A rapid and precise probe for measurement of liquid xenon polarization.

The relaxation time of liquid (129)Xe is very long (>15 min) and the signal at thermal equilibrium is weak. Therefore, determination of the absolute polarization enhancement of hyperpolarized (129)Xe by direct measurement is tedious. We demonstrate a fast and precise alternative, based on the dipolar field created by liquid hyperpolarized (129)Xe contained in a cylindrical sample tube.

Orientation, structure, wet-spinning, and molecular basis for supercontraction of spider dragline silk.

This manuscript reviews work from our laboratory that addresses the orientation, secondary structure, wet-spinning, and molecular basis for supercontraction of spider silk. It identifies the poly(alanine) runs as the crystalline regions, establishes the degree of orientation of these regions, and identifies the secondary structural elements of the conserved L-G-X-Q (X = G, S, or N) regions. It also describes methods for spinning very small amounts of protein polymers and it sets forth several molecular-level hypotheses concerning supercontraction.