An Ice-Core-Based, Late Holocene History for the Transantarctic Mountains, Antarctica

Ice core records (major anions and cations, MSA, oxygen isotopes and particles) developed from two shallow (~200 m depth) sites in the Transantarctic Mountains provide documentation of much of the Holocene paleoenvironmental history of this region. From the more southerly site, Dominion Range, an ~7000-year-long record reveals change in the influence of tropospheric transport to the region. At this site, milder conditions and increased tropospheric inflow prior to ~1500 yr BP are characterized by increased seasalt (ss), terrestrial and marine biogenic inputs. Increased persistence and/or extent of polar stratospheric clouds accompanying generally cooler conditions characterize much of the period since ~1500 yr BP. From the more northerly site, Newall Glacier, the dramatic influence of the retreat of grounded ice from McMurdo Sound dated at[Denton et al., 1989] dominates much of the ice core record. This regional environmental change is documented by massive influxes to the core site of evaporitic salts from areas exposed during low lake level stands. During the past ~150 yr, both Dominion Range and Newall Glacier appear to be experiencing an overall increase in the exposure of ice-free terrain

Structural basis of quinolone inhibition of type IIA topoisomerases and target-mediated resistance

Quinolone antibacterials have been used to treat bacterial infections for over 40 years. A crystal structure of moxifloxacin in complex with Acinetobacter baumannii topoisomerase IV now shows the wedge-shaped quinolone stacking between base pairs at the DNA cleavage site and binding conserved residues in the DNA cleavage domain through chelation of a noncatalytic magnesium ion. This provides a molecular basis for the quinolone inhibition mechanism, resistance mutations and invariant quinolone antibacterial structural feature

Structural basis of quinolone inhibition of type IIA topoisomerases and target-mediated resistance

Quinolone antibacterials have been used to treat bacterial infections for over 40 years. A crystal structure of moxifloxacin in complex with Acinetobacter baumannii topoisomerase IV now shows the wedge-shaped quinolone stacking between base pairs at the DNA cleavage site and binding conserved residues in the DNA cleavage domain through chelation of a noncatalytic magnesium ion. This provides a molecular basis for the quinolone inhibition mechanism, resistance mutations and invariant quinolone antibacterial structural feature