Martin F. Jarrold, Professor
Department of Chemistry
Northwestern University

E-mail: mfj@northwestern.edu
Phone: 847-491-3504
Web: http://nano.chem.northwestern.edu/jarrold/

BSc, PhD, University of Warwick
NATO Postdoctoral Fellow, University of California, Santa Barbara

Research Areas
Our research is focused on biological mass spectrometry, the biophysics of peptides and proteins, and the characterization of metal and semiconductor clusters. The common thread that runs through our different projects is the use of sophisticated mass spectrometry-based techniques such as ion mobility measurements and resonant two-photon ionization. We have active collaborations within the department with Professors Ratner and Van Duyne and with many other groups around the world.

The recent development of gentle ionization techniques (such as electrospray and matrix-assisted laser desorption) has made it possible to study biological molecules by mass spectrometry. For example, we are using electrospray/ion mobility measurements to obtain information on the three-dimensional structure of unsolvated peptides. We are studying the classic secondary structure elements, helices and sheets, in the absence of a solvent. We use computer simulations to design peptides with particular conformations, synthesize the peptides, and then test the predictions. Measurements performed as a function of temperature provide information about secondary structure stability. We are currently working towards obtaining a scale of the intrinsic helix propensities of the different amino acids.

In related work we are collaborating with a group in France to develop a new experiment to measure the dipole moments of unsolvated peptides and proteins. We also are studying proteins and peptides solvated with a known number of water molecules.

The properties of a material change as its dimensions drop below a micrometer and enter the nanometer range. Atomic clusters containing tens of atoms lie at the small end of the size scale. In this size regime both the structure and the properties are often very different from the bulk. We are using surface plasmon polariton enhanced Raman spectroscopy and ion mobility measurements, along with density functional theory, to characterize the geometries. Our recent work is focused on the Group 4 clusters Ñ Cn, Sin, Gen, and Snn. In addition to determining the structures, we are interested in examining physical properties such as melting points and in determining how they change as a function of cluster size.

Related Publications
"Helix Formation in Unsolvated Alanine-Based Peptides: Helical Monomers and Helical Dimers" [with R. R. Hudgins], J. Am. Chem. Soc. 121:3494-3501 (1999).

"Unfolding, Refolding, and Hydration of Proteins in the Gas Phase," Acc. Chem. Res. 32:360-67 (1999).

"Design of Helices That Are Stable in Vacuo" [with R. R. Hudgins and M. A. Ratner], J. Am. Chem. Soc. 120:12974-75 (1998).

"Raman Spectra and Calculated Vibrational Frequencies of Size-Selected C16, C18, and C20 Clusters" [with A. K. Ott, G. A. Rechtsteiner, C. Felix, O. Hampe, R. P. Van Duyne, and K. Raghavachari], J. Chem. Phys. 109:9652-55 (1998).

"Structures of Medium-Sized Silicon Clusters" [with K.-M. Ho, A. A. Shvartsburg, B. C. Pan, Z.-Y. Lu, C.-Z. Wang, J. G. Wacker, and J. L. Fye], Nature 392:582-85 (1998).