(2), have been synthesized via decomposition of zirconium fluoride complexes. Their structures were determined by single crystal and X-ray powder diffraction, respectively. The structure of 1 is made of infinite single chains composed of insular Zr octahedra vertex-linked to four PO 4 tetrahedra. Each zirconium is trans-coordinated to two F atoms. The structure of 2 is composed of double chains that can be seen as two condensed single chains of 1, with the elimination of a fluorine atom from the zirconium coordination sphere. Zirconium is octahedrally coordinated, with three triply connected and two doubly connected phosphate tetrahedra, and with a fluorine atom. The structural connection between 1, 2, and layered a-and c-zirconium phosphates is discussed and verified by interconversion experiments. 1 was found to convert into 2 after ageing in its mother liquor, while 2 can be converted into a-ZrP in acidic media. 1 and 2 were found to swell and form stable colloidal dispersions on elution with 0.1 M hydrochloric acid solution. These properties make these one-dimensional zirconium phosphates interesting compounds for application in nanocomposite materials synthesis.

Crystalline ZrPO(4)Cl(CH(3))(2)SO was prepared by direct precipitation in the presence of oxalic acid as a zirconium complexing agent. The structure of ZrPO(4)Cl(CH(3))(2)SO, refined with the Rietveld method using X-ray powder diffraction data, was confirmed to be close to that of the compound prepared using gamma-zirconium phosphate as a precursor. Chloride anions directly bonded to zirconium were found to act as weak ligands; this made possible their replacement with other monodentate anionic ligands. The preparation and a preliminary characterization of a series of inorganic derivatives obtained by topotactic replacement of Cl with OH, Br, MSO(4) (M = H, NH(4), Na), NaMoO(4), and HCrO(4) anions is reported. The possibility of replacement of chloride also with organic anions, such as alkoxides and carboxylates, and the possibility of substituting also dimethyl sulfoxide with other neutral ligands, as shown by preliminary study, makes ZrPO(4)Cl(CH(3))(2)SO a useful and very flexible precursor for materials chemistry.

This paper reports the preparation and characterization of a series of organic derivatives of ZrPO(4)Cl(CH(3))(2)SO obtained by topotactic anion exchange of chloride ligands with several n-alkoxide (RO) and carboxylate groups (RCOO). Exchange with alkoxides, with an alkyl chain length from 2 to 8 carbon atoms, gave products of general formula ZrPO(4)RO(CH(3))(2)SO. In these derivatives alkoxide groups, covalently bonded to zirconium atoms via Zr-O bonds, point toward the interlayer region. Carboxylate derivatives, of general formula ZrPO(4)[(RCOO)(CH(3))(2)SO](1)(-)(x)(OH H(2)O)(x), were obtained using benzoate (x = 0), nitrobenzoate (x = 0.3), and phenylacetate (x = 0.2) groups. The thermal behavior of these organic derivatives is discussed. Due to this reactivity, ZrPO(4)Cl(CH(3))(2)SO is an attractive precursor for materials chemistry.

Obligate intracellular parasites have evolved a remarkable assortment of strategies to scavenge nutrients from the host cells they parasitize. Most apicomplexans form a parasitophorous vacuole (PV) within the invaded cell, a replicative niche within which they survive and multiply. As well as providing a physical barrier against host cell defense mechanisms, the PV membrane (PVM) is also an important site of nutrient uptake that is essential for the parasites to sustain their metabolism. This means nutrients in the extracellular milieu are separated from parasite metabolic machinery by three different membranes, the host plasma membrane, the PVM, and the parasite plasma membrane (PPM). In order to facilitate nutrient transport from the extracellular environment into the parasite itself, transporters on the host cell membrane of invaded cells can be modified by secreted and exported parasite proteins to maximize uptake of key substrates to meet their metabolic demand. To overcome the second barrier, the PVM, apicomplexan parasites secrete proteins contained in the dense granules that remodel the vacuole and make the membrane permissive to important nutrients. This bulk flow of host nutrients is followed by a more selective uptake of substrates at the PPM that is operated by specific transporters of this third barrier. In this review, we recapitulate and compare the strategies developed by Apicomplexa to scavenge nutrients from their hosts, with particular emphasis on transporters at the parasite plasma membrane and vacuolar solute transporters on the parasite intracellular digestive organelle.

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