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May 8, 1990

Dr. Lederberg
President
The Rockefeller University

Dear Dr. Lederberg:

As soon as we can improve our detection efficiency for
high molecular mass (low velocity) ions we will try to
measure virus particles. At present, our detector runs out
of steam at about m/z 150,000-200,000.

SENSITIVITY: We normally load a total of 0.1-1.0 pmole
of protein onto the probe tip, but actually bombard only 1%
of the total area of the probe tip - so that only 1-10 fmole
of sample is actually consumed to obtain a mass spectrum.
Our sensitivity is presently limited by our sample handling
techniques (which need to be improved) - we_like to work
with protein concentration in excess of 10°’ M.

MS/MS: We have constructed a second TOF instrument
with a two laser system. The second laser will be used to
try to induce photo-dissociation of ions in flight.

Thanks again,

Sincerely,
Brian Chait L
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