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You searched for subject:(Electrostatic Stabilization). Showing records 1 – 3 of 3 total matches.

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University of Toronto

1. Ba Tis, Faez Saleh Ahmed. Novel Electrostatic Actuators with Applications.

Degree: PhD, 2017, University of Toronto

High-end smartphone cameras suffer from large size, high power consumption, and slow performance. These issues are mainly due to the poor performance of the voice coil motors (electromagnetic actuators) used to achieve autofocus (AF) and Optical Image Stabilization (OIS) features in these cameras. Due the superior performance of Micro-Electro-Mechanical-Systems (MEMS) electrostatic actuators over that of other actuation technologies in terms of achieving low power consumption and fast response, micro-electrostatic actuators are being pursued to achieve AF and OIS in smartphone cameras. The maximum mass load displaced by MEMS electrostatic actuators reported in the literature has been limited to 2 mg (corresponds to the mass of a single lens). However, the required mass load to be displaced in order to achieve AF and OIS is in the order of 62 mg mass which represents the mass of a typical lens barrel containing 5 lenses. In this thesis, a novel design of a MEMS piston-tube electrostatic actuator was developed to meet the actuation requirements for AF and OIS in smartphone cameras. The new design overcomes the limitations of the initial design of the piston-tube electrostatic actuator, previously developed by the author. These limitations include the generation of an insufficient out-of-plane translation stroke which is limited to only 24 µm and a low output force also limited to displacing only a 1 mg mass. Two versions of the new design were developed, fabricated, and tested. The latest version was specifically developed to meet the actuation requirements for AF and OIS in smartphone cameras. A new fabrication process, i.e. the MMDL fabrication process, was developed at the university of Toronto cleanrooms to meet the fabrication requirements for this version. The MMDL-fabricated actuator provides for 3 degrees of freedom motion and was able to translate and rotate a 62-mg lens barrel a stroke of 65.5 µm and an angle of rotation of ±0.4°, respectively. The actuator was integrated within a camera module to evaluate how well the actuator meets the requirements of the AF. The actuator achieved autofocus form 15 cm to infinity within 0.5 s, whereas high-end smartphone cameras achieve autofocus within 0.68 s.

2019-11-09 00:00:00

Advisors/Committee Members: Ben-Mrad, Ridha, Mechanical and Industrial Engineering.

Subjects/Keywords: Autofocus; Electrostatic actuators; Large force; Large stroke; MEMS; Optical image stabilization; 0548

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APA (6th Edition):

Ba Tis, F. S. A. (2017). Novel Electrostatic Actuators with Applications. (Doctoral Dissertation). University of Toronto. Retrieved from http://hdl.handle.net/1807/97291

Chicago Manual of Style (16th Edition):

Ba Tis, Faez Saleh Ahmed. “Novel Electrostatic Actuators with Applications.” 2017. Doctoral Dissertation, University of Toronto. Accessed March 28, 2020. http://hdl.handle.net/1807/97291.

MLA Handbook (7th Edition):

Ba Tis, Faez Saleh Ahmed. “Novel Electrostatic Actuators with Applications.” 2017. Web. 28 Mar 2020.

Vancouver:

Ba Tis FSA. Novel Electrostatic Actuators with Applications. [Internet] [Doctoral dissertation]. University of Toronto; 2017. [cited 2020 Mar 28]. Available from: http://hdl.handle.net/1807/97291.

Council of Science Editors:

Ba Tis FSA. Novel Electrostatic Actuators with Applications. [Doctoral Dissertation]. University of Toronto; 2017. Available from: http://hdl.handle.net/1807/97291


University of California – Berkeley

2. Bhowmick, Asmit. Understanding and Improving Designed Enzymes by Computer Simulations.

Degree: Chemical Engineering, 2016, University of California – Berkeley

AbstractUnderstanding and Improving Designed Enzymes by Computer SimulationsBy Asmit BhowmickDoctor of Philosophy in Chemical EngineeringUniversity of California, BerkeleyProfessor Teresa Head-Gordon, ChairThe ability to control for protein structure, electrostatics and dynamical motions is a fundamental problem that limits our ability to rationally design catalysts for new chemical reactions not known to have a natural biocatalyst. Current computational approaches for de novo enzyme design seek to engineer a small catalytic construct into an accommodating protein scaffold as exemplified by the Rosetta strategy. Here we consider 3 designed enzymes for the Kemp elimination reaction (KE07, KE70 and KE15) that showed minimal catalytic activity. KE07 and KE70 were subsequently improved by 2 orders of magnitude in catalytic efficiency by directed evolution and highlighted the shortcomings of the design process. This work studies two keys issues plaguing the designs – side chain conformational variability and electrostatics.For the first part, a new Monte Carlo sampling method was developed that uses a physical forcefield and coupled with backbone variability and a backbone dependent rotamer library. Using transition state theory with energies/entropies calculated from Monte Carlo simulations, it is shown that in both KE07 and KE70, the initial design was over-optimized to stabilize the enzyme-substrate complex. Mutations introduced by directed evolutions led to destabilization of the enzyme-substrate complex and stabilization of the transition state. Furthermore, analysis of residue correlations via mutual information yielded hotspots, several of which were mutations during directed evolution. Laboratory mutations of these hotspots in the best variant of KE07 led to a drop in catalytic performance, demonstrating their importance. The metrics identified in KE07/KE70 studies were used to predict mutations to improve enzyme KE15 that had not been improved prior to this study. Several mutants, all predicted through computer simulations have now yielded better catalytic activity in the laboratory with the best one 10-fold better than the starting enzyme. In order to quantify the role of electrostatics, a new method was developed using the AMOEBA polarizable forcefield that allowed splitting the contribution of electric field at the substrate by residues and solvent. The improvement in KE07 series could be tracked directly through changes in electric field at the substrate. In comparison, KE70 did not show a significant shift in electrostatic field, suggesting other factors like substrate binding may have been the reason for enhancement of activity. However, the common theme in both enzymes was the lack of participation (and in fact detrimental role) of the scaffold in the reaction. Future design efforts would benefit from an expanded theozyme and careful selection of scaffold based on electrostatic properties. Generating efficient biocatalysts without using laboratory directed evolution would be an inflection point in the…

Subjects/Keywords: Chemical engineering; Biophysics; Physical chemistry; Electrostatic Stabilization; Enzyme Design; Molecular Dynamics; Monte Carlo; Mutual Information; Protein Engineering

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Bhowmick, A. (2016). Understanding and Improving Designed Enzymes by Computer Simulations. (Thesis). University of California – Berkeley. Retrieved from http://www.escholarship.org/uc/item/9t13q8v7

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Bhowmick, Asmit. “Understanding and Improving Designed Enzymes by Computer Simulations.” 2016. Thesis, University of California – Berkeley. Accessed March 28, 2020. http://www.escholarship.org/uc/item/9t13q8v7.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Bhowmick, Asmit. “Understanding and Improving Designed Enzymes by Computer Simulations.” 2016. Web. 28 Mar 2020.

Vancouver:

Bhowmick A. Understanding and Improving Designed Enzymes by Computer Simulations. [Internet] [Thesis]. University of California – Berkeley; 2016. [cited 2020 Mar 28]. Available from: http://www.escholarship.org/uc/item/9t13q8v7.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Bhowmick A. Understanding and Improving Designed Enzymes by Computer Simulations. [Thesis]. University of California – Berkeley; 2016. Available from: http://www.escholarship.org/uc/item/9t13q8v7

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation


Universitat Pompeu Fabra

3. Khan, Abdul Kareem. Electrostaticanalisys the Ras active site.

Degree: Departament de Ciències Experimentals i de la Salut, 2009, Universitat Pompeu Fabra

The electrostatic preorganization of the active site has been put forward as the general framework of action of enzymes. Thus, enzymes would position "strategic" residues in such a way to be prepared to catalyze reactions by interacting in a stronger way with the transition state, in this way decreasing the activation energy g cat for the catalytic process. It has been proposed that such electrostatic preorientation should be shown by analyzing the electrostatic stability of individual residues in the active site. Ras protein is an essential signaling molecule and functions as a switch in the cell. The structural features of the Ras protein in its active state (ON state) are different than those in its inactive state (OFF state). In this thesis, an exhaustive analysis of the stability of residues in the active and inactive Ras active site is performed. Advisors/Committee Members: [email protected] (authoremail), true (authoremailshow), Villà i Freixa, Jordi (director).

Subjects/Keywords: dinàmica; centre actiu; relacions d'estructura activitat; preorganització; reorganització; estat de transició; estat actiu; estabilitat electrostàtica; interacción proteïna-proteïna; test de ranks de Wilcoxon; P-loop; G1 motif; HVR; metastability; RMSD; substrate assisted catalysis; sequence alignment; beta sheet; helix; Z-test; wilcoxon rank test; protein-protein interactions; electrostatic stability; active state; dynamics; signal transduction; electrostatic stabilization; ras effectors; guanine exchange factor; GTPase-activating proteins; quantum mechanics/molecular; PDLD/S-LRA; X-ray crystallography; solvation energy; free energy perturbation; statistical analysis; GTP hydrolysis; guanosine diphosphate; guanosine triphosphate; computer simulation; thermodynamics; protein conformation; electrostatics; interruptor II; interruptor I; llaç P; motiu G1; HVR (regions altament variables); metaestabilita; RMSD; catàlisi assistida pel substrat; aliniament de seqüència; fulla beta; hèlix; test Z; transducció del senyal; estabilització electrostàtica; efectors de ras; factor de bescamvi de guanina; proteïnes activadores de l'activitat; mecànica quàntica/mecànica; PDLD/S-LRA; cristalografia de raigs X; energia de solvatació; perturbació de l'energia lliure; anàlisi estadística; hidròlisi de GTP; difosfat de guanosina; trifosfat de guanosina; simulació computacional; termodinàmica; conformació proteïca; electrostàtica; switch-I; switch-II; 537; 576

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Khan, A. K. (2009). Electrostaticanalisys the Ras active site. (Thesis). Universitat Pompeu Fabra. Retrieved from http://hdl.handle.net/10803/7161

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Khan, Abdul Kareem. “Electrostaticanalisys the Ras active site.” 2009. Thesis, Universitat Pompeu Fabra. Accessed March 28, 2020. http://hdl.handle.net/10803/7161.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Khan, Abdul Kareem. “Electrostaticanalisys the Ras active site.” 2009. Web. 28 Mar 2020.

Vancouver:

Khan AK. Electrostaticanalisys the Ras active site. [Internet] [Thesis]. Universitat Pompeu Fabra; 2009. [cited 2020 Mar 28]. Available from: http://hdl.handle.net/10803/7161.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Khan AK. Electrostaticanalisys the Ras active site. [Thesis]. Universitat Pompeu Fabra; 2009. Available from: http://hdl.handle.net/10803/7161

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

.