Initial Growth of Single-Crystalline Nanowires: From 3D Nucleation to 2D Growth

The initial growth stage of the single-crystalline Sb and Co nanowires with preferential orientation was studied, which were synthesized in porous anodic alumina membranes by the pulsed electrodeposition technique. It was revealed that the initial growth of the nanowires is a three-dimensional nucleation process, and then gradually transforms to two-dimensional growth via progressive nucleation mechanism, which resulting in a structure transition from polycrystalline to single crystalline. The competition among the nuclei inside the nanoscaled-confined channel and the growth kinetics is responsible for the structure transition of the initial grown nanowires

Specific Y14 domains mediate its nucleo-cytoplasmic shuttling and association with spliced mRNA

Pre-mRNA splicing deposits multi-protein complexes, termed exon junction complexes (EJCs), on mRNAs near exon-exon junctions. The core of EJC consists of four proteins, eIF4AIII, MLN51, Y14 and Magoh. Y14 is a nuclear protein that can shuttle between the nucleus and the cytoplasm, and binds specifically to Magoh. Here we delineate a Y14 nuclear localization signal that also confers its nuclear export, which we name YNS. We further identified a 12-amino-acid peptide near Y14's carboxyl terminus that is required for its association with spliced mRNAs, as well as for Magoh binding. Furthermore, the Y14 mutants, which are deficient in binding to Magoh, could still be localized to the nucleus, suggesting the existence of both the nuclear import pathway and function for Y14 unaccompanied by Magoh

Intratumor genetic heterogeneity in squamous cell carcinoma of the oral cavity

BackgroundWe sought to evaluate intratumor heterogeneity in squamous cell carcinoma of the oral cavity (OCC) and specifically determine the effect of physical separation and histologic differentiation within the same tumor.MethodsWe performed whole exome sequencing on five biopsy sites—two from well‐differentiated, two from poorly differentiated regions, and one from normal parenchyma—from five primary OCC specimens.ResultsWe found high levels of intratumor heterogeneity and, in four primary tumors, identified only 0 to 2 identical mutations in all subsites. We found that the heterogeneity inversely correlated with physical separation and that pairs of well‐differentiated samples were more similar to each other than analogous poorly differentiated specimens. Only TP53 mutations, but not other purported “driver mutations” in head and neck squamous cell carcinoma, were found in multiple biopsy sites.ConclusionThese data highlight the challenges to characterization of the mutational landscape of OCC with single site biopsy and have implications for personalized medicine.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/150549/1/hed25719.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/150549/2/hed25719_am.pd

Three-Dimensional Structure of N-Terminal Domain of DnaB Helicase and Helicase-Primase Interactions in Helicobacter pylori

Replication initiation is a crucial step in genome duplication and homohexameric DnaB helicase plays a central role in the replication initiation process by unwinding the duplex DNA and interacting with several other proteins during the process of replication. N-terminal domain of DnaB is critical for helicase activity and for DnaG primase interactions. We present here the crystal structure of the N-terminal domain (NTD) of H. pylori DnaB (HpDnaB) helicase at 2.2 Å resolution and compare the structural differences among helicases and correlate with the functional differences. The structural details of NTD suggest that the linker region between NTD and C-terminal helicase domain plays a vital role in accurate assembly of NTD dimers. The sequence analysis of the linker regions from several helicases reveals that they should form four helix bundles. We also report the characterization of H. pylori DnaG primase and study the helicase-primase interactions, where HpDnaG primase stimulates DNA unwinding activity of HpDnaB suggesting presence of helicase-primase cohort at the replication fork. The protein-protein interaction study of C-terminal domain of primase and different deletion constructs of helicase suggests that linker is essential for proper conformation of NTD to interact strongly with HpDnaG. The surface charge distribution on the primase binding surface of NTDs of various helicases suggests that DnaB-DnaG interaction and stability of the complex is most probably charge dependent. Structure of the linker and helicase-primase interactions indicate that HpDnaB differs greatly from E.coli DnaB despite both belong to gram negative bacteria

A search for the decay modes B+/- to h+/- tau l

We present a search for the lepton flavor violating decay modes B+/- to h+/- tau l (h= K,pi; l= e,mu) using the BaBar data sample, which corresponds to 472 million BBbar pairs. The search uses events where one B meson is fully reconstructed in one of several hadronic final states. Using the momenta of the reconstructed B, h, and l candidates, we are able to fully determine the tau four-momentum. The resulting tau candidate mass is our main discriminant against combinatorial background. We see no evidence for B+/- to h+/- tau l decays and set a 90% confidence level upper limit on each branching fraction at the level of a few times 10^-5.Comment: 15 pages, 7 figures, submitted to Phys. Rev.

Evidence for an excess of B -> D(*) Tau Nu decays

Based on the full BaBar data sample, we report improved measurements of the ratios R(D(*)) = B(B -> D(*) Tau Nu)/B(B -> D(*) l Nu), where l is either e or mu. These ratios are sensitive to new physics contributions in the form of a charged Higgs boson. We measure R(D) = 0.440 +- 0.058 +- 0.042 and R(D*) = 0.332 +- 0.024 +- 0.018, which exceed the Standard Model expectations by 2.0 sigma and 2.7 sigma, respectively. Taken together, our results disagree with these expectations at the 3.4 sigma level. This excess cannot be explained by a charged Higgs boson in the type II two-Higgs-doublet model. We also report the observation of the decay B -> D Tau Nu, with a significance of 6.8 sigma.Comment: Expanded section on systematics, text corrections, improved the format of Figure 2 and included the effect of the change of the Tau polarization due to the charged Higg

Observation and study of baryonic B decays: B -> D(*) p pbar, D(*) p pbar pi, and D(*) p pbar pi pi

We present a study of ten B-meson decays to a D(*), a proton-antiproton pair, and a system of up to two pions using BaBar's data set of 455x10^6 BBbar pairs. Four of the modes (B0bar -> D0 p anti-p, B0bar -> D*0 p anti-p, B0bar -> D+ p anti-p pi-, B0bar -> D*+ p anti-p pi-) are studied with improved statistics compared to previous measurements; six of the modes (B- -> D0 p anti-p pi-, B- -> D*0 p anti-p pi-, B0bar -> D0 p anti-p pi- pi+, B0bar -> D*0 p anti-p pi- pi+, B- -> D+ p anti-p pi- pi-, B- -> D*+ p anti-p pi- pi-) are first observations. The branching fractions for 3- and 5-body decays are suppressed compared to 4-body decays. Kinematic distributions for 3-body decays show non-overlapping threshold enhancements in m(p anti-p) and m(D(*)0 p) in the Dalitz plots. For 4-body decays, m(p pi-) mass projections show a narrow peak with mass and full width of (1497.4 +- 3.0 +- 0.9) MeV/c2, and (47 +- 12 +- 4) MeV/c2, respectively, where the first (second) errors are statistical (systematic). For 5-body decays, mass projections are similar to phase space expectations. All results are preliminary.Comment: 28 pages, 90 postscript figures, submitted to LP0