The nucleus contains the genetic information of the cell and all of the regulatory factors that process the genome effectively. The genome is encapsulated by a dense, filamentous meshwork called the nucleoskeleton, which is located at the inner nuclear membrane. The components of the nucleoskeleton are involved in cellular signaling (Wilson and Berk, 2010), but they are also necessary for maintaining nuclear structure, preventing rupture of the nucleus under force and possibly assisting in force transduction (Wang et al., 2009). Here, we present the integrated mechanical structures of the nucleoskeleton, including lamin filaments, multisubunit proteins, short actin filaments and the genome. We also discuss the integration of mechanical elements from the cytoskeleton into the nucleoskeleton. Based on the mechanical contributions of the individual elements, we demonstrate how mutations in nuclear structures might impact force-dependent etiologies of disease. The accompanying poster aims to provide a translational overview between the cell biology of the nucleus and the biophysics of its underlying polymeric structures.
The authors demonstrate the operation of a nanoscale field-effect pH sensor engineered from a functionalized silicon nanowire. With this nanofabricated pH sensor, the change in the hydrogen ion concentration or the pH value of a solution can be detected by the corresponding change in the nanowire differential conductance with a resolution of ±5nS∕pH. Fabrication of selective side gates on the nanowire sensor allows field-effect control of the surface charge on the nanowire by controlling the accumulation of charge carriers with the side-gate voltage. A simple physical model is used to analyze the observed data and to quantify the dependence of the conductance on pH. The development of a nanoscale sensor with physically engineered gates offers the possibility of highly parallel labeling and detection of chemical and biological molecules with selective control of individual array elements.
Dynamical response of nanomechanical cantilever structures immersed in a viscous fluid is important to in vitro single-molecule force spectroscopy, biomolecular recognition of disease-specific proteins, and the study of microscopic protein dynamics. Here we study the stochastic response of biofunctionalized nanomechanical cantilever beams in a viscous fluid. Using the fluctuation-dissipation theorem we derive an exact expression for the spectral density of displacement and a linear approximation for resonance frequency shift. We find that in a viscous solution the frequency shift of the nanoscale cantilever is determined by surface stress generated by biomolecular interaction with negligible contributions from mass loading due to the biomolecules.
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