Back to the bench (sans camera)

I'll be going to the university across town on Friday, partly to hear an informal talk about the evolution of recombination hotspots (a problem we pioneered) and partly to try to get cells to attach to DNA-coated beads using the optical tweezers.

I haven't done anything with the tweezers since before we submitted our latest CIHR grant proposal (Beads and cells).  That attempt used beads that had been incubated with DNA and thoroughly washed, but I hadn't taken the time to check how much (if any) DNA was actually bound to the beads.  This time I want to be sure that there's DNA on the beads, so after I wash them I'll use Picogreen to measure the bound DNA.

So I'll first incubate the streptavidin-coated polystyrene beads (2.1 µm diameter) with biotin-tagged chromosomal DNA (how much?) for a couple of hours, inverting the mixture on the roller wheel to keep the beads from clumping.  Then I'll dilute the beads and wash them by trapping them on a 0.2 µm filter, pouring lots of TE through them.  Then I'll resuspend the beads in a small volume of TE and measure the DNA concentration.  Maybe I'll also use the beads in a transformation assay to check that DNA is present and the cells can take it up.