Glacial-interglacial changes in central tropical Pacific surface seawater property gradients

Much uncertainty exists about the state of the oceanic and atmospheric circulation in the tropical Pacific over the last glacial cycle. Studies have been hampered by the fact that sediment cores suitable for study were concentrated in the western and eastern parts of the tropical Pacific, with little information from the central tropical Pacific. Here we present information from a suite of sediment cores collected from the Line Islands Ridge in the central tropical Pacific, which show sedimentation rates and stratigraphies suitable for paleoceanographic investigations. Based on the radiocarbon and oxygen isotope measurements on the planktonic foraminifera Globigerinoides ruber, we construct preliminary age models for selected cores and show that the gradient in the oxygen isotope ratio of G. ruber between the equator and 8°N is enhanced during glacial stages relative to interglacial stages. This stronger gradient could reflect enhanced equatorial cooling (perhaps reflecting a stronger Walker circulation) or an enhanced salinity gradient (perhaps reflecting increased rainfall in the central tropical Pacific).This is the publisher’s final pdf. The article is copyrighted by American Geophysical Union and published by John Wiley & Sons Ltd. It can be found at: http://agupubs.onlinelibrary.wiley.com/agu/journal/10.1002/%28ISSN%291944-9186/Keywords: tropical Pacific, oxygen isotopes, foraminifer

Combinatorial chemistry and natural products: Determination of the biological activity of on-bead, double cleavable teicoplanin aglycone (TD)

Teicoplanin aglycone (TD), a derivative of the naturally occurring antibiotic, was coupled to Tentagel resin beads using a releasable linker technique. The biological properties of the compound were examined in growth inhibition assays after cleavage of the linker under different pH conditions. The results show that combinatorial techniques on solid-phase can be used for large, complex molecules, and that the biological method described may be generally useful for high volume screening of large combinatorial chemical libraries