Mechanical properties of living cells determined by cytoskeletal elements play a crucial role in a wide range of biological functions. However, low-stress mapping of mechanical properties with nanoscale resolution but...

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very important. Noncontact topography images can be acquired via the Scanning Ion-Conductance Microscopy (SICM), which uses an electrolytic current through a nanopipette as a measure for pipette-surface distance. There are two definitely different methods of topography mapping allowed by SICM. The first one calculates cell stiffness depending on the current drop, due to the probe approach to the cell surface. The second one uses additional hydrostatic pressure through a nanopipette while the pipette-sample separation is kept constant above the cell surface. These approaches have been validated on living cells (Human prostate adenocarcinoma). As a result, two different SICM scanning methods were compared. The first method with the pipette-tip radius of 38 nm showed 895.69 5 195.95 Pa membrane stiffness. The second one, with the tip radius 120 nm and additional pressure from 3kPa to 6kPa, showed 887.41 5 178.31 Pa membrane stiffness. In connection with that, these methods are comparable, and give the same mechanical properties.

network model, we show that such motor-driven networks with high concentrations of Arp2/3 complexes show inhibited dynamics because of the saturation of nucleation sites on actin filaments by the Arp2/3 complexes, while low Arp2/ 3 concentrations aggravate contractility of the networks with hallmarks of short contraction time and small actin clusters. At intermediate Arp2/3 concentrations, sudden collapses of actin clusters in the networks, or ''avalanches'', occur. We have implemented graph theory to quantify the higher-order organization among actomyosin networks, powerful to visualize the hierarchy of the complex networks as well as to extract unprecedented insights on the dynamics of actomyosin networks that can be validated experimentally.

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