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Von: Sasha Klibanov alk6n(at)virginia.edu
Date: 30 May 2003
Remote Name: 220.127.116.11
Dear Sarah; yes indeed microbubbles come out of the prep in all possible sizes, large and small, sorry about that. Unfortunately bubbles also dislike pressurization, even quite mild. Filtration through nitrocellulose gets everything stuck, as you have seen. Filtration through Nuclepore filters lets many bubbles through (larger bubbles seem to deform and get through the filter pores - but this may depend on the shell you use- I use lipids mostly). That leaves flotation to use for sizing. FIrst to study this in detail were Kvale S, Jakobsen HA, Asbjornsen OA, Omtveit T: Size fractionation of gas-filled microspheres by flotation, SEPARATIONS TECHNOLOGY 6 (4): 219-226 OCT 1996. I do not invite you to build the contraption they have designed (suitable to deal with liters of bubbles at a time) but use the same principles. Leave bubbles in a vertical syringe; large one go up faster than small ones. You can then drain the small ones. Centrifugation speeds up the process (bucket rotor, up to 1500 rpm works fine in my hands). Good luck! Let me know if you have more questions. Sasha.