2,459 research outputs found
USD Nurses’ Honor Society Photograph: Research Day, June 2 1979, Dr. Reif and Dr. Davis
No full textResearch Day, June 2 1979, Dr. Reif (R) and Dr. Davis (C)https://digital.sandiego.edu/nursing-photographs/1013/thumbnail.jp
USD Nurses’ Honor Society Photograph: Research Day, June 2, 1979, Speakers: Dr. Davis, Dr. Reif, and Dr. Walker
No full textResearch Day, June 2, 1979, Speakers: Dr. Davis (L), Dr. Reif (C), and Dr. Walker (R)https://digital.sandiego.edu/nursing-photographs/1009/thumbnail.jp
Determination of methyl order parameters using solid state NMR under off magic angle spinning
No full textQuantification of dipolar couplings in biological solids is important for the understanding of dynamic processes. Under Magic Angle Spinning (MAS), order parameters are normally obtained by recoupling of anisotropic interactions involving the application of radio frequency pulses. We have recently shown that amide backbone order parameters can be estimated accurately in a spin-echo experiment in case the rotor spinning angle is slightly mis-calibrated. In this work, we apply this method to determine methyl order parameters in a deuterated sample of the SH3 domain of chicken α-spectrin in which the methyl containing side chains valine and leucine are selectively protonated
Accurate Determination of 1H-15N Dipolar Couplings Using Inaccurate Settings of the Magic Angle in Solid-State NMR Spectroscopy
No full textMagic-angle spinning (MAS) is an essential ingredient in a wide variety of solid-state NMR experiments. The standard procedures to adjust the rotor angle are not highly accurate, resulting in a slight misadjustment of the rotor from the magic angle (θRL = tan-1 √2) on the order of a few millidegrees. This small missetting has no significant impact on the overall spectral resolution, but is sufficient to reintroduce anisotropic interactions. Shown here is that site-specific 1H-15N dipolar couplings can be accurately measured in a heavily deuterated protein. This method can be applied at arbitrarily high MAS frequencies, since neither rotor synchronization nor particularly high radiofrequency field strengths are required. The off-MAS method allows the quantification of order parameters for very dynamic residues, which often escape an analysis using existing methods
Rotaxane- and Catenane-based Molecular Machines and Motors
No full textThe concept of (macroscopic) machine can be extended to the molecular level. A molecular machine can be defined as an assembly of a discrete number of molecular components (i.e., a supramolecular system) in which the component parts can display changes in their relative positions as a result of some external stimulus. Rotaxanes and catenanes are promising systems for the construction of artificial molecular machines. The design, synthesis and investigation of chemical systems able to function as molecular machines and motors is of interest not only for basic research, but also for the growth of nanoscience and the development of nanotechnology. A few examples of molecular machines taken from our own research will be illustrated
ADEQUATE, a New Set of Experiments to Determine the Constitution of Small Molecules at Natural Abundance
No full textRighting an injustice or American Taliban? the removal of Confederate statues
No full textIn recent years, several racial instances have occurred in the United States that have reinvigorated and demanded action concerning Confederate flags, statues and symbology. The Charleston massacre in 2015 prompted South Carolina to finally remove the Confederate battle flag from state grounds. The Charlottesville riots in 2017 accelerated the removal of Confederate statues from the public square. However, the controversy has broadened the discussion of how the Civil War monuments are to be viewed, especially in the public square. Many of the monuments were not built immediately following the Civil War, but later, during the era of Jim Crow and the disenfranchisement of African Americans during segregation in the South. Are they tributes to heroes or are they relics of a racist past that sought not to remember as much as to intimidate and bolster white supremacy?
This work seeks to break up the eras of Confederate monument building and demonstrate that different monuments were built at different times (and are still being built). The monuments reflect other events in the country happening at the time, as well as the thinking of those who built them. This author hopes that these nuances will add to the general discussion and the usual three responses toward the statues of either taking them down to either destroy them, keep them, but add context, or place them in museums, cemeteries or private property. These nuances are important, possibly rendering all three as valid decisions. This author will use multiple lenses, including Union, Confederate, and African American lenses as interpreters for the various eras discussed. (Author abstract)Reif, A.W. (2018). Righting an injustice or American Taliban? the removal of Confederate statues. Retrieved from http://academicarchive.snhu.eduMaster ArtsHistoryCollege of Online and Continuing Educatio
Field and magic angle spinning frequency dependence of proton resonances in rotating solids.
No full textProton detection in solid state NMR is continuously developing and allows one to gain new insights in structural biology. Overall, this progress is a result of the synergy between hardware development, new NMR methodology and new isotope labeling strategies, to name a few factors. Even though current developments are rapid, it is worthwhile to summarize what can currently be achieved employing proton detection in biological solids. We illustrate this by analysing the signal-to-noise ratio (SNR) for spectra obtained for a microcrystalline α-spectrin SH3 domain protein sample by (i) employing different degrees of chemical dilution to replace protons by incorporating deuterons in different sites, by (ii) variation of the magic angle spinning (MAS) frequencies between 20 and 110 kHz, and by (iii) variation of the static magnetic field B0. The experimental SNR values are validated with numerical simulations employing up to 9 proton spins. Although in reality a protein would contain far more than 9 protons, in a deuterated environment this is a sufficient number to achieve satisfactory simulations consistent with the experimental data. The key results of this analysis are (i) with current hardware, deuteration is still necessary to record spectra of optimum quality; (ii) 13CH3 isotopomers for methyl groups yield the best SNR when MAS frequencies above 100 kHz are available; and (iii) sensitivity increases with a factor beyond B0 3/2 with the static magnetic field due to a transition of proton-proton dipolar interactions from a strong to a weak coupling limit
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