User:Anthony Salvagno/Notebook/Research/2009/12/23/Beads, Tethers, and Optical Traps

After yesterday I will need to progress. In recap, I tried tethering in different bead scenarios, and eventually moved to just putting beads in a channel with no DNA or anti-dig. Today I will expand a little bit especially because we got a new badass detector yesterday. Details below.

QPD and Amplifier
Yesterday just messing around I noticed that this new detector eliminated a little bit of noise. Today we discovered that the halogen light from overhead illumination adds some noise. To combat this I ordered a RG-1000 filter from Edmunds Optics. Anyways the detector/amplifier (2 pieces) is from On-Trak. I don't know what the model of the detector is, but the amp is OT-301.

I made a sample of beads in high salt (1:100 dilution of beads from stock in 4M NaCl) so that we could get quick surface adhesion and few beads. Koch and I then took the sample to the Tweezers and did some cool tweezer analysis by scanning the laser back and forth over a single stuck bead. We tried this for several beam diameters (by moving the condensor around). Here is some sample data below: I don't know too much about the data yet, but the graph on the left is position vs time of the laser in the x direction and the right plot is the sum signal of x and y over time. In the plot on the right, I am showing 4 experiment sets, but in the plot on the left I have zoomed in to just the last data set (equivalent to the 4th hump in the right plot).

Beads and Tethers
Yesterday I learned a ton about beads in solution and potential problems and I have been working to try and minimize these problems. It seems the best option right now is just a lot of dilution of stock beads (about 1:25 or so).

I just received the new beads (.97um diameter) and I will try tethering with these new beads. I will also try to see if I have those clumping issues in BGB/POP and so forth. But first things first.