Search for axion-like particles through nuclear Primakoff production using the GlueX detector

We report on the results of the first search for the production of axion-like particles (ALP) via Primakoff production on nuclear targets using the GlueX detector. This search uses an integrated luminosity of 100 pb$^{-1}\cdot$nucleon on a $^{12}$C target, and explores the mass region of 200 < $m_a$ < 450 MeV via the decay $X\rightarrow\gamma\gamma$. This mass range is between the $\pi^0$ and $\eta$ masses, which enables the use of the measured $\eta$ production rate to obtain absolute bounds on the ALP production with reduced sensitivity to experimental luminosity and detection efficiency. We find no evidence for an ALP, consistent with previous searches in the quoted mass range, and present limits on the coupling on the scale of $O$(1 TeV). We further find that the ALP production limit we obtain is hindered by the peaking structure of the non-target-related dominant background in GlueX, which we treat by using data on $^4$He to estimate and subtract these backgrounds. We comment on how this search can be improved in a future higher-statistics dedicated measurement

Intestinal Inflammatory Responses to the Indigenous Microbiota

209 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2001.The potential for inflammatory cytokines to sensitize intestinal epithelial cells to indigenous bacteria was evaluated in HT-29 cells associated with Lactobacillus plantarum 299v in the presence or absence of tumor necrosis factor-alpha (TNF-alpha). Co-culture of TNF-alpha-stimulated HT-29 cells with L. plantarum 299v increased interleukin-8. (IL-8) mRNA expression above levels observed for cells treated with TNF-alpha alone. The ability of TNF-alpha-to upregulate CD14 and Toll-like receptor (TLR) expression and thereby enhance IL-8 mRNA expression in response to L. plantarum 299v was investigated. Baseline expression of CD14 mRNA and cell-surface CD14 was not altered by TNF-alpha. HT-29 cells did not express TLR2 mRNA. However TNF-alpha increased baseline HT-29 expression of TLR4 mRNA, and co-culture with L. plantarum 299v further enhanced TLR4 mRNA expression in TNF-alpha-treated HT-29 cells. These results indicate that neither CD 14 nor TLRs 2 and 4 are involved in the IL-8 mRNA response by HT-29 cells to L. plantarum 299v. However, these results indicate that intestinal epithelial cell responses to indigenous bacteria may contribute to intestinal inflammation.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

TNF-alpha Sensitizes HT-29 Colonic Epithelial Cells to Intestinal Lactobacilli.

The ability of the proinflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) to influence epithelial interleukin (IL)-8 responses to the intestinal bacterium Lactobacillus plantarum 299v was analyzed in the human HT-29 colonic epithelial cell line. In the absence of TNF-alpha, IL-8 mRNA expression was not detectable by Northern blot analysis in HT-29 cells alone or in HT-29 cells co-cultured with L. plantarum 299v. However, TNF-alpha induced IL-8 mRNA expression, and co-culture of TNF-alpha-treated HT-29 cells with L. plantarum 299v significantly increased IL-8 mRNA expression above levels induced by TNF-alpha alone in an adhesion-dependent manner. The increase in IL-8 mRNA expression was not observed in TNF-alpha-treated HT-29/L. plantarum 299v co-cultures using heat-killed lactobacilli or when L. plantarum adhesion was prevented using mannoside or a trans-well membrane. Paradoxically, IL-8 secretion was decreased in TNF-alpha-treated HT-29 cells with L. plantarum 299v relative to cells treated with TNF-alpha alone. TNF-alpha-mediated responsiveness to L. plantarum 299v was further investigated by analyzing expression of a coreceptor for bacterial cell wall products CD14. HT-29 cells expressed CD14 mRNA and cell-surface CD14; however, TNF-alpha did not alter CD14 mRNA or cell-surface expression, and blockade of CD14 with monoclonal antibody MY4 did not alter the IL-8 response to L. plantarum 299v in TNF-alpha-treated HT-29 cells. These results indicate that although TNF-alpha sensitizes HT-29 epithelial cells to intestinal lactobacilli, the bacteria exert a protective effect by downregulating IL-8 secretion

Tyrosyl radicals in enzyme catalysis: Some properties and a focus on photosynthetic water oxidation

Enzymes that require a redox-active amino acid for catalysis or function have emerged as a distinct class of proteins. For the tyrosine-based radical enzymes, we show that the spin-density distribution in the radical follows an odd alternate pattern that is invariant to within 10% across the class. General properties of the radical enzymes are summarized from which we conclude that their essential role in catalysis is to initiate substrate metabolism by hydrogen-atom abstraction. These ideas are extended to the Y-Z and Y-D tyrosines in Photosystem II and a radical-based hydrogen-atom abstraction model for water oxidation is discussed. Differences in rates of oxidation of Y-Z and Y-D by the reaction-center chlorophyll, P680(+), under various conditions, are considered and rationalized on the basis of changes in reorganization energy induced by the local protein structure and by the presence or absence of the (Mn)(4) cluster that binds substrate water