Mr. David R. Murdock Profile

David R. Murdock

at Rice Univ

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Author

Publications (4)

Proceedings Article | 18 October 2004 Paper

Measurements of cell wall mechanical properties using optically trapped fluorescent microspheres

Sergey Ermilov, Feng Qian, David Murdock, William Brownell, Bahman Anvari

Proceedings Volume 5514, (2004) https://doi.org/10.1117/12.559717

KEYWORDS: Phase modulation, Plasma, Optical tweezers, Luminescence, Ferroelectric materials, Mechanics, Visualization, Bandpass filters, Imaging systems, Cytoskeletons

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Information on plasma membrane (PM) and cell wall mechanical properties is important for many biophysical applications, especially for those, which involve cells, undergoing significant mechanical stress (red blood cells, outer hair cells, fibrocytes, etc.). Optical tweezers is frequently used to study PM mechanics, particularly by pulling long PM tethers. One of the limitations on using optical tweezers to study cell wall mechanics is associated with transillumination technique of the trapped object position sensing, which prevents accurate mechanical testing in the proximity to the cell. In this work we use an optical tweezers in conjunction with a position-sensing system, which spectrally separates signals from the trapped fluorescent microsphere and imaging background. We have used this setup to study mechanics of the cell wall and PM separated from the underlying cytoskeleton on human embryonic kidney cells. We measured the force exerted by the cell on the trapped microsphere as a function of the cell wall displacement during the process of tether formation, and as a function of time during the process of tether growth and relaxation. Tethering force - cell wall displacement profiles have shown a behavior, implying that tether formation process starts with elastic deformation of the intact cell wall, followed by the plastic deformations and sliding of the PM over the underlying cytoskeleton, and ends with the local separation of a PM. Tethering force - cell wall displacement profiles have been used to estimate tether formation force, stiffness parameter of the cell wall and the works of tether formation, elastic and plastic deformations of the cell wall, related to the mechanical properties of a composite cell wall and cell wall - plasma membrane association strength. Temporal steady-state and relaxation tethering force profiles have been similar to the ones measured using transillumination position sensing, however average force values have been smaller in our case, due to the methodological differences. Our results demonstrate that measurements of cell wall and PM mechanical properties using optically-trapped fluorescent microspheres presents a versatile technology for studying of the cellular mechanics, especially effective in the proximity of the trapped microsphere to the cell.

Proceedings Article | 1 June 2004 Paper

Optical tweezers study of viscoelastic properties in the outer hair cell plasma membrane

David Murdock, Sergey Ermilov, Feng Qian, William Brownell, Bahman Anvari

Proceedings Volume 5331, (2004) https://doi.org/10.1117/12.529597

KEYWORDS: Plasma, Optical tweezers, Photodetectors, Data modeling, Neodymium, Phase modulation, Cytoskeletons, Mechanics, Calibration, Molecules

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Proceedings Article | 1 June 2004 Paper

Membrane tether formation from voltage-clamped outer hair cells using optical tweezers

Feng Qian, Sergey Ermilov, David Murdock, William Brownell, Bahman Anvari

Proceedings Volume 5331, (2004) https://doi.org/10.1117/12.528540

KEYWORDS: Optical tweezers, Plasma, Luminescence, Mirrors, Calibration, Electromechanical design, Photodetectors, Optical amplifiers, Objectives, Microscopes

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Proceedings Article | 12 September 2003 Paper

Studies of cochlear outer hair cell membrane mechanics using optical tweezers

David Murdock, Sergey Ermilov, William Brownell, Bahman Anvari

Proceedings Volume 4949, (2003) https://doi.org/10.1117/12.476469

KEYWORDS: Optical tweezers, Plasma, Photodetectors, Mechanics, Phase modulation, Cytoskeletons, Calibration, Kidney, Molecules, Microscopes

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