A Few Intimidating But Inventive Tryptophan synthase Blueprints

Taking into account the surface density of avidin on the beads and the contact area given by the JKR theory and the thickness of the PLL-g-PEG layer, ?140 avidin molecules contribute to the adhesion. http://www.selleckchem.com/products/PLX-4032.html With a reported binding strength of ?160 pN per avidin-biotin bond ( 34), this gives a theoretical maximum adhesion of ?22 nN. Adhesion curve shape implies, however, that not all connections were broken at the same time, which resulted in a smaller maximum adhesion that scales with the number of available bonds. Repeated contact between the same avidin-coated bead and the PLL-g-PEG-biotin-coated surface resulted in a decay of contact adhesion. Fig.?5 shows the adhesion normalized by the first contact. The adhesion gradually dropped to SB431542 price directly onto the substrate and then detach them one by one. This enables long interaction times between colloid Tryptophan synthase and substrate, and exploration of many different substrate sites each with a fresh bead in quick succession. We applied this protocol to study the interaction between human embryonic kidney 293 cells (HEK) and concanavalin A (ConA)-coated polystyrene beads. HEK cells are popular in the field of electrophysiology (37) but only a few studies have tried to quantify their mechanical and adhesion properties (17, 38?and?39), which will represent the reference for our work. ConA is known to bind to the manose residues on the cell membrane strongly enough to be used for single cell force spectroscopy (SCFS) (25, 40?and?41). In standard SCFS experiments, single cells are linked chemically to an AFM tipless cantilever to measure their adhesion to a substrate. Typically, in SFCS, only one cell can be examined per cantilever, as the interaction between cell and ConA cannot be established a second time and thus is irreversible. Additionally, long contact times between the ConA-coated surface and the cell are needed to measure stronger cell-substrate adhesion forces. This either limits the incubation time of the cells to a few minutes, so they cannot spread and adhere too strongly, or it drastically reduces the acquired data points per experiment if fully spread cells are investigated (42). This drawback was recently improved by detaching cells from substrate directly with FluidFM (17).