Manganese oxides occur naturally as minerals in at least 30 different crystal structures, providing a rigorous test system to explore the significance of atomic positions on the catalytic efficiency of water oxidation. In this study, we chose to systematically compare eight synthetic oxide structures containing Mn(III) and Mn(IV) only, with particular emphasis on the five known structural polymorphs of MnO2. We have adapted literature synthesis methods to obtain pure polymorphs and validated their homogeneity and crystallinity by powder X-ray diffraction and both transmission and scanning electron microscopies. Measurement of water oxidation rate by oxygen evolution in aqueous solution was conducted with dispersed nanoparticulate manganese oxides and a standard ruthenium dye photo-oxidant system. No Ru was absorbed on the catalyst surface as observed by XPS and EDX. The post reaction atomic structure was completely preserved with no amorphization, as observed by HRTEM. Catalytic activities, normalized to surface area (BET), decrease in the series Mn2O3 > Mn3O4 ≫ λ-MnO2, where the latter is derived from spinel LiMn2O4 following partial Li(+) removal. No catalytic activity is observed from LiMn2O4 and four of the MnO2 polymorphs, in contrast to some literature reports with polydispersed manganese oxides and electro-deposited films. Catalytic activity within the eight examined Mn oxides was found exclusively for (distorted) cubic phases, Mn2O3 (bixbyite), Mn3O4 (hausmannite), and λ-MnO2 (spinel), all containing Mn(III) possessing longer Mn-O bonds between edge-sharing MnO6 octahedra. Electronically degenerate Mn(III) has antibonding electronic configuration e(g)(1) which imparts lattice distortions due to the Jahn-Teller effect that are hypothesized to contribute to structural flexibility important for catalytic turnover in water oxidation at the surface.

Allergen-specific type 2 helper T (TH2) cells play a central role in initiating and orchestrating the allergic and asthmatic inflammatory response pathways. One major factor limiting the use of such atopic disease–causing T cells as both therapeutic targets and clinically useful biomarkers is the lack of an accepted methodology to identify and differentiate these cells from overall nonpathogenic TH2 cell types. We have described a subset of human memory TH2 cells confined to atopic individuals that includes all allergen-specific TH2 cells. These cells are terminally differentiated CD4+ T cells (CD27− and CD45RB−) characterized by coexpression of CRTH2, CD49d, and CD161 and exhibit numerous functional attributes distinct from conventional TH2 cells. Hence, we have denoted these cells with this stable allergic disease–related phenotype as the TH2A cell subset. Transcriptome analysis further revealed a distinct pathway in the initiation of pathogenic responses to allergen, and elimination of these cells is indicative of clinical responses induced by immunotherapy. Together, these findings identify a human TH2 cell signature in allergic diseases that could be used for response-monitoring and designing appropriate immunomodulatory strategies.

Herein we describe the molecular Co(4)O(4) cubane complex Co(4)O(4)(OAc)(4)(py)(4) (1), which catalyzes efficient water oxidizing activity when powered by a standard photochemical oxidation source or electrochemical oxidation. The pH dependence of catalysis, the turnover frequency, and in situ monitoring of catalytic species have revealed the intrinsic capabilities of this core type. The catalytic activity of complex 1 and analogous Mn(4)O(4) cubane complexes is attributed to the cubical core topology, which is analogous to that of nature's water oxidation catalyst, a cubical CaMn(4)O(5) cluster.

Nanocrystalline spinel LiMn(2)O(4) has been prepared and treatment of LiMn(2)O(4) with dilute nitric acid solution resulted in the delithiation of the framework, while maintaining the spinel structure, lambda-MnO(2). LiMn(2)O(4) is not a catalyst for water oxidation. Upon removal of the lithium, the cubical Mn(4)O(4) cores become active sites for oxidizing water to molecular oxygen, which was investigated with the photochemical [Ru(2+)(2,2'-bpy)(3)]/persulfate system at pH 5.8. The nanosize lambda-MnO(2) obtained from the nanocrystalline LiMn(2)O(4), which was synthesized by the citrate route, shows a significantly higher water oxidation catalytic activity (Turnover Frequency: 3 x 10(-5) mol O(2)/s/mol Mn) than that obtained via solid state reaction with micrometer and irregular particle sizes (Turnover Frequency: 5 x 10(-6) mol O(2)/s/mol Mn).

Background The main obstacle to elucidating the role of CD4+ T cells in allergen-specific immunotherapy has been the absence of an adequately sensitive approach to directly characterize rare allergen-specific T cells without introducing substantial phenotypic modifications by in vitro amplification. Objective To monitor in physiological conditions, the allergen-specific CD4+ T cells generated during natural pollen exposure and during allergy vaccine. Methods Alder pollen allergy was used as a model for studying seasonal allergies. Allergen-specific CD4+ T cells were tracked and characterized in twelve alder pollen-allergic, six non-allergic and nine allergy vaccine-treated individuals using peptide-MHC class II tetramers. Results Allergen-specific CD4+ T cells were detected in all of the alder pollen-allergic and non-allergic subjects tested. Pathogenic responses (CRTH2 expression and TH2-cytokine production) are specifically associated with terminally differentiated (CD27−) allergen-specific CD4+ T cells, which dominate in allergic individuals but are absent in non-allergic individuals. In contrast, CD27 expressing allergen-specific CD4+ T cells are present at low frequencies in both allergic and non-allergic individuals and reflect classical features of the protective immune response with high expression of IL-10 and IFN-γ. Restoration of a protective response during allergen-specific immunotherapy appears to be due to the preferential deletion of pathogenic (CD27−) allergen-specific CD4+ T cells accompanied by IL-10 induction in surviving CD27+ allergen-specific CD4+ T cells. Conclusions Differentiation stage divides allergen-specific CD4+ T cells into two distinct subpopulations with unique functional properties and different fates during allergen-specific immunotherapy.