Development of a Tetrameric Streptavidin Mutein with Reversible Biotin Binding Capability: Engineering a Mobile Loop as an Exit Door for Biotin

A novel form of tetrameric streptavidin has been engineered to have reversible biotin binding capability. In wild-type streptavidin, loop3–4 functions as a lid for the entry and exit of biotin. When biotin is bound, interactions between biotin and key residues in loop3–4 keep this lid in the closed state. In the engineered mutein, a second biotin exit door is created by changing the amino acid sequence of loop7–8. This door is mobile even in the presence of the bound biotin and can facilitate the release of biotin from the mutein. Since loop7–8 is involved in subunit interactions, alteration of this loop in the engineered mutein results in an 11° rotation between the two dimers in reference to wild-type streptavidin. The tetrameric state of the engineered mutein is stabilized by a H127C mutation, which leads to the formation of inter-subunit disulfide bonds. The biotin binding kinetic parameters (koff of 4.28×10−4 s−1 and Kd of 1.9×10−8 M) make this engineered mutein a superb affinity agent for the purification of biotinylated biomolecules. Affinity matrices can be regenerated using gentle procedures, and regenerated matrices can be reused at least ten times without any observable reduction in binding capacity. With the combination of both the engineered mutein and wild-type streptavidin, biotinylated biomolecules can easily be affinity purified to high purity and immobilized to desirable platforms without any leakage concerns. Other potential biotechnological applications, such as development of an automated high-throughput protein purification system, are feasible

Very -Large -Scale Motions in Wall -Bounded Turbulent Flows

242 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2001.Overall, results indicate that the hairpin vortex and its organization into packets is a robust and significant feature of wall-bounded turbulence over a wide range of Reynolds numbers. The hairpin-vortex-packet model of turbulence provides a consistent explanation for the distribution of energy among the largest scales of the flow and underscores the importance of the very-large scales.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

Very -Large -Scale Motions in Wall -Bounded Turbulent Flows

242 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2001.Overall, results indicate that the hairpin vortex and its organization into packets is a robust and significant feature of wall-bounded turbulence over a wide range of Reynolds numbers. The hairpin-vortex-packet model of turbulence provides a consistent explanation for the distribution of energy among the largest scales of the flow and underscores the importance of the very-large scales.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

The role of TlpA in the chemotaxis of Bacillus subtilis and its homology to similar proteins in Escherichia coli

Thesis (B.S.)--Univeristy of Illinois at Urbana-Champaign, 1997.Includes bibliographical reference (leaf 31)U of I OnlyTheses restricted to UIUC community onl

Unsteady dynamics and organized structures from DNS over an idealized building canopy (In special issue: Urban Climatology ICUC6)

A numerical study is performed to elucidate the dominant turbulent processes that occur in urban areas. Comprehensive data from direct numerical simulations (DNS) over idealized three-dimensional arrays of buildings are analysed to study the unsteady and organized aspects of the turbulent flow. The accuracy of the DNS is evaluated by comparing turbulence statistics with a high quality wind-tunnel dataset. The simulation results are studied using flow visualization as well as statistical methods including quadrant analysis, space-time two-point correlations and conditional averaging. Three regimes of the flow are identified. First, the rough wall flow above the buildings has turbulent organized structures that resemble the hairpin vortices and low momentum regions that are well known to occur in the turbulent boundary layer over smooth walls. These hairpin-like vortices contribute dominantly to vertical momentum transport. Secondly, shear layers develop over the tops of the buildings and shed structures that may sometimes impinge upon downstream buildings and drive a robust recirculation within the building canopy. These unsteady canopy-top shear layers and their interaction with the larger eddies above provide important mechanisms for coupling with the flow within the canopy. Thirdly, the flow within the building canopy is the result of complicated interactions between the above and eddies shed off the vertical edges of the buildings, and their distortion caused by impacting buildings. Mean flow patterns around the buildings are important and lead to significant dispersive stresses. Implications for scalar transport and dispersion are briefly discussed

Talismans et amulettes chinois

International audienc

A tranquil virtual reality experience to reduce subjective stress among COVID-19 frontline healthcare workers

Objective The novel coronavirus-19 (COVID-19) has taken an immense physical, social, and emotional toll on frontline healthcare workers. Research has documented higher levels of anxiety, depression, and burnout among healthcare workers during the pandemic. Thus, creative interventions are needed now more than ever to provide brief, accessible support to frontline workers. Virtual reality is a rapidly growing technology with potential psychological applications. In this study, we piloted a three-minute Tranquil Cinematic-VR simulation of a nature scene to lower subjective stress among frontline healthcare workers in COVID-19 treatment units. We chose to film a nature scene because of the extensive empirical literature documenting the benefits of nature exposure and health. Methods A convenience sample of frontline healthcare workers, including direct care providers, indirect care providers, and support or administrative services, were recruited from three COVID-19 units located in the United States. Inclusion criteria for participation included adults aged 18 years and older who could read and speak in English and were currently employed by the healthcare system. Participants viewed a 360-degree video capture of a lush, green nature preserve in an Oculus Go or Pico G2 4K head-mounted display. Prior to viewing the simulation, participants completed a brief demographic questionnaire and the visual analogue scale to rate their subjective stress on a 10-point scale, with 1 = ‘Not at all stressed’ to 10 = ‘Extremely stressed.’ We conducted paired t-tests to examine pre- and post-simulation changes in subjective stress as well as Kruskal-Wallis tests and Mann-Whitney U tests to examine differences by demographic variables. All analyses were conducted in SPSS statistical software version 28.0. We defined statistical significance as a p-value less than .05. Results A total of 102 individuals consented to participate in the study. Eighty-four (82.4%) participants reported providing direct patient care, 73 (71.6%) identified as women, 49 (48.0%) were between the ages of 25–34 years old, and 35 (34.3%) had prior experience with VR. The pre-simulation mean stress score was 5.5±2.2, with a range of 1 to 10. Thirty-three (32.4%) participants met the 6.8 cutoff for high stress pre-simulation. Pre-simulation stress scores did not differ by any demographic variables. Post-simulation, we observed a significant reduction in subjective stress scores from pre- to post-simulation (mean change = -2.2 ±1.7, t = 12.749, p \u3c .001), with a Cohen’s d of 1.08, indicating a very large effect. Further, only four (3.9%) participants met the cutoff for high stress after the simulation. Post-simulations scores did not differ by provider type, age range, gender, or prior experience with virtual reality. Conclusions Findings from this pilot study suggest that the application of this Tranquil Cinematic-VR simulation was effective in reducing subjective stress among frontline healthcare workers in the short-term. More research is needed to compare the Tranquil Cinematic-VR simulation to a control condition and assess subjective and objective measures of stress over time