Zeev Luz (1932–2018)

1979 was one of the most productive and enjoyable years of my life. I spent the year at the Weizmann Institute of Science with Zeev Luz. Early in my stay, Luz walked me through the labs in the Perlman Building so that I might get my bearings. Luz had particular pride about one item, a relic from an earlier era – a crude, homemade, iron-core magnet. I was puzzled until Luz explained with understated excitement and historical reverence how in the early 1950s Saul Meiboom had energised this magnet, one of the world’s first NMR magnets, taking down the entire power supply of the Institute[1]. His delight over that achievement was something only a fellow NMR geek could share. Luz was always a happy iconoclast, willing to say anything or try anything, and he questioned everything. When he met my wife, he argued with her over the spelling of her name, teaching us both the meaning of chutzpah (or, as the Greeks say, thrasos, which translates roughly as boldness). And yet he always had an air of quiet courtliness and old-world gentility. It was a privilege to have Luz argue with you over something.

1. (Colour online) Formal dinner photograph dating from the International Liquid Crystal meeting in Japan in 2000. From left to right, Zeev Luz, Carol Shumate, Herbert Zimmermann and Ed Samulski.

I didn’t realise it then but Luz’s own name had changed multiple times: He was born in Munich in 1932 as Wolfgang Emanuel Nussbaum. Then, his father moved the family to Israel in 1934 where his surname Nussbaum (nut-tree) was changed to its Hebrew translation, Egozi. When he entered kindergarten, his teacher re-named him Zeev, a translation of Wolfgang. Eggoz means nut in Hebrew, and in adolescence he attended an agricultural school where his friends called him Luz, after the hazelnut. They evidently thought him to be a particular kind of nut, ‘a round, brown, hard-shelled nut’, according to the dictionary. Zeev’s impervious side was apparent to all. According to his daughter Naomi, his kindergarten teacher threw up her hands and said, ‘It’s him or me,’ and Zeev was kicked up to first grade. From then on, he was called Luz more often than Zeev, even by his wife Avigail. To me, his evolving nomenclature is appropriate for one who had no attachment to the way things should be, no expectations and therefore no disappointments, only the pleasure of discovery. When we did experiments together that year, he always sat with baited breath watching the spectrum as it printed out. We were hot on the trail of the Blue Phase of cholesteric liquid crystals, but no matter what we found, he was eager to see it and to fit it into his vast mental picture of nature. Years later, when he was mostly blind, he was doing the same thing: waiting for the spectrum to print out with the eager excitement of a child, scrutinising it as if communing psychically with the underlying molecular origins.

It was more common for Luz to ask questions than to argue, and his questions were often more intimidating than commands. His didactic teaching style was legendary – with his senior colleagues as well as his students. Geoffrey Luckhurst related the following: ‘In 1983 Jim Emsley organized the NATO Advanced Study Institute titled Nuclear Magnetic Resonance of Liquid Crystals held in San Miniato. This was attended by Luz and it occurred to me to take advantage of this, as well as his encyclopedic knowledge, to seek his advice about an NMR problem that had been bothering me for some time. However, rather than giving me the solution as I had expected Luz suggested that I describe the problem to him and explain my thoughts on a solution. Of course, his approach was inspirational; I certainly learnt far more from it than if he had simply told me his solution’.

When young Luz joined Meiboom’s research group, Meiboom was pioneering the application of the then-new NMR technique to chemistry – molecular structure determination using spin–spin couplings and how chemical reaction kinetics manifest in the spectrum – as well as developing the underlying quantum mechanical understanding of those phenomena. In 1961, after completing his doctoral studies, Luz rejoined his mentor Meiboom at Bell Telephone Laboratory in New Jersey as a postdoctoral researcher where he continued to pursue chemical kinetics using ESR and NMR, returning to the Weizmann Institute in 1964. It was during this period that Saupe and Englert published their famous paper, ‘High-resolution nuclear magnetic resonance spectra of oriented molecules’ [2]. Their discovery ‘launched an industry’ of molecular structure determination in liquid crystals. This breakthrough was widely appreciated at Bell Labs: in 1965 staff scientist Lawrence Snyder published a method for quantifying the average orientation of molecules dissolved in liquid crystals [3] and in December of 1968 Meiboom and Snyder reviewed the field for Science [4]. In retrospect, it is reasonable to infer that Luz was inspired by the potential of NMR to investigate liquid crystals during his stay at Bell Labs but the topic appears to have gestated for nearly a decade before he and Meiboom jointly started exploring NMR for characterising the supramolecular organisation [5] and, of course, exploiting the potential of incompletely averaged, proton dipolar interactions for determining the kinetics of intramolecular processes [6].

Early on it was apparent that structure determinations in liquid crystals using proton NMR would soon be exhausted by the complexity of the spectra of multi-spin solutes. Initially, deuterium labelling appeared to be a viable method of simplifying H NMR spectra as the direct dipolar interaction with the deuteron nucleus was much smaller. Then it became clear that the incompletely averaged deuterium nuclear quadrupolar interactions themselves in both solutes and in mesogens provided new information about liquid crystal phases [7].

However, to exploit this valuable source of detailed insights into molecular conformations and dynamics, it was essential that Luz have access to deuterium labelled molecules. He needed a chemist who might judiciously label molecules so that he could answer specific questions about LC phases and the dynamics therein. In 1977, he found one. While spending a leave in Alex Pines’ lab in Berkeley, Luz met the outstanding synthetic chemist Herbert Zimmermann, of the Max Planck Institute in Heidelberg, Germany [8]. They established a life-long symbiotic relationship, one that enabled them and Weizmann Institute students and visitors to explore many aspects of liquid crystals. In the 1980s, they published seminal papers on discotics [9], subtle intramolecular kinetics phenomena [10,11], phase transitions [12], lyotropics [13,14] and pyramidics [15]; additionally, the ordered fluid phases provided a platform for introducing new methodologies that also depended on labelling chemistry [16]. Zimmermann describes the stressful process of co-authorship with Luz: ‘I would write about how I managed to put a deuterium into a certain position in a liquid crystal, knowing that whatever I wrote would be rewritten by Luz as he was an excellent writer’. Once Zimmermann tried to ‘outsmart’ Luz by asking an English postdoc in the Pines’ lab to take his experimental write-up and ‘put it into the King’s English’. Without mentioning the postdoc’s help, Zimmermann proudly presented the result to Luz, whom he called his ‘English teacher’. This time Luz completely rewrote it – ‘with even more additions and corrections than usual’.

When Luz visited me in North Carolina in 1995, it was not a social visit. He was intent on understanding the model of solute orientation in liquid crystals advanced by visiting faculty collaborator, Demetri Photinos. Our postdoctoral researcher Andreas Terzis lamented: ‘Day after day Luz insisted that I explain every single aspect of our process to him; he wouldn’t accept anything without a clear rationale’. Photinos added that producing our paper with Luz was one of the most challenging writing experiences of his career, but one that led to a much stronger and clearer exposition [17]. One can get a sense of Luz’s fastidious and exhaustive approach to recherché topics by merely perusing the 2015 review, ‘Enantiotopic discrimination in the NMR spectrum of prochiral solutes in chiral liquid crystals’ [18].

I returned to Israel several times to work with Luz and each time we made further discoveries. Luz and his colleague Raphy Poupko created an infectious ‘can-do’ attitude at the Weizmann Institute. When I would propose some devilishly difficult experiment to them – ‘Can we do X?’ – they would reply, ‘Lama lo? [Why not?]’. For example, a prerequisite to our work on the Blue Phase necessitated the labelling of cholesteryl nonanoate with deuterium. ‘No problem’, Luz said and he introduced me to organic chemists at the Institute. With their help, I succeeded in labelling the mesogen, and together we went on to demonstrate how molecular dynamics was impacted by the organisation in that metastable cubic phase [19,20].

Our understanding of liquid crystals is so much deeper because a distinguished pioneer in magnetic resonance was inspired to examine the multifaceted signature associated with NMR in ordered fluid phases. Zeev Luz taught me about much more than the influence of molecular dynamics in liquid crystals. That year in Rehovot was wonderful in part because he shared his social life with my wife and me, including us in every holiday and every party. Luz was such an important figure at the Weizmann that to be in his social circle was to be surrounded with wonderful people. I learned then the immense value and necessity of collegial relationships for doing good science.