Reversible and Irreversible Interactions of Poly(3-hexylthiophene) with Oxygen Studied by Spin-Sensitive Methods

Understanding of degradation mechanisms in polymer:fullerene bulk-heterojunctions on the microscopic level aimed at improving their intrinsic stability is crucial for the breakthrough of organic photovoltaics. These materials are vulnerable to exposure to light and/or oxygen, hence they involve electronic excitations. To unambiguously probe the excited states of various multiplicities and their reactions with oxygen, we applied combined magneto-optical methods based on multifrequency (9 and 275 GHz) electron paramagnetic resonance (EPR), photoluminescence (PL), and PL-detected magnetic resonance (PLDMR) to the conjugated polymer poly(3-hexylthiophene) (P3HT) and polymer:fullerene bulk heterojunctions (P3HT:PCBM; PCBM = [6,6]-phenyl-C61-butyric acid methyl ester). We identified two distinct photochemical reaction routes, one being fully reversible and related to the formation of polymer:oxygen charge transfer complexes, the other one, irreversible, being related to the formation of singlet oxygen under participation of bound triplet excitons on the polymer chain. With respect to the blends, we discuss the protective effect of the methanofullerenes on the conjugated polymer bypassing the triplet exciton generation

DNA Topoisomerase II Modulates Insulator Function in Drosophila

Insulators are DNA sequences thought to be important for the establishment and maintenance of cell-type specific nuclear architecture. In Drosophila there are several classes of insulators that appear to have unique roles in gene expression. The mechanisms involved in determining and regulating the specific roles of these insulator classes are not understood. Here we report that DNA Topoisomerase II modulates the activity of the Su(Hw) insulator. Downregulation of Topo II by RNAi or mutations in the Top2 gene result in disruption of Su(Hw) insulator function. This effect is mediated by the Mod(mdg4)2.2 protein, which is a unique component of the Su(Hw) insulator complex. Co-immunoprecipitation and yeast two-hybrid experiments show that Topo II and Mod(mdg4)2.2 proteins directly interact. In addition, mutations in Top2 cause a slight decrease of Mod(mdg4)2.2 transcript but have a dramatic effect on Mod(mdg4)2.2 protein levels. In the presence of proteasome inhibitors, normal levels of Mod(mdg4)2.2 protein and its binding to polytene chromosomes are restored. Thus, Topo II is required to prevent Mod(mdg4)2.2 degradation and, consequently, to stabilize Su(Hw) insulator-mediated chromatin organization

THE SURGICAL STAGE OF PULMONARY TUBERCULOSIS TREATMENT USING MOLECULAR-GENETIC METHODS TO TEST SUSCEPTIBILITY TO RIFAMPICIN

The objective of the study: to analyze the frequency and patterns of drug resistance of Mycobacterium tuberculosis (MTB) according to the results of microbiological tests of surgical specimens of the patients who underwent surgery due to tuberculosis, and to compare them with the results of sputum tests done in the pre-operative period. Subjects and methods. The data of surgical specimens from 170 patients operated due to tuberculosis were analyzed. The surgical specimens were sent for histological and microbiological tests (detection of MTB DNA and rifampicin resistance by GeneXpert, culture on solid media with drug sensitivity testing). Results. The molecular genetic testing of surgical specimens by GeneXpert was highly effective for detection of rifampicin resistance; in 97.8% of cases, there was a match with the results of sputum culture with consecutive DST performed before the surgery. Molecular genetic tests of surgical specimens allowed detecting MTB DNA in 66.1% of patients in whom no MTB or MTB DNA was detected in sputum and bronchial washings prior to the surgery, and of them in 28.2% of cases, rifampicin resistance was detected, which was unknown before the surgery. These data allowed prescribing adequate chemotherapy immediately after surgery