Helicobacter pylori CagA Disrupts Epithelial Patterning by Activating Myosin Light Chain

Helicobacter pylori infection is a leading cause of ulcers and gastric cancer. We show that expression of the H. pylori virulence factor CagA in a model Drosophila melanogaster epithelium induces morphological disruptions including ectopic furrowing. We find that CagA alters the distribution and increases the levels of activated myosin regulatory light chain (MLC), a key regulator of epithelial integrity. Reducing MLC activity suppresses CagA-induced disruptions. A CagA mutant lacking EPIYA motifs (CagAEPISA) induces less epithelial disruption and is not targeted to apical foci like wild-type CagA. In a cell culture model in which CagAEPISA and CagA have equivalent subcellular localization, CagAEPISA is equally potent in activating MLC. Therefore, in our transgenic system, CagA is targeted by EPIYA motifs to a specific apical region of the epithelium where it efficiently activates MLC to disrupt epithelial integrity

Cryogenic Infrared Action Spectroscopy Fingerprints the Hydrogen Bonding Network in Gas-Phase Coumarin Cations

We report cryogenic vibrational spectra of gas-phase cations of two common hydroxycoumarins, scopoletin and esculetin, as well as their glycosidic derivatives, scopolin and esculin. The study allows direct observation of the intramolecular interactions between the hydroxyl groups of these molecules. We use cryogenic messenger-tagging IR action spectroscopy to detect vibrational bands in the 3100-3800 cm(-1 )spectral range and discuss the corresponding structural characteristics and hydrogen bonding networks that they imply. The experimental data are supported by a thorough computational evaluation, including investigation of the conformational space. Through comparison of the calculated conformers with the experimental results, we identify the main types of OH oscillators and infer how protonation and sodiation affect the structural arrangement of these molecules. The results presented here provide direct evidence of how slight structural differences sensitively affect the hydrogen bonding network in coumarin derivatives

Teaching the Spin Selection Rule: An Inductive Approach

In the group exercise described, students are guided through an inductive justification for the spin conservation selection rule (ΔS = 0). Although the exercise only explicitly involves various states of helium, the conclusion is one of the most widely applicable selection rules for the interaction of light with matter, applying, in various ways, to atoms and molecules of all sizes. Connections are made among several concepts routinely covered in physical chemistry courses including the Pauli Principle, orthonormal wave functions, overlap integrals, atomic term symbols, multiplicity, radiative lifetimes, fluorescence, and phosphorescence. Detailed student directions are included in the Supporting Information