Oligoamide Foldamers as Helical Chloride Receptors-the Influence of Electron-Withdrawing Substituents on Anion-Binding Interactions.

The anion-binding properties of three closely related oligoamide foldamers were studied using NMR spectroscopy, isothermal titration calorimetry and mass spectrometry, as well as DFT calculations. The H NMR spectra of the foldamers in [D ]acetone solution revealed partial preorganization by intramolecular hydrogen bonding, which creates a suitable cavity for anion binding. The limited size of the cavity, however, enabled efficient binding by the inner amide protons only for the chloride anion resulting in the formation of a thermodynamically stable 1:1 complex.

Structural Tuning and Conformational Stability of Aromatic Oligoamide Foldamers.

A series of aromatic oligoamide foldamers with two or three pyridine-2,6-dicarboxamide units as their main folding motifs and varying aromatic building blocks as linkers have been synthetized to study the effects of the structural variation on the folding properties and conformational stability. Crystallographic studies showed that in the solid state the central linker unit either elongates the helices and more open S-shaped conformations, compresses the helices to more compact conformations, or acts as a rigid spacer separating the pyridine-2,6-dicarboxamide units, which for their part add the predictability of the conformational properties. Multidimensional NMR studies showed that, even in solution, foldamers show conformational stability and folded conformations comparable to the solid-state structures.

Scintigraphy and sonography in the investigation of liver metastases.

77 livers of cancer patients were examined with nuclear scintigraphy (NS) and ultrasonography (US). The overall accuracy of NS was 86% and of US 87%. The place of NS and US in the investigation of liver metastases is discussed.