52 research outputs found
Moving Difference (MDIFF) Non-adiabatic Rapid Sweep (NARS) EPR of Copper(II)
Non-adiabatic rapid sweep (NARS) EPR spectroscopy has been introduced for application to nitroxide-labeled biological samples (Kittell et al., 2011). Displays are pure absorption, and are built up by acquiring data in spectral segments that are concatenated. In this paper we extend the method to frozen solutions of copper-imidazole, a square planar copper complex with four in-plane nitrogen ligands. Pure absorption spectra are created from concatenation of 170 5-gauss segments spanning 850 G at 1.9 GHz. These spectra, however, are not directly useful since nitrogen superhyperfine couplings are barely visible. Application of the moving difference (MDIFF) algorithm to the digitized NARS pure absorption spectrum is used to produce spectra that are analogous to the first harmonic EPR. The signal intensity is about four times higher than when using conventional 100 kHz field modulation, depending on line shape. MDIFF not only filters the spectrum, but also the noise, resulting in further improvement of the SNR for the same signal acquisition time. The MDIFF amplitude can be optimized retrospectively, different spectral regions can be examined at different amplitudes, and an amplitude can be used that is substantially greater than the upper limit of the field modulation amplitude of a conventional EPR spectrometer, which improves the signal-to-noise ratio of broad lines
Wild-caught Hybrids Between Sailfin and Shortfin Mollies (Poeciliidae, Poecilia): Morphological and Molecular Verification
This study documents four wild-caught, interspecific hybrids between sailfin mollies (Poecilia velifera or P. petenensis) and shortfin mollies (P. mexicana or P. orri) from the Yucatán peninsula and Isthmus of Tehuantepec regions of México. In canonical discriminant analysis of morphological data all four putative hybrid males were intermediate in shape between shortfin and sailfin molly species, falling well outside 95% confidence ellipses for those putative parental species. For two of the four hybrid individuals, we used allele size differences at the nuclear Xsrc gene between sailfin and shortfin species to determine that one was a first (F1) or early generation (F2, BC1) hybrid and the other was a later generation (>F1) hybrid. Sequences of the mtDNA control region (483 bp) and Xsrc nuclear gene (636 bp) indicated that the female parent of the early generation hybrid individual was P. mexicana and the male parent was P. velifera. Thus, while rare in the wild, interspecific hybridization and introgression between sailfin and shortfin mollies does occasionally occur despite the existence of behavioral pre-mating isolating mechanisms
Analysis and cloning of the synthetic pathway of the phytohormone indole-3-acetic acid in the plant-beneficial Bacillus amyloliquefaciens SQR9
Relationships among invasive Chinese privet, plant diversity, and small mammal captures in southeastem deciduous forest
Effects of Full-Stream Carbon Filtration on the Development of Head and Lateral Line Erosion Syndrome (HLLES) in Ocean Surgeon
A diffusion-limited reaction model for self-propagating Al/Pt multilayers with quench limits
Recent Experiments with the ElectricOIL Laser System
In this paper we report on studies of a continuous wave laser at 1315 nm on the I( 2 P 1/2 ) → I( 2 P 3/2 ) transition of atomic iodine where the O 2 (a 1 Δ) used to pump the iodine was produced by a radio frequency excited electric discharge. The electric discharge was sustained in He/O 2 and Ar/O 2 gas mixtures upstream of a supersonic cavity which is employed to lower the temperature of the continuous gas flow and shift the equilibrium of atomic iodine in favor of the I( 2 P 1/2 ) state. The results of experimental studies for several different flow conditions, discharge arrangements, and mirror sets are presented. The highest laser output power obtained in these experiments was 520 mW in a stable cavity composed of two 99.995% reflective mirrors
Binding of Crumbs to the Par‑6 CRIB-PDZ Module Is Regulated by Cdc42
Par-6 is a scaffold protein that organizes other proteins into
a complex required to initiate and maintain cell polarity. Cdc42-GTP
binds the CRIB module of Par-6 and alters the binding affinity of
the adjoining PDZ domain. Allosteric regulation of the Par-6 PDZ domain
was first demonstrated using a peptide identified in a screen of typical
carboxyl-terminal ligands. Crumbs, a membrane protein that localizes
a conserved polarity complex, was subsequently identified as a functional
partner for Par-6 that likely interacts with the PDZ domain. Here
we show by nuclear magnetic resonance that Par-6 binds a Crumbs carboxyl-terminal
peptide and report the crystal structure of the PDZ–peptide
complex. The Crumbs peptide binds Par-6 more tightly than the previously
studied carboxyl peptide ligand and interacts with the CRIB-PDZ module
in a Cdc42-dependent manner. The Crumbs:Par-6 crystal structure reveals
specific PDZ–peptide contacts that contribute to its higher
affinity and Cdc42-enhanced binding. Comparisons with existing structures
suggest that multiple C-terminal Par-6 ligands respond to a common
conformational switch that transmits the allosteric effects of GTPase
binding
- …