Police and academics in Cambridge are trying to find a graffiti artist who could be Britain's brightest vandal.
The formula was spray-painted outside the Cavendish laboratory
The artist spray-painted part of a chemical component of DNA on the road outside a lab where the double helix was unveiled 50 years ago.
Atop the design - described by one academic as "really nice" work - the artist wrote the word "phospholipase".
Some suspect it to be the work of a chemistry student on the way home after a night of post-exam celebration.
Dr Jonathan Goodman, a lecturer in Cambridge University's chemistry department, said: "The graffiti is of a molecule called guanine.
"There is a picture of [the molecule] on the chemistry department web page.
"It is one of the structures, or bases, which make up DNA - one of the four which Watson and Crick realised could fit together to form DNA in 1953."
He added: "Phospholipase C is an enzyme which many people are studying."
Professor Alan Dawson, emeritus professor of biochemistry at the University of East Anglia in Norwich, said: "It is a really nice bit of standard first or second-year biochemistry."
A spokeswoman for Cambridge University said: "We think it is more likely to be the work of a post-graduate student because this appeared prior to the start
"We certainly don't want students spraying graffiti on roads and it's not something we condone."
Last month, police and councillors in Cambridge launched a campaign to highlight the problem of graffiti in Cambridge, with police saying they would operate a "zero-tolerance" approach.