1,720,981 research outputs found
In Silico Engineering of Enzyme Access Tunnels
No full textEnzyme engineering is a tailoring process that allows the modification of naturally occurring enzymes to provide them with improved catalytic efficiency, stability, or specificity. By introducing partial modifications to their sequence and to their structural features, enzyme engineering can transform natural enzymes into more efficient, specific and resistant biocatalysts and render them suitable for virtually countless industrial processes. Current enzyme engineering methods mostly target the active site of the enzyme, where the catalytic reaction takes place. Nonetheless, the tunnel that often connects the surface of an enzyme with its buried active site plays a key role in the activity of the enzyme as it acts as a gatekeeper and regulates the access of the substrate to the catalytic pocket. Hence, there is an increasing interest in targeting the sequence and the structure of substrate entrance tunnels in order to fine-tune enzymatic activity, regulate substrate specificity, or control reaction promiscuity. In this chapter, we describe the use of a rational in silico design and screening method to engineer the access tunnel of a fructosyl peptide oxidase with the aim to facilitate access to its catalytic site and to expand its substrate range. Our goal is to engineer this class of enzymes in order to utilize them for the direct detection of glycated proteins in diabetes monitoring devices. The design strategy involves remodeling of the backbone structure of the enzyme, a feature that is not possible with conventional enzyme engineering techniques such as single-point mutagenesis and that is highly unlikely to occur using a directed evolution approach. The proposed strategy, which results in a significant reduction in cost and time for the experimental production and characterization of candidate enzyme variants, represents a promising approach to the expedited identification of novel and improved enzymes. Rational enzyme design aims to provide in silico strategies for the fast, accurate, and inexpensive development of biocatalysts that can meet the needs of multiple industrial sectors, thus ultimately promoting the use of green chemistry and improving the efficiency of chemical processes
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
Rational backbone redesign of a fructosyl peptide oxidase to widen its active site access tunnel
No full textFructosyl peptide oxidases (FPOXs) are enzymes currently used in enzymatic assays to measure the concentration of glycated hemoglobin and albumin in blood samples, which serve as biomarkers of diabetes. However, since FPOX are unable to work directly on glycated proteins, current enzymatic assays are based on a preliminary proteolytic digestion of the target proteins. Herein, to improve the speed and costs of the enzymatic assays for diabetes testing, we applied a rational design approach to engineer a novel enzyme with a wider access tunnel to the catalytic site, using a combination of Rosetta design and molecular dynamics simulations. Our final design, L3_35A, shows a significantly wider and shorter access tunnel, resulting from the deletion of five-amino acids lining the gate structures and from a total of 35 point mutations relative to the wild-type (WT) enzyme. Indeed, upon experimental testing, our engineered enzyme shows good structural stability and maintains significant activity relative to the WT
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
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
Molecular Modelling Of Small Molecule Diffusion In Biopolymer Blends Membranes For Biomedical Applications
No full textAge- and diabetes-related nonenzymatic cross-links in collagen fibrils: candidate amino acids involved in advanced glycation end-products.
No full textCarbohydrate-functionalized collagen matrices: design and characterization of a novel neoglycosylated biomaterial
No full textCollagen matrices have been neoglycosylated with lactose by reductive amination at lysine side chains. AFM analysis highlights that the chemical does not affect molecular assembly into fibrils. Moreover, ELLA biochemical assays show that the glycan moiety is efficiently exposed on the matrix surface for receptor recognition
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