Simultaneous Infrared Detection of the ICH₂OO Radical and Criegee Intermediate CH₂OO: The Pressure Dependence of the Yield of CH₂OO in the Reaction CH₂I + O₂

The simplest Criegee intermediate CH₂OO, important in atmospheric reactions, has been recently produced from the reaction of CH₂I + O₂ and detected with various methods. In this reaction, the yield of CH₂OO decreases with increasing pressure because of the stabilization of the adduct ICH₂OO, but no definitive spectral identification of ICH₂OO has been reported. We recorded the infrared spectrum of ICH₂OO using the same reaction under high pressure; the spectrum agrees with that simulated according to theoretical predictions. With direct detection of both CH₂OO and ICH₂OO, we determined the pressure dependence of the yield of CH₂OO. The yield of CH₂OO near 1 atm is greater than previously reported values, which might have significant consequences in atmospheric chemistry

Modeling the CH Stretch/Torsion/Rotation Couplings in Methyl Peroxy (CH₃OO)

The manifestations of CH stretch/torsion/rotation coupling in the region of the CH stretch fundamentals are explored in the CH₃OO radical. Following our earlier study of the fundamental in the totally symmetric CH stretch (the ν₂ fundamental), this work focuses on the other two CH stretch fundamentals, ν₁ and ν₉, which would be degenerate in the absence of a barrier in the potential along the methyl torsion coordinate. The simplest model, which assumes a decoupling of the CH stretch vibrations from the torsion, fails to reproduce several important features of the spectrum. Specifically, the absence of a strong peak around the origin of the ν₁ fundamental and broadening of the strong peak near the origin in the observed spectrum of the ν₉ fundamental are not captured by this model. The origins of these features are explored through two more sophisticated treatments of the torsion/CH stretch couplings. In the first, a four-dimensional potential based on the three CH stretches and the torsion is developed and shown to reproduce both of these features. On the basis of the results of these calculations, the calculated parameters are adjusted to simulate the recorded spectrum. To further explore the torsion/CH stretch couplings in CH₃OO, a 9-state model Hamiltonian is developed and discussed. The implications of various types of couplings on the observed energy level patterns are also discussed

Application of flow cytometry for evaluating clinical prognosis and histopathological grade of human glioma

<p><b>Objectives:</b> Flow cytometry was applied to predict the biological parameters of tumor behavior based on the DNA content distribution of tumors. We used flow cytometry to determine the number of cell cycles for the characterization of intracranial gliomas and its possible prognostic role.</p> <p><b>Methods:</b> Flow cytometric analysis of the DNA content was performed for 37 fresh operative glioma specimens. The expression of Ki-67 in glioma specimens was detected using immunohistochemistry staining. The check points of G2/M-phase fractions, cyclin B, and pCdk1 (Y15) were analyzed using Western immunoblotting.</p> <p><b>Results:</b> Compared to low-grade (grade I/II) gliomas, significant differences in the Ki-67, cyclin B, G2/M-phase, and S+G2/M-phase expressions were found in high-grade (grade III/IV) gliomas. Furthermore, receiver operating characteristic (ROC) analysis indicated optimal cutoff points for the G2/M-phase and S+G2/M-phase fractions of 13.47 and 17.26%, respectively, which can be used to differentiate cases with low- and high-grade gliomas. Additionally, both G2/M-phase and S+G2/M-phase fractions had significant association with the expression of Ki-67 in the gliomas. The gliomas were classified by the DNA content. We found that patients with high-grade glioma had worse survival rate than patients with low-grade glioma. Meanwhile, ROC curve analysis gave cutoffs for G2/M-phase of 9.4% and for S+G2/M-phase fractions of 15.04% as best predicting survival. The patients with glioma had poor survival when the levels of G2/M-phase and S+G2/M-phase were more than 9.4 and 15.04%, respectively. In contrast, no significant association between the DNA content of glioma patients and their age, tumor recurrence, and tumor size was found.</p> <p><b>Discussion:</b> Our results indicate that flow cytometry analysis for G2/M-phase and S+G2/M-phase fractions can be used for tumor grading for rapidly differentiating low- from high-grade gliomas.</p