Functional complexity and regulation through RNA dynamics

Changes to the conformation of coding and non-coding RNAs form the basis of elements of genetic regulation and provide an important source of complexity, which drives many of the fundamental processes of life. Although the structure of RNA is highly flexible, the underlying dynamics of RNA are robust and are limited to transitions between the few conformations that preserve favourable base-pairing and stacking interactions. The mechanisms by which cellular processes harness the intrinsic dynamic behaviour of RNA and use it within functionally productive pathways are complex. The versatile functions and ease by which it is integrated into a wide variety of genetic circuits and biochemical pathways suggests there is a general and fundamental role for RNA dynamics in cellular processes.     

Synthesis of titanium oxycarbonitride by carbothermal reduction and nitridation of ilmenite with recycling of polyethylene terephthalate (PET)

An innovative and sustainable carbothermal reduction and nitridation (CTRN) process of ilmenite (FeTiO₃) using a mixture of polyethylene terephthalate (PET) and coal as the primary reductant under an H₂-N₂ atmosphere was proposed.The use of PET as an alternative source of carbon not only enhances the porosity of the pellets but also results in the separation of Fe from titanium oxycarbonitride (TiO_xC_yN_z) particles because of the differences in surface tension.The experiments were carried out at 1250℃ for 3 h using four different PET contents ranging from 25wt% to 100wt% in the reductant.X-ray diffraction (XRD),scanning electron microscopy (SEM) in conjunction with energy-dispersive X-ray spectroscopy (EDX),and LECO elemental analysis were used to study the phases and microstructures of the reduced samples.In the case of 75wt% PET,iron distinctly separated from the synthesized TiO_xC_yN_z phase.With increasing PET content in the sample,the reduction and nitridation rates substantially increased.The synthesis of an oxycarbonitride with stoichiometry of TiO_0.02C_0.13N_0.85 with minimal intermediate titanium sub-oxides was achieved.The results also showed that the iron particles formed from CTRN of FeTiO₃ exhibited a spherical morphology,which is conducive for Fe removal via the Becher process.     

非线性对流扩散方程的迎风有限元格式

本文讨论二维非线性对流扩散方程的一类迎风有限元格式，其中非线性对流项用三角形网格对偶网格上的有限体积型方法逼近，非线性扩散项用伽辽金法逼近。在某些假定下证明了离散最大值原理和近似解的收敛性。     

Effect of quarry dust addition on the performance of controlled low-strength material made from industrial waste incineration bottom ash

The performance of industrial waste incineration bottom ash in controlled low-strength material (CLSM) was investigated in this paper, as the quarry dust was added. CLSM mixtures were made from the industrial waste incineration bottom ash, quarry dust, and cement. Tests for fresh density, bleeding, compressive strength, shear strength, hydraulic conductivity, and excavatability were carried out. The compressive strength ranges from 60 kPa to 6790 kPa, the friction angle varies from 5° to 19°, and the cohesion is from 4 to 604 kPa. Most of the mixtures are found to be non-excavatable. It is indicated that the quarry dust addition increases the compressive strength and shear parameters, decreases bleeding, and increases the removability modulus.     

Immunization with a synthetic T-cell receptor V-region peptide protects against experimental autoimmune encephalomyelitis

T cells expressing the alpha beta T-cell receptor (TCR) for antigen can elicit anti-idiotypic antibodies specific for the TCR that regulate T-cell function. Defined sequences of the TCR, however, have not been used to elicit specific antibodies and the role of cellular immunity directed against TCR determinants has not been studied. We immunized Lewis rats with a synthetic peptide representing a hypervariable region of the TCR V beta 8 molecule. Subsequent induction of experimental autoimmune encephalomyelitis, a paralytic disease of the central nervous system mediated primarily by V beta 8+ T cells specific for myelin basic protein was prevented. T cells specific for the TCR V beta 8 peptide conferred passive protection against the disease to naive rats, apparently by shifting the predominant T-cell response away from the major encephalitogenic epitope of basic protein. This is the first report demonstrating the use of a synthetic TCR V-region peptide to induce specific regulatory immunity and has important implications for the regulation of human disease characterized by common TCR V-gene usage.     

Visualizing spatially correlated dynamics that directs RNA conformational transitions

RNAs fold into three-dimensional (3D) structures that subsequently undergo large, functionally important, conformational transitions in response to a variety of cellular signals. RNA structures are believed to encode spatially tuned flexibility that can direct transitions along specific conformational pathways. However, this hypothesis has proved difficult to examine directly because atomic movements in complex biomolecules cannot be visualized in 3D by using current experimental methods. Here we report the successful implementation of a strategy using NMR that has allowed us to visualize, with complete 3D rotational sensitivity, the dynamics between two RNA helices that are linked by a functionally important trinucleotide bulge over timescales extending up to milliseconds. The key to our approach is to anchor NMR frames of reference onto each helix and thereby directly measure their dynamics, one relative to the other, using 'relativistic' sets of residual dipolar couplings (RDCs). Using this approach, we uncovered super-large amplitude helix motions that trace out a surprisingly structured and spatially correlated 3D dynamic trajectory. The two helices twist around their individual axes by approximately 53 degrees and 110 degrees in a highly correlated manner (R = 0.97) while simultaneously (R = 0.81-0.92) bending by about 94 degrees. Remarkably, the 3D dynamic trajectory is dotted at various positions by seven distinct ligand-bound conformations of the RNA. Thus even partly unstructured RNAs can undergo structured dynamics that directs ligand-induced transitions along specific predefined conformational pathways.