Biographical Memoirs Volume 65 (1994) / Chapter Skim
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20. John Warren Williams
20. John Warren Williams
Pages 374-390
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From page 375... ...
Williams was one of the first to deduce molecular structure from measurements of dipole moments using theory formulated by P
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From page 376... ...
Williams's first independent research began with measurements of the dielectric constants of liquid mixtures. His interest in the electrical properties of matter was probably influenced by close contacts with the departments of physics and mathematics, where Max Mason and Warren Weaver were collaborating on their classic treatise, The E1tectromagnetic Field.
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From page 377... ...
lack Williams built his own instruments for both resonance and bridge methods, and meticulously purified his materials. By mid-1927, he and his students had cletermined the dipole moments of some thirty compounds and shown that, in several cases, the results were essentially incle penclent of the choice of the nonpolar solvent.
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From page 378... ...
Subsequently, Williams and his students chose for this purpose the proteins zein, gliadin, and secalin, with molecular weights in the range of 25,000-40,000, which, unlike most proteins, are soluble in alcohol-water mixtures with conductivities low enough to make dielectric constant measurements by the same methods used for solutions in organic liquids. For zein, the frequency dependence corresponcled to two relaxation times which could be attributed to rotation of an ellipsoid of revolution about its major and
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From page 379... ...
(Meanwhile, Oncley at Harvard had developed an impedance bridge method for dielectric measurements over a wide frequency range on aqueous solutions with substantially higher conductivities. This permittecl measurements on many other proteins; he showed how rotational relaxation times for these macromolecules could be combiner!
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From page 380... ...
came on a visit to Williams's laboratory anti, together with Harold I~unclgren, they began to measure the molecular weights of cliptheria toxin and antitoxin and to analyze the stoichiometry of the soluble complexes that are formed in antigen excess. The aim was to provide a physico-chemical framework for Marrack's lattice theory of antigen-antibocly precipitation.
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From page 381... ...
He enlisted the collaboration of Harold Deutsch in the Physiological Chemistry Department at Maclison, and several of his own students, notably Robert Alberty, Eugene Hess, and Louis Costing, joined in. Alberty went on to show that bounciary-speading measurements clemonstratecl the existence of antibody molecuTes with different isoelectric points within the 7~ and 72 globulin fractions, and at Caltech John G Kirkwooc3 built an electrophoresis convection apparatus which could separate molecules according to their isoelectric points.
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From page 382... ...
easily operated instrument, and many biochemists began to use analytical ultracentrifuges. At that time, protein molecular weights were measured chiefly from sedimentation velocity and diffusion experiments, by use of the Sveciberg equation.
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From page 383... ...
This happened when Kensal Van Holde en cl Robert Baldwin, who not long before had been members of Williams's research group, used the Mason-Weaver solution to the differential equation for the ultracentrifuge to show that equilibrium could be reached in a day instead of two weeks, by using a short column of solution. The classic 1923 paper on sedimentation equilibrium by Max Mason and Warren Weaver, both then at Wisconsin, was inspired by Sveclberg's extended visit to the Chemistry Department at Madison.
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From page 384... ...
viscosities and steadystate compliances (a measure of elastic recovery) of a series of polyisobutylene samples and found that the latter, surprisingly at the time, correlated not with the molecular weight but with the molecular-weight distribution.
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He was especially attentive to the development of the undergraduate physical chemistry laboratory. Here he had a keen sense for spotting research talent and identifying promising students for graduate work.
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386 BIOGRAPHICAL MEMOIRS spent several winter weeks at the California Institute of Technology, where he hacI been visiting professor in 1946-47 and 1953-54. After retirement in 1968 at the age of seventy, Jack WilIams continuccI work with postdoctoral associates for several years, mostly on self-association equilibria of proteins as determinecT from sedimentation equilibrium.
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From page 387... ...
31 :27-31. Molekulare Dipolmomente und ihre Bedeutung fur die chemische Forschung.
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From page 388... ...
Study of the viscoelastic behavior and molecular weight distribution of polyisobutylene.
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From page 389... ...
The sedimentation velocity experiment and the determination of molecular weight distributions.
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