Abstract:Ein geschlossenes Gefäß molekularer Dimension, das durch Ansäuern geöffnet werden kann, besteht aus einer synthetischen Vesikel, deren Poren reversibel mit einem „Stopfen”︁ aus 1 verschlossen werden könne. Eine Voraussetzung für das Verschließen war die Verwendung einer Membran aus einem ungeladenen Bola‐Amphiphil und dem Kanalbildner Monensinpyromellitat.
“…Thus, there is so far no other controllable pore available which is not based on proteins. Similar results have been reported for anionic monensin derivatives in MLM vesicles, which were closed by a dicationic bola. , 42 Membranes become leaky for dye molecules if they are treated with “harpoon” amphiphiles, carrying a hydrophobic end with bulky tert- butyl groups. Water-soluble porphyrins containing copper ions pass a “harpoonized” membrane.…”
“…Thus, there is so far no other controllable pore available which is not based on proteins. Similar results have been reported for anionic monensin derivatives in MLM vesicles, which were closed by a dicationic bola. , 42 Membranes become leaky for dye molecules if they are treated with “harpoon” amphiphiles, carrying a hydrophobic end with bulky tert- butyl groups. Water-soluble porphyrins containing copper ions pass a “harpoonized” membrane.…”
“…Results reported recently in the literature also agree with the present picture: methylviologen MV2+ itself associates o 0' e P o' N strongly with sodium dihexadecyl phosphate vesicles (33) and diffuses through the membrane above 30'C (34); lipophilic derivatives of MV2" dissolve in membranes and may act as transmembrane electron carriers (35,36); long, terminal aliphatic diquaternary ammonium cations may span anionic vesicle membranes (37).…”
Molecular wires, which would allow electron flow to take place between different components, are important elements in the design of molecular devices. An approach to such species would be molecules possessing an electron-conducting conjugated chain, terminal electroactive polar groups, and a length sufficient to span a lipid membrane. To this end, bispyridinium polyenes of different lengths have been synthesized and their incorporation into the bilayer membrane of sodium dihexadecyl phosphate vesicles has been studied. Since they combine the features of carotenoids and of viologens, they may be termed caroviologens. Vesicles containing the caroviologen whose length approximately corresponds to the thickness of the sodium dihexadecyl phosphate bilayer display temperature-dependent changes of its absorption spectrum reflecting the gel --liquidcrystal phase transition of the membrane. The data agree with a structural model in which the caroviologens of sufficient length span the bilayer membrane, the pyridinium sites being close to the negatively charged outer and inner surfaces of the sodium dihexadecyl phosphate vesicles and the polyene chain crossing the lipidic interior of the membrane. These membranes may now be tested in processes in which the caroviologen would function as a continuous, transmembrane electron channel-i.e., as a molecular wire. Various further developments may be envisaged along these lines.Molecular devices may be defined as structurally organized and functionally integrated chemical systems built into supramolecular architectures. The development of such devices requires the design of molecular components performing a given function (e.g., photoactive, electroactive, ionoactive, thermoactive, or chemoactive) and suitable for assembly into an organized array. A major requirement is that these components and the devices that they build up should perform their function(s) at the molecular and supramolecular (1) levels, as distinct from the level of the bulk material.
“…For the most part, these compounds incorporated isophthalic acid headgroups and one or two “tails” of various descriptions. These compounds were not bolaamphiphiles, as were the Co 2+ transporters reported by Fuhrhop and co‐workers,20 and they were active in bilayers. The focus of the Fyles study was “well‐behaved ion channel behavior rather than nonspecific detergent or membrane‐disrupting activity.” A twin alkyl chained isophthalic acid derivative reported by Fyles et al 19.…”
A number of synthetic ion channels have been reported in recent years that incorporate unusual or sophisticated design elements. The present work demonstrates that extremely simple compounds can function as ion channels (insert in bilayers, exhibit open-close behavior) if they meet minimum criteria. A simple membrane spanning structure may function as a channel if 1) it possesses polar headgroups (is bolaamphiphilic), 2) possesses a "central relay," and 3) channel function (open-close behavior) must be detected after insertion of the amphiphile directly into the aqueous liposomal or cellular suspension. We show here compounds that are simple spans to which we have given the name "aplosspan" (from the Greek alpha pi lambda omicron sigma + span) that meet these criteria. They are similar to, but simpler than, structures reported in the literatures that incorporate more complex design features.
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