Manuel Cortés 《合成通讯》2013,43(11):1963-1974
The chemical synthesis, starting from deoxycholic acid methyl ester, of several brassinosteroids analogues with different oxygenated functions in ring C, is described. Three of them showed growth-promoting activity 相似文献
763.
Andr Augusto Gomes Faraco Jos Dias De Souza Filho Maria Auxiliadra Fontes Prado Ricardo Jos Alves Renata Fontes Prado Norma Beatriz D'Accorso 《Journal of heterocyclic chemistry》1999,36(5):1129-1133
The tetrazoles 5-(6′-acetamido-6′-deoxy-1′,2′:3′,4′-di-O-isopropylidene-D-glycero-α-D-galactohexopyranos-6′-yl)tetrazole ( 1 ) and 5-(6′-acetamido-6′-deoxy-1′,2′:3′,4′–di-O-isopropylidene-L-glycero-α-D-galacto-hexopyranos-6′-yl)-tetrazole ( 2 ) were synthesized by the 1,3-dipolar cycloaddition reaction of the epimeric α-acetamidonitriles 5 and 6 , respectively, with sodium azide. Reaction of tetrazole 1 with acetic anhydride in the presence of pyridine afforded the N-acetyl-1,3,4-oxadiazole derivative 3 and the N-acetylacetamido-1,3,4-oxadiazole derivative 7 . The N-acetylacetamido-1,3,4-oxadiazole derivative ( 8 ) was isolated when the tetrazole 2 was allowed to react under the same conditions. The physical and spectroscopic data of the five new compounds 1, 2, 3, 7 and 8 are presented. 相似文献
764.
Fast Quantitation of Target Analytes in Small Volumes of Complex Samples by Matrix‐Compatible Solid‐Phase Microextraction Devices 下载免费PDF全文
Dr. Hamed Piri‐Moghadam Fardin Ahmadi MSc. German Augusto Gómez‐Ríos Dr. Ezel Boyacı MSc. Nathaly Reyes‐Garcés Dr. Ali Aghakhani Dr. Barbara Bojko Prof. Janusz Pawliszyn 《Angewandte Chemie (International ed. in English)》2016,55(26):7510-7514
Herein we report the development of solid‐phase microextraction (SPME) devices designed to perform fast extraction/enrichment of target analytes present in small volumes of complex matrices (i.e. V≤10 μL). Micro‐sampling was performed with the use of etched metal tips coated with a thin layer of biocompatible nano‐structured polypyrrole (PPy), or by using coated blade spray (CBS) devices. These devices can be coupled either to liquid chromatography (LC), or directly to mass spectrometry (MS) via dedicated interfaces. The reported results demonstrated that the whole analytical procedure can be carried out within a few minutes with high sensitivity and quantitation precision, and can be used to sample from various biological matrices such as blood, urine, or Allium cepa L single‐cells. 相似文献
765.
α‐Arylation/Heteroarylation of Chiral α‐Aminomethyltrifluoroborates by Synergistic Iridium Photoredox/Nickel Cross‐Coupling Catalysis 下载免费PDF全文
Dr. Mirna El Khatib Dr. Ricardo Augusto Massarico Serafim Prof. Gary A. Molander 《Angewandte Chemie (International ed. in English)》2016,55(1):254-258
Direct access to complex, enantiopure benzylamine architectures using a synergistic iridium photoredox/nickel cross‐coupling dual catalysis strategy has been developed. New C(sp3)? C(sp2) bonds are forged starting from abundant and inexpensive natural amino acids. 相似文献
766.
Incoronata Tritto Laura Boggioni Maria Carmela Sacchi Paolo Locatelli Dino R. Ferro Augusto Provasoli 《Macromolecular rapid communications》1999,20(5):279-283
A series of ethylene‐norbornene copolymers were synthesized in the presence of zirconocenes with different symmetries and ligand patterns and at different norbornene (N)/ethylene (E) mole ratios. Copolymers were characterized by 13C NMR spectroscopy; Inadequate NMR sequences were used also. The comparison of 13C NMR spectra of copolymers prepared with different norbornene content and the correlation between 13C NMR chemical shifts and conformational structures of the chain on the basis of molecular mechanics calculations were performed. Preliminary assignments were revised and new comonomer sequences such as ENNE which contain meso and racemo NN dyads were assigned. 相似文献
767.
Juliana dos Santos Fernandes Julia Oliveira Fernandes Cassiano Augusto Rolim Bernardino Claudio Fernando Mahler Bernardo Ferreira Braz Ricardo Erthal Santelli Fernando Henrique Cincotto 《Electroanalysis》2022,34(5):863-871
Electrochemical sensors to quantify concentrations of emerging pollutants have attracted great attention from the industry and scientific community. Nanomaterials such as carbon black have been applied in sensors to identify substances that are toxic to the environment and human health due to their excellent electroanalytical properties. The aim of the study was to develop a novel electrochemical sensor for the endocrine disruptor hormone determination. To our knowledge, for the first time the synthesis of material based on carbon black containing immobilized palladium nanoparticles, with the application for the hormone ethinylestradiol, is reported in the literature. The material was synthesized, characterized, and applied to the determination in tap water and human urine of the synthetic hormone 17α-ethinylestradiol (EE2), which is currently considered an emerging pollutant. The morphology, structure and electrochemical performance of the sensors were characterized by scanning electron microscopy (SEM) and cyclic voltammetry (CV). Differential pulse voltammetry (DPV) in sodium phosphate buffer solution at pH 5.0 allowed the generation of a method to quantify the concentration of 17α-ethinylestradiol in a linear range of 0.5–119.0 μmol L−1, obtaining 81.0 nmol L−1 of calculated limit of detection (LOD). The system was efficient in detecting 17α-ethinylestradiol in real urine samples and showed no interferences for ascorbic acid, uric acid, progesterone, and dopamine. It is noteworthy that the results obtained showed good recovery values, considering that the urine samples were not previously treated or pre-concentrated, which suggests the development of an electrochemical sensor that works in situ and in real time to monitor relevant substances in the control clinical and environmental, with the possibility of point-of-care analyses. 相似文献
768.
Antonio Ranieri Marco Borsari Stefano Casalini Giulia Di Rocco Marco Sola Carlo Augusto Bortolotti Gianantonio Battistuzzi 《Molecules (Basel, Switzerland)》2021,26(16)
Cytochrome c is a small globular protein whose main physiological role is to shuttle electrons within the mitochondrial electron transport chain. This protein has been widely investigated, especially as a paradigmatic system for understanding the fundamental aspects of biological electron transfer and protein folding. Nevertheless, cytochrome c can also be endowed with a non-native catalytic activity and be immobilized on an electrode surface for the development of third generation biosensors. Here, an overview is offered of the most significant examples of such a functional transformation, carried out by either point mutation(s) or controlled unfolding. The latter can be induced chemically or upon protein immobilization on hydrophobic self-assembled monolayers. We critically discuss the potential held by these systems as core constituents of amperometric biosensors, along with the issues that need to be addressed to optimize their applicability and response. 相似文献
769.
Dr. Kelly A. D. F. Castro Letícia D. Costa Juliana A. Prandini Dr. Juliana C. Biazzotto Prof. Dr. Augusto C. Tomé Prof. Dr. Michael R. Hamblin Prof. Dr. Maria da Graça P. M. S. Neves Prof. Dr. M. Amparo F. Faustino Prof. Dr. Roberto S. da Silva 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(6):1990-1994
Photodynamic therapy (PDT) is a promising alternative to overcome the resistance of melanoma to conventional therapies. Currently applied photosensitizers (PS) are often based on tetrapyrrolic macrocycles like porphyrins. Unfortunately, in some cases the use of this type of derivative is limited due to their poor solubility in the biological environment. Feasible approaches to surpass this drawback are based on lipid formulations. Besides that, and inspired in the efficacy of potassium iodide (KI) for antimicrobial photodynamic therapy (aPDT), the combined effect of singlet oxygen (1O2) with KI was assessed in this work, as an alternative strategy to potentiate the effect of PDT against resistant melanoma cells. 相似文献
770.
Javier Espinoza Manuel Chacn-Fuentes Andrs Quiroz Leonardo Bardehle Paul Escobar-Bahamondes Emilio Ungerfeld 《Molecules (Basel, Switzerland)》2021,26(4)
Haematobia irritans is an obligate bloodsucking ectoparasite of cattle and is the global major pest of livestock production. Currently, H. irritans management is largely dependent upon broad-spectrum pesticides, which lately has led to the development of insecticide resistance. Thus, alternative control methods are necessary. Endophyte-infected grasses have been studied as an alternative due to their capability to biosynthesize alkaloids associated with anti-insect activities. Thus, the main aim of this study was to evaluate the antifeedant and repellent activity of lolines obtained from endophyte-infected tall fescue against H. irritans adults in laboratory conditions. The alkaloid extract (ALKE) was obtained by acid–base extraction. N-formyl loline (NFL) and N-acetyl loline (NAL) were isolated by preparative thin layer chromatography (pTLC) and column chromatography (CC), and the loline was prepared by acid hydrolysis of a NFL/NAL mixture. Loline identification was performed by gas chromatography coupled to mass spectrometry (GC/MS). Feeding behavior was evaluated by a non-choice test, and olfactory response was evaluated using a Y-tube olfactometer. Accordingly, all samples showed antifeedant activities. NFL was the most antifeedant compound at 0.5 µg/µL and 1.0 µg/µL, and it was statistically equal to NAL but different to loline; however, NAL was not statistically different to loline. NFL and NAL at 0.25 µg/µL were more active than loline. All samples except loline exhibited spatial repellency in the olfactometer. Thus, the little or non-adverse effects for cattle and beneficial activities of those lolines make them suitable candidates for horn fly management. 相似文献