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  • Conformational analysis  (1)
  • erythrocytes  (1)
  • 1990-1994  (2)
  • 1930-1934
  • 1
    ISSN: 1434-4475
    Keywords: Dihetero[2.2]orthometacyclophane ; Dynamic NMR spectroscopy ; Conformational analysis ; Ring interconversion of 9-membered ring
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die N,N′-Ditosyl-diaza[2.2]orthometacyclophane5a, b wurden aus N,N-Ditosylmetaphenylendiamin durch Umsetzung mit (Z)-1,4-Dichlorbuten bzw. 1,2-Bisbrommethylbenzol gewonnen. Tieftemperatur-NMR-Untersuchungen ergaben, daß5b als 1:1 Mischung einer Sessel- und einer Bootkonformation des gespanntenE,Z-Diazanonadienringes vorliegt. Bei Raumtemperatur ist die zugehörige Ringinversion schnell in der NMR-Zeitskala, die entsprechenden Protonen in beiden Konformeren, auch die aller CH2-Brückenprotonen, ergeben gemittelte Signale. Bei tiefen Temperaturen wird zunächst die Inversion der Methylenbrücken eingefroren (Signale für zweiexo- und zweiendo-CH2-Protonen werden erhalten, ΔG ≠ ca. 52 kJ mol−1). Bei weiterer Temperatursenkung können nach Einfrieren eines zweiten dynamischen Prozesses Sessel- und Bootkonformer anhand von getrennten Signalsätzen identifiziert werden (die freie Aktivierungsenthalpie für den zugehörigen Sessel-Boot-Flip beträgt ΔG ≠ ca. 43.5 kJ mol−1). Die Zuordnung der1H- und13C-NMR-Resonanzen wurde mit Hilfe von zweidimensionalen NMR-Experimenten gesichert.
    Notes: Summary The N,N′-ditosyl-diaza[2.2]orthometacyclophanes5a, b were synthesized from N,N-ditosyl-metaphenylenediamine by reaction with (Z)-1,4-dichlorobutene and 1,2-bis-bromomethylbenzene, respectively. Low temperature NMR studies showed that the compound5b exists as a 1:1 mixture of chair and boat form of the strained (E,Z)-diazanonadiene ring. At room temperature all corresponding resonances are averaged on the NMR time scale (including all four ethylene bridge protons). Going to lower temperatures, in a first step the methylene bridge inversion is frozen (giving twoexo H and twoendo H, ΔG ≠ ca. 52kJmol−1). In a second step the chair and boat form can be observed separately (ΔG ≠ ca. 43.5 kJ mol−1 for the chair/boat flip). The assignments were confirmed by 2D NMR experiments.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-4935
    Keywords: erythrocytes ; cell shape transformation ; transmembrane potential ; chlorpromazine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The effect of chlorpromazine (CPZ) on the shape of human erythrocytes with different values of transmembrane potential (TMP) was investigated. The shape of red blood cells with negative values of the TMP remained unchanged after the formation of stomatocytes by chlorpromazine, while cells with positive TMP showed a characteristic time course of shape change during the incubation with CPZ. Experiments with vanadate show that this might be due to a difference in the activity of the phospholipid-translocase at different values of TMP.
    Type of Medium: Electronic Resource
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