The complexation ability of some linear crown ether‐siloxane copolymers of ester or amide type with cations as K+ and NH4+ was investigated spectrophotometrically in order to select the polysiloxane receptors that achieve good ion transport ability by bulk liquid membrane systems. The transport properties of the potassium picrate through a liquid membrane using siloxane‐crown ether polyamide as carrier were discussed. 相似文献
Permethylcyclopolysilanes are most often prepared by Würtz-type coupling of Me2SiCl2 with Na K alloy in THI: When nonpolar solvents like benzene were used, only linear polysilanes (Me2Si)n were produced, but the addition of a catalytic amount of crown ether 18-crown-6 was found to increase significantly the amount of cyclic oligomers. The ratio of (Me2Si)6 to (Me2Si)5 decreased from 18:1 to 6:1 in the presence of crown ether in a typical synthesis in THF. An explanation based on solvated electron theory has been proposed. 相似文献
Na+,Cl?and K+are the most abundant electrolytes present in biological fluids that are essential to the regulation of pH homeostasis,membrane potential and cell volume in living organisms.Herein,we report synthetic crown ether-thiourea conjugates as a cation/anion symporter,which can transport both Na+and Cl–across lipid bilayers with relatively high transport activity.Surprisingly,the ion transport activities were diminished when high concentrations of K+ions were present outside the vesicles.This unusual behavior resulted from the strong affinity of the transporters for K+ions,which led to predominant partitioning of the transporters as the K+complexes in the aqueous phase preventing the transporter incorporation into the membrane.Synthetic membrane transporters with Na+,Cl?and K+transport capabilities may have potential biological and medicinal applications. 相似文献
The synthesis of N-cyclohexyl carbamate-attached fluorene-alt-phenylene copolymer (PFPNCC) and the use of PFPNCC as a “ligand-free” fluorescent chemosensor for Cu(II) are described. Addition of Cu(II) can efficiently quench the fluorescence of PFPNCC in nucleophilic solvents such as DMF and DMSO, but not in low nucleophilic solvents such as 1,4-dioxane and THF. Ultraviolet-visible spectra of the mixture of the conjugated polymer and Cu(II) indicate the presence of a reduced Cu(I) ion in the solution. Furthermore, fluorescence recovery of PFPNCC observed at low temperature suggests that the quenching and reducing mechanism is most probably due to a photo-induced electron transfer from excited PFPNCC to Cu(II). Our findings provide a novel strategy for highly selective conjugated polymer-based chemosensors for various target analytes, albeit “ligand-free”. 相似文献
Protein unfolding inside immobilized polymerosomes : One of the most interesting properties of polymeric vesicles is their remarkable stability against extreme temperatures and osmotic stress, and their longevity even under harsh environmental conditions. We have demonstrated, in an application on protein folding, that surface‐tethered polymerosomes are suitable for performing time‐resolved single molecule studies with encapsulated proteins, as illustrated here.
