The Rainy Day

https://digitalcommons.library.umaine.edu/mmb-me/1734/thumbnail.jp

BMQ

BMQ: Boston Medical Quarterly was published from 1950-1966 by the Boston University School of Medicine and the Massachusetts Memorial Hospitals

A Preliminary Study of the Activated Sludge Process

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Description of a freely dropped instrument for measuring current velocity

A new form of freely dropped instrument for current-velocity measurements is described. Operational procedures for using the instrument and its auxiliary equipment are given

MsbA-dependent translocation of lipids across the inner membrane of Escherichia coli

MsbA is an essential ABC transporter in Escherichia coli required for exporting newly synthesized lipids from the inner to the outer membrane. It remains uncertain whether or not MsbA catalyzes trans-bilayer lipid movement (i.e. flip-flop) within the inner membrane. We now show that newly synthesized lipid A accumulates on the cytoplasmic side of the inner membrane after shifting an E. coli msbA missense mutant to the non-permissive temperature. This conclusion is based on the selective inhibition of periplasmic, but not cytoplasmic, covalent modifications of lipid A that occur in polymysin-resistant strains of E. coli. The accessibility of newly synthesized phosphatidylethanolamine to membrane impermeable reagents, like 2,4,6-trinitrobenzene sulfonic acid, is also reduced severalfold. Our data showed that MsbA facilitates the rapid translocation of some lipids from the cytoplasmic to the periplasmic side of the inner membrane in living cells