Imaging plasma membrane phase behaviour in live cells using a thiophene-based molecular rotor

Molecular rotors have emerged as versatile probes of microscopic viscosity in lipid bilayers, although it has proved difficult to find probes that stain both phases equally in phase-separated bilayers. Here, we investigate the use of a membrane-targeting viscosity-sensitive fluorophore based on a thiophene moiety with equal affinity for ordered and disordered lipid domains to probe ordering and viscosity within artificial lipid bilayers and live cell plasma membranes

Synthesis of 2-acetamido-1,2-dideoxy-d-galacto-nojirimycin [DGJNAc] from d-glucuronolactone: the first sub-micromolar inhibitor of α-N-acetylgalactosaminidases

2-Acetamido-1,2-dideoxy-d-galacto-nojirimycin [DGJNAc], prepared in 20% overall yield from d-glucuronolactone, is the first potent competitive sub-micromolar inhibitor of α-N-acetyl-galactosaminidases (Ki 0.081 μM from chicken liver, Ki 0.136 μM from Charonia lampas). DGJNAc is a good competitive-whereas the enantiomer l-DGJNAc is a very weak but non-competitive-inhibitor of β-hexosaminidases. © 2010

Synthesis of 2-acetamido-1,2-dideoxy-D-galacto-nojirimycin [DGJNAc] from D-glucuronolactone: the first sub-micromolar inhibitor of alpha-N-acetylgalactosaminidases

2-Acetamido-1,2-dideoxy-d-galacto-nojirimycin [DGJNAc], prepared in 20% overall yield from d-glucuronolactone, is the first potent competitive sub-micromolar inhibitor of α-N-acetyl-galactosaminidases (Ki 0.081 μM from chicken liver, Ki 0.136 μM from Charonia lampas). DGJNAc is a good competitive-whereas the enantiomer l-DGJNAc is a very weak but non-competitive-inhibitor of β-hexosaminidases. © 2010

Self-assembling dipeptide antibacterial nanostructures with membrane disrupting activity

Peptide-based supramolecular assemblies are a promising class of nanomaterials with important biomedical applications, but their antibacterial properties can be overlooked. Here the authors show the antibacterial activity of self-assembled diphenylalanine, which emerges as the minimal model for antibacterial supramolecular polymers

Visualizing Attack of Escherichia coli by the Antimicrobial Peptide Human Defensin 5

Human α-defensin 5 (HD5) is a 32-residue cysteine-rich host-defense peptide that exhibits broad-spectrum antimicrobial activity and contributes to innate immunity in the human gut and other organ systems. Despite many years of investigation, its antimicrobial mechanism of action remains unclear. In this work, we report that HD5[subscript ox], the oxidized form of this peptide that exhibits three regiospecific disulfide bonds, causes distinct morphological changes to Escherichia coli and other Gram-negative microbes. These morphologies include bleb formation, cellular elongation, and clumping. The blebs are up to ∼1 μm wide and typically form at the site of cell division or cell poles. Studies with E. coli expressing cytoplasmic GFP reveal that HD5[subscript ox] treatment causes GFP emission to localize in the bleb. To probe the cellular uptake of HD5[subscript ox] and subsequent localization, we describe the design and characterization of a fluorophore–HD5 conjugate family. By employing these peptides, we demonstrate that fluorophore–HD5[subscript ox] conjugates harboring the rhodamine and coumarin fluorophores enter the E. coli cytoplasm. On the basis of the fluorescence profiles, each of these fluorophore–HD5[subscript ox] conjugates localizes to the site of cell division and cell poles. These studies support the notion that HD5[subscript ox'], at least in part, exerts its antibacterial activity against E. coli and other Gram-negative microbes in the cytoplasm.United States. Army Research Office. Institute for Soldier Nanotechnologies (Contract W911NF-13-D-0001)National Science Foundation (U.S.) (Grant 007031)Massachusetts Institute of Technology (MIT UROP Program funds)Royal Thai Government (RTG) (Fellowship)Massachusetts Institute of Technology (2014 Richard R. Schrock summer graduate fellowship)National Institutes of Health (U.S.) (NIH Office of the Director, grant DP2OD007045