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Regiospecificity modification of Geobacillus zalihae T1 lipase via molecular engineering approaches
Get PDFTo date, only a few lipases have been reported to have sn-1, sn-2, or sn-3-
regioselectivity. This single selectivity offers various important applications, especially
the most valuable is producing chiral products for the drug and food industries. T1 lipase,
which was isolated from Geobacillus zalihae with specific regioselectivity at sn-1,3, was
used in this study. This work aims to study the potential of implementing rational and
semi-rational protein design methods to target the lid and binding site area of sn-1,3-
regiospecific T1 lipase. Three strategies were applied for modifying T1 lipase
regiospecificity, and this modification is essential to improve the T1 lipase industrial
application, especially in the production of chiral molecules. The first strategy targeted
the lid area by a semi-rational protein design method and resulted in 7 variants (F180C,
F180G, F180S, F180L, F180I, F180N, and F180Y). The resulting variants showed an
increased and decreased in their optimum temperature and thermal denaturation point
ranging from 60 to 75 °C, and 63 to 78 °C, respectively, compared to wt-T1, which has
an optimum temperature of 70 °C and thermal denaturation point at a temperature of 73
°C. The resulting variants from this strategy have optimum pH as wt-T1 lipase and
displayed a modified selectivity toward long-chain pNP-ester (C10-C18) compared to
wt-T1 lipase, which has a preference towards C10-C14. All resulting variants displayed
different catalytic efficiencies ranging from 309 to 604 ×10-6 s-1 /mM compared to wt-
T1 catalytic efficiency of 518.4 ×10-6 s-1 /mM. However, this strategy didn’t show any
regioselectivity modification. The second strategy applied was rational design around
the binding site, and this approach resulted in only one variant with five (5) mutation
sites (1M/F25L/I262V/E189K/V247I). This resulting variant did not show any changes
at optimum temperature and pH but enhanced the selectivity toward long-chain pNPester
(C14-C18) compared to wt-T1 lipase. The resulting variant showed improved
catalytic efficiency around 5472 ×10-6 s-1 /mM compared to wt-T1 lipase but did not
result in any regiospecific modifications. The third strategy targeted both the lid by
rational design (F180G/F181S) and the oxyanion hole by semi-rational design strategy,
which resulted in twelve (12) variants (F16X, X=C, G, V, Y, D, H, S, L, I, W, F, N). The
newly generated variants conserved the optimum temperature of 70 ℃. However, thermal
denaturation was negatively affected, and this was represented by a decline in the
denaturation temperature ranging from 5 to 7 °C. However, these targeted mutations
shifted the optimum pH to 10 for some variants compared to pH 9 for wt-T1. Regarding
the selectivity study, the resulting variant showed improved selectivity toward pNP-ester
long-chain fatty acids from C12-C18 compared to wt-T1 lipase. In addition, the variants
of this strategy displayed different catalytic efficiencies, ranging from 86.4 to 777 ×10-
6 s-1 /mM compared to wt-T1 lipase. Furthermore, six variants, F16I, F16V, F16W, F16S,
F16G, and F16C, displayed a regioselectivity modification from sn-1,3 regioselectivity
of wt-T1 to only sn-3. Gas- chromatography (GC) with flame ionization detection of
these six variants confirmed the regioselectivity modification. The modified
regiospecific variants were shown to have a varied preference toward different palm
stearin fatty acids lengths ranging from C16 to C20:1 compared to wt-T1 lipase with the
specificity of C16 to C18:1. The sn-3 modified regiospecific structure (F16W) and wt-
T1 lipase structures were remodelled and predicted within open conformation, then
subjected to docking and molecular simulation (MD) study complexed with an
acylglycerol analogue as a substrate. The docking study showed that sn-3 modified
regiospecific structure has a higher affinity toward sn-3 acylglycerol chain than wt-T1,
which displayed binding affinity toward sn-1,3 acylglycerol chain. Whereas the MD
simulation study showed conformational changes that occurred were approximately on
the lid domain and distant from the oxyanion hole mutation site (Zn2+ coordination
domain), consisting of helices α3 and α5. The conformational changes resulting from
altering bulky side-chain residues of the lid and oxyanion hole have increased binding
site flexibility and affected the hydrogen networking of the Zn2+ coordination domain.
In conclusion, the substitution of lid and oxyanion hole residues (strategy three)
successfully modified regioselectivity and shifted lipase specificity and activity.
Therefore, targeting both the lid and binding site (strategy three) is sufficient to create a
novel regiospecificity of an enzyme. Thus, sn-3 lipase is essential in producing pure
fatty acids with high specificity, which can be applied to obtain high-value chemicals for
drug and food industries
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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