Alexander Spector, Ph.D.Research Professor in Biomedical Engineering and Mechanical EngineeringTraylor 411
410-502-6955
aspector AT jhu.edu
Website Research InterestsWe develop computational models to better understand cell mechanics and biophysics. Cellular mechanical properties (stiffness, viscosity, adhesion, motility, etc.) are now considered as fine indicators of pathological conditions, including the stage of the disease. Cellular biophysics, such as analyses of motor proteins, membranes, and cytoskeleton, helps explain molecular mechanisms of cell performance. A variety of techniques, micropipette aspiration, optical tweezers, atomic force microscopy, and magnetic cytometry, are used to extract the mechanical and biophysical properties of cells.
Our particular focus is the hair cells in the cochlea of the inner ear. Outer hair cells in the mammalian (human) cochleae are effector cells critically important to sound amplification and sharp frequency selectivity of the ear. We analyze the outer hair cell performance at three interrelated, organ, cellular, and molecular, levels. We have developed a model of this cell’s performance in the cochlear environment, including the outer hair cell interaction with the cochlear fluids and solid structures. We have proposed a piezoelectric model of the outer hair cell’s active force production. We apply our computational models of the outer hair cell composite membrane to the design and interpretation of two, micropipette aspiration and tether pulling, experiments aimed at the estimation of the cell membrane mechanical and biophysical properties. Our molecular-level studies focus on a better understanding of the outer hair cell motor complex and its critical part, the membrane protein prestin. Prestin is the fastest known molecular motor, and we have recently developed a model to explain prestin-associated electric charge transfer in response to the application of high-frequency transmembrane electric fields.
Selected PublicationsK.R. Schumacher, A.S. Popel, B. Anvari, W.E. Brownell, and A.A. Spector. Modeling the mechanics of tethers pulled from the outer hair cell membrane. J. Biomech. Eng. , 2008, 130, art. 31007.
A.M. Cheshire, B.E. Kerman, W.R. Zipfel, A.A. Spector, and D.J. Andrew. Kinetic and mechanical analysis of live tube morphogenesis. Developmental Dynamics, 2008, 237, 2874-2888.
Z. Liao, S. Feng, A.S. Popel, W.E. Brownell, and A.A. Spector. Outer hair cell active force generation in the cochlear environment. Journ. Acoust. Soc. Am., 2007, 122, 2215-2225.
C.M. Nelson, R.P. Jean, J.L. Tan, W.F. Liu, N.J. Sniadecki, A.A. Spector, and C.S. Chen. Emerging patterns of growth controlled by multicellular form and mechanics. Proc. Natl. Acad. Sci. USA, 2005, 102, 11594-11599.
R.P. Jean, C.S. Chen, and A.A. Spector. Finite-element analysis of the adhesion-cytoskeleton-nucleus mechanotransduction pathway during endothelial cell rounding: Axisymmetric model. J. Biomech. Eng., 2005, 127, 594-600.
W.E. Brownell, A.A. Spector, R.M. Raphael, and A.S. Popel. Micro- and nanomechanics of the cochlear outer hair cell wall. Annu. Rev. Biomed. Eng., 2001, 3, 169-194.
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