Help with Enzymatic Calculations

Ramon 'Jammin' Cuevas rcuevas at
Sat Jun 5 01:05:06 EST 1993

I hope somebody can help me out with this (potentially easy) problem.  :)
I'm currently a second year biology student, and I'm gradually learning the
laboratory techniques involved with molecular biology (ie. electrophoresis,
blotting, uses of enzymes/buffer/DNA solutions, etc.)  Right now, I'm learning
the methods involved with restriction enzyme digestion, and I must admit that
I'm having a difficult time understanding how to determine the "correct"
amount of restriction enzyme to use for a given amount of DNA sample - to be
more specific, I don't understand how the concept of "units" fits into the
overall schema (I haven't had any formal classes in molecular biology or
genetics, so I don't know if this is an "elementary"-type of question.) For
example, given that I have 500ng=0.5ug of DNA diluted in 20uL of solution, and
also given that the enzyme (stock) solution contains 20,000 "units" per mL,
how do I determine the volume amount of enzyme solution to use (based on the
"units" concept).  Any help is most greatly appreciated. Thanks!

Ramon F. Cuevas
rcuevas at

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