1,720,999 research outputs found
Chemistry of sulphenyl halides and sulphenamides
No full textThe chemistry of sulphenyl halides. sulphenamides and related compounds has been reviewed several times in a comprehensive way' . l8 . The reader should therefore refer to these articles for a detailed account of the extremely rich chemistry of these compounds . The aim of the present chapter is to present the most significant advances in the chemistry of sulphenyl halides and sulphenamides. from both the synthetic and theoretical point of view . Therefore only the most important classes of compounds and their reactions will be reviewed
Reversible aggregation/deaggregation of gold nanoparticles induced by a cleavable dithiol linker
No full textAqueous solutions of Au colloids (12 +/- 4 nm size) when treated with a blend of mono- and dithiols aggregate forming stable clusters, as evidenced by the shift of their surface plasmon (SP) band from 512 to ca. 600 nm. The presence of carboxylate ester functions on the dithiol allows its cleavage by addition of a cleaving agent, such as hydrazine. The cleavage process results in the breaking down of the clusters of nanoparticles and the shift of the SP band back to lower wavelengths. Further addition of dithiol causes the formation of the clusters again. The aggregation/deaggregation process may be monitored visually by following the color change from pink-red to purple and vice versa in the forward and backward steps, respectively
Procédé pour la fabrication de composés aldéhydiques ou cétoniques et aldéhydes et cétones obtenus par ce procédé
No full textThe phenylsulfenium cation: electronic structure and gas-phase reactivity
No full textThe energies and the geometries of the phenylsulfenium cation (PhS+) in the singlet and triplet states have been optimized ab initio at the MP2/6-31G*//MP2/6-31G* level. The (1A) PhS+ state is more stable by 63.0 kJ mol−1 than the (3A) PhS+ state. The PhS+ ion reacts in the gas-phase with ethylene and carbon monoxide affording the addition products [PhS+CO]+ and [PhS+CH2CH2]+ respectively. Ab initio calculations and MS/MS spectra suggest that the additions of CH2CH2 and CO occur at the sulfur center
Gold nanoparticles-based protease assay
Full text linkWe describe here a simple assay that allows the visual detection of a protease. The method takes advantage of the high molar absorptivity of the plasmon band of gold colloids and is based on the color change of their solution when treated with dithiols. We used C- and N-terminal cysteinyl derivatives of a peptide substrate exploiting its selective recognition and cleavage by a specific protease. Contrary to the native ones, cleaved peptides are unable to induce nanoparticles aggregation; hence, the color of the solution does not change. The detection of two proteases is reported: thrombin (involved in blood coagulation and thrombosis) and lethal factor (an enzyme component of the toxin produced by Bacillus anthracis). The sensitivity of this nanoparticle-based assay is in the low nanomolar range
Nanozymes: Gold-nanoparticle-based transphosphorylation catalysts
No full textThe self-assembly of triazacyclonane-functionalized thiols on the surface of nanosize gold particles provides a facile entry to functional gold nanoparticles that, upon complexation with ZnII, turn into powerful catalysts for the cleavage of phosphate esters (see scheme). Because of their RNase-like behavior they are dubbed nanozymes
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
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
- …
