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81.
Madalina Tudose Florin D. Badea Gabriela Ionita Maria Maganu Miron T. Caproiu Petre Ionita Titus Constantinescu Alexandru T. Balaban 《Structural chemistry》2010,21(6):1227-1234
Starting from 4-chloro-3,5-dinitrobenzoic acid 1, compounds 2–10 (N-alkoxy-3,5-dinitro-4-aminobenzoic acid esters where alkoxy stands for methoxy, carboxymethoxy, triphenylmethoxy, or corresponding
amides) have been obtained, from which compounds 3–5 and 7–10 are new, and for the known compounds 2 and 6 the synthetic procedure has been improved. The new derivatives have been characterized by appropriate means (IR, UV–Vis,
1H- and 13C-NMR, fluorescence) and their properties were studied. Thus, depending on their structure, the compounds have acid properties,
fluorescence and complexing properties with alkaline cations. 相似文献
82.
Madalina Tudose Florin D. Badea Miron T. Caproiu Adrian Beteringhe Maria Maganu Petre Ionita Titus Constantinescu Alexandru T. Balaban 《Central European Journal of Chemistry》2010,8(4):789-796
Starting from N-hydroxyphthalimide 1 and the reactive fluoro- or chloro-nitroaryl derivatives 2, 3 and 4a-e (2-chloro-3,5-dinitropyridine; 3, NBD-chloride; 4a, 1-fluoro-2,4-dinitrobenzene; 4b, picryl chloride; 4c, 4-chloro-3,5-dinitrobenzotrifluoride; 4d, 2-chloro-3,5- dinitrobenzotrifluoride; 4e, 4-chloro-3,5-dinitrobenzoic acid) the corresponding N-(2-nitroaryloxy)-phthalimide derivatives 5a-e, or 6 and 7 were obtained and characterized by IR, UV-Vis 1H-NMR and 13C-NMR spectroscopy. The TLC behavior and the hydrophobicity of these derivatives have been experimentally evaluated by RM0 parameters (using RP-TLC). The experimental RM0 parameters were compared with the calculated partition coefficient, log P. A QSPR study was also performed to establish possible
correlations between the structure and physical properties (λmax and RM0) of compounds 5a-e, 6, and 7.
相似文献
83.
Yang Luo Tuo Li Fang Yu Tal Kramer Ileana M. Cristea 《Journal of the American Society for Mass Spectrometry》2010,21(1):34-46
Current biological studies have been advanced by the continuous development of robust, accurate, and sensitive mass spectrometric
technologies. The MALDI LTQ Orbitrap is a new addition to the Orbitrap configurations, known for their high resolving power
and accuracy. This configuration provides features inherent to the MALDI source, such as reduced spectra complexity, forgiveness
to contaminants, and sample retention for follow-up analyses with targeted or hypothesis-driven questions. Here we investigate
its performance for characterizing the composition of isolated protein complexes. To facilitate the assessment, we selected
two well characterized complexes from Saccharomyces cerevisiae, Apl1 and Nup84. Manual and automatic MS and MS/MS analyses readily resolved their compositions, with increased confidence
of protein identification compared with our previous reports using MALDI QqTOF and MALDI IT. CID fragmentation of singly-charged
peptides provided sufficient information for conclusive identification of the isolated proteins. We then assessed the resolution,
accuracy, and sensitivity provided by this instrument in the context of analyzing the isolated protein assemblies. Our analysis
of complex mixtures of singly-charged ions up to m/z 4000 showed that (1) the resolving power, inversely proportional to the square root of m/z, had over four orders of magnitude dynamic range; (2) internal calibration led to improved accuracy, with an average absolute
mass error of 0. 5 ppm and a distribution centered at 0 ppm; and (3) subfemtomole sensitivity was achieved using both CHCA
and DHB matrices. Additionally, our analyses of a synthetic phosphorylated peptide in mixtures showed subfemtomole level of
detection using neutral loss scanning. 相似文献
84.
We consider the aromaticity of biphenylene and structurally related linear or angular [n]phenylenes for which the direct application of the model of conjugated circuits does not offer valid expressions for resonance energy and aromaticity. We located the cause of this problem as being due to Kekulé valence structures in which neighboring benzenoid rings are connected by two CC double bonds. By restricting the selection of Kekulé valence structures to those that contribute to Clar structures of such systems, we were able to show that linear and angular [n]phenylenes have approximately similar resonance energies, with angular [n]phenylenes being slightly more stable due to second order contributions arising from disjoint conjugated circuits. Expressions for resonance energies of [n]phenylenes up to n = 8 are listed and recursion expressions for higher n values are outlined. 相似文献
85.
Alexandru C. Razus Liviu Birzan Mihaela Cristea Eugenia Andreea Dragu Anamaria Hanganu 《Monatshefte für Chemie / Chemical Monthly》2011,40(9):1271-1282
Abstract
Two synthesis strategies were used for the generation of azulene-1-yl diazenes substituted at C-3 with a phenyl-chalcogenyl moiety, the synthesis of azulenes substituted at C-3 followed by azo-coupling and azulene substitution at C-3 in azulene-azo dyes. The last synthetic route seems to give more satisfactory results for the synthesis of the desired chalcogenic derivatives. Another target of this study was to investigate the changes induced by the phenyl-chalcogenic substitution on the NMR and UV-vis spectra, and also to compare this effect with the one exerted by halogen atoms and by strongly electron donating groups such as AcNH or PhCOO. Whereas the latter groups exhibit a strong influence on the NMR and UV-vis spectra, PhS, PhSe, or PhTe groups as well as halogen atoms produce only a small effect because of the moderate change in electron distribution over the entire molecule. 相似文献86.
Recent developments in bioanalytical instrumentation, MS detection, and computational data analysis approaches have provided researchers with capabilities for interrogating the complex cellular glycoproteome, to help gain a better insight into the cellular and physiological processes that are associated with a disease and to facilitate the efforts centered on identifying disease-specific biomarkers. This review describes the progress achieved in the characterization of protein glycosylation by using advanced capillary and microfluidic MS technologies. The major steps involved in large-scale glycoproteomic analysis approaches are discussed, with special emphasis given to workflows that have evolved around complex MS detection functions. In addition, quantitative analysis strategies are assessed, and the bioinformatics aspects of glycoproteomic data processing are summarized. The developments in commercial and custom fabricated microfluidic front-end platforms to ESI- and MALDI-MS instrumentation, for addressing major challenges in carbohydrate analysis such as sensitivity, throughput, and ability to perform structural characterization, are further evaluated and illustrated with relevant examples. 相似文献
87.
88.
Alexandru Vlasceanu Dr. Søren L. Broman Anne S. Hansen Anders B. Skov Prof. Dr. Martina Cacciarini Prof. Dr. Anders Kadziola Prof. Dr. Henrik G. Kjaergaard Prof. Dr. Kurt V. Mikkelsen Prof. Dr. Mogens Brøndsted Nielsen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(31):10796-10800
The conversion and efficient storage of solar energy is recognized to hold significant potential with regard to future energy solutions. Molecular solar thermal batteries based on photochromic systems exemplify one possible technology able to harness and apply this potential. Herein is described the synthesis of a macrocycle based on a dimer of the dihydroazulene/vinylheptafulvene (DHA/VHF) photo/thermal couple. By taking advantage of conformational strain, this DHA–DHA macrocycle presents an improved ability to absorb and store incident light energy in chemical bonds (VHF–VHF). A stepwise energy release over two sequential ring‐closing reactions (VHF→DHA) combines the advantages of an initially fast discharge, hypothetically addressing immediate energy consumption needs, followed by a slow process for consistent, long‐term use. This exemplifies another step forward in the molecular engineering and design of functional organic materials towards solar thermal energy storage and release. 相似文献
89.
Felicia Dragan I. Bratu Gh. Borodi Mihaela Toma A. Hernanz S. Simon Gh. Cristea R. Peschar 《Journal of inclusion phenomena and macrocyclic chemistry》2007,59(1-2):125-130
Aqueous-solution complexes of β-cyclodextrin (β-CD) with metoprolol tartrate (MET) have been analysed with 1H NMR and UV–vis spectroscopy. With 1H NMR a [1:1] stoichiometry could be established for the β-CD-MET complex while its stability constant was determined with
UV–vis spectroscopy. Powder diffraction data of a polycrystalline sample of the β-CD-MET complex show that a novel product
has been formed, likely to be a β-CD-MET [1:1] inclusion complex. Also Hyperchem MM+ molecular-dynamics results suggest an
inclusion complex and from 1H NMR data it is inferred that probably the MET is docked in the CD with the formers methoxyethyl-benzene moiety in front.
Mihaela Toma is Socrates/Erasmus student at UNED Madrid 相似文献
90.
By adopting the convention that shared double bonds in polycyclic conjugated hydrocarbons contribute with one -electron and unshared ones with two -electrons, a partition of -electrons in each ring (-electron content, EC) can be obtained by averaging over all Kekulé structures, which are assumed to have equal weights. This affords a simple measure of local aromaticity that is comparable with other such local aromaticity indices in polycyclic benzenoids. 相似文献