The cover story of the November 18^th issue of The Journal of the American Chemical Society will feature an article from the Casey Group exploring oxygen-isotope-exchange reactions of nanometer-size polyoxometalate ions in water. The Casey laboratory specializes broadly in aqueous chemistry related to the environmental and geological  sciences, employing model systems to approximate processes that occur in the natural environment. Eric Villa and Andy Ohlin of the Casey group found that simple metal substitutions profoundly change the reactivity of the ion, even to the extent of inverting the rates of isotopic-oxygen exchange. A single oxygen cannot be viewed in isolation because reaction requires concerted motion of atoms throughout the structure. This paper is soon to be published in The Journal of the American Chemical Society, http://pubs.acs.org/doi/abs/10.1021/ja905166c, and complements the Casey Group's previous study on the reaction dynamics of the decaniobate ion that was reported in Angewandte Chemie International Edition: http://www3.interscience.wiley.com/journal/119230111/abstract, which was selected as an Editor's Choice in Science Magazine, http://www.sciencemag.org/content/vol320/issue5881/twil.dtl#320/5881/1263a