A PKC-Dependent Recruitment of MMP-2 Controls Semaphorin-3A Growth-Promoting Effect in Cortical Dendrites

There is increasing evidence for a crucial role of proteases and metalloproteinases during axon growth and guidance. In this context, we recently described a functional link between the chemoattractive Sema3C and Matrix metalloproteinase 3 (MMP3). Here, we provide data demonstrating the involvement of MMP-2 to trigger the growth-promoting effect of Sema3A in cortical dendrites. The in situ analysis of MMP-2 expression and activity is consistent with a functional growth assay demonstrating in vitro that the pharmacological inhibition of MMP-2 reduces the growth of cortical dendrites in response to Sema3A. Hence, our results suggest that the selective recruitment and activation of MMP-2 in response to Sema3A requires a PKC alpha dependent mechanism. Altogether, we provide a second set of data supporting MMPs as effectors of the growth-promoting effects of semaphorins, and we identify the potential signalling pathway involved

Observation of electron transfer mediated decay in aqueous solution

Photoionization is at the heart of X ray photoelectron spectroscopy XPS , which gives access to important information on a sample s local chemical environment. Local and non local electronic decay after photoionization in which the refilling of core holes results in electron emission from either the initially ionized species or a neighbour, respectively have been well studied. However, electron transfer mediated decay ETMD , which involves the refilling of a core hole by an electron from a neighbouring species, has not yet been observed in condensed phase. Here we report the experimental observation of ETMD in an aqueous LiCl solution by detecting characteristic secondary low energy electrons using liquid microjet soft XPS. Experimental results are interpreted using molecular dynamics and high level ab initio calculations. We show that both solvent molecules and counterions participate in the ETMD processes, and different ion associations have distinctive spectral fingerprints. Furthermore, ETMD spectra are sensitive to coordination numbers, ion solvent distances and solvent arrangemen

Parallelization of four-component calculations. II. Symmetry-driven parallelization of the 4-spinor CCSD algorithm

Given the importance of the Coupled-cluster (CC) method as an efficient and accurate way to take electron correlation into account, we extend the parallelization technique in the second part of this series also to the 4-Spinor CCSD algorithm implemented in the Dirac-Fock packages DIRAC and MOLFDIR. The present implementation is based on the availability of the transformed molecular two-electron integrals on an external storage medium. The linearity of the CC equations in these two-electron integrals is used in a parallelization strategy that is based on distribution of the two largest integral classes that carry three or four virtual spinor indices. The corresponding partial contributions to the

Long Range Interatomic Coulombic Decay in ArXe Clusters Experiment and Theory

We report autoionization channels of Ar inner valence ionized states in mixed ArXe clusters and compare our experimental data obtained by electron–electron coincidence spectroscopy to our theoretical simulations for representative cluster structures. The combined experimental and theoretical data show that the autoionization of Ar 3s^–1 in ArXe is dominated by interatomic coulombic decay (ICD) to Xe atoms in the second and higher coordination shells of the originally excited atom. Clusters with a range of sizes, compositions, and structures were probed. The Xe content in the clusters was varied between 10% and 53%. Besides ICD, also electron transfer mediated decay (ETMD(3)) was found important in many of the calculated spectra, although it is seen with less intensity in the experimental spectra. From the calculations, we identify structural motifs in which the ETMD rate is minimized vs the ICD rate and suggest that these are preferentially realized in our experiment, in which clusters are formed by supersonic expansion of an Ar–Xe mixture. Suggested cluster structures either feature a clear segregation between Ar and Xe fractions, e.g., Xe core−Ar shell systems, or contain a few Xe atoms singled out at surface sites on an Ar cluster. These structures differ significantly from the majority of calculated minimum energy structures for ArXe systems of 38 atoms, which might show that the latter, annealed structures are not realized in our experiment. We show experimentally that the relaxation of Ar inner valence states by ICD and ETMD together has an efficiency of unity, within the experimental accuracy, for all clusters probed, except those with the lowest Xe content. The outer valence photoelectron spectra of ArXe are discussed also