1,721,119 research outputs found
Fig. 2 in A pair of threonines mark ent-kaurene synthases for phytohormone biosynthesis
Full text linkFig. 2. Representative phylogenetic tree for plant KS(L)/TPS-e subfamily. Green lines indicate KS activity, red lines KSL that mediate alternative product outcome. Green text indicates KS with known or assumed role in phytohormone biosynthesis, while blue text indicates enzymes known to produce 1 for secondary metabolism – i.e., in maize (Fu et al., 2016).Published as part of Brown, Reid, Jia, Meirong & Peters, Reuben J., 2021, A pair of threonines mark ent-kaurene synthases for phytohormone biosynthesis, pp. 1-6 in Phytochemistry (112672) 184 on page 2, DOI: 10.1016/j.phytochem.2021.112672, http://zenodo.org/record/829205
Fig. 4 in A pair of threonines mark ent-kaurene synthases for phytohormone biosynthesis
No full textFig. 4. TT motif is not required for the production of ent-kaurene (1). Extracted ion (m/z = 272) chromatograms demonstrating the production of 1 by all mutants (as indicated) by comparison to wild-type (WT) AtKS.Published as part of Brown, Reid, Jia, Meirong & Peters, Reuben J., 2021, A pair of threonines mark ent-kaurene synthases for phytohormone biosynthesis, pp. 1-6 in Phytochemistry (112672) 184 on page 3, DOI: 10.1016/j.phytochem.2021.112672, http://zenodo.org/record/829205
Between scents and sterols: Cyclization of labdane-related diterpenes as model systems for enzymatic control of carbocation cascades
No full textThe citrus scent arises from the volatile monoterpene limonene, whose cyclic nature can be viewed as a miniaturized form of the polycyclic sterol triterpenoids. In particular, these rings are all formed from poly-isoprenyl precursors via carbocation cascades. However, the relevant reactions are initiated by distinct mechanisms, either lysis/ionization of an allylic diphosphate ester bond, as in limonene synthases, or protonation of a terminal olefin or epoxide, as in lanosterol synthases. Labdane-related diterpenoids are unique in their utilization of both types of reactions. With over 7000 such natural products known, this pair of reactions clearly generates privileged scaffolds, hydrocarbon backbones from which biological activity is readily derived. Moreover, the relevant enzymes serve as model systems for terpene cyclization more generally. Indeed, investigation of their enzymatic structure-function relationships has highlighted the importance of catalytic base positioning within the active site cavity in specifying product outcomes. Conversely, comparison to the cyclases for other types of terpenoid natural products suggests new directions for discovery and/or engineering of the catalytic activity of those from labdane-related diterpenoid biosynthesis.This article is published as Peters, Reuben J. "Between scents and sterols: Cyclization of labdane-related diterpenes as model systems for enzymatic control of carbocation cascades." Journal of Biological Chemistry 301, no. 2 (2025). doi:10.1016/j.jbc.2024.10814
Two rings in them all: The labdane-related diterpenoids
Full text linkIn his original exposition of the biogenetic isoprenoid rule, L. Ruzicka noted the structural identity between the fused A/B rings of triterpenoids/sterols and certain multicyclic diterpenoids as part of the impetus leading to that profound insight. His prescient hypothesis that this chemical structure relationship reflects similarities in the initial cyclization of these diterpenoids with that occurring in triterpenoid biosynthesis has since been verified. However, this chemical structure relationship does not continue to hold true for the additional rings found in many of these di- and tri- terpenoid natural products. This is now appreciated to arise from differences in their subsequent biogenesis, specifically further cyclization and/or rearrangement of these diterpenoids after formation of an initial bicyclic intermediate in a separately catalyzed reaction. The trivial name for the hydrocarbon skeleton of the most commonly found version of the corresponding unique intermediate forms the basis for a unifying “labdane-related” designation. This defines a large super-family of diterpenoids that contains nearly 7,000 already known natural products. Many of these are found in plants, where the requisite biosynthetic machinery for gibberellin phytohormones, particularly the relevant diterpene cyclases, provides a biosynthetic reservoir that appears to have been repeatedly drawn upon to evolve new labdane-related diterpenoids. The potent biological activity of the “ancestral” gibberellins, which has led to the independent evolution of distinct gibberellin biosynthetic pathways in plants, fungi, and bacteria, is further discussed as an archetypical example of the selective pressure driving the observed diversification of the large super-family of labdane-related diterpenoid natural products.This is a manuscript of an article published as Peters, Reuben J. "Two rings in them all: the labdane-related diterpenoids." Natural product reports 27, no. 11 (2010): 1521-1530. doi: 10.1039/C0NP00019A . Posted with permission.</p
Peters, Reuben
No full textSee entry in Lauderdale County volume 1, page 53: https://digital.archives.alabama.gov/digital/collection/voter/id/179
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
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
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