Syntheses of novel bifunctional poly(methyl methacrylate) (PMMA)-, poly(styrene) (PS)-, and (poly ε-caprolactone) (PCL)-based atom transfer radical polymerization (ATRP) macroinitiators derived from ...p-xylene-bis(1-hydroxy-3-thia-propanoloxy) core were carried out to obtain ABA-type block copolymers. Firstly, a novel bifunctional ATRP initiator, 1,4-phenylenebis(methylene-thioethane-2,1-diyl)bis(2-bromo-2-methylpropanoat) (PXTBR), synthesized the reaction of p-xylene-bis(1-hydroxy-3-thia-propane) (PXTOH) with α-bromoisobutryl bromide. The PMMA and PS macroinitiators were prepared by ATRP of methyl methacrylate (MMA) and styrene (S) as monomers using (PXTBR) as the initiator and copper(I) bromide/N,N,N′,N″,N″-pentamethyldiethylenetriamine (CuBr/PMDETA) as a catalyst system. Secondly, di(α-bromoester) end-functionalized PCL–based ATRP macronitiator (PXTPCLBr) was prepared by esterification of hydroxyl end groups of PCL-diol (PXTPCLOH) synthesized by Sn(Oct)2–catalyzed ring opening polymerization (ROP) of ε-CL in bulk using (PXTOH) as initiator. Finally, ABA-type block copolymers, PXT(PS-b-PMMA-b-PS), PXT(PMMA-b-PS-b-PMMA), PXT(PS-b-PCL-b-PS), and PXT(PMMA-b-PCL-b-PMMA), were synthesized by ATRP of MMA and S as monomers using PMMA-, PS-, and PCL-based macroinitiators in the presence of CuBr/PMDETA as the catalyst system in toluene or N,N-dimethylformamide (DMF) at different temperatures. In addition, the extraction abilities of PCL and PS were investigated under liquid–liquid phase conditions using heavy metal picrates (Ag+, Cd2+, Cu2+, Hg2+, Pb2+, and Zn2+) as substrates and measuring with UV-Vis the amounts of picrate in the 1,2–dichloroethane phase before and after treatment with the polymers. The extraction affinity of PXTPCL and PXTPS for Hg2+ was found to be highest in the liquid–liquid phase extraction experiments. Characterizations of the molecular structures for synthesized novel initiators, macroinitiators, and the block copolymers were made by spectroscopic (FT–IR, ESI–MS, 1H NMR, 13C NMR), DSC, TGA, chromatographic (GPC), and morphologic SEM.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Polymeric nanoparticles, based on amphiphilic copolymers, have been extensively evaluated as a potential material for drug delivery systems (DDS), because they present a clear capability of forming ...micelles under an aqueous medium. Besides the amphiphilic properties, the thermosensitivity of polymers under aqueous media has attracted great attention for DDS. In this work, a well-defined amphiphilic poly(ε-caprolactone)-
b
-poly(
N
-isopropylacrylamide) (PCL-
b
-PNIPAAm) was used to prepare thermosensitive micelles as potential candidates for applications in drug delivery systems. First, hydroxyl-terminated PCL (PCL-OH) was synthesized by ROP, and then, the PCL-OH was converted to PCL-Br through reaction with 2-bromopropionyl bromide, followed by a chemical modification to ethyl xanthate in PCL-end chains through substitution reaction. The PCL-
b
-PNIPAAm block copolymers were obtained by RAFT polymerization of
N
-isopropylacrylamide (NIPAAm) monomer from the PCL-EX macroagent. Different size chains of PCL and PNIPAAm were evaluated as also their influence on the capacity of micelles formation. The polymers and their synthesis efficacy were characterized by chemical composition, molecular weight, and thermal and crystallinity properties. The CMC of the copolymers and the LCST of the micelles increased with the increase in the segmental length of PNIPAAm and decreased with the increase in PCL segmental length. The DLS demonstrated an increase in the micelles size with the increase of the proportion of both hydrophobic and hydrophilic segments. Finally, the morphology observed by AFM demonstrated that the micelles are of spherical shape.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Polarized cell expansion plays an important role in plant morphogenesis. Tip growth is a dramatic form of this process, which is widely used as a model to study its regulation by RAC/ROP GTPase ...signalling. During the dominant haploid phase of its life cycle, the moss Physcomitrella patens contains different types of cells that expand by tip growth. Physcomitrella is a highly attractive experimental system because its genome has been sequenced, and transgene integration by homologous recombination occurs in this plant at frequencies allowing effective gene targeting. Furthermore, together with the vascular spikemoss Selaginella moellendorffii, whose genome has also been sequenced, the non-vascular moss Physcomitrella provides an evolutionary link between green algae and angiosperms. BLAST searches established that the Physcomitrella and Selaginella genomes encode not only putative RAC/ROP GTPases, but also homologues of all known regulators of polarized RAC/ROP signalling, as well as of key effectors acting in signalling cascades downstream of RAC/ROP activity. Nucleotide sequence relationships within seven different families of Physcomitrella, Selaginella, Arabidopsis thaliana and Nicotiana tabacum (tobacco) genes with distinct functions in RAC/ROP signalling were characterized based on extensive maximum likelihood and Neighbor–Joining analyses. The results of these analyses are interpreted in the light of current knowledge concerning expression patterns and molecular functions of RAC/ROP signalling proteins in angiosperms. A key aim of this study is to facilitate the use of Physcomitrella as a model to investigate the molecular control of tip growth in plants.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
Затруднительно или невозможно создать программное обеспечение, не содержащее ошибок. Ошибки могут приводить к тому, что переданные в программу данные вызывают нештатный порядок выполнения ее ...машинного кода. Разбиение на подпрограммы приводит к тому, что инструкции возврата из подпрограмм могут использоваться для проведения атаки. Существующие средства защиты в основном требуют наличия исходных текстов для предотвращения таких атак. Предлагаемая методика защиты направлена на комплексное решение проблемы. Во-первых, затрудняется получение атакующим контроля над исполнением программы, а во-вторых, снижается количество участков программ, которые могут быть использованы в ходе атаки. Для затруднения получения контроля над исполнением применяется вставка защитного кода в начало и конец подпрограмм. При вызове защищенной подпрограммы производится защита адреса возврата, а при завершении – восстановление – при условии отсутствия повреждения его атакующим. Для снижения количества пригодных для атак участков применяются синонимичные замены инструкций, содержащие опасные значения. Предложенные меры не изменяют алгоритм работы исходного приложения. Для проверки описанных решений была выполнена программная реализация и проведено ее тестирование с использованием синтетических тестов, тестов производительности и реальных программ. Тестирование показало правильность принятых решений, что обеспечивает устранение пригодных для атак участков и невозможность использования штатных инструкций возврата для проведения атак. Тестирование производительности показало 14 % падения скорости работы, что находится на уровне ближайших аналогов. Сравнение с аналогами показало, что количество реализуемых сценариев атаки для предложенного решения меньше, а применимость выше.
Pituitary adenylate cyclase–activating polypeptide (PACAP) is a neuropeptide having trophic and protective functions in neural tissues, including the retina. Previously, we have shown that ...intravitreal PACAP administration can maintain retinal structure in the animal model of retinopathy of prematurity (ROP). The purpose of this study is to examine the development of ROP in PACAP-deficient and wild-type mice to reveal the function of endogenous PACAP. Wild-type and PACAP-knockout (KO) mouse pups at postnatal day (PD) 7 were maintained at 75% oxygen for 5 consecutive days then returned to room air on PD12 to develop oxygen-induced retinopathy (OIR). On PD15, animals underwent electroretinography (ERG) to assess visual function. On PD16, eyes were harvested for either immunohistochemistry to determine the percentage of the central avascular retinal area or molecular analysis to assess angiogenesis proteins by array kit and anti-apoptotic protein kinase B (Akt) change by western blot. Retinas of PACAP-deficient OIR mice showed a greater central avascular area than that of the wild types. ERG revealed significantly decreased b-wave amplitude in PACAP KO compared to their controls. Several angiogenic proteins were upregulated due to OIR, and 11 different proteins markedly increased in PACAP-deficient mice, whereas western blot analysis revealed a reduction in Akt phosphorylation, suggesting an advanced cell death in the lack of PACAP. This is the first study to examine the endogenous effect of PACAP in the OIR model. Previously, we have shown the beneficial effect of exogenous local PACAP treatment in the rat OIR model. Together with the present findings, we suggest that PACAP could be a novel retinoprotective agent in ROP.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Objective: To determine whether earlier treatment of high-risk, prethreshold retinopathy of prematurity (ROP) improves retinal structural outcome at 2 years of age. Methods: Infants with bilateral ...high-risk prethreshold ROP had one eye randomly assigned to treatment with peripheral retinal ablation. The fellow eye was managed conventionally, and either treated at threshold ROP or observed if threshold was never reached. In patients with asymmetrical disease, the high-risk, prethreshold eye was randomised to earlier treatment or to conventional management. At 2 years of age, children were examined comprehensively by certified ophthalmologists to determine structural outcomes for their eyes. For the purposes of this study, an unfavourable structural outcome was defined as (1) a posterior retinal fold involving the macula, (2) a retinal detachment involving the macula or (3) retrolental tissue or “mass” obscuring the view of the posterior pole. Results of the 2-year examination were compared with those from the 9 months examination. Results: Data were available on 339 of 374 (90.6%) surviving children. Unfavourable structural outcomes were reduced from 15.4% in conventionally managed eyes to 9.1% in earlier-treated eyes (p = 0.002) at 2 years of age. Ophthalmic side effects (excluding retinal structure) from the ROP or its treatment were similar in the earlier-treated eyes and the conventionally managed eyes. Conclusion: The benefit of earlier treatment of high-risk prethreshold ROP on retinal structure endures to 2 years of age, and is not counterbalanced by any known side effect caused by earlier intervention. Earlier treatment improves the chance for long-term favourable retinal structural outcome in eyes with high-risk prethreshold ROP. Long-term follow-up is planned to determine structural and functional outcomes at 6 years of age.
Blindness due to retinopathy of prematurity (ROP) is an increasing problem worldwide as improved levels of neonatal care are provided in countries with developing neonatal intensive care units. The ...occurrence of ROP blindness varies dramatically with the socioeconomic development of a country. In regions with high levels of neonatal care and adequate resources, ROP blindness is largely restricted to premature infants with very low birth weight and low gestational age while in middle- and low-income countries with regional variation in technology and capacity, limited health resources may well limit the care of the premature newborn.
Largely known for attack scenarios, code reuse techniques at a closer look reveal properties that are appealing also for program obfuscation. We explore the popular return-oriented programming ...paradigm under this light, transforming program functions into ROP chains that coexist seamlessly with the surrounding software stack. We show how to build chains that can withstand popular static and dynamic deobfuscation approaches, evaluating the robustness and overheads of the design over common programs. The results suggest a significant amount of computational resources would be required to carry a deobfuscation attack for secret finding and code coverage goals.
We have synthesized indium complexes incorporating bifunctional thiolate ligands and examined their utility as initiators for the ring-opening polymerization of rac-lactide and ε-caprolactone. The ...facile reaction of Me3In with the corresponding bifunctional thiols in diethyl ether or thf resulted in the formation of MeIn(SCH2C(O)OMe)22 (5), MeIn(SCH2CH2NMe2)2 (6) or Me2In(SCH2C(O)OMe) (7). The solid-state structure of 5 is dimeric via short intermolecular In⋯S interactions, yielding an asymmetric In2S2 core. One pendant and one chelating methyl thioglycolate ligand gives a distorted trigonal bipyramidal S3OC bonding environment for indium. Compound 6 shows a bicyclic monomeric structure with a distorted trigonal bipyramidal S2N2C bonding environment for indium. Compound 5 polymerized bulk rac-lactide rapidly with high conversion, but yielded broad PDIs and low MWs. Solution polymerizations using one equivalent of benzyl alcohol per metal centre were reasonably well controlled at 70 °C, though molecular weights were lower than theoretical values. Compound 6 was also an efficient mediator of bulk rac-lactide polymerization when initiated by benzyl alcohol, reaching >90% conversion in 15 min. Molecular weights were in excellent agreement with the theoretical values and the PDIs were narrow. Solution polymerizations utilizing 6 in conjunction with benzyl alcohol were much slower than the analogous reactions using 5. Compound 5 was less efficient at controlling the ROP of ε-caprolactone versus rac-lactide, while 6 was inactive towards ε-caprolactone under a variety of conditions. This work represents the first study of indium thiolate complexes for the ROP of cyclic esters, and contains rare examples of structurally characterized organoindium bis(thiolate) compounds, the first to be prepared via the hydrocarbon elimination reaction.
The reaction of Me3In with bifunctional thiols afforded the compounds MeIn(SCH2C(O)OMe)22 and MeIn(SCH2CH2NMe2)2. X-ray crystal structures show monocyclic dimeric and bicyclic monomeric structures, respectively. The complexes are reactive as initiators for the ring-opening polymerization of rac-lactide and ε-caprolactone. Display omitted
► The 1:2 reaction of Me3In and bifunctional thiols yields MeIn(SR)2 compounds. ► Rare examples of structurally characterized RIn(SR′)2 compounds. ► The first study of organoindium thiolate complexes for the ROP of cyclic esters.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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