On the quantification of OH*, CH*, and C2* chemiluminescence in flames

Nau P, Krüger J, Lackner A, Letzgus M, Brockhinke A. On the quantification of OH*, CH*, and C2* chemiluminescence in flames. APPLIED PHYSICS B. 2012;107(3):551-559.Absolute concentrations of all important chemiluminescent species, OH-A, CH-A, CH-B, and C-2-d have been measured for the first time in methane-oxygen flames at low pressure. The optical detection system for chemiluminescence measurements has been calibrated with Rayleigh and Raman scattering of a cw laser, with the latter approach yielding superior results. The measured ratio between the concentration of CH-B and CH-A suggests that the electronically excited CH* is formed close to thermal equilibrium. Introduction of different rate constants for reactions leading to CH-A and CH-B were not necessary to explain the experimental results. Results are compared with a recent numerical model. Deviations in profile shape and peak positions are relatively small for stoichiometric flames, but become more pronounced in richer mixtures. Larger discrepancies are observed for the absolute concentrations, depending on the chemiluminescent species and the stoichiometry. In an attempt to find an alternative method for the quantification of chemiluminescent species, MIR-CRDS has been performed around 3.9 mu m. While H2O and OH-X could be measured, the sensitivity was not high enough to detect the low sub-ppb concentration of OH-A-in part due to the limited reflectivity of mirrors in the MIR, in part due to a significant background of hot H2O lines

A Bni4-Glc7 Phosphatase Complex That Recruits Chitin Synthase to the Site of Bud Emergence

Bni4 is a scaffold protein in the yeast Saccharomyces cerevisiae that tethers chitin synthase III to the bud neck by interacting with septin neck filaments and with Chs4, a regulatory subunit of chitin synthase III. We show herein that Bni4 is also a limiting determinant for the targeting of the type 1 serine/threonine phosphatase (Glc7) to the bud neck. Yeast cells containing a Bni4 variant that fails to associate with Glc7 fail to tether Chs4 to the neck, due in part to the failure of Bni4(V831A/F833A) to localize properly. Conversely, the Glc7-129 mutant protein fails to bind Bni4 properly and glc7-129 mutants exhibit reduced levels of Bni4 at the bud neck. Bni4 is phosphorylated in a cell cycle-dependent manner and Bni4(V831A/F833A) is both hyperphosphorylated and mislocalized in vivo. Yeast cells lacking the protein kinase Hsl1 exhibit increased levels of Bni4-GFP at the bud neck. GFP-Chs4 does not accumulate at the incipient bud site in either a bni4::TRP1 or a bni4(V831A/F833A) mutant but does mobilize to the neck at cytokinesis. Together, these results indicate that the formation of the Bni4-Glc7 complex is required for localization to the site of bud emergence and for subsequent targeting of chitin synthase