For years, the crystallographer and biochemist Ada Yonath had to contend with the disdain and sometimes derision of many of her contemporaries after she set herself the challenge of mapping the molecular structure of the ribosome.
Ribosomes are found in all living cells. Effectively they are tiny factories that synthesise proteins, complex molecules that are vital for building and repairing the tissues and organs of animals and plants. Many scientists believed hers was a fruitless endeavour because ribosomes are so small – sometimes only 20 nanometres in diameter – irregular in shape and lacking internal symmetry. James Watson, one of the Nobel prizewinning discoverers of the double-helix structure of DNA, had tried and failed. But Yonath, who has died aged 87, proved her doubters wrong, and was rewarded with the 2009 Nobel prize in chemistry, only the fourth woman to receive it, which she shared with the biologist Venkatraman Ramakrishnan and biochemist Thomas Steitz.
“I was met with disbelief, even ridicule in the international scientific community,” she said later. “I was called a dreamer, a fantasist, even the village idiot. But when I succeeded, it created an overwhelming internal joy and those who once called me crazy or stupid became supporters.”
It was in the late 1970s, while being laid up following a bicycle accident, and indulging in some “easier” reading, that Yonath, then a young scientist based at the Weizmann Institute of Science in Rehovot, Israel, chanced upon the article that would lead to her eventual breakthrough. Reading about the biology of polar bears, she learned that the bears pack their ribosomes in an orderly way in their cells prior to hibernating. “These stay intact and functional for months. So, if polar bears knew how to do it, we could too,” she reasoned.
Yonath surmised that, if she could crystallise an organism, and hence its ribosomes, she would be able to study their internal structure using X-rays and electron microscopy. However, ribosomes are fragile. Unlike other cell parts, they have no outer protective membrane and are easily damaged. Figuring that ribosomes of organisms that live in harsh conditions were likely to be hardier and more able to survive crystallisation, she attempted to crystallise the thermophile bacteria Geobacillus stearothermophilus, found in austere environments around thermal vents and in desert sands.
It took more than 25,000 attempts, but in the mid-80s, Yonath succeeded. She then froze the bacteria at –185°C, to stabilise its internal structure and to protect it from the X-rays, a technique she was an early successful pioneer of, now known as cryo bio-crystallography. Finally, in 2001 and 2002, after almost two decades of research, Yonath’s team succeeded in mapping, in three dimensions, the bacteria’s ribosome.
The significance of this discovery extended beyond pure science. Many antibiotics work by binding to sites on a bacterium’s ribosome, stopping it from reproducing. Previously, making antibiotics was a hit-and-miss process because often they would attack human ribosomes as well as those of the bacteria. But, armed with knowledge of the structure of different ribosomes, scientists could now deduce where on a ribosome an antibiotic would bind and so make the necessary structural alterations to the drug.
Yonath demonstrated how more than 20 antibiotics function, paving the way for new products, and also studied how antibiotic resistance might be overcome. The Nobel committee specifically noted this work in its citation, highlighting the “fundamental and medically important aspects of ribosome function” leading to “the development of novel antibiotic drugs in the ongoing medical struggle against ever emerging drug resistance among bacterial pathogens”.
Born in Jerusalem, into an Orthodox Jewish family, Ada was the elder daughter of parents who had emigrated from Poland to what was then British-mandated Palestine in 1933. Her father, Hillel Lifshitz, a rabbi and grocer, died when she was 11. Her mother, Esther, then moved with her two daughters to Tel Aviv, where she became a clerk. Despite her modest income, she recognised her daughter’s keen intellect and obtained her a place at the fee-paying Tichon Hadash high school, where Ada taught maths lessons in lieu of school fees.
In 1959, after two years of mandatory military service, she returned to Jerusalem to take a degree in chemistry at the Hebrew University, graduating in 1962, then a master’s in biochemistry (1964). Four years later she received a PhD from the Weizmann Institute for studies into the structure of collagen using X-ray crystallography.
She accepted postdoctoral positions in the US, at the Massachusetts Institute of Technology and Carnegie Mellon University, in Pittsburgh, before returning to the Weizmann Institute, where, in 1970, she began her research into ribosomes and where she remained for the rest of her career. Despite the scepticism of many of her peers, she did receive long-term support and funding from Heinz-Günter Wittman at the Max Planck Institute for Molecular Genetics in Berlin, frequently travelling to Germany to exchange data and compare notes.
In addition to her Nobel prize, Yonath received numerous awards, including the 2007 Wolf prize in chemistry, second only in importance to the Nobel, and was elected as a foreign member of the UK’s Royal Society.
Outside her work, Yonath was politically outspoken and critical of the Israeli government. Most recently, she criticised Israeli judicial reforms as a “genuine peril to democracy” and to Israeli scientific enterprise.
In 2018, when asked what qualities made a good scientist, she said: “Curiosity, first. Second, curiosity. And third, curiosity. Also, one has to love, and not be afraid of, a challenge.”
Her marriage to Moshe Yonath, a schoolteacher, ended in divorce. Her daughter, Hagith, and a granddaughter, Noa, survive her.
Ada Esther Yonath, crystallographer and biochemist, born 22 June 1939; died 31 August 2026
