1,720,989 research outputs found
Organocatalytic Asymmetric Methodologies towards the Synthesis of Atropisomeric N-Heterocycles
No full textA perspective on the literature dealing with the organocatalytic asymmetric preparation of axially chiral N-heterocycles is provided. A particular focus is devoted to rationalize the synthetic strategies employed in each case. Moreover, specific classes of organocatalysts are shown to stand out as privileged motives for the stereoselective preparation of such synthetically challenging molecular architectures. Finally, an overview of the main trends in the field is given. 1 Introduction 2 Five-Membered Rings 2.1 Arylation 2.2 Dynamic Kinetic Resolution 2.3 Ring Construction 2.4 Central-to-Axial Chirality Conversion and Chirality Transfer 2.5 Desymmetrization 3 Six-Membered Rings 3.1 Desymmetrization 3.2 (Dynamic) Kinetic Resolution 3.3 Ring Construction 3.4 Central-to-Axial Chirality Conversion 4 Conclusion
Catalyst- and Additive-Free Electrochemical CO2 Fixation into Morita-Baylis-Hillman Acetates
Full text linkThe electrochemical carboxylation of Morita-Baylis-Hillman (MBH) acetates with CO2 is presented. The process proceeds in the absence of transition metal catalysts and relies on the cathodic reduction of MBH acetates to generate nucleophilic anions able to trap low-pressure CO2. Valuable succinate derivatives are obtained (20 examples) in high yields (up to 90%) and high functional group tolerance. A remarkable substrate controlled (electronic nature) regioselectivity of the transformation was documented along with a mechanistic rationale based on control experiments
IMMUNOCHEMICAL LOCALIZATION OF CALCIUM CALMODULIN-DEPENDENT PROTEIN-KINASE-I
No full textCa2+/calmodulin-dependent protein kinase I (CaM kinase I) was originally identified in rat brain based on its ability to phosphorylate site 1 of synapsin I. Recently a cDNA for the rat brain enzyme has been cloned and the primary structure elucidated [Picciotto et al. (1993), J. Biol. Chem., 268:26512-26521]. The rat cDNA encoded a protein of 374 amino acids with a calculated M(r) of 41,636. Antibodies have now been raised against the recombinant kinase expressed in E. coli as a glutathione-S-transferase fusion protein. Immunoblot analysis of rat cortex lysates revealed two major immunoreactive bands of similar to M(r) 38,000 and 42,000. Minor immunoreactive species of slightly lower M(r) were also detected. Two distinct CaM kinase I activities were partially purified from rat brain and shown to correspond to the two major immunoreactive species. A variety of immunoreactive species of M(r) 35-43,000 were detected in ́ ́brain ́ ́ tissue from cow, zebra finch, goldfish, Xenopus, lamprey, and Drosophila. In rat brain, immunocytochemistry revealed strong staining in cortex, hippocampus, amygdala, hypothalamus, brain stem, and choroid plexus. The labelling was mainly observed in neuropil but clusters of intensely labelled neuronal cell bodies were also detected all along the neuraxis. Neuronal nuclei and glial cells did not appear to be stained. Subcellular fractionation studies confirmed the cytosolic localization of the kinase in the brain. In various rat non-neuronal tissues and in a number of cell lines, immunoreactive species of similar to M(r) 38,000 and similar to 42,000 were detected at lower levels than that detected in brain. The M(r) 38,000 and 42,000 species were also found in different ratios and at different levels in the non-neuronal tissues. These results support a role for CaM kinase I in the regulation of multiple neuronal processes. Furthermore, the widespread cell and tissue distribution suggests that CaM kinase I may function as a ubiquitous multi-functional protein kinase. Finally, the multiple immunoreactive species may represent isoforms of CaM kinase I
Fibroblasts behavior after N-acetylcysteine and amino acids exposure: extracellular matrix gene expression.
No full textReactive oxygen species (ROS) are chemically reactive molecules with impaired electrons that make them unstable and able to react easily with a great variety of molecules. The main targets of ROS are DNA, proteins, and membrane phospholipids. In the skin, ROS are able to affect the production of collagen and elastin, the main components of the extracellular matrix (ECM). This action contributes to the skin's aging. N-Acetylcysteine (NAC) is an acetylated cysteine residue with excellent anti-oxidant activity that boosts glutathione (GSH) levels. This study evaluates the effect of a solution of NAC and amino acids, which is used in aesthetic medicine as an intra-dermal injective treatment, on fibroblast behavior. To this aim, the expression levels of some ECM-related genes (HAS1, HYAL1 ELN, ELANE, MMP2, MMP3, MMP13, COL1A1, COL3A1) were analyzed on cultured dermal fibroblasts using real-time reverse transcription polymerase chain reaction (RT-PCR). All but two collagen genes were up-regulated after 24 hr of treatment
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Organocatalytic Enantioselective 1,3-Dipolar [6+4] Cycloadditions of Tropone
No full textA highly stereoselective 1,3-dipolar [6+4] cycloaddition towards bridged azabicyclo[4.3.1]decane scaffolds has been developed, reacting aldehydes, 2-aminomalonates and tropone under mild conditions in the presence of a chiral phosphoric acid catalyst. The scope is demonstrated for a series of aldehydes and 2-aminomalonates, and the reaction proceeds in high yields, >95:5 d.r. and up to 99 % ee. A series of transformations, as well as a mechanistic proposal, are presented
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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