Educational Background

Kristin Kumashiro received her B.S. from University of Hawai’i at Manoa in 1988 and Ph.D. from Yale University in 1995. She did postdoctoral research at the University of Massachusetts at Amherst (1995-1997) in the Departments of Chemistry and Polymer Science and Engineering. She joined the faculty of the University of Hawai’i in the spring of 1997.

Her research program is centered about the applications and methodology development of high-resolution solid-state nuclear magnetic resonance (NMR) for the study of novel systems, such as connective tissue proteins. Extramural support for Dr. Kumashiro’s research program includes a CAREER award from the National Science Foundation.

Current research projects focus on elastin,a vertebrate protein with remarkable biomechanical properties. The elastic properties of a number of physiological structures, such as blood vessels and skin, are believed to originate from elastin, an amorphous, crosslinked protein comprised largely of small hydrophobic amino acids. The three-dimensional structures of insoluble elastin remains elusive, as crystallographic tools and even the most sophisticated solution NMR spectroscopy cannot be used to study this insoluble protein. Therefore, for many years, the true nature of elasticity in biological systems has remained controversial, as none of the existing models could be confirmed or rebutted with high-resolution structural data.

Now, with the advent of high magnetic fields and a growing number of high-resolution solid-state NMR experiments, the structural characterization of elastin is in progress in our laboratories. Solid-state NMR has proven to be a powerful tool in the characterization of molecular and bulk properties of many compounds. For instance, isotropic chemical shift and chemical shift anisotropy are relative measures of the shielding of a specific nucleus and are sensitive probes of chemical or electronic environments. More elaborate experiments are used to ascertain other structural parameters, such as internuclear distances or torsion angles, as demonstrated by others for a range of peptides and proteins. In addition, a number of experiments are used to determine dynamical features. These experiments include, e.g., relaxation measurements that are analogous to those done in the solution state. Finally, in addition to the application of now-routine solid-state NMR experiments for structural studies of proteins and polymers, we have also endeavored to develop, adapt, and apply new methods for these samples.

We have adopted an approach that includes use of a wide range of elastin and elastin peptide samples. In this manner, we anticipate that a global model for biological elasticity will emerge, rather than a set of observations that may or may not be specific for a given elastin-based motif.

One set of work focuses on characterization of the natural-abundance 13C populations in elastin isolated from tissue, in addition to elastin peptides from numerous collaborators. With regards to the latter, these ongoing collaborations include elastin peptides from synthesis as well as recombinant methods.

In addition to the natural-abundance 13C work, we have developed a unique approach to isotopic labeling of this vertebrate protein. As bacterial expression methods lack the natural mechanism for crosslinking, we have adapted a protocol using a mammalian cell line to produce insoluble elastin with 13C, 15N, and 2H-labels at key amino acids. Not only does this approach provide unambiguous structural assignments for the enriched sites, but it increases the number of NMR experiments that are now feasible for this complex system.

Our early work, which includes both the natural-abundance and isotopically-enriched preparations, highlight the unusual mobility of large segments of elastin. Furthermore, our data show strong support for models of elastin structure that involve significant structural heterogeneity (rather than regular or repeating structures). The curious reader is encouraged to consult recent publications from this lab for additional information.