Friday, July 22, 2016

More Spinning and a Wee Bit O' Fun

I didn't have ICP gas to run my samples from last week spin cleaning so instead on Monday I ran UV vis on the supernatant samples to confirm that the free DNA concentration decreased with each spin. The free DNA in solution plummeted after the first spin so I am confident that the spinning protocol is enough to clean the free DNA out of the solution leaving only bound DNA- NP complexes.

This was Sarah's last week so on Wednesday we took time out of the day to get lunch and ice cream. Since this took most of my day on Wednesday I did not try to start another spinning procedure until Thursday. I prepared 4 new DNA-NP solutions with new concentrations of DNA (20 ug/mL, 30 ug/mL, 40 ug/mL, and 50 ug/mL), characterised them and repeated the cleaning protocol with 3 washes of TE-10 mM NaCl and 2 of pure water. Similar to last week I saw much more aggregation following the water washes than with the salt TE. The UV-vis data showed very little shift in the spectra but a decrease in concentration and an increase in aggregation following the washes. The most interesting part of the characterisation data was that the six of the particles jumped from ~60 nm prewash to ~80-100 nm after being washed in the salt and the water. The jump in size was most pronounced in the lower concentration. The 50 ug/mL sample was back down at ~66 nm. This is interesting because no jump was seen in the samples from last week which could be due to subtle differences in the procedure or the fact that a different sample of sheared DNA was used. Next week I will run ICP which should give me more insight into the complexes.


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