1,720,989 research outputs found
Structural studies on human and parasite enzymes related to disease
No full textMacromolecular X-ray crystallography plays a key role in the drug discovery process, providing essential clues to explain the mechanism of action of protein targets and to elucidate the inhibitor binding mode. The detailed analysis of crystal structures is precious to conceive powerful inhibitors, through a rational structure-based drug discovery approach, that may lead to the development of new drugs. During my PhD, I had the opportunity to face two relevant topics related to human
diseases, namely human and parasite Heat shock protein 90 (Hsp90) and human 14-3-3σ, and to study them through X-ray crystallography. In the first chapter, X-ray crystallography was exploited to characterize the role on nucleotide binding of both Arg97 in the N-terminal domain (NTD) of Leishmania braziliensis Hsp90 and of Lys112 in the human counterpart to find new determinants to selectively target the parasite enzyme. In details, we investigated the contribution of parasite Arg97 through the introduction of this residue, by site-directed mutagenesis, in the human protein generating the “leishmanized” variant of human Hsp90-NTD. The alanine variant was also generated to deeply understand the role of this non-conserved residue in human and parasite proteins. A variety of ADP and ATP analogues and cAMP were used to probe the role of these residues. According to our structural results residue Arg97 of Leishmania braziliensis Hsp90-NTD and Lys112 in the human protein are not crucial for substrate binding, making them not exploitable for the development of
selective inhibitors targeting parasite Hsp90 over the human counterpart. In the second chapter, an X-ray crystallographic screening was performed on human 14-3- 3σ using small molecular weight compounds to identify new modulators of proteinprotein interactions (PPIs) involving this target. As a matter of fact, human 14-3-3σ protein is crucial for various cellular cascades, making it a target for the development of new anticancer and antileukemia drugs. The crystal structure of h14-3-3σ was solved in complex with pyridoxal phosphate (PLP) and inosine monophosphate (IMP). Notably, our
structures revealed the fundamental contribution of the phosphate moiety present in both compounds for h14-3-3σ recognition and binding. The structural informationachieved will guide the rational design of new h14-3-3σ PPIs inhibitors based on these innovative scaffolds
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
Validation of recombinant chicken liver bile acid binding protein as a tool for cholic acid hosting
Full text linkBile acids (BAs) are hydroxylated steroids derived from cholesterol that act at the intestinal level to facilitate the absorption of several nutrients and also play a role as signaling molecules. In the liver of various vertebrates, the trafficking of BAs is mediated by bile acid‐binding proteins (L‐BABPs). The ability to host hydrophobic or amphipathic molecules makes BABPs suitable for the distribution of a variety of physiological and exogenous substances. Thus, BABPs have been proposed as drug carriers, and more recently, they have also been employed to develop innovative nanotechnology and biotechnology systems. Here, we report an efficient protocol for the production, purification, and crystallization of chicken liver BABP (cL‐BABP). By means of target expression as His6‐tag cL‐BABP, we obtained a large amount of pure and homogeneous proteins through a simple purification procedure relying on affinity chromatography. The recombinant cL‐BABP showed a raised propensity to crystallize, allowing us to obtain its structure at high resolution and, in turn, assess the structural conservation of the recombinant cL‐BABP with respect to the liverextracted protein. The results support the use of recombinant cL‐BABP for the development of drug carriers, nanotechnologies, and innovative synthetic photoswitch systems
Catechol-O-methyltransferase (COMT)
No full textCatechol-O-methyltransferase (COMT) is a magnesium-dependent enzyme responsible for the catalytic O-methylation reaction of endogenous catecholamines and neurotransmitters. It is also involved in the metabolic process of various hormones and drugs incorporating catecholic structures. COMT has become an attractive biological target in the central nervous system (CNS) disorders associated with dopamine depletion, such as Parkinson’s disease (PD), schizophrenia, and depression. In this chapter, we will provide a thorough description of COMT structural features and its physiopathological roles. Then, we will discuss the different generations of compounds proposed as COMT inhibitors from a medicinal chemistry perspective, including a structure-activity relationship analysis for the best-performing classes of analogues. In addition, updated information about the clinical benefits of the most relevant inhibitors will be highlighted
Dynamic interplay between copper toxicity and mitochondrial dysfunction in Alzheimer’s disease
Full text linkAlzheimer’s disease (AD) is a neurodegenerative disorder, affecting millions of people worldwide, a number expected to exponentially increase in the future since no effective treatments are available so far. AD is characterized by severe cognitive dysfunctions associated with neuronal loss and connection disruption, mainly occurring in specific brain areas such as the hippocampus, cerebral cortex, and amygdala, compromising memory, language, reasoning, and social behavior. Proteomics and redox proteomics are powerful techniques used to identify altered proteins and pathways in AD, providing relevant insights on cellular pathways altered in the disease and defining novel targets exploitable for drug development. Here, we review the main results achieved by both-omics techniques, focusing on the changes occurring in AD mitochondria under oxidative stress and upon copper exposure. Relevant information arises by the comparative analysis of these results, evidencing alterations of common mitochondrial proteins, metabolic cycles, and cascades. Our analysis leads to three shared mitochondrial proteins, playing key roles in metabolism, ATP generation, oxidative stress, and apoptosis. Their potential as targets for development of innovative AD treatments is thus suggested. Despite the relevant efforts, no effective drugs against AD have been reported so far; nonetheless, various compounds targeting mitochondria have been proposed and investigated, reporting promising results
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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