Agrin-induced acetylcholine receptor clustering in mammalian muscle requires tyrosine phosphorylation.

Agrin is thought to be the nerve-derived factor that initiates acetylcholine receptor (AChR) clustering at the developing neuromuscularjunction. We have investigated the signaling pathway in mouse C2 myotubes and report that agrin induces a rapid but transient tyrosine phosphorylation of the AChR beta subunit. As the beta-subunit tyrosine phosphorylation occurs before the formation of AChR clusters, it may serve as a precursor step in the clustering mechanism. Consistent with this, we observed that tyrosine phosphorylation of the beta subunit correlated precisely with the presence or absence of clustering under several experimental conditions. Moreover, two tyrosine kinase inhibitors, herbimycin and staurosporine, that blocked beta-subunit phosphorylation also blocked agrin-induced clustering. Surprisingly, the inhibitors also dispersed preformed AChR clusters, suggesting that the tyrosine phosphorylation of other proteins may be required for the maintenance of receptor clusters. These findings indicate that in mammalian muscle, agrin-induced AChR clustering occurs through a mechanism that requires tyrosine phosphorylation and may involve tyrosine phosphorylation of the AChR itself

Structure of the Nucleon and its Excitations

The structure of the ground state nucleon and its finite-volume excitations are examined from three different perspectives. Using new techniques to extract the relativistic components of the nucleon wave function, the node structure of both the upper and lower components of the nucleon wave function are illustrated. A non-trivial role for gluonic components is manifest. In the second approach, the parity-expanded variational analysis (PEVA) technique is utilised to isolate states at finite momenta, enabling a novel examination of the electric and magnetic form factors of nucleon excitations. Here the magnetic form factors of low-lying odd-parity nucleons are particularly interesting. Finally, the structure of the nucleon spectrum is examined in a Hamiltonian effective field theory analysis incorporating recent lattice-QCD determinations of low-lying two-particle scattering-state energies in the finite volume. The Roper resonance of Nature is observed to originate from multi-particle coupled-channel interactions while the first radial excitation of the nucleon sits much higher at approximately 1.9 GeV.Comment: 8 pages, 4 figures. Proceedings of the 35th International Symposium on Lattice Field Theory (Lattice 2017), 18 - 24 June 2017, Granada, Spai

Detecting Majorana fermions by use of superconductor-quantum Hall liquid junctions

The point contact tunnel junctions between a one-dimensional topological superconductor and single-channel quantum Hall (QH) liquids are investigated theoretically with bosonization technology and renormalization group methods. For the $\nu=1$ integer QH liquid, the universal low-energy tunneling transport is governed by the perfect Andreev reflection fixed point with quantized zero-bias conductance $G(0)=2e^{2}/h$, which can serve as a definitive fingerprint of the existence of a Majorana fermion. For the $\nu =1/m$ Laughlin fractional QH liquids, its transport is governed by the perfect normal reflection fixed point with vanishing zero-bias conductance and bias-dependent conductance $G(V) \sim V^{m-2}$. Our setup is within reach of present experimental techniques.Comment: 6 pages, 1 figure, Added references,Corrected typo

A Sage on Two Stages: What a Black Academic Taught a White Scholar About Cross-Cultural Mentoring

Cross-cultural mentoring can be loosely defined as a reciprocal mentoring relationship where the mentor and mentee do not share any one of many personal identities. In this study, personal narratives convey what a White scholar learned about cross-cultural mentoring from a Black academic, focusing on two events. Critical findings and reflections include the necessity for White allies in cross-cultural mentoring relationships to anticipate difference rather than discomfort, to commit to paying analytic and holistic attention to their mentor, and to seek opportunities to mitigate any cultural taxation that people of color may pay inside and outside of the relationship.Educatio