1,721,176 research outputs found
Solvent effects on stereoselectivity: More than just an environment
No full textStereoselectivity is a major topic in organic synthesis. Intensive investigations into the role of solvents on diastereo- and enantioselective reactions, as well as temperature-dependent measurements of diastereomeric and enantiomeric ratios, have shed light on the existence of dynamic solvation effects. In this tutorial review, several examples of non-linear Eyring plots in stereoselective nucleophilic additions, cycloadditions, photochemical and enzymatic reactions are reported. Experimental data and spectroscopic analyses obtained in aliphatic and aromatic hydrocarbons, halohydrocarbons, ethers and mixtures lead to the formulation of a hypothesis on the inversion temperature phenomenon as being due to an equilibrium between distinct solute–solvent clusters, which are the real reactive species in solution. © 2009 The Royal Society of Chemistry
Changes in the biosynthesis of S-adenosylmethionine and in the protein methyl esyetification during cell aging: cultured bovine lenses as a model system
No full textSelective Deamidation and Enzymatic Methylation of Seminal Ribonuclease
No full textIsoenzymatic forms alfa2, alfa-beta, and beta2 of bovine seminal ribonuclease are generated by the transformation of beta-type into alfa-type subunit through deamidation of a single amide group. The residue involved in this selective deamidation has been identified as Asn67 . Deamidation occurs by formation of a cyclic imide intermediate involving the Gly at position 68. Opening of the cyclic imide may occur on either side of the nitrogen, generating
both the normal alfa-aspartyl and an isoaspartyl residue at position 67. The alfa-carboxyl of the isoaspartyl residue is effectively methylated by bovine brain protein carboxylmethyltransferase
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
INCREMENTO DELLA METILESTERIFICAZIONE DELLE PROTEINE DI MEMBRANA ERITROCITARIA IN SEGUITO A STRESS OSMOTICO
No full textVariations 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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
- …
