Visible Light-Controlled Living Cationic Polymerization of Methoxystyrene

Photo-controlled living polymerization has received great attention in recent years. However, despite the great success therein, the report on photo-controlled living cationic polymerization has been greatly limited. We demonstrate here a novel decolorable, metal-free and visible light-controlled living cationic polymerization system by using tris(2,4-dimethoxyphenyl)methylium tetrafluoroborate as the photocatalyst and phosphate as the chain transfer agent (CTA) for polymerization of 4-methoxystyrene. This polymerization reaction under green LED light irradiation shows clear living characteristics including predictable molar mass, narrow molar-mass dispersity (Đ = 1.25), and sequential polymerization capability. In addition, the photocata-lytic system exits excellent “on-off” photo switchability and shows the longest “off period” of 36 h up to now for photo-controlled cationic polymerization. Furthermore, the residual photo-catalyst is easily deactivated and decolored with addition of a base after the polymerization.

Visible Light-Controlled Living Cationic Polymerization of Methoxystyrene

Photo-controlled living polymerization has received great attention in recent years. However, despite the great success therein, the report on photo-controlled living cationic polymerization has been greatly limited. We demonstrate here a novel decolorable, metal-free and visible light-controlled living cationic polymerization system by using tris(2,4-dimethoxyphenyl)methylium tetrafluoroborate as the photocatalyst and phosphate as the chain transfer agent (CTA) for polymerization of 4-methoxystyrene. This polymerization reaction under green LED light irradiation shows clear living characteristics including predictable molar mass, narrow molar-mass dispersity (Đ = 1.25), and sequential polymerization capability. In addition, the photocata-lytic system exits excellent “on-off” photo switchability and shows the longest “off period” of 36 h up to now for photo-controlled cationic polymerization. Furthermore, the residual photo-catalyst is easily deactivated and decolored with addition of a base after the polymerization.

Insights into the genome architecture and evolution of Shiga toxin encoding bacteriophages of Escherichia coli

Background A total of 179 Shiga toxin-producing Escherichia coli (STEC) complete genomes were analyzed in terms of serotypes, prophage coding regions, and stx gene variants and their distribution. We further examined the genetic diversity of Stx-converting phage genomes (Stx phages), focusing on the lysis-lysogeny decision and lytic cassettes. Results We show that most STEC isolates belong to non-O157 serotypes (73 %), regardless the sources and geographical regions. While the majority of STEC genomes contain a single stx gene (61 %), strains containing two (35 %), three (3 %) and four (1 %) stx genes were also found, being stx2 the most prevalent gene variant. Their location is exclusively found in intact prophage regions, indicating that they are phage-borne. We further demonstrate that Stx phages can be grouped into four clusters (A, B, C and D), three subclusters (A1, A2 and A3) and one singleton, based on their shared gene content. This cluster distribution is in good agreement with their predicted virion morphologies. Stx phage genomes are highly diverse with a vast number of 1,838 gene phamilies (phams) of related sequences (of which 677 are orphams i.e. unique genes) and, although having high mosaicism, they are generally organized into three major transcripts. While the mechanisms that guide lysis–lysogeny decision are complex, there is a strong selective pressure to maintain the stx genes location close to the lytic cassette composed of predicted SAR-endolysin and pin-holin lytic proteins. The evolution of STEC Stx phages seems to be strongly related to acquiring genetic material, probably from horizontal gene transfer events. Conclusions This work provides novel insights on the genetic structure of Stx phages, showing a high genetic diversity throughout the genomes, where the various lysis-lysogeny regulatory systems are in contrast with an uncommon, but conserved, lytic system always adjacent to stx genes.

THROMBOELASTOGRAPHY IN EXPRESS ESTIMATION OF HEMOSTATIC SYSTEM IN PATIENTS WITH ACUTE PANCREATITIS

The problem of diagnostics and treatment of acute pancreatitis (AP) is relevant for emergency surgery. Both clinicians and specialists in paraclinical disciplines thoroughly examine pathogenesis of this serious disease, as their observations will contribute greatly to targeted therapy. The problem of hemostatic disorders still remains one of the poorly studied. The aim of the work is to assess the hemostatic system in patients with acute pancreatitis of various severity upon admission to the clinic. Materials and Methods. The authors examined 48 patients with acute pancreatitis, who were divided into two groups: group 1 (control, n=24) consisted of patients with mild AP; Group 2 (comparison, n=24) included patients with severe AP. Moreover, healthy individuals were also examined during the trial (norm, n=14). Disease severity is determined according to APACHE II Scoring System and national clinical guidelines. Blood coagulation-lytic system was evaluated by a number of biochemical tests (APTT, IPT, and fibrinogen) and according to some thromboelastography parameters (reaction time, coagulation time, α-angle and maximum amplitude) (TEG® 5000 Thrombelastograph®, USA). Results. It was found out that on admission thromboelastography allows clinicians to get an integrated picture of the blood coagulation system in the shortest possible time and on a full scale. These data significantly supplement the information on the coagulation-lytic system obtained by the biochemical method. It turned out that on admission patients with acute pancreatitis demonstrated significant disorders of the hemostatic system humoral component, such as hypercoagulemia and fibrinolytic inhibition. It is shown that disorders of the hemostatic system are associated with the severity of pathology. Conclusions. The information obtained can serve as the key element for targeted timely vector therapy in correction (prevention) of hemostatic derangements, the most important link in microcirculatory disorders. Keywords: hemostasis, coagulation, acute pancreatitis, thromboelastography. Проблема диагностики и лечения острого панкреатита (ОП) остается актуальной для неотложной хирургии. Усилия клиницистов и специалистов параклинических дисциплин направлены на углубленное изучение патогенеза этой тяжелой болезни, результаты которого обеспечат проведение целенаправленной терапии. Одним из малоизученных является вопрос гемостатических нарушений. Целью работы явилась оценка состояния системы гемостаза у больных ОП различной тяжести при поступлении в клинику. Материалы и методы. Проведено исследование 48 пациентов с острым панкреатитом, разделенных на группы: І группа (контроль, n=24) – пациенты с ОП легкой формы; ІІ группа (сравнение, n=24) – пациенты с ОП тяжелой степени. Для сравнения были обследованы здоровые лица (норма, n=14). Степень тяжести заболевания определена с помощью шкалы АРАСНЕ-ІІ и в соответствии с национальными клиническими рекомендациями. Состояние коагуляционно-литической системы крови оценено по ряду биохимических тестов (АЧТВ, ПТИ и фибриноген) и при помощи некоторых параметров (реакционное время, время коагуляции, величина α-угла и максимальная амплитуда) тромбоэластографии (TEG® 5000 Thrombelastograph®, USA). Результаты. Выявлено, что проведение тромбоэластографии при госпитализации позволяет получить интегральную картину состояния свертывающей системы крови в кратчайший срок и в полном объеме. Эти данные существенно дополняют сведения о состоянии коагуляционно-литической системы, полученные биохимическим путем. Оказалось, что при поступлении в клинику у больных ОП регистрируются значительные расстройства гуморального компонента системы гемостаза в виде гиперкоагулемии и угнетения фибринолиза. Показано, что расстройства в системе гемостаза сопряжены с тяжестью патологии. Выводы. Полученные сведения могут служить основой для целенаправленной своевременной векторной терапии при коррекции (предупреждении прогрессирования) гемостатических расстройств – важнейшего звена нарушения микроциркуляции. Ключевые слова: гемостаз, коагуляция, острый панкреатит, тромбоэластография.