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A homing receptor-IgG chimera as a probe for adhesive ligands of lymph node high endothelial venules.
The binding of lymphocytes to high endothelial venules (HEV) within peripheral lymph nodes (pln) is thought to be mediated by a lectinlike adhesion molecule termed the pln homing receptor (pln HR). The cloning and sequencing of cDNAs encoding both murine and human pln HR revealed that these adhesion molecules contain protein motifs that are homologous to C-type or calcium dependent lectin domains as well as to epidermal growth factor (egf) and complement-regulatory protein domains. We have produced a novel, antibody-like form of the murine HR by joining the extracellular region of the receptor to a human IgG heavy chain. This antibody-like molecule is capable of recognizing carbohydrates, blocking the binding of lymphocytes to pln HEV, and serving as a histochemical reagent for the staining of pln HEV. This murine HR-IgG chimera should prove useful in analyzing the distribution of the HR ligand(s) in normal as well as in inflammatory states
The complement binding-like domains of the murine homing receptor facilitate lectin activity.
The leukocyte homing receptor (HR), the endothelial leukocyte adhesion molecule, and gmp140/platelet activation-dependent granule membrane protein are members of a family of adhesion molecules, termed the lectin cell adhesion molecules (LEC-CAMS) which are unified by a multi-domain structure containing a lectin motif, an epidermal growth factor-like (egf) motif, and variable numbers of a complement binding-like (CB) motif. Previous data have indicated a predominant role for the lectin motif in cell adhesion directed by the LEC-CAMS, although the egf-like domain of the HR may also play a potential role in cell binding. While the role(s) of the CB domains in the LEC-CAMS is currently not understood, they have been hypothesized to act as rigid spacers or stalks for lectin and perhaps, egf domain presentation. In this paper, we analyze the functional characteristics of murine HR-IgG chimeras containing the lectin, lectin plus egf, and lectin plus egf plus CB domains. The Mel 14 mAb, an adhesion blocking antibody which recognizes a conformational determinant in the N-terminus of the HR lectin domain, shows a significantly decreased affinity for a HR construct which lacks the CB motifs, consistent with the possibility that the CB domains are involved with lectin domain structure. In agreement with this conjecture, HR mutants lacking the CB domains show a profound decrease in lectin-specific interaction with the carbohydrate polyphosphomannan ester, suggesting that the changes in Mel 14 affinity for the lectin domain are reflected in lectin functionality. Various assays investigating the interactions between the HR deletion mutants and the peripheral lymph node high endothelium, including cell blocking, immunohistochemical staining, and radioactively labeled ligand binding, all showed that removal of the CB domains results in a lack of HR adhesive function. These results imply that the CB domains of the HR, and, by analogy, the other members of the LEC-CAM family, may play important structural roles involving induction of lectin domain conformation and resultant functionality
THE EQUILIBRIUM STATES OF A HEAVY ROTATING COLUMN
A heavy, rotating vertical column is clamped
at one end and free at the other end.
The stability boundaries
are found by both analytical approximations and numerical
integration.
The problem depends on two non-dimensional
parameters: beta representing the importance of gravity to
rigidity and alpha representing the importance of rotation to
rigidity.
Buckled shapes for the different modes are also
obtained
Large Deformations of a Whirling Elastic Cable
The large deformations of a whirling elastic cable is studied. The ends of the cable are hinged but otherwise free to translate along the rotational axis. The nonlinear governing equations depend on a rotation-elasticity parameter J. Bifurcation about the straight, axially rotating case occurs when J is greater than or equal to n(pi). Perturbation solutions about the bifurcation points and matched asymptotic solutions for large J are found to second order. Exact numerical solutions are obtained using quasi-Newton and homotopy methods
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Syk-dependent Phosphorylation of CLEC-2: A Novel Mechanism of Hem-Immunoreceptor Tyrosine-Based Activation Motif Signaling
The C-type lectin-like receptor CLEC-2 signals via phosphorylation of a single cytoplasmic YXXL sequence known as a hem-immunoreceptor tyrosine-based activation motif (hemITAM). In this study, we show that phosphorylation of CLEC-2 by the snake toxin rhodocytin is abolished in the absence of the tyrosine kinase Syk but is not altered in the absence of the major platelet Src family kinases, Fyn, Lyn, and Src, or the tyrosine phosphatase CD148, which regulates the basal activity of Src family kinases. Further, phosphorylation of CLEC-2 by rhodocytin is not altered in the presence of the Src family kinase inhibitor PP2, even though PLCγ2 phosphorylation and platelet activation are abolished. A similar dependence of phosphorylation of CLEC-2 on Syk is also seen in response to stimulation by an IgG mAb to CLEC-2, although interestingly CLEC-2 phosphorylation is also reduced in the absence of Lyn. These results provide the first definitive evidence that Syk mediates phosphorylation of the CLEC-2 hemITAM receptor with Src family kinases playing a critical role further downstream through the regulation of Syk and other effector proteins, providing a new paradigm in signaling by YXXL-containing receptors
Stellar Velocity Dispersion Measurements in High-Luminosity Quasar Hosts and Implications for the AGN Black Hole Mass Scale
We present new stellar velocity dispersion measurements for four luminous
quasars with the NIFS instrument and the ALTAIR laser guide star adaptive
optics system on the Gemini North 8-m telescope. Stellar velocity dispersion
measurements and measurements of the supermassive black hole masses in luminous
quasars are necessary to investigate the coevolution of black holes and
galaxies, trace the details of accretion, and probe the nature of feedback. We
find that higher-luminosity quasars with higher-mass black holes are not offset
with respect to the MBH-sigma relation exhibited by lower-luminosity AGNs with
lower-mass black holes, nor do we see correlations with galaxy morphology. As
part of this analysis, we have recalculated the virial products for the entire
sample of reverberation-mapped AGNs and used these data to redetermine the mean
virial factor hfi that places the reverberation data on the quiescent
M_BH-sigma relation. With our updated measurements and new additions to the AGN
sample, we obtain = 4.31 +/- 1.05, which is slightly lower than, but
consistent with, most previous determinations.Comment: Accepted for publication in ApJ. For a brief video highlighting the
results of this paper, see: http://www.youtube.com/watch?v=Mxx80aOVw1
Self-assembling DNA-caged particles: nanoblocks for hierarchical self-assembly
DNA is an ideal candidate to organize matter on the nanoscale, primarily due
to the specificity and complexity of DNA based interactions. Recent advances in
this direction include the self-assembly of colloidal crystals using DNA
grafted particles. In this article we theoretically study the self-assembly of
DNA-caged particles. These nanoblocks combine DNA grafted particles with more
complicated purely DNA based constructs. Geometrically the nanoblock is a
sphere (DNA grafted particle) inscribed inside a polyhedron (DNA cage). The
faces of the DNA cage are open, and the edges are made from double stranded
DNA. The cage vertices are modified DNA junctions. We calculate the
equilibriuim yield of self-assembled, tetrahedrally caged particles, and
discuss their stability with respect to alternative structures. The
experimental feasability of the method is discussed. To conclude we indicate
the usefulness of DNA-caged particles as nanoblocks in a hierarchical
self-assembly strategy.Comment: v2: 21 pages, 8 figures; revised discussion in Sec. 2, replaced 2
figures, added new reference
Steady Viscous Flow in a Triangular Cavity
Steady recirculating viscous flow inside an equilateral triangular cavity is generated by translating one side. The Navier-Stokes equations are solved numerically using finite difference on a transformed geometry. The results show a primary eddy and a series of secondary eddies at the stagnant corner. For high Reynolds numbers the interior of the primary eddy has constant vorticity, but its value cannot be predicted by the mean-squared law
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