We found that the S74E mutation in Medicago ROP6 and Arabidopsis ROP4 prevented the binding of these proteins to their plant-specific upstream activator the plant-specific ROP nucleotide exchanger (PRONE)-domain-containing

3-MA order RopGEF (guanine nucleotide exchange factor) protein and abolished the PRONE-mediated nucleotide exchange reaction in vitro. Structural modeling supported the hypothesis that potential phosphorylation of the S74 residue interferes with the binding of the PRONE-domain to the adjacent plant-specific R76 residue which plays an important role in functional ROP-PRONE interaction. Moreover, we show that while the binding of constitutively active MsROP6 to the effector protein RIC (ROP-interactive CRIB-motif-containing protein) was not affected by the S74E mutation, the capability of this mutated protein to bind and activate the RRK1 kinase in vitro was reduced. These observations are in agreement with the morphology of tobacco pollen tubes expressing mutant forms of yellow fluorescent protein (YFP):MsROP6. The S74E mutation in MsROP6 had no influence on pollen tube morphology and attenuated the phenotype of a constitutively active form MLN4924 of MsROP6. The presented Medicago

and Arabidopsis data support the notion that the phosphorylation of the serine residue in ROPs corresponding to S74 in Medicago ROP6 could be a general principle for regulating ROP activation and signaling in plants.”
“Separation of rare cells from blood stream using paramagnetic/superparamagnetic beads in microfluidic device has gained importance in recent years for early diagnosis of several critical diseases. However, the performance of immunomagnetophoretic cell sorters (ICS) crucially depends on their design and operational conditions. this website Here, we present a three-dimensional

CFD model based on the Navier-Stokes equations governing the fluid dynamics and continuum descriptions for the cell, bead and cell-bead complexes for a continuous ICS. The spatial-temporal evolution of the concentration fields are governed by convection-diffusion equations for non-magnetic cells and Nernst-Planck type equations for beads and cell-bead(s) complexes. The attachment rates between cells, cell-bead(s) complexes and beads are deduced from the collision probabilities which are derived by means of classical scattering theory. The CFD model is used to investigate the performance of a generic continuous cell separation system. Since the cells are larger in diameter, more than one bead can get attached to the cells. Multiple beads binding to the cell has been considered in this study, which has not been reported in literature till date. Exemplarily, we investigate the performance of Y-shaped geometry used for contacting of cells and beads. (C) 2010 Elsevier B.V. All rights reserved.