Vlada Hanuš, a pioneer of molecular mass spectrometry

Abstract

The dramatic expansion of mass spectrometry in the last four decades has been due in large part to its unique, complementary capabilities for the characterization of molecules. In 1958 only a handful of scientists were interested in the mass spectrometry of samples with molecular weights > 150. Mass spectrometric studies of petroleum products far outnumbered those of more functionalized molecules, and mechanisms of gaseous ion dissociations postulated to explain mass spectral peaks engendered little respect. However, the field now has thousands of professionals, and the great majority of these are molecular mass spectrometrists. Of the true pioneering scientists in this field, Vladimir Hanus’ early critical contributions are probably the least appreciated and recognized internationally. A major reason for this has been the unusual humility and generosity of my very good friend Vlada who always insisted on sharing most of the credit with others. A Special Issue dedicated to his landmark scientific contributions to mass spectrometry is an excellent step to correct this oversight, and I am delighted to have this opportunity to add my own personal testimony concerning the importance of his scientific experimental discoveries, mechanistic insights, enthusiasm and generous sharing of ideas that were so vital to early progress in this field. Hanus did indeed have highly talented collaborators in the great Heyrovský Institute in Prague, named for the Nobel Laureate whose discovery of polarography had a dramatic effect on analytical chemistry. Hanus’ training and early research were in polarography. However, in the 1950s he and his colleagues Vladimir Iermak and Zdenek Herman initiated pioneering mass spectrometry research, such as in the physical chemistry and physics of gaseous ion reactions, that utilized specially modified mass spectrometers. Hanus’ unusual skills contributed to this instrumentation, and his research on the physical-organic chemistry aspects of molecular polarography helped him to be one of the first to recognize the importance of Sy Meyerson’s breakthrough postulation of the tropylium ion. The Hanus 1959 paper in Nature gives substantial experimental and mechanistic support for this postulate. He and his colleagues published mass spectra of eight C7H8 isomers and other tropylium precursors in a series of papers illuminating this novel gaseous ion chemistry. His careful studies of such “glamorous” molecules as adamantane and quadricyclene at this time helped to attract the attention and appreciation of mainline organic chemists to this new field of gaseous ion chemistry. I particularly enjoyed discussing ion fragmentation methods with him because of his broad mechanistic understanding developed with careful correlations from compound types such as alkynes, thiophenes and Schiff bases, as well as alkaloids and steroids. However, the most important revolution in mass spectrometry was the one that started 40 years ago with the discovery of methods to measure the mass spectra of natural products and other larger molecules, despite their low volatility. M.J. (Jack) O’Neal developed the direct probe insertion of samples into the ion source to give mass spectra of much larger petroleum molecules, while Rowland Ivor Reed was one of the first to use a similar device for flavones, carbohydrates and other natural products. In this area, the mass spectrometric characterization studies of Einar and Stina Stenhagen and Ragnar Ryhage with fatty acids, Klaus Biemann with peptides and alkaloids, Jim Shannon with triterpenoids and heterocyclic compounds and Carl Djerassi with alkaloids and steroids were especially important. However, it is little recognized that Hanus published over a dozen definitive papers on the structural characterization and ion fragmentation mechanisms of alkaloids and other natural products in the early 1960s, with many more such studies later. The most amazing part of this is something that I do not believe has ever been published, and certainly has had almost no recognition. I saw this firsthand in an early visit to his Prague laboratory. His only mass spectrometer was an