PubMed · 2464837
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K E Cooper, P Y Gates, R S Eisenberg. 1988. Surmounting barriers in ionic channels.. https://doi.org/10.1017/s0033583500004480
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We report charge inversion, the sign reversal of the effective surface charge in the presence of multivalent counterions, for the biologically relevant regimes of divalent ions and mixtures of monovalent and multivalent ions. Using streaming currents, the pressure-driven transport of countercharges in the diffuse layer, we find that charge inversion occurs in rectangular silica nanochannels at high concentrations of divalent ions. Strong monovalent screening is found to cancel charge inversion, restoring the original surface charge polarity. An analytical model based on ion correlations successfully describes our observations.
This critical review covers synthetic ion channels and pores created between January 2004 and December 2005 comprehensively. The discussion of a rich collection of structural motifs may particularly appeal to organic, biological, supramolecular and polymer chemists. Functions addressed include ion selectivity and molecular recognition, as well as responsiveness to light, heat, voltage and membrane composition. The practical applications involved concern certain topics in medicinal chemistry (antibiotics, drug delivery), catalysis and sensing. An introduction to principles and methods is provided for the non-specialist; some new sources of inspiration from fields beyond chemistry are highlighted.
A series of 1-aryl-1,2,3,4-tetrahydroisoquinoline and 8-methyl-1-aryl-1,2,3,4-tetrahydroisoquinoline derivatives was evaluated for affinity to the PCP binding site of the NMDA receptor complex. The (S)-configured tetrahydroisoquinoline derivative (S)-4 e x HCl bearing a 2-methylphenyl substituent in position 1 of the heterocyclic ring system and a methyl group in position 8 was found to exhibit the highest affinity among the derivatives with a K(i)-value of 0.0374 microM. In addition, this compound shows a remarkable enantioselectivity of binding by being almost 90 times more potent than the corresponding (R)-enantiomer (R)-4 e x HCl. Additionally, a convenient and efficient synthetic approach to racemic 1-aryl-1,2,3,4-tetrahydroisoquinoline derivatives is described.