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1.
An intermolecular aldol reaction of 20S-camptothecin-7-aldehyde in the presence of strong bases affords an unusual dimeric compound, the structure and stereochemistry of which was assigned on the basis of NMR analysis and MM2 calculations. 相似文献
2.
Crovella S Antcheva N Zelezetsky I Boniotto M Pacor S Verga Falzacappa MV Tossi A 《Current protein & peptide science》2005,6(1):7-21
Host defense peptides (HDPs) are endogenous antibiotics that play a multifunctional role in the innate immunity of mammals. Among these, beta-defensins contribute to mucosal and epithelial defense, also acting as signal molecules for cellular components of innate and adaptive immunity. Numerous members of this family have been identified in mammalian and avian species, and genomic studies in human and mouse indicate a considerable complexity in their gene organization. Recent reports on the evolution of primate and rodent members of this family indicate quite a complex pattern of variation. In this review we briefly discuss the evolution of mammalian beta-defensins in relation to other types of defensins, and then concentrate on the evolution of beta-defensins 1 to 4 in primates. In particular, the surprisingly varied patterns of evolution, which range from neutral or weakly purifying, to positive selection to a high level of conservation are analyzed in terms of possible genetics, structural or functional implications, as well as to observed variations on the antimicrobial activity in vitro. The role of polymorphisms in the genes encoding for these host defense peptides in determining susceptibility to human diseases are also briefly considered. 相似文献
3.
Dissociative electron transfers (ET) are reactions in which the ET is associated with the cleavage of a sigma bond. Although a rather satisfactory amount of information is currently available on the intermolecular and heterogeneous dissociative ET reactions, less is known for the corresponding intramolecular processes, despite the relevance of these reactions in both chemistry and biochemistry. This tutorial review focuses on the most recent developments in this area, with particular emphasis on the reactions occurring in well-defined Donor-Spacer-Acceptor molecular systems. The goal is to provide the reader with the essential background to understand and possibly predict the feasibility and rates of these reactions, as well as to stimulate the application of the intramolecular dissociative ET concepts and related issues to still unexplored molecular systems. 相似文献
4.
Mathematical Notes - The Boros–Moll polynomials $$P_m(a)$$ arise in the evaluation of a quartic integral. In the past few years, there has been some remarkable research on the properties of... 相似文献
5.
Gioacchini AM Menotta M Bertini L Rossi I Zeppa S Zambonelli A Piccoli G Stocchi V 《Rapid communications in mass spectrometry : RCM》2005,19(17):2365-2370
This study describes a rapid method to identify different truffle species by analysis of their volatile compound fraction using static headspace solid-phase microextraction gas chromatography/mass spectrometry. The volatile organic compounds (VOCs) were extracted using a new 2-cm 50/30 microm DVB/CAR/PDMS fiber placed for 10 min in the headspace of the truffle sample with the vial maintained at 20 degrees C (in a thermostatically controlled analysis room). The mass spectra of the VOC chromatograms were represented as 'fingerprints' of the analysed samples. Next, stepwise factorial discriminant analysis afforded a limited number of characteristic fragment ions that allowed a classification of the truffle species studied. This new method provides an effective approach to rapid quality control and identification of truffle species by analysis of their volatile fraction. Moreover, this method offers the advantage of minimizing thermal, mechanical, and chemical modifications of the truffles, thereby reducing the risk of analytical artifacts. 相似文献
6.
[reaction: see text] 2,3-Disubstituted furo[3,2-b]pyridines, 2,3-disubstituted furo[2,3-b]pyridines, and 2,3-disubstituted furo[2,3-c]pyridines are readily prepared under mild conditions via the palladium-catalyzed cross-coupling of 1-alkynes with o-iodoacetoxy- or o-iodobenzyloxypyridines, followed by electrophilic cyclization by I(2) or by PdCl(2) under a balloon of carbon monoxide. 相似文献
7.
Zusammenfassung Es wird über Strom-Spannungskurven in Phenylphosphoroxydichlorid berichtet, welche mit verschiedenen Elektrodenkombinationen erhalten wurden. Die bei der Polarographie leitsalzfreier Phenylphosphoroxydichloridlösungen beobachteten Erscheinungen werden auf Migrationsströme zurückgeführt.Mit 3 Abbildungen3. Mitt.:H. Dehn, V. Gutmann undG. Schöber, Mh. Chem.94, 312 (1963). 相似文献
8.
[reaction: see text] An expedient synthesis of diverse 2-amino-4-heteroarylpyrimidines via a 2-chloropyrimidine intermediate is described. A series of potentially biologically active analogues have been synthesized in two parallel steps to afford focused arrays. 相似文献
9.
Sabrina H. J. De Beukeleer H. O. Desseyn 《Journal of Thermal Analysis and Calorimetry》1996,47(1):135-142
Dithiomalonamide [H2A, CH2(CSNH2)2] and 2,2-dimethyldithiomalonamide [H2B, C(CH3)2(CSNH2)2] can act as bidentate ligands and form stable, cationic 1∶2 complexes with general formula M2(H2L)2X2 [M=Ni2+, Pd2+, Pt2+;X=C1, Br, I; H2L=H2A, H2B] in strong acidic medium. An elaborate thermal study is presented, based on results from elemental analyses and vibrational studies (IR and Raman spectroscopy). The H2A complexes start to decompose by releasing two HX molecules whereafter a stable intermediate M(HA)2 is formed. The H2B complexes degrade in a different way; the metal-sulphur bond is broken and the ligand is expelled as a whole. Influences of the metal ion and of the halogenide counterions are investigated. 相似文献
10.
Lidiane C. Castro Yasmim R. Jaconiano Tereza C. S. Evangelista Sabrina B. Ferreira 《合成通讯》2019,49(10):1316-1324
The synthesis and characterization of three novel N2O-donor ligands containing the group 4-[1-β-d-2,3,4,6-tetra-O-acetyl-galactosyl)]benzaldehyde are presented. The insertion of this group was designed to increase the absorption of the prodrug in tumor cells, and is part of an ongoing work in our group with tridentate ligands to develop potential cobalt(III) prodrugs. The synthetic route described here allowed the isolation of pure ligands with yields ranged 81–89%. Finally, compounds were characterized by IR, NMR and HRMS (ESI+). 相似文献