Here we show the preparation of a series of water‐based physically cross‐linked polymeric materials utilizing cucurbit8uril (CB8) ternary complexes displaying a range of binding, and therefore ...cross‐linking, dynamics. We determined that the mechanical strength of these materials is correlated directly with a high energetic barrier for the dissociation of the CB8 ternary complex cross‐links, whereas facile and rapid self‐healing requires a low energetic barrier to ternary complex association. The versatile CB8 ternary complex has, therefore, proven to be a powerful asset for improving our understanding of challenging property–structure relationships in supramolecular systems and their associated influence on the bulk behavior of dynamically cross‐linked materials.
Supramolekulare Hydrogele wurden durch Nutzung der Wirt‐Gast‐Wechselwirkungen des Makrocyclus Cucurbit8uril (CB8) mit verschiedenen Gastmolekülen erzeugt. Die mechanische Stärke dieser Materialien korreliert direkt mit der Energiebarriere für die Dissoziation der ternären CB8‐Komplexe, während für die Selbstheilung eine niedrige Energiebarriere der Assoziatbildung notwendig ist.
Basische Gruppen durch Säurehydrolyse: 1,3,5‐Triazaadamantane (TAAs) werden in saurem Milieu unter Bildung basischer Begleitprodukte abgebaut (siehe Schema). Die Hydrolysegeschwindigkeit kann über ...die Wahl der Substituenten an den aromatischen Ringen eingestellt werden. Wegen der verzweigten Architektur der TAAs können TAA‐haltige Dendrimere einfach synthetisiert werden.
Fragmentierungsfrei gelingt die massenspektrometrische Analyse von biologischen Makromolekülen unter Anwendung der sanften Laserdesorption, einer Technik, die durch Arbeiten von Koiji Tanaka ...entscheidend geprägt wurde (siehe Schema; UFMP=ultrafeines Metallpulver). Für diese bahnbrechende Entwicklung wurde er mit dem Nobel‐Preis für Chemie 2002 ausgezeichnet.
Measurements of erythropoietin in fetal blood obtained by cordocentesis or in umbilical cordblood and maternal blood have shown a lack of correlation indicating an independent regulation of EPO ...concentration in fetal and maternal compartments. There is a good correlation between amniotic fluid EPO concentration in fetal blood levels. Fetal EPO concentration therefore might serve as an indicator of chronic fetal hypoxia with fetal EPO production being responsive to tissue hypoxia early on in pregnancy. The lack of human placental permeability for EPO was further investigated using a dual in vitro perfusion system of an isolated cotyledon in freshly delivered term placentae. With recirculation of both circuits trace amounts of EPO (0.04% of the amount added to the maternal compartment) were transferred to the fetal side during 4-5 hours of perfusion. This transfer is comparable to the rate determined in the same experiments for albumine, and the biological significance of this very slow transfer is questionable. A very low rate of diffusion across the human placenta has also been shown for dextran, horseradish peroxidase and heparin using an in vitro perfusion system. The only exception among macromolecules are immunoglobulines G, which towards the end of pregnancy are transferred by an Fc-receptor mediated transcellular mechanism from the mother to the fetus. It is concluded, that there is no easy exchange of EPO across the human placenta between maternal and fetal compartments. Changes in EPO concentration in the fetal compartment therefore could serve as indicator of fetal hypoxia. A therapeutic application of EPO in the mother for the treatment of chronic anemia would not have any effect on fetal tissues.
PDF
