David A. Usher

Retired Associate Professor David A. Usher died at home on 6 October 2017.
David was born in England on 1 November 1936 and moved with his family to
New Zealand when he was eleven. He earned a B.Sc. and an M.Sc from Victoria
University of Wellington, NZ, a Ph.D. from Cambridge University with Dan
Brown, and did post-doctoral research at Harvard University with Frank
Westheimer.
He came to Cornell in 1965 and taught generations of students the basics of
Organic Chemistry until he retired in June of 2016. He also taught general
chemistry courses for non-scientists and for science majors, organic chemistry
for chemistry majors, and graduate level courses in enzyme mechanisms,
nucleotide chemistry, and chemical aspects of biological processes.
His research interests in phosphate chemistry led to work on the mechanism of
the enzyme ribonuclease, work which defined the geometry of the phosphate
group at the cleavage site.
His study of phosphate stereochemistry also led to an interest in prebiotic
chemical evolution and a prediction that the 3',5'-linkage between nucleotides
seen in natural biological RNA would be stabilized against hydrolysis in a double
helix, while a non-natural 2',5'-linked RNA would actually be de-stabilized.
Experimental testing of this hypothesis showed it to be correct, demonstrating
a selective advantage for the linkage used by biological organisms. These
experiments were also an early demonstration of catalysis by RNA in the
increased rate of hydrolysis of 2',5'-linked RNA when bound to a
complementary strand of RNA. His research interests also included antisense
technology, models of prebiotic formation of peptide bonds using
oligonucleotide carriers and templates, and possible chemical evolution on
Saturn's moon Titan.
He served on advisory committees for NASA and for the Space Science Board
of the National Academy of Sciences, including co-chairing a task force to
determine important goals for future research in space science.
Spanning the years from 1972 until 2004, David appeared at intervals as the
tenor lead in thirteen Cornell Savoyards' productions of Gilbert and Sullivan
operettas, including such roles as Nanki-Poo, Captain Fitzbattleaxe, and Prince
Hilarion as well as the more sedately named Colonel Fairfax and Ralph (Rafe)
Rackstraw.
He served for many years as the Faculty Advisor for the Cornell Women's
Tennis Team and was delighted to congratulate them on their first-ever Ivy
League co-championship last Spring.
David is survived by his wife, Barbara, his children, Jonathan, Cathryn, Elizabeth
and Michael, and by grandchildren Josh, Sophie, Alex, and Edward; also by his
sister, Audrey, and nieces Patricia and Julia