Stretch-activated sensors

Two different types of membrane-based osmosensors have been proposed for animal cells extracellular solute sensors and membrane stretch-activated sensors. The former sensors are conjectured to function by detecting changes in the concentration of specific ions, for instance, sodium ion, in the external fluids. There is some indirect evidence for sodium-specific sensors in animal cells, and sodium-gated cation channels have been proposed as candidates for this role. However, no direct evidence for their involvement as upstream osmoregulatory elements has yet been presented. 

Membrane stretch-activated sensors, membrane-localized proteins whose activities are modulated by mechanical forces generated in the membrane due to stress, appear to be more promising candidates for the role of... 

Stretch-activated proteins in animal cell membranes that are candidates for osmosensing activity include mechanosensitive ion channels and the membrane-localized enzyme phospholipase A2 (PLA2). The former proteins remain to be conclusively linked to osmosensing. Activity of PLA2 is sensitive to packing of the lipid bilayer of the cell and is responsive to osmotic changes, two attributes that mark it as a prime candidate for a stretch-activated sensor (Lehtonen and Kinnunen, 1995). 

Ferrocenylated ODNs were first immobilized in a self-assembled redox-active monolayer on Au electrodes by Letsinger and co-workers.Upon hybridization of a complementary strand, the electrochemical potential of the ferrocene changes. In addition to applications as electrochemical DNA sensors, such self-assembled DNA monolayers with electro-active groups may provide information on the mechanism of electron transfer through DNA, and indirectly also on molecular mobility within short stretches of DNA. " We have recently extended this idea by the use of immobilized metallocene-labeled PNA on Au electrodes. Because PNA is an uncharged molecule, a surface with improved properties forms, and electrochemical detection, also of single mismatches, is facilitated. 

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