Two-dimensional heterogeneous photonic bandedge laser

We proposed and realized a two-dimensional (2D) photonic bandedge laser surrounded by the photonic bandgap. The heterogeneous photonic crystal structure consists of two triangular lattices of the same lattice constant with different air hole radii. The photonic crystal laser was realized by room-temperature optical pumping of air-bridge slabs of InGaAsP quantum wells emitting at 1.55 micrometer. The lasing mode was identified from its spectral positions and polarization directions. A low threshold incident pump power of 0.24mW was achieved. The measured characteristics of the photonic crystal lasers closely agree with the results of real space and Fourier space calculations based on the finite-difference time-domain method.Comment: 14 pages, 4 figure

Homeoprotein Hbx4 represses adhesion molecule governing cytokinesis and development

Homeobox genes encode proteins with a highly conserved DNA-binding motif and provoke morphological diversification of body segments by differentially controlling the expression of downstream targets. Here, we have identified _hbx4_, one of many homeobox genes in _Dictyostelium discoideum_ and investigated its role during growth and development. In suspension, Hbx4-overexpressing cells, Hbx4^OE^, showed defects in cytokinesis and growth rate. During development, Hbx4^OE^ and _hbx4_-disrupting cells, _hbx4¯_ made differences in shape of mound and slug, cell-type proportioning from wild type KAx3 cells. These phenotypes were similar to those of mutant defective in _cadA_ encoding Ca^2+^-dependent cell adhesion molecule so that we investigated the relationship between _hbx4_ and _cadA_. Overexpression of Hbx4 inhibited the expression of _cadA_ and cAMP also failed to stimulate _cadA_ in Hbx4^OE^. Furthermore, gel mobility shift assay showed the promoter of _cadA_ contained Hbx4-binding site, indicating Hbx4 negatively regulates the expression of _cadA_. Proteome analysis revealed that overexpression of Hbx4 repressed the _rdiA_ and _abpB_ encoding rho guanine nucleotide dissociation inhibitor1, RhoGDI1 and actin bundling protein 34, ABP34, respectively. And the overexpression of _cadA_ in Hbx4^OE^ cells rescued the defects and increased mRNA level of _rdiA_, _abpB_ and one of Rho GTPase, _rac1b_. These results suggested that Hbx4 can modulate cytokinesis, cell sorting and cell-type proportioning by repressing _cadA_ that regulates GTPase-dependent signaling pathway

Vav1 inhibits RANKL-induced osteoclast differentiation and bone resorption

Vav1 is a Rho/Rac guanine nucleotide exchange factor primarily expressed in hematopoietic cells. In this study, we investigated the potential role of Vav1 in osteoclast (OC) differentiation by comparing the ability of bone marrow mononuclear cells (BMMCs) obtained from Vav1-deficient (Vav1−/−) and wild-type (WT) mice to differentiate into mature OCs upon stimulation with macrophage colony stimulating factor and receptor activator of nuclear kappa B ligand in vitro. Our results suggested that Vav1 deficiency promoted the differentiation of BMMCs into OCs, as indicated by the increased expression of tartrate-resistant acid phosphatase, cathepsin K, and calcitonin receptor. Therefore, Vav1 may play a negative role in OC differentiation. This hypothesis was supported by the observation of more OCs in the femurs of Vav1−/− mice than in WT mice. Furthermore, the bone status of Vav1−/− mice was analyzed in situ and the femurs of Vav1−/− mice appeared abnormal, with poor bone density and fewer number of trabeculae. In addition, Vav1-deficient OCs showed stronger adhesion to vitronectin, an αvβ3 integrin ligand important in bone resorption. Thus, Vav1 may inhibit OC differentiation and protect against bone resorption

Notch1 intracellular domain suppresses APP intracellular domain—Tip60–Fe65 complex mediated signaling through physical interaction

AbstractThe amyloid beta-precursor protein (APP) and the Notch receptor are both type 1 integral transmembrane proteins, and both are cleaved by presenilin-dependent gamma-secretase activity. In this study, we have demonstrated that the Notch intracellular domain (Notch1-IC) suppresses APP-intracellular domain (AICD)-mediated ROS generation and cell death after being processed by gamma secretase. Notch1-IC physically interacts with AICD, Fe65, and Tip60, thereby disrupting the association of the AICD–Fe65–Tip60 trimeric transcription activator complex in AICD signaling. AICD–Fe65–Tip60 mediated reactive oxygen species generation was found to be suppressed by Notch1-IC. Furthermore, AICD–Fe65–Tip60 was shown to mediate cell death in human neuroblastoma cells, and the overexpression of Notch1-IC inhibited cell death induced by AICD–Fe65–Tip60. Collectively, our findings indicate that Notch1-IC plays the role of a negative regulator in AICD signaling via the disruption of the AICD–Fe65–Tip60 trimeric complex

High resolution crystal structure of PedB: a structural basis for the classification of pediocin-like immunity proteins

<p>Abstract</p> <p>Background</p> <p>Pediocin-like bacteriocins, ribosomally-synthesized antimicrobial peptides, are generally coexpressed with cognate immunity proteins in order to protect the bacteriocin-producer from its own bacteriocin. As a step for understanding the mode of action of immunity proteins, we determined the crystal structure of PedB, a pediocin-like immunity protein conferring immunity to pediocin PP-1.</p> <p>Results</p> <p>The 1.6 Å crystal structure of PedB reveals that PedB consists of an antiparallel four-helix bundle with a flexible C-terminal end. PedB shows structural similarity to an immunity protein against enterocin A (EntA-im) but some disparity to an immunity protein against carnobacteriocin B2 (ImB2) in both the C-terminal conformation and the local structure constructed by α3, α4, and their connecting loop. Structure-inspired mutational studies reveal that deletion of the last seven residues of the C-terminus of PedB almost abolished its immunity activity.</p> <p>Conclusion</p> <p>The fact that PedB, EntA-im, and ImB2 share a four-helix bundle structure strongly suggests the structural conservation of this motif in the pediocin-like immunity proteins. The significant difference in the core structure and the C-terminal conformation provides a structural basis for the classification of pediocin-like immunity proteins. Our mutational study using C-terminal-shortened PedBs and the investigation of primary sequence of the C-terminal region, propose that several polar or charged residues in the extreme C-terminus of PedB which is crucial for the immunity are involved in the specific recognition of pediocin PP-1.</p

(E)-4-{[(Pyridin-4-yl­methyl­idene)amino]­meth­yl}benzoic acid

The title mol­ecule, C14H12N2O2, exhibits a V-shaped conformation with a dihedral angle of 59.69 (3)° between the benzene and pyridine rings. In the crystal, O—H⋯N hydrogen bonds link the mol­ecules into zigzag chains along [010]