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BACKGROUND We investigated the encapsulation mechanism of enzymes into liposomes. The existing protocols to achieve high encapsulation efficiencies are basically optimized for chemically stable molecules. Enzymes, however, are fragile and encapsulation requires in addition the preservation of their functionality. Using acetylcholinesterase as a model, we(More)
The lining of the maltodextrin-specific maltoporin (LamB) channel exhibits a string of aromatic residues, the greasy slide, part of which has been shown previously by crystallography to be involved in substrate binding. To probe the functional role of the greasy slide, alanine scanning mutagenesis has been performed on the six greasy slide residues and Y118(More)
We have studied the phenomenological origin of 1/f noise in a solute-specific bacterial ion channel, maltoporin. We show that after excision of small, but resolvable stepwise changes in the recordings of the current through a single open channel, the 1/f noise component disappears and the channel exhibits noise that is "white" below 100 Hz. Combined with(More)
BACKGROUND Multi-drug resistant (MDR) infections have become a major concern in hospitals worldwide. This study investigates membrane translocation, which is the first step required for drug action on internal bacterial targets. beta-lactams, a major antibiotic class, use porins to pass through the outer membrane barrier of Gram-negative bacteria. Clinical(More)
All-atom molecular dynamics simulations of the ion current through OmpF, the major porin in the outer membrane of Escherichia coli, were performed. Starting from the crystal structure, the all-atom modeling allows us to calculate a parameter-free ion conductance in semiquantitative agreement with experiment. Discrepancies between modeling and experiment(More)
Gram-negative bacteria are responsible for a large proportion of antibiotic-resistant bacterial diseases. These bacteria have a complex cell envelope that comprises an outer membrane and an inner membrane that delimit the periplasm. The outer membrane contains various protein channels, called porins, which are involved in the influx of various compounds,(More)
We investigate the permeability of lipid membranes for fluorescence dyes and ions. We find that permeability reaches a maximum close to the chain melting transition of the membranes. Close to transitions, fluctuations in area and compressibility are high, leading to an increased likelihood of spontaneous lipid pore formation. Fluorescence correlation(More)
The Pseudomonas secretin XcpQ forms an oligomeric complex, which is involved in the translocation of proteins across the outer membrane via the type II secretion pathway. Pseudomonas aeruginosa produces only small amounts of this complex, 50 to 100 copies per bacterium, and overexpression is lethal to these cells. However, overexpression of Pseudomonas(More)
Fusion is obtained between electropermeabilized mammalian cells and intact large unilamellar lipid vesicles. This is monitored by a fluorescence assay. Prepulse contact is obtained by Ca2+ when negatively charged lipids are present in the liposomes. The mixing of the liposome content in the cell cytoplasm is observed under conditions preserving cell(More)