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71.
D M Blakaj K J McConnell D L Beveridge A M Baranger 《Journal of the American Chemical Society》2001,123(11):2548-2551
Molecular dynamics (MD) simulations and free energy component analysis have been performed to evaluate the molecular origins of the 5.5 kcal/mol destabilization of the complex formed between the N-terminal RNP domain of U1A and stem loop 2 of U1 snRNA upon mutation of a conserved aromatic residue, Phe56, to Ala. MD simulations, including counterions and water, have been carried out on the wild type and Phe56Ala peptide-stem loop 2 RNA complexes, the free wild type and Phe56Ala peptides, and the free stem loop 2 RNA. The MD structure of the Phe56Ala-stem loop 2 complex is similar to that of the wild type complex except the stacking interaction between Phe56 and A6 of stem loop 2 is absent and loop 3 of the peptide is more dynamic. However, the MD simulations predict large changes in the structure and dynamics of helix C and increased dynamic range of loop 3 for the free Phe56Ala peptide compared to the wild type peptide. Since helix C and loop 3 are highly variable regions of RNP domains, this indicates that a significant contribution to the reduced affinity of the Phe56Ala peptide for RNA results from cooperation between highly conserved and highly variable regions of the RNP domain of U1A. Surprisingly, these structural effects, which are manifested as cooperative free energy changes, occur in the free peptide, rather than in the complex, and are revealed only by study of both the initial and final states of the complexation process. Free energy component analysis correctly accounts for the destabilization of the Phe56Ala-stem loop 2 complex, and indicates that approximately 80% of the destabilization is due to the loss of the stacking interaction and approximately 20% is due to differences in U1A adaptation. 相似文献
72.
73.
Mn(II)(TCNE)[C(4)(CN)(8)](1/2) (TCNE = tetracyanoethylene) exhibits a reversible pressure-induced piezomagnetic transition from a low magnetization antiferromagnetic state to a high magnetization ferrimagnetic state above 0.50 ± 0.15 kbar. In the ferrimagnetic state, the critical temperature, T(c), increases with increasing hydrostatic pressure and is ~97 K at 12.6 kbar, the magnetization increases by 3 orders of magnitude (1000-fold), and the material becomes a hard magnet with a significant remnant magnetization. 相似文献
74.
75.
To improve the efficiency of confocal optical beam induced current (OBIC) and the non-destructive, high-resolution analysis
of semiconductor media we report the application of a white-light supercontinuum laser source capable of confocal OBIC across
a wide spectral range. To demonstrate the capability of this source, we performed confocal OBIC of light emitting diodes with
varying absorption and emission properties in the visible spectrum. Using the wavelength flexibility afforded by the broadband
laser source, we were able to determine and apply the optimum excitation wavelength range for efficient confocal OBIC instead
of applying inferior fixed wavelength laser sources.
PACS 87.64.Tt; 85.30.De 相似文献
76.
We give a self-contained proof of Wedderburn's theorem which constructs a large class of non-commutative division algebras generalising Hamilton's quaternions. 相似文献
77.
78.
Lapidus SH McConnell AC Stephens PW Miller JS 《Chemical communications (Cambridge, England)》2011,47(27):7602-7604
Mn(II)(TCNE)I(OH(2)) was isolated from the reaction of tetracyanoethylene (TCNE) and MnI(2)(THF)(3), and has a 2-D structure possessing an unusual, asymmetric bonded μ(4)-[TCNE]˙(-). Direct antiferromagnetic coupling between the S = 5/2 Mn(II) and S = 1/2 [TCNE]˙(-) leads to magnetic ordering as a canted antiferrimagnet at a T(c) of 171 K. 相似文献
79.
Park HJ McConnell JT Boddohi S Kipper MJ Johnson PA 《Colloids and surfaces. B, Biointerfaces》2011,83(2):237-203
The influence of particle size on the activity and recycling capabilities of enzyme conjugated magnetic nanoparticles was studied. Co-precipitation and oxidation of Fe(OH)(2) methods were used to fabricate three different sizes of magnetic nanoparticles (5 nm, 26 nm and 51 nm). Glucose oxidase was covalently bound to the magnetic nanoparticles by modifying the surfaces with 3-(aminopropyl)triethoxysilane (APTES) and a common protein crosslinking agent, glutaraldehyde. Analysis by Transmission Electron Microscopy (TEM) showed that the morphology of the magnetic nanoparticles to be spherical and sizes agreed with results of the Brunauer, Emmett, and Teller (BET) method. Magnetic strength of the nanoparticles was analyzed by magnetometry and found to be 49 emu g(-1) (5 nm), 73 emu g(-1) (26 nm), and 85 emu g(-1) (51 nm). X-ray photoelectron spectroscopy (XPS) confirmed each step of the magnetic nanoparticle surface modification and successful glucose oxidase binding. The immobilized enzymes retained 15-23% of the native GOx activity. Recycling stability studies showed approximately 20% of activity loss for the large (51 nm) and medium (26 nm) size glucose oxidase-magnetic nanoparticle (GOx-MNP) bioconjugate and about 96% activity loss for the smallest GOx-MNP bioconjugate (5 nm) after ten cycles. The bioconjugates demonstrated equivalent total product conversions as a single reaction of an equivalent amount of the native enzyme after the 5th cycle for the 26 nm nanoparticles and the 7th cycle for the 51 nm nanoparticles. 相似文献
80.
Carbon-13 hyperfine splittings equal to 41±3 gauss have been observed in the paramagnetic resonance of a mixture of C12H3 and C13H3 radicals produced by x-irradiation of CH3I at 77°k. The observed splitting provides strong evidence that CH3 is a planar molecule. 相似文献