Showing 1971 - 1980 of 4695 Items

Context-dependent protein stabilization by methionine-to-leucine substitution shown in T4 lysozyme

Date: 1998-01-01

Creator: Leigh Ann Lipscomb

Nadine C. Gassner

Sheila D. Snow

Aimee M. Eldridge

Walter A., Baase

Devin L. Drew

Brian W. Matthews

Access: Open access

The substitution of methionines with leucines within the interior of a protein is expected to increase stability both because of a more favorable solvent transfer team as well as the reduced entropic cost of holding a leucine side chain in a defined position. Together, these two terms are expected to contribute about 1.4 kcal/mol to protein stability for each Met ā†’ Leu substitution when fully buried. At the same time, this expected beneficial effect may be offset by steric factors due to differences in the shape of leucine and methionine. To investigate the interplay between these factors, all methionines in T4 lysozyme except at the amino-terminus were individually replaced with leucine. Of these mutants, M106L and M120L have stabilities 0.5 kcal/mol higher than wild-type T4 lysozyme, while M6L is significantly destabilized (-2.8 kcal/mol). M102L, described previously, is also destabilized (-0.9 kcal/mol). Based on this limited sample it appears that methionine-to-leucine substitutions can increase protein stability but only in a situation where the methionine side chain is fully or partially buried, yet allows the introduction of the leucine without concomitant steric interference. The variants, together with methionine-to-lysine substitutions at the same sites, follow the general pattern that substitutions at rigid, internal sites tend to be most destabilizing, whereas replacements at more solvent-exposed sites are better tolerated.


A measurement of B(D+S ā†’ Ļ†l+Ī½) B(D+S ā†’ Ļ†Ļ€+)

Date: 1994-03-31

Creator: F. Butler

X. Fu

G. Kalbfleisch

W. R. Ross

P., Skubic

J. Snow

P. L. Wang

M. Wood

D. N. Brown

J. Fast

R. L. McIlwain

T. Miao

D. H. Miller

M. Modesitt

D. Payne

E. I. Shibata

I. P.J. Shipsey

P. N. Wang

M. Battle

J. Ernst

Y. Kwon

S. Roberts

E. H. Thorndike

C. H. Wang

J. Dominick

M. Lambrecht

S. Sanghera

V. Shelkov

T. Skwarnicki

R. Stroynowski

I. Volobouev

Access: Open access

Using the CLEO II detector at CESR, we have measured the ratio of branching fractions B(D+S ā†’ Ļ†l+Ī½) B(D+S ā†’ Ļ†Ļ€+) = 0.54 Ā± 0.05 Ā± 0.04. We use this measurement to obtain a model dependent estimate of B(D+S ā†’ Ļ†Ļ€+). Ā© 1994.


Bubbles & Bought-Ins: Reevaluating Price Movements in the Art Market

Date: 2020-01-01

Creator: Silas Wuerth

Access: Open access

Employs two tests for bubbles in the art market. First, a right-hand forward recursive augmented Dickey-Fuller test to identify explosive price movements. Second, a test for the statistical significance of hedonic regression price index coefficients after controlling for equity market performance. Finds strong evidence for a speculative bubble in the pre-Great Recession "Post-War & Contemporary" market. Evidence for this bubble diminishes but does not dissipate after accounting for the effect of failed sales on index returns.


A Bayesian hierarchical mixture model with continuous-time Markov chains to capture bumblebee foraging behavior

Date: 2021-01-01

Creator: Max Thrush Hukill

Access: Open access

The standard statistical methodology for analyzing complex case-control studies in ethology is often limited by approaches that force researchers to model distinct aspects of biological processes in a piecemeal, disjointed fashion. By developing a hierarchical Bayesian model, this work demonstrates that statistical inference in this context can be done using a single coherent framework. To do this, we construct a continuous-time Markov chain (CTMC) to model bumblebee foraging behavior. To connect the experimental design with the CTMC, we employ a mixture model controlled by a logistic regression on the two-factor design matrix. We then show how to infer these model parameters from experimental data using Markov chain Monte Carlo and interpret the results from a motivating experiment.


Narrative painting and visual gossip at the early-twentieth-century royal academy

Date: 2009-06-01

Creator: Pamela Fletcher

Access: Open access

Narrative paintings of modern life were immensely popular at the Royal Academy from the 1850s well into the early twentieth century. Perfectly suited to the Academy's culture of conversation, the pictures invited viewers to respond to the scenes as if they were real life situations, and gossip about the depicted characters as if they were real people. While such responses were routinely derided by critics as evidence of the public's lack of aesthetic sophistication, they offer tantalizing glimpses of the pictures' social lives. This article argues that taking gossip seriously as a mode of engagement with art both amplifies our understanding of the meanings, functions, and pleasures of narrative painting, and suggests specific connections between exhibition culture and the meanings of pictures. Using the richly documented reception of the 'problem pictures' of the 1910s and 1920s as the primary evidence, this article establishes a taxonomy of gossipy modes of engagement with narrative painting, and argues that gossiping about pictures allowed for the performance of individual identity, the creation of social and artistic groups, and connected public and private understandings of the world.


The Role of Social Media for Knowledge Sharing and Collaboration in Distributed Teams

Creator: Nicole Ellison

Matthew Weber

Access: Open access

Social media are providing a medium through which individuals are reshaping how they do many things ā€“ finding romantic partners, providing social support, grieving for loved ones, even buying mundane items like toothpaste. They are also reshaping organizations ā€“ the way they function, the relationships they contain, and the ways organizations interact with external stakeholders. In this paper, we consider the changes that social media have introduced to organizational knowledge-sharing practices. We believe the social and technical affordances of social media create new challenges for organizations and necessitate research examining the ways in which: (1) technological affordances impact knowledge sharing within and between teams, (2) interpersonal and relationship development processes shape knowledge sharing among distributed team members and their individual social networks, and (3) organizational social networks influence knowledge sharing among distributed team members.


A nuclear narrative: Robert Oppenheimer, autobiography, and public authority

Date: 2010-12-01

Creator: David K. Hecht

Access: Open access



Preparing for and managing change: Climate adaptation for biodiversity and ecosystems

Date: 2013-11-01

Creator: Bruce A. Stein

Amanda Staudt

Molly S. Cross

Natalie S. Dubois

Carolyn, Enquist

Roger Griffis

Lara J. Hansen

Jessica J. Hellmann

Joshua J. Lawler

Access: Open access

The emerging field of climate-change adaptation has experienced a dramatic increase in attention as the impacts of climate change on biodiversity and ecosystems have become more evident. Preparing for and addressing these changes are now prominent themes in conservation and natural resource policy and practice. Adaptation increasingly is viewed as a way of managing change, rather than just maintaining existing conditions. There is also increasing recognition of the need not only to adjust management strategies in light of climate shifts, but to reassess and, as needed, modify underlying conservation goals. Major advances in the development of climate-adaptation principles, strategies, and planning processes have occurred over the past few years, although implementation of adaptation plans continues to lag. With ecosystems expected to undergo continuing climate-mediated changes for years to come, adaptation can best be thought of as an ongoing process, rather than as a fixed endpoint. Ā© The Ecological Society of America.


The (Far) Backstory of the U.S.-Colombia Free Trade Agreement

Date: 2013-10-10

Creator: Stephen Meardon

Access: Open access

In two pairs of episodes, first in 1824 and 1846 and then in 1892 and 1935, similar U.S.-Colombia trade agreements or their enabling laws were embraced first by protectionists and then by free traders. The history of the episodes supports the view that although political institutions exist to curb de facto political power, such power may be wielded to undo the institutionsā€™ intended effects. The doctrinal affinities and interests of political actors are more decisive determinants of the free-trade or protectionist orientation of trade agreements than the agreementsā€™ texts or legal superstructures. The long delay from signing to passage of the current U.S.-Colombia Free Trade Agreement is another case in point.


Formation of oral and pharyngeal dentition in teleosts depends on differential recruitment of retinoic acid signaling

Date: 2010-09-01

Creator: Yann Gibert

Laure Bernard

Melanie Debiais-Thibaud

Franck Bourrat

Jean Stephane, Joly

Karen Pottin

Axel Meyer

Sylvie Retaux

David W. Stock

William R. Jackman

Pawat Seritrakul

Gerrit Begemann

Vincent Laudet

Access: Open access

One of the goals of evolutionary developmental biology is to link specific adaptations to changes in developmental pathways. The dentition of cypriniform fishes, which in contrast to many other teleost fish species possess pharyngeal teeth but lack oral teeth, provides a suitable model to study the development of feeding adaptations. Here, we have examined the involvement of retinoic acid (RA) in tooth development and show that RA is specifically required to induce the pharyngeal tooth developmental program in zebrafish. Perturbation of RA signaling at this stage abolished tooth induction without affecting the development of tooth-associated ceratobranchial bones. We show that this inductive event is dependent on RA synthesis from aldh1a2 in the ventral posterior pharynx. Fibroblast growth factor (FGF) signaling has been shown to be critical for tooth induction in zebrafish, and its loss has been associated with oral tooth loss in cypriniform fishes. Pharmacological treatments targeting the RA and FGF pathways revealed that both pathways act independently during tooth induction. In contrast, we find that in Mexican tetra and medaka, species that also possess oral teeth, both oral and pharyngeal teeth are induced independently of RA. Our analyses suggest an evolutionary scenario in which the gene network controlling tooth development obtained RA dependency in the lineage leading to the cypriniforms. The loss of pharyngeal teeth in this group was cancelled out through a shift in aldh1a2 expression, while oral teeth might have been lost ultimately due to deficient RA signaling in the oral cavity. Ā© FASEB.