Henryk (Heini) Eisenberg (1921–2009): From polymer chemistry to halophilic enzymes to chromatin and back

On December 17 2009, polymer chemist Henryk (Heini) Eisenberg, whose name has been associated with prominent scientists such as Paul Flory, Peter Debye, and Aharon Katchalsky, passed away at his home in Rehovot (Israel). Heini was born in Berlin on March 7, 1921 to a devoted Jewish father (Issay) and Russian mother (Inna). It was the ethnical and religious diversity of his parents that led him to state: “I myself have always put the happiness and welfare of man before limiting religious or nationalistic dogmas of any kind, through accepting the deep manifold cultural connections to one's own past” [Eisenberg, H., Comprehensive Biochemistry, Semenza, G., and Jaenicke, R. (Eds.) vol.37, pp. 265–348, Elsevier, Amsterdam]. It is therefore not surprising that during his long scientific career, Heini collaborated with an extensive number of colleagues, and acted as a mentor to many graduate students and postdoctoral fellows of diverse backgrounds. In 1939, he moved from Romania to the Hebrew University in Jerusalem in Palestine. His academic life was soon interrupted in 1942 when he joined the Royal Engineers of the British army near Cairo in support of the fight against the advance of Rommel's troops in Egypt. It was at that time he met and married his wife Nutzi, with whom he spent the rest of his life. Nearly five years after his departure, he returned to the Herbrew University to continue his postdoctoral studies. His initiation in the polymer field took place during this time, under the guidance of Aharon Katchalsky. This work, which was in part published in Nature [Kuhn, W., Harigatay, B., Katchalsky, A. and Eisenberg, H. (1950) 514–516], demonstrated, in Heini's own words, “…that polyelectrolyte coils in solution expand and contract depending on charge and ionic strength.” This concept was later applied to the biophysical characterization of nucleic acids and chromatin carried out in his lab. With the official opening of Rehovot's Weizmann Institute in 1949, Heini became one of its founding members, and most of his scientific career was spent at this wonderful research institution. He travelled extensively though, and visited many countries. His early work with Ray Fuoss at Yale (1952–1953), and his interactions with Peter Debye at Cornell, set the basis for his interest in polyelectrolytes. A short visit to Strasbourg upon his return from Yale extended this work to the study of nucleic acids (DNA and RNA) as biological polyelectrolyte macromolecules through the use of a Couette viscometer which he helped design, in combination with sedimentation in the analytical ultracentrifuge, and light scattering techniques. The year 1958 was of important relevance in Heini's scientific career, as he joined the Mellon Institute in Pittsburgh, which at that time was directed by Paul Flory. The study of polysulfonic acid solutions in collaboration with Ed Casassa led them to an important development in the theory of multicomponent macromoleclar polylectrolyte solutions [summarized in: Casassa, E.F. and Eisenberg, H. (1964) Adv. Prot. Chem. 19: 287–395]. Years later, this resulted in a book publication [Biological Macromolecules and Polyelectrolytes in Solution, Clarendon Press, 1976, 272 pp.] that remains today a milestone and solid reference for researchers in the field. This theory has been instrumental for the theoretical development of the analysis involved in various techniques such as osmotic pressure, analytical ultracentrifuge, light, X-ray and neutron scattering which Heini himself used extensively throughout his research (see below). Subsequent to these rigorous early theoretical studies, Heini devoted an important part of his research to implementing them in the biophysical characterization of naturally occurring complex biological systems, namely halophilic enzymes and chromatin, using the aforementioned experimental approaches. His work on glutamate dehydrogenase and halophilic ferredoxin from Halobacterium marismortui showed that the unusually large amounts of salt and water bound (hydration) by these proteins is the result of their unique tertiary and higher order structural organization. His interest in chromatin likely began during his stay at the Mellon Institute, and as a result of its proximity to the Biophysical Laboratory at the University of Pittsburgh where Gary Felsenfeld was working at the time. The strong friendship established between the two resulted in tight research collaboration, eventually leading to the characterization of the nucleosome. However, the most significant contributions to that field came from Heini's own research at the Polymer Department of the Weizmann Institute in the early 1980s. An important effort was devoted at that time to studying the conformational transitions of nucleosomes and the ionic dependence of chromatin folding in solution. This was also when Heini had just won his first battle with colon cancer. His always active personality, his passion for science, and the excitement of these studies must have certainly been an important factor in his triumph over cancer. One aspect of his chromatin work that, with the advent of the plethora of chromatin remodelling complexes, seems to have been forgotten is the demonstrated ability of exogenous histone octamers to bind to the nucleosome [Voordow, G. and Eisenberg, H. (1978) Nature 273, 446–448]; a discovery that may have relevance to different aspects of chromatin functioning. Such binding could be important in the intermediate transitional stages leading to displacement of the histone octamer at some of the promoters of transcriptionally active genes. With the recent renaissance of interest in analytical ultracentrifuge after Beckman's development of the XL-analytical ultracentrifuge line in the 90s, one of Heini's last papers on this topic resulted in a controversial rebuttal. While there is no denying about the powerful apparent useful validity of the two component system approximation using computer assistance for the analysis of the data obtained with this technique [Lebowitz, J., Lewis, M.S. Schuck, P. (2003) Protein Sci. 12, 2649–2650], a rigorous development of the analysis of biological macromolecules such as the halophilic enzymes and chromatin should necessarily go back, no matter what, to his multicomponent macromolecular polyelectrolyte theory [Eisenberg, H. (2003) Protein Sci.12, 2647–2649]. But not all in Heini's life was rigorous science. He spent much time organizing International meetings (EMBO), and he was Vice-President and elected member of the International Union of Pure and Applied Biophysics (IUPAB). During all his time at the Weizmann Institute, Heini and Nutzi were the perfect hosts to many entertaining get together parties at their home located within the beautiful campus of the institute. The gatherings were attended by postdocs in his lab and by many salient members of the local scientific community such as Ada Yonath, with whom the Eisenbergs maintained a strong friendship. Those of us who had the privilege to attend have fond memories of such enticing and memorable social events. He was wise man, the best address to come for an advice in difficult matters scientific and personal life of his friends would bring about. In one of his recollection papers, Heini stated: “Rheology is the science of flow, theology studies the flow of the wisdom of God to mankind on earth” [Eisenberg, H. (2004) Biophys. Chem. 112: 229–231]. Heini's life contribution to the study of the flow of macromolecules in solution will be everlasting. His house in the lush Weizmann Institute campus had, as many of the gardens around Rehovot, orange trees. It is difficult to have spent time at the Institute and not remember the pleasant scent of the blossoming orange trees in the balmy winters of the area. It was during the time the orange trees blossomed that Heini's life and science went away, with the flow of their gentle scent. Let his soul and his spirit rest in the Wisdom of God.

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