Abstract
CHEMISTRY Surface diffusion of large organic molecules on atomically flat metal surfaces can exhibit direction anisotropy. Eichberger et al. show how this process can be further influenced by the interactions that result between the molecules during collisions. They used fast scanning tunneling
Highlights
Compact semiconductor lasers find a host of applications from optical information storage media to chemical sensors
The window from which the light is emitted can be on the order of just a few micrometers. This small size generally results in poor collimation; the beam fans out, which is detrimental to the areal reading capacity and requires the laser to be driven harder for sensing applications
They calibrated their tree with six fossils and determined that the common ancestor of the grasses appeared approximately 94 million years ago (Ma) in the upper Cretaceous and that C4 photosynthesis originated approximately 32 Ma in the Oligocene during a period when atmospheric CO2 levels declined
Summary
Iron is an essential component of many enzymes, and microbes synthesize and secrete siderophores—small molecules that bind avidly to free iron in soils and in oceans—for the purpose of sequestering as much of it as they can Many of these siderophores contain 2,3-dihydroxybenzoic acid (2,3-DHBA) as an ironchelating moiety; not coincidentally, the mammalian innate immunity protein siderocalin defends against pathogens by enveloping 2,3DHBA siderophores and blocking bacterial iron acquisition. Using biochemical and structural analyses, Pfleger et al show that the Bacillus anthracis protein AsbF catalyzes the conversion of 3dehydroshikimate (3-DHS) into 3,4-DHBA via a manganese-dependent formation of an enolate intermediate, followed by elimination of the C5 hydroxyl.
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