Observation and measurement of internucleotide 2JNN coupling constants between 15N nuclei with widely separated chemical shifts

Scalar coupling correlations between hydrogen bonded 15N nuclei in non Watson–Crick base pairs is a critical step in the structure determination of unusual nucleic acids. For observing the 2JNN coupling constant between far upfield N2,N6 (amino) nitrogens and far downfield (N1,N3,N7) nitrogens (separated by 150–160 ppm), the HNN-COSY experiment (Dingley and Grzesiek, 1998) is rather insensitive, due to technical difficulties associated with simultaneous excitation of both extremes of the 15N spectrum. These nuclei may be correlated by treating them in a pseudo-heteronuclear manner, using 15N selective pulses. The wide chemical shift separation allows accurate measurement of the 2JNN coupling constant using spin-echo difference methods. Pulse sequences for observation and measurement of 2JNN coupling constants between amino and N7 nuclei are presented and demonstrated on an A-A mismatch segment of the uniformly (15N,13C) labelled DNA sample, d(GGAGGAT)2.     

On Estimating Stratified PH Model with Single Covariate from Sparse Data with Application to Brain Metastases Study

The estimation of the unknown parameters in the stratified Cox's proportional hazard model is a typical example of the trade‐off between bias and precision. The stratified partial likelihood estimator is unbiased when the number of strata is large but suffer from being unstable when many strata are non‐informative about the unknown parameters. The estimator obtained by ignoring the heterogeneity among strata, on the other hand, increases the precision of estimates although pays the price for being biased. An estimating procedure, based on the asymptotic properties of the above two estimators, serving to compromise between bias and precision is proposed. Two examples in a radiosurgery for brain metastases study provide some interesting demonstration of such applications.     

Prompt Molten Na Infusion and Fluidic Transport by Virtue of Versatile Nano Canal Defects on Tin Oxide Sodiophilic Hosts

Intrinsically weak metal affinity and sluggish sodium (Na) nucleation/molten fluidic transport of conventional hosts impede the fabrication of high-capacity Na anodes. Mediating surface free energies (SFEs) of hosts and reinforcing their intermolecular attraction to viscous Na fluids can radically solve these problems. Herein, “canaled” tin oxide nanorod arrays grown on a 3D carbon cloth (CC) matrix exhibit distinct polar/nonpolar SFE components that markedly elevate the solid–liquid wettability for molten Na is reported. Such nanocanal defects render strong capillary forces for spontaneous molten Na imbibition and help to instantly activate Na─Sn alloying and Na nucleation reactions. Furthermore, sodiophilic Na₁₅Sn₄ interlayers evolved in former alloying procedures also aid in reducing Na nucleation energy barriers and guide the planar electro-deposition/dispersion, alleviating the uncontrolled Na dendrite growth. The derived Na/Na₁₅Sn₄/CC anodes can thus keep stable after 2000 h of galvanostatic cycling at 1 mA cm⁻² or high-rate testing, without notable dendritic formation. The packed full cells also show superior rate capability and cyclability (capacity retention over 91.5% after all cycling at 1 C). This work provides a smart nano-engineering way to trigger a fast infusion of molten metals into hosts and synergistically facilitate Na fluidic transport, which may push forward the scalable application of Na metal batteries.     

ONECUT2 which is targeted by hsa-miR-15a-5p enhances stemness maintenance of gastric cancer stem cells

Gastric cancer is the third dominating cause of cancer-associated death. MiroRNAs are potential clinical tools for cancer diagnosis and therapy. In this project, we demonstrated significant overexpression of ONECUT2 and down-regulation of hsa-miR-15a-5p in gastric cancer via bioinformatics analysis and in vitro assays. Meanwhile, ONECUT2 expression is related to clinical prognosis in gastric cancer and inversely proportional to the differentiation degree of gastric adenocarcinoma according to immunohistochemistry results. Then, we separated CD133+/CD44+ MKN45 by flow cytometry and found that, compared with parental MKN45, CD133+/CD44+ MKN45 gastric cancer stem cells (GCSCs) had higher levels of ONECUT2 and lower levels of hsa-miR-15a-5p. In addition, we applied both in vivo and ex vivo assays to demonstrate hsa-miR-15a-5p regulates the stemness maintenance, epithelial–mesenchymal transition, and chemosensitivity of GCSCs through targeting ONECUT2. Also, hsa-miR-15a-5p inhibits G0 phase block of GCSCs by regulating ONECUT2/β-catenin signaling pathway. However, this study has provided novel perspective into the dynamic control of cancer stem cells for advanced gastric cancer treatment.     

Estimation and Prediction of Generalized Growth Curve with Grouping Variances in AR(q) Dependence Structure

In this paper we consider maximum likelihood analysis of generalized growth curve model with the Box‐Cox transformation when the covariance matrix has AR(q) dependence structure with grouping variances. The covariance matrix under consideration is Σ = D _σ CD _σ where C is the correlation matrix with stationary autoregression process of order q, q < p and D _σ is a diagonal matrix with p elements divided into g(≤ p) groups, i.e., D _σ is a function of {σ₁, …, σ_g} and – 1 < ρ < 1 and σ_l, l = 1, …, g, are unknown. We consider both parameter estimation and prediction of future values. Results are illustrated with real and simulated data.     

Assessing site-isolation of amine groups on aminopropyl-functionalized SBA-15 silica materials via spectroscopic and reactivity probes

The average degree of separation and the accessibility of aminopropyl groups on SBA-15 silica materials prepared using different silane grafting approaches are compared. Three specific synthetic approaches are used: (1) the traditional grafting of 3-aminopropyltrimethoxysilane in toluene, (2) a protection/deprotection method using benzyl- or trityl-spacer groups, and (3) a cooperative dilution method where 3-aminopropyltrimethoxysilane and methyltrimethoxysilane are co-condensed on the silica surface as a silane mixture. The site-isolation and accessibility of the amine groups are probed via three methods: (a) evaluation of pyrene groups adsorbed onto the solids using fluorescence spectroscopy, (b) the reactions of chlorodimethyl(2,3,4,5-tetramethyl-2,4-cyclopentadien-1-yl)silane (Cp′Si(Me)₂Cl) and chloro(cyclopenta-2,4-dienyl)dimethylsilane (CpSi(Me)₂Cl) with the tethered amine sites, and (c) comparison of the reactivity of zirconium constrained-geometry-inspired catalysts (CGCs) prepared using the Cp′Si(Me)₂-modified aminosilicas in the catalytic polymerization of ethylene to produce poly(ethylene). The spectroscopic probe of site-isolation suggests that both the protection/deprotection method and the cooperative dilution method yield similarly isolated amine sites that are markedly more isolated than sites on traditional aminosilica. In contrast, both reactivity probes show that the protection/deprotection strategy leads to more uniformly accessible amine groups. It is proposed that the reactivity probes are more sensitive tests for accessibility and site-isolation in this case.     

The role of ammonia volatilization in controlling the natural 15N abundance of a grazed grassland

Although the variation in natural ¹⁵N abundance in plants and soils is well characterized, mechanisms controlling N isotopic composition of organic matter are still poorly understood. The primary goal of this study was to examine the role of NH₃ volatilization from ungulate urine patches in determining ¹⁵N abundance in grassland plants and soil in Yellowstone National Park. We additionally used isotopic measurements to explore the pathways that plants in urine patches take up N. Plant, soil, and volatilized NH₃¹⁵N were measured on grassland plots for 10 days following the addition of simulated urine. Simulated urine increased ¹⁵N of roots and soil and reduced ¹⁵N of shoots. Soil enrichment was due to the volatilization of isotopically light NH₃. Acid-trapped NH₃¹⁵N increased from –28 (day 1) to –0.3 (day 10), and was lighter than the original urea-N added (1.2). A mass balance analysis of urea-derived N assimilated by plants indicated that most of the N taken up by plants was in the form of ammonium through roots. However, isotope data also showed that shoots directly absorbed ¹⁵N – depleted NH₃-N that was volatilized from simulated urine patches. These results indicate that NH₃ volatilization from urine patches enriches grassland soil with ¹⁵N and shoots are a sink for volatilized NH₃, which likely leads to accelerated cycling of excreted N back to herbivores.     

Mass spectrometrical analysis of phosphoprotein enriched in astrocytes of 15 kDa in mouse hippocampi

Summary. Phosphoprotein enriched in astrocytes of 15kDa (PEA-15) is a small protein that was first identified as an abundant phosphoprotein in brain. PEA-15 was characterised so far at the immunochemical level and by a microsequencing attempt. In order to update characterisation of this important structure by advanced methodology unambiguously identifying proteins independent of antibody availability and specificity, we used a proteomic method for this purpose: Performing protein profiling in mouse hippocampi using two dimensional gel electrophoresis with subsequent mass spectrometrical (MS/MS) identification we detected this protein and demonstrate proteomic characterisation of PEA-15 (Q62048). This study enables further specific and unambiguous determination serving as an analytical tool.     

Lack of mitochondrial nitric oxide production in the mouse brain

Based on our initial finding that the nitric oxide (NO) sensitive fluorochrome diaminofluorescein (DAF) was localized to mitochondria in cultured primary neurons, we investigated whether brain mitochondria produce NO through a mitochondrial NO synthase (mtNOS) enzyme. Isolated brain mitochondria were loaded with DAF and subjected to flow cytometry analysis. Neither the application of NOS inhibitors nor the genetic disruption of either NOS gene diminished the DAF-fluorescence. However, peroxynitrite scavengers reduced the mitochondrial DAF fluorescence, indicating that the DAF signal is not specific to NO. Chemiluminescence detection in the head space gas and a Clark-type NO-sensitive electrode in the solution failed to detect NO release in brain mitochondria. NOS activity in mitochondria was only 1% of the whole brain NOS activity level, which may be attributed to extramitochondrial contamination. Extensive immunoblotting and immunoprecipitation experiments failed to show the presence of endothelial, neuronal, or inducible NOS in mouse brain mitochondria using a variety of primary antibodies. Arginine, calmodulin or 2,5-ADP affinity purification protocols successfully concentrated eNOS and nNOS from full brain tissue but failed to show any signal in mitochondria. We conclude that mouse brain mitochondria do not contain NOS isoforms, nor do they produce NO through a NOS-dependent mechanism.