15-Sep-2026
Obituary by Joel Sussman, Weizmann Institute of Science
Professor Ada E. Yonath, who died on 31 August 2026 at the age of 87, changed structural biology by refusing to accept that an extraordinarily difficult experiment was impossible. For too many decades, she pursued the atomic structure of the ribosome, the immense, flexible ribonucleoprotein machine responsible for translating genetic information into protein, at a time when many accomplished scientists regarded crystallizing it, let alone determining its structure, as unrealistic. She persisted because the question mattered to her, and because each technical failure suggested another experiment. Ada did not easily give up.
Her beginnings gave little indication that she would one day stand in Stockholm receiving the Nobel Prize in Chemistry. Ada was born in Jerusalem on 22 June 1939 into a family of very modest means. Her parents, who had emigrated from Poland, had little formal education. Her father was a rabbi, and the family attempted to make a living from a small grocery shop. They lived crowded together with other families, with very little money. Yet poverty did nothing to suppress Ada’s curiosity. As a child, she wanted to know why things were as they were and devised experiments of her own. In one frequently recounted episode, at the age of five, she attempted to determine the height of the family balcony by constructing an improvised tower of furniture; the experiment ended with a fall and a broken arm.
Her father suffered from prolonged illness and died when Ada was only eleven. The family’s already precarious circumstances became still more difficult. Ada worked cleaning, babysitting, and tutoring to help her mother and younger sister. After the family moved to Tel Aviv, she taught mathematics and chemistry to help pay her school fees. Her parents had nevertheless always regarded education as something worth sacrificing for, and a perceptive kindergarten teacher had recognized very early that this relentlessly questioning child needed intellectual encouragement. Ada later described science itself as almost a luxury in the circumstances in which she grew up. Perhaps that early experience helps explain why, once given the freedom to do science, she used that freedom so fearlessly.
After her compulsory military service, she studied chemistry at the Hebrew University of Jerusalem and then came to the Weizmann Institute of Science for doctoral studies. Working with Wolfie Traub, she completed her PhD in X-ray crystallography in 1968. Her doctoral research concerned fibrous biological structures, including collagen, rather than the high-resolution macromolecular crystallography, which later became the technique of choice. She subsequently undertook postdoctoral work at Carnegie Mellon University and at MIT, where she was exposed more directly to the emerging possibilities of protein crystallography. Returning to Rehovot in 1970, she established Israel’s first protein crystallography laboratory, which, for almost a decade, was the only one of its kind in the country.
I remember my first meeting with Ada very clearly. It was in 1972, when I was doing a very short postdoc at the Hebrew University in Jerusalem, after completing my PhD with Cyrus Levinthal. I had just obtained small crystals of an RNA fragment and wanted to determine whether they diffracted. I asked around and learned that the only X-ray system suitable for testing them was at the Weizmann Institute, and that I should contact Ada Yonath.
I did, and, to my amazement, she immediately invited me to come to Rehovot. I was a young postdoc whom she did not know, yet she readily gave me her time and access to the equipment, and together we set about testing the crystals. Her openness and generosity, and the seriousness with which she listened to my questions and offered scientific advice, went far beyond anything I could have expected. She treated my small experiment as something worth her time and attention.
What is perhaps most remarkable is that this never changed. As Ada’s career progressed and the demands on her time grew enormously, she remained extraordinarily generous in helping others and sharing her scientific insight. At the same time, her own scientific ambitions were growing. She was becoming increasingly drawn to what was then one of the largest and most difficult problems in structural biology. This problem would occupy her for decades and ultimately define her scientific career.
The question that came to dominate her research was simple to state: how does the ribosome actually work?
By the late 1970s, the overall role of ribosomes was well established. Messenger RNA was read, tRNAs delivered amino acids, peptide bonds were formed, and proteins emerged. But for a structural biologist, this description left the essential question unanswered. Where were these components in three dimensions? How were substrates positioned? What produced fidelity? How was the growing peptide accommodated? And, ultimately, what constituted the catalytic heart of this enormous assembly?
Ada believed that only structure could provide the answer. The obstacle was the ribosome itself. Compared with the proteins routinely studied by crystallographers of the period, it was gigantic. It was an asymmetric complex of RNA and proteins, conformationally mobile, chemically heterogeneous, readily damaged, and notoriously prone to losing biological activity. Eminent laboratories had already encountered formidable difficulties trying to crystallize ribosomal particles. To many colleagues, therefore, Ada’s program seemed impossibly ambitious.
She did not interpret failure by others as evidence that she should stop. Quite the opposite. She once remarked, in effect, that if distinguished scientists could fail at the problem, she was quite prepared to join them.
Her work also grew out of earlier ribosome research at the Weizmann Institute. David Elson, Ada Zamir, Ruth Miskin, and colleagues had investigated reversible ribosomal inactivation and the biochemical conditions required to preserve functional particles. Related work by Zamir, Nahum Sonenberg, and Meir Wilchek used affinity and photoaffinity probes to investigate the peptidyl-transferase center and, remarkably, pointed to an intimate role for 23S rRNA long before atomic structures established the essentially RNA nature of the catalytic center. For Yonath, one principle from this work became particularly important: the ribosome preparation had to be homogeneous, intact, and, critically, active. Inactive particles might be easier to regard merely as material; Ada wanted crystals of a biologically meaningful state.
An unexpected observation then gave Ada an important clue about how ribosomes might be crystallized. While recovering from a serious bicycle accident, Ada read about the ordered packing of ribosomes in cells of hibernating animals. Ribosomes could apparently remain densely and regularly organized during prolonged inactivity and subsequently resume function. To Ada, this was compelling evidence that ribosomes could form highly ordered arrays while remaining intact. If nature could persuade ribosomes to form highly ordered arrays without destroying them, there could be no fundamental physical law preventing ribosomes from packing into a crystal.
Her memorable conclusion was: “If polar bears know how to do it, we can do it too1,2.”
The polar bears were not, strictly speaking, the reason she became interested in ribosomes; the biological problem came first. But they supplied something equally valuable: evidence that her apparently impossible experiment was not intrinsically impossible.
She therefore sought more stable ribosomes. If ordinary ribosomes were insufficiently stable, why not obtain them from organisms whose entire biology demanded molecular robustness? With Heinz-Günter Wittmann and colleagues at the Max Planck Institute for Molecular Genetics in Berlin, she turned initially to the large ribosomal subunit from the thermophile Bacillus stearothermophilus, now known as Geobacillus stearothermophilus. Later, highly stable ribosomes from organisms inhabiting still more extreme environments, including the Dead Sea halophile Haloarcula marismortui, became crucial experimental systems.
In 1980, Yonath, Müssig, Tesche, Lorenz, Erdmann, and Wittmann3 reported three-dimensional crystals of the B. stearothermophilus 50S subunit. In 2005, I emailed Ada to ask whether this was the first paper on ribosome crystals she had published. Her reply was brief: “Indeed, that was the first.” The crystals were not yet capable of yielding an atomic model, but the paper established a decisive point: isolated ribosomal subunits could crystallize. Conceptually, an important barrier had been broken.
Her collaboration with Wittmann also marked the beginning of an increasingly important scientific connection with Germany. In 1986, Ada became Head of the Max Planck Research Unit for Ribosome Structure at DESY in Hamburg. For the next eighteen years, until 2004, she effectively led two research groups in parallel, one at the Weizmann Institute in Rehovot and the other at DESY in Hamburg. It was an unusual arrangement, and one that gave her access to both the scientific environment and the synchrotron facilities, which would become increasingly important as the ribosome project progressed (Fig. 1).
Fig. 1 Ada in Beijing, China, at the Molecular Structure: Chemical Reactivity and Biological Activity Conference, September 1986, where she reported on her progress on ribosomal research.
Obtaining the first ribosome crystals was only the beginning. It would take roughly two further decades of work, improving crystal quality, limiting severe radiation damage, devising workable data-collection and phasing strategies, and taking advantage of progressively more powerful synchrotron sources. before atomic-resolution structures became attainable. As Alon Chen, President of the Weizmann Institute of Science, noted in announcing her death4, some 25,000 crystallization experiments were carried out along the way. Ada and her collaborators also had to adapt emerging crystallographic approaches to the exceptional challenges posed by ribosome crystals. In the late 1980s, Håkon Hope visited the Weizmann Institute to work with Joel Sussman and Felix Frolow on reviving a crystal-supercooling method that could protect crystals from radiation damage during X-ray diffraction. Michael Rossmann and David Haas had originally developed the underlying approach during Haas’s time at the Weizmann Institute in the late 1960s, when Yonath was completing her PhD5-7. Hope, Frolow, and Sussman demonstrated the method with a 13-mer DNA crystal8 being studied by Leemor Joshua-Tor, then a student in Sussman’s laboratory. Building on that proof of principle, Yonath adapted cryogenic crystal preservation to ribosome crystals9. She went on to play a major role in developing, establishing, and popularizing cryo-biocrystallography as an essential component of macromolecular crystallography.
Ada’s own 2005 description of those early years captures both the hostility she encountered and her delight in answering it experimentally. Writing about her 1982 paper on parameters governing ribosomal-subunit crystallization10, she said that it had been written to show her “friends” that the project was not a “wishful dream” and her enemies that it was not a “lie.” That sentence was vintage Ada: mischievous, combative, funny, and entirely serious about the science.
By 1987, working with Leonard and Wittmann11, she used electron microscopy of negatively stained, two-dimensional 50S crystalline sheets, combined with three-dimensional image reconstruction, to reveal a tunnel through the large ribosomal subunit. Remarkably, they proposed that this tunnel provided the path for the nascent polypeptide chain, an interpretation confirmed more than a decade later by atomic structures.
In 2000 and 2001, the long campaign by Ada, later joined by several other groups, finally yielded high-resolution structures of ribosomal subunits and their functional complexes. The structures transformed our understanding of translation. They revealed the extraordinary architecture of ribosomal RNA, the organization of the decoding and peptidyl-transferase centers, the nascent-chain tunnel, and the structural basis by which numerous antibiotics selectively interfere with bacterial protein synthesis. Subsequent work from Ada’s laboratory explored antibiotic binding and resistance, ribosome evolution, and what she believed might be remnants of a primordial RNA apparatus for peptide-bond formation.
For those working in structural biology at the time, the structures changed what seemed technically imaginable. They also made it possible to ask mechanistic questions about translation and antibiotic binding in structural terms. In 2009, Ada shared the Nobel Prize in Chemistry with Venkatraman Ramakrishnan and Thomas Steitz “for studies of the structure and function of the ribosome.” She was the first Israeli woman to receive a Nobel Prize and the first woman in 45 years to receive the Chemistry prize. The Nobel joined an extraordinary list of distinctions that included the Israel Prize, the Wolf Prize, the Harvey Prize, the Louisa Gross Horwitz Prize, and many others.
The prizes mattered, but they were not what animated her scientific life. What drove Ada was curiosity, and that curiosity was contagious. Ada’s commitment to synchrotron science eventually extended beyond her own research. She became an enthusiastic supporter of SESAME, the synchrotron facility established in Jordan to serve scientists throughout the Middle East. SESAME represented something she believed deeply: that science could cross boundaries that politics could not.
I saw a striking example of this at the SESAME Users’ Meeting in Petra, Jordan, in November 2009, only weeks after Ada had received official word that she would receive the Nobel Prize. Scientists had come from across the region, including countries with little or no political contact with Israel. After Ada’s lecture, a group of young Iranian scientists, several of them women, gathered excitedly around her. They wanted to speak with her, to be photographed with her, and to be near someone whose scientific achievements and her achievements as a woman in science had inspired them. One young Iranian woman even embraced her, and a photograph from that meeting captures the moment beautifully: Ada surrounded by these young scientists, with no hint of the political hostility between their countries (Fig. 2).
Fig. 2 Ada (center), flanked by young Iranian students at the 8th SESAME Users Meeting in Petra, Jordan, November 2009. (Photo reprinted with permission of Eliezer Yaar.)
For me, that photograph expresses something important about both Ada and SESAME. The political differences had not disappeared, but for those few minutes, they were irrelevant. They were scientists talking to another scientist, united by curiosity and a common language. It was a small but very real example of something Ada believed in: science as a bridge between people, science in the service of peace.
I remember seeing this firsthand in Chennai, India, in 2018. After a full day of scientific lectures, including her keynote lecture, Ada was asked to take part in a festive evening event honoring a group of young undergraduate women who had just completed internships in biotechnology. She was asked to present each student with a certificate and say a few words to each. I still remember the incredible excitement on their faces as they came forward to meet her. It was clear that this brief personal encounter with Ada meant something very special to them, and I could not help thinking about the impact that meeting her might have on their lives and on their confidence in pursuing science.
Ada was also very supportive of Israel’s participation in European scientific projects. She and her group interacted particularly closely with the Israeli Instruct-ERIC Centre, the Israel Structural Proteomics Center at the Weizmann Institute on many of her projects.
Ada repeatedly advised younger scientists to be curious, then more curious, and to choose problems about which they felt genuine passion, because a life in science inevitably contains long periods of darkness. She knew something about those periods herself. For much of her career, progress came not in dramatic Eureka moments but in small, hard-won increments: a slightly better crystal, a few additional reflections, less radiation damage, another heavy-atom derivative, a somewhat more interpretable map. Ada had the remarkable ability to take encouragement from advances that to others might have seemed disappointingly small. She understood that, in science, those small steps are often what eventually make the seemingly impossible possible.
She continued doing science almost to the end of her life. Her publication list extends into 2026. Even after the ribosome had become one of the most structurally characterized machines in biology, Ada still saw unanswered questions: the origins of translation, species-specific antibiotic interactions, ribosomopathies, and the evolutionary pathway from an ancient RNA world to the modern ribosome.
There was also another side of Ada, known especially to her daughter Hagith and her granddaughter Noa. Ada became a mother during her doctoral years and often worked unconventional hours to combine laboratory life with raising a child. She never regarded family as an impediment to science. Rather, she spoke of motherhood as a privilege.
Among the many medals, honorary degrees, and international prizes Ada received during her remarkable career, one distinction was especially dear to her. It came not from Stockholm or from one of the great scientific academies, but from her granddaughter Noa: the “World’s Best Grandma Award” (Fig. 3). Ada often spoke of it with particular pride. It is a fitting reminder that this formidable scientist was also a devoted mother and grandmother, a colleague and a friend.
Fig. 3 Grama of the Year award given to Ada by her granddaughter, Noa.
For structural biologists, Ada leaves an extraordinary scientific legacy. She chose a problem that most of the field considered beyond the reach of crystallography and pursued it for more than two decades, through poor crystals, radiation damage, inadequate methods, and considerable skepticism. She dared to take a long shot, the imagination to find ways around one obstacle after another, and, perhaps most importantly, the persistence not to give up; our understanding of the ribosome, and of what structural biology can attempt, is different because she did not.
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