Dr Alexander Rich

James Watson and Francis Crick worked out the spiral structure of DNA in 1953, but they were not proved right until Dr. Alexander Rich used X-rays to produce a distinct image of the famous double helix in 1973. After he saw it, Dr. Watson phoned Dr. Rich to thank him; it was the first good night’s sleep Dr. Watson had enjoyed in 20 years.

For nearly six decades, Dr. Rich, who died at 90 on April 27 in Boston, doggedly investigated DNA and RNA, the fundamental molecules of life. He helped puzzle out the structure of collagen, a protein that is abundant in ligaments and skin, and he discovered that DNA can exist in an odd zigzag form, which he called Z-DNA. His work provided insights into how cells manufacture proteins, and laid the groundwork for techniques that scientists use to identify, manipulate and replace bits of genetic material. Diagnostics for H.I.V. infection and tests for genes that cause breast cancer are among the technologies built on his discoveries.

“I can think of no one else who has made as many major contributions to all facets of modern molecular biology,” said Dr. Robert C. Gallo, a co-discoverer of the AIDS virus and a professor at the University of Maryland.
In 1995, President Bill Clinton awarded Dr. Rich the National Medal of Science, the highest scientific honor bestowed by the federal government.
His death was announced by the Massachusetts Institute of Technology, where he had been a professor since 1958.