random shear

[Maria Cristina Costanzo]

Dear Netters,
    We are thinking about constructing a random shear library and have been
experimenting with shearing total yeast genomic DNA.  Young et al. (PNAS
82:2583,1985) sheared DNA (0.35 mg/ml) to an average of 5 kb with 150
passages
through a 25-gauge needle. We started with DNA at about 0.15 mg/ml and
after 350 passagess through a 25-gauge needle, it was largely unaffected,
with the smallest fragments about 15 kb.  Does anyone have any suggestions
about how to shear DNA efficiently ?  Does the concentration affect
shearing efficiency ? Any suggestions would be appreciated.  You may
contact me directly at mcc9 at cornell.edu, or post here; I will post a
summary of the replies. Thank you!
    Maria Costanzo