I received an AB in Physics (1961) and a PhD in Biophysics (1968) from Harvard University. For the latter I worked in the laboratory of Keith R. Porter on the morphogenetic action of microtubules in changing the shape of developing cells. Towards the end of that project I became fascinated by the role of microtubules in mitosis and have continued to work largely on that subject ever since. I stayed in the Harvard Biology Dept. for two years but moved to Colorado in 1970, where I have worked ever since. I served briefly as department Chair in the late 1970s, but this experience immunized me against such jobs in the future. In 1984 I became director of the Boulder Lab for 3-D Electron Microscopy, and I served in that capacity for 22 years. In 2000 I was appointed a Distinguished Professor of the University of Colorado, and in 2006, I “retired”, switching to the very pleasurable existence of doing the research and writing I chose, but abstaining from academic committee work and undergraduate teaching. Over the last 45 years, I have taught freshman biology, cell biology, cancer biology, and various graduate courses in cell structure and function. More recently, I have taught cell biology and done research in both East and West Africa with support from a Fulbright fellowship and the Carnegie Corporation.

Research Interests

For many years our focus was on the identification of motor enzymes that contribute to spindle formation and chromosome motion. However, our studies have demonstrated that some important aspects of chromosome motion will occur in the absence of motors, leading us to focus on the ability of microtubule polymerization and depolymerization to drive motile processes. We have shown that shortening microtubules can drag chromosomes at physiological speeds over distances as great as a cell's diameter, and more recently we have characterized several spindle proteins that can serve as couplers to attach a load to dynamic microtubules. We have also used electron tomography to characterize the structure of the junction between mammalian chromosomes and spindle microtubules, drawing attention to fibrous proteins that appear to be the principal connecting elements. Recent work used laser tweezers to characterize the biophysics of such dynamic linkages and mass spectrometry to identify proteins that may be of particular importance in the coupling processes. Currently, we are using electron cryotomography to characterize the ends of growing and shrinking microtubules, thereby identifying structural intermediates in the processes of tubulin dynamics. Our results challenge all existing models for tubulin polymerization, a delightful situation.

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Primary Section

Section 22: Cellular and Developmental Biology

Secondary Section

Section 29: Biophysics and Computational Biology