Scott A. Riley

Capture and manipulation of magnetically aligned Pf1 with an aqueous polymer gel.

The magnetic alignment of the Pseudomonas bacteriophage Pf1 is captured indefinitely in a gel of the aqueous triblock copolymer Pluronic F-127. In addition to preserving high-resolution liquids NMR spectra for dissolved solutes, the gel prevents the reorientation of the phage allowing mechanical manipulation of the angle between the axis of the phage alignment and the static magnetic field. The residual 2H quadrupolar couplings for several solutes dissolved in this material as a function of the angle Theta between the non-spinning sample tube and the static magnetic field are consistent with the value of P(2)(cosTheta)=(3cos(2)Theta-1)/2. The variable-angle correlation spectrum for these solutes is shown to separate residual quadrupolar effects from isotropic chemical shifts. Finally, the compatibility of Pluronic F-127 with NMR studies of aqueous biological macromolecules is demonstrated in a measurement of residual dipolar couplings in an 15N-labeled nucleic acid.

Spin-echo in the phosphorescent triplet state of crystalline 2-indanone

Abstract The relative ordering of the three sublevels of the phosphorescent triplet state of 2-indanone was determined by correlating optically detected magnetic resonance (ODMR) spectra taken with the sample in a Zeeman field with calculated spectra. Spin coherence was observed in the phosphorescent triplet state of 2-indanone in neat and doped single crystals by conventional and real time detection. The Hahn electron spin-echo signal was observed in real time by a pulse sequence which terminates with a continuous-wave low power field (LPF). The Fourier transform of the echo decay as a function of τ yielded a peak at 9.0 MHz which was attributed by isotopic substitution studies to nuclear coupling of the triplet electrons via the α-protons in the molecule. Dephasing of the Hahn and stimulated spin echo in 2-indanone due to energy trapping was measured with chemically mixed crystals of 2-indanone prepared with varying concentrations of quinoxaline. Energy transfer to quinoxaline which served as a deep trap contributed to the dephasing of the echo.

High-voltage pulse switching hardware for electro-optic studies of conducting aqueous solutions

The hardware necessary for the electro-optic study of conducting polyelectrolyte solutions is frequently not commercially available or financially practical. The designs of an electrical rectangular pulse switch and polarity-reversing relay switch capable of producing 3 kV 5 A direct current pulses lasting longer than 100 μs are presented. As an example of the operation of this equipment, the electric birefringence of an aqueous solution of the Pseudomonas bacteriophage Pf1 in tris/EDTA buffer is presented.