The self-assembly of dinuclear triple helical lanthanide ion complexes (helicates), in aqueous solution, is investigated utilizing laser-induced, lanthanide luminescence spectroscopy. A series of dinuclear lanthanide (III) helicates (Ln(III)) based on 2,6-pyridinedicarboxylic acid (dipicolinic acid, dpa) coordinating units was synthesized by linking two dpa moieties using the organic diamines (1R,2R)-diaminocyclohexane (chxn-R,R) and 4,4'-diaminodiphenylmethane (dpm). Luminescence excitation spectroscopy of the Eu3+ 7F0-->5D0 transition shows the apparent cooperative formation of neutral triple helical complexes in aqueous solution, with a [Eu2L3] stoichiometry. Eu3+ excitation peak wavelengths and excited-state lifetimes correspond to those of the [Eu(dpa)3]3- model complex. CD studies of the Nd(III) helicate Nd2(dpa-chxn-R,R)3 reveal optical activity of the f-f transitions, indicating that the chiral linking group induces a stable chirality at the metal ion center. Molecular mechanics calculations using CHARMm suggest that the delta delta configuration at the Nd3+ ion centers is induced by the chxn-R,R linker. Stability constants were determined for both ligands with Eu3+, yielding identical results: log K = 31.6 +/- 0.2 (K in units of M-4). Metal-metal distances calculated from Eu3+-->Nd3+ energy-transfer experiments show that the complexes have metal-metal distances close to those calculated by molecular modeling. The fine structure in the Tb3+ emission bands is consistent with the approximate D3 symmetry as anticipated for helicates.

The alpha-1 and alpha-2 [P(2)W(17)O(61)](10)(-) isomers, derivatives of the Wells-Dawson molecule, [alpha-P(2)W(18)O(62)](6)(-), may be useful ligands for stabilizing high-valent metal ions and lanthanides and actinides. However, the potential utility of the [alpha1-P(2)W(17)O(61)](10)(-) ligand has not been realized. Specifically, for the lanthanides, the stoichiometry, structure, and purity of the lanthanide complexes of the [alpha1-P(2)W(17)O(61)](10)(-) isomer are ambiguous. We have prepared lanthanide (Ln) complexes of the [alpha1-P(2)W(17)O(61)](10)(-) isomer in >/=98% isomeric purity, according to (31)P NMR data. (183)W NMR data clearly showed, for the first time, that the C(1) symmetry of the [alpha1-P(2)W(17)O(61)](10)(-) lanthanide complexes was maintained in solution. We determined the stoichiometry of the lanthanide complexes of the [alpha1-P(2)W(17)O(61)](10)(-) isomer in solution by two different methods: a complexometric titration method and excited state lifetime measurements and luminescence titrations for the europium(III) analogue. All experiments show a 1:1 Ln:[alpha1-P(2)W(17)O(61)](10)(-) ratio. The (31)P NMR data showed that the lanthanides with smaller ionic radii (higher charge-size ratio) form stable complexes, even surviving crystallization from hot water. On the other hand, the lanthanum analogues were not stable in solutions of high lithium content. The tetrabutylammonium salt of the [Lu(alpha1-P(2)W(17)O(61))](7)(-) complex showed >/=98% isomeric purity and the C(1) symmetry required for a derivative of [alpha1-P(2)W(17)O(61)](10)(-). Also the tetrabutylammonium cation stabilized the [Lu(alpha1-P(2)W(17)O(61))](7)(-) complex; a mixed tetrabutylammonium, lithium salt was stable in water for weeks according to (31)P NMR spectroscopy.

e Campylobacter jejuni is a leading cause of human foodborne gastroenteritis worldwide. The interactions between this pathogen and the intestinal microbiome within a host are of interest as endogenous intestinal microbiota mediates a form of resistance to the pathogen. This resistance, termed colonization resistance, is the ability of commensal microbiota to prevent colonization by exogenous pathogens or opportunistic commensals. Although mice normally demonstrate colonization resistance to C. jejuni, we found that mice treated with ampicillin are colonized by C. jejuni, with recovery of Campylobacter from the colon, mesenteric lymph nodes, and spleen. Furthermore, there was a significant reduction in recovery of C. jejuni from ampicillin-treated mice inoculated with a C. jejuni virulence mutant (⌬flgL strain) compared to recovery of mice inoculated with the C. jejuni wildtype strain or the C. jejuni complemented isolate (⌬flgL/flgL). Comparative analysis of the microbiota from nontreated and ampicillin-treated CBA/J mice led to the identification of a lactic acid-fermenting isolate of Enterococcus faecalis that prevented C. jejuni growth in vitro and limited C. jejuni colonization of mice. Next-generation sequencing of DNA from fecal pellets that were collected from ampicillin-treated CBA/J mice revealed a significant decrease in diversity of operational taxonomic units (OTUs) compared to that in control (nontreated) mice. Taken together, we have demonstrated that treatment of mice with ampicillin alters the intestinal microbiota and permits C. jejuni colonization. These findings provide valuable insights for researchers using mice to investigate C. jejuni colonization factors, virulence determinants, or the mechanistic basis of probiotics.