A water-soluble polyphosphonium polymer was synthesized and directly compared with its ammonium analog in terms of siRNA delivery. The triethylphosphonium polymer shows transfection efficiency up to 65% with 100% cell viability, whereas the best result obtained for the ammonium analog reaches only 25% transfection with 85% cell viability. Moreover, the nature of the alkyl substituents on the phosphonium cations is shown to have an important influence on the transfection efficiency and toxicity of the polyplexes. The present results show that the use of positively charged phosphonium groups is a worthy choice to achieve a good balance between toxicity and transfection efficiency in gene delivery systems.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
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Gebruikmakend van archiefmateriaal en persoonlijke getuigenissen reconstrueer ik de omstandigheden waaronder Bourdieu in 1993 de Gouden Medaille van het Centre National de la Recherche Scientifique ontving, de hoogste Franse wetenschappelijke onderscheiding, bij wijze van casestudy van de existentiële situatie en het institutionele vertoon van wetenschappelijke consecratie. Zijn acceptatierede en de plechtigheid waarop hij die uitsprak zijn in drie opzichten van belang voor de geschiedenis van de sociologie en de sociologie. Zij laten zien hoe het verband tussen wetenschap, gezag en macht door een toonaangevende figuur in het vakgebied persoonlijk is ervaren, beschouwd en overdacht, en hoe hij in de praktijk daartussen laveerde. De toespraak en de ceremonie uit 1993 vormden dan ook een keerpunt in Bourdieus intellectuele ontwikkeling; zij leidden tot een nieuwe onderzoekagenda, waarin de staat als overheersende symbolische macht, de alchemie van de groepsvormingen de niet ingeloste belofte van democratische politiek op de voorgrondtraden. Ze verklaren mede waarom Bourdieu in de jaren negentig met meer overtuiging deelnam aan het publieke debat. Zijn ambivalente aanvaarding van de prijs is tevens een illustratie van Bourdieus concept van de ‘realpolitik van de rede’ en maakte nadrukkelijk een einde aan de verduistering van Durkheim door de sociologie haar rechtmatige positie in het wetenschappelijke zenit terug te geven, in het land waar ze ontstond.
Long-term imbalance in light absorption and electron transport by photosystem I (PSI) and photosystem II (PSII) in chloroplasts brings about changes in the composition, structure, and function of thylakoid membranes. The response entails adjustment in the photosystem ratio, which is optimized to help the plant retain a high quantum efficiency of photosynthesis (W.S. Chow, A. Melis, J.M. Anderson [1990] Proc Nat Acad Sci USA 87: 7502-7506). The dynamics of photosystem ratio adjustment were investigated upon the transfer of pea {Pisum sativum} plants from a predominantly PSI-light to a predominantly PSII-light environment and vice versa. The concentration of functional components (primary electron accepting plastoquinone of PSII [QA], P700) and that of constituent proteins were monitored during acclimation by A difference spectrophotometry and immunoblot analysis, respectively. Fully reversible changes in photosystem ratio occurred with a half-time of about 20 h. They involved closely coordinated changes in the concentration of the QA, reaction center protein D1, D2, and the 9-kD apoprotein of the cytochrome b559 for PSII. Similarly, closely coordinated changes in the relative concentration of P700 and reaction center proteins of PSI were observed. The level of chlorophyll b and that of the light-harvesting complex II changed in accordance with the concentration of PSII in the acclimating thylakoids. Overall, adjustments in the photosystem ratio in response to PSI- or PSII-light conditions appeared to be a well-coordinated reaction in the chloroplast. The response was absent in the chlorophyll b-less chlorina f2 mutant of barley (Hordeum vulgare) and in a phycobilisomeless mutant of Agmenellum quadruplicatum, suggesting that photosystem accessory pigments act as the light-quality perception molecules and that PSI and PSII themselves play a role in the signal transduction pathway.
Reaction of [(diene)RhCl]2 with 2 equiv of KOSi(OtBu)3 afforded [(diene)Rh[mu-OSi(OtBu)3]]2, where diene=cod (1) and nbd (2). Multinuclear NMR studies reveal that 1 and 2 have a dimeric structure with bridging tris(tert-butoxy)siloxy ligands. These dimers are folded along the O...O axis. Complexes and reacted with PR3(R=Me, Ph) to give monomeric products, the formulae of which depend on the amount of PR3 added ((diene)Rh[OSi(OtBu)3](PR3) and Rh[OSi(OtBu)3](PMe3)3). The behavior of 1 towards water and methanol is discussed. Thermogravimetric analyses (TGAs) of 1 and 2 reveal rather sharp conversions to rhodium-containing materials. Thermolysis of 1 in toluene at 180 degrees C resulted in formation of a black precipitate, which contained rhodium nanoparticles with an average diameter of 22 nm, as determined by powder X-ray diffraction (PXRD), after calcination at 300 degrees C for 1 h.
