1,720,962 research outputs found
Exploring the effect of a peptide additive on struvite formation and morphology: a high-throughput method
No full textPrecipitation of struvite (MgNH4PO4·6H2O), a slow-release fertilizer, provides a means of recycling phosphate from wastewater streams. In this work, a high-throughput struvite precipitation method is developed to investigate the effects of a peptide additive. The reactions occurred in small volumes (300 μL or less) in a 96-well plate for 45 minutes. The formation of struvite was monitored by fitting absorbance at 600 nm over time to a first order model with induction time, with the addition of peptide inducing significant changes to the yield parameter and formation constant in that model. The impact of struvite seed dosing was also investigated, highlighting the importance of optimization when peptide is present. The composition of the precipitate was confirmed through Fourier-transform infrared spectroscopy, while morphology and crystal size were analyzed through optical microscopy. Crystals had a higher aspect ratio when precipitated with the peptide. Finally, the utility of the high-throughput platform was demonstrated with a 25 full factorial design to capture the effects and interactions of: magnesium dose, mixing time, seed dose, pH, and temperature. Overall, this study quantifies novel effects of a sequence-defined peptide on struvite formation and morphology via a newly developed high throughput platform
Self-Assembly and Rearrangement of a Polyproline II Helix Peptide on Gold
No full textPolyproline peptide sequences have gained popularity as anchors for peptide-based self-assembled monolayers (SAMs) due to their attractive properties. In this work, peptides containing the polyproline II helix (PPII) conformation were designed and assembled on gold (Au). A quartz crystal microbalance with dissipation was used to characterize SAM formation kinetics and related properties. Peptides were designed with the sequence (GPPPPPG)2C. It was discovered that a biexponential adsorption and rearrangement model describes the binding kinetics of the PPII-containing peptide on Au. In this model, an initial reversible binding step is followed by an irreversible rearrangement step, given by parameter kt. This study found kt to be approximately 0.00064 s–1 for the PPII-containing peptides. Similarly, we found that the adsorption of the PPII-containing peptide on Au, given by ΔGads, was thermodynamically favorable (−7.8 kcal mol–1) and comparable to other common thiol terminated SAMs on Au. Furthermore, we characterized SAM properties via QCM-D, Fourier-transform infrared (FTIR) spectroscopy, and electrochemical techniques to reveal high molecular density SAMs consisting of PPII helices. In addition, these SAMs were found to have high antifouling properties. Overall, this study characterizes the fundamental assembly mechanisms, particularly, rearrangement of PPII-containing peptides for the first time, which will be useful in the designing of future peptide-based SAMs with high surface coverage and antifouling properties
Self-Assembly and Rearrangement of a Polyproline II Helix Peptide on Gold
No full textPolyproline peptide sequences have gained popularity as anchors for peptide-based self-assembled monolayers (SAMs) due to their attractive properties. In this work, peptides containing the polyproline II helix (PPII) conformation were designed and assembled on gold (Au). A quartz crystal microbalance with dissipation was used to characterize SAM formation kinetics and related properties. Peptides were designed with the sequence (GPPPPPG)2C. It was discovered that a biexponential adsorption and rearrangement model describes the binding kinetics of the PPII-containing peptide on Au. In this model, an initial reversible binding step is followed by an irreversible rearrangement step, given by parameter kt. This study found kt to be approximately 0.00064 s–1 for the PPII-containing peptides. Similarly, we found that the adsorption of the PPII-containing peptide on Au, given by ΔGads, was thermodynamically favorable (−7.8 kcal mol–1) and comparable to other common thiol terminated SAMs on Au. Furthermore, we characterized SAM properties via QCM-D, Fourier-transform infrared (FTIR) spectroscopy, and electrochemical techniques to reveal high molecular density SAMs consisting of PPII helices. In addition, these SAMs were found to have high antifouling properties. Overall, this study characterizes the fundamental assembly mechanisms, particularly, rearrangement of PPII-containing peptides for the first time, which will be useful in the designing of future peptide-based SAMs with high surface coverage and antifouling properties
Exploring the effect of a peptide additive on struvite formation and morphology: a high-throughput method
No full textPrecipitation of struvite (MgNH4PO4·6H2O), a slow-release fertilizer, provides a means of recycling phosphate from wastewater streams. In this work, a high-throughput struvite precipitation method is developed to investigate the effects of a peptide additive. The reactions occurred in small volumes (300 μL or less) in a 96-well plate for 45 minutes. The formation of struvite was monitored by fitting absorbance at 600 nm over time to a first order model with induction time, with the addition of peptide inducing significant changes to the yield parameter and formation constant in that model. The impact of struvite seed dosing was also investigated, highlighting the importance of optimization when peptide is present. The composition of the precipitate was confirmed through Fourier-transform infrared spectroscopy, while morphology and crystal size were analyzed through optical microscopy. Crystals had a higher aspect ratio when precipitated with the peptide. Finally, the utility of the high-throughput platform was demonstrated with a 25 full factorial design to capture the effects and interactions of: magnesium dose, mixing time, seed dose, pH, and temperature. Overall, this study quantifies novel effects of a sequence-defined peptide on struvite formation and morphology via a newly developed high throughput platform
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
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