Mullis practiced clandestine chemistry throughout his graduate studies, specializing in the synthesis of LSD; according to his friend Tom White, "I knew he was a good chemist because he'd been synthesizing hallucinogenic drugs at UC Berkeley."[18] He detailed his experiences synthesizing and testing various psychedelic amphetamines and a difficult trip on DET in his autobiography.[50]: 167–170  In a Q&A interview published in the September 1994 issue of California Monthly, Mullis said, "Back in the 1960s and early 1970s I took plenty of LSD. A lot of people were doing that in Berkeley back then. And I found it to be a mind-opening experience. It was certainly much more important than any courses I ever took."[55][verification needed] During a symposium held for centenarian Albert Hofmann, Hofmann said Mullis had told him that LSD had "helped him develop the polymerase chain reaction that helps amplify specific DNA sequences".[56]