A macrocyclic aromatic pyridine pentamer was found to exhibit patterned recognition of metal ions and efficiently extract larger ions, such as Cs(+), Ba(2+), Tl(+), Au(+), K(+) and Rb(+) preferentially over the other 18 smaller metal ions from the aqueous phase into the chloroform layer.

Hydrogen migrations in the molecular ions of 1,3-diphenylpropane, preceding the fragmentations to [C7H,]' and [C,H& ions, have been investigated by use of deuterated derivatives. By comparing the distribution of deuterium labels in the [C,(H, D)Jt products from metastable molecular ions with the distribution patterns calculated for various exchange models, it is shown that the H migrations occu...

We present a large number of examples of sidechain interactions in which it appears at first that highly unfavorable positive charges are in close proximity. In particular, we examine pairs of arginines (resp., lysines) whose sidechain Cζ (resp., Nζ) atoms are very close. We screen PDB files to find such pairs for which there are no plausible counter ions. On the other hand, we show that invari...

Photochemistry, Fluorescence, Crown Ethers, Biology The complexing of thallous ions (T1+), with the crown ether dibenzo 18 crown-6 polyether (DB) has been studied by NMR, fluorescence, and pulse radiolysis techniques. NMR data show a strong interaction of the T1+ ions with the aromatic moieties. This is also illustrated by a static quenching of the aromatic fluorescence by Tl+. The rates of rea...

Applying isotachophoresis (ITE’) superimposed on capillary zone electrophoresis (CZE), which will be denoted the ITPlCZE mode, components migrate in an ITP way on top of a background electrolyte. In such an ITPKZE system the leading electrolyte consists of a mixture of an ionic species L, with a high mobility (the leading ion of the ITP system), an ionic species L, with low mobility (the co-ion...

It is shown that y-type ions, after losing C-terminal H2O or NH3, can lose an internal backbone carbonyl (CO) from different peptide positions and yield structurally different product fragment ions upon collision-induced dissociation (CID). Such CO losses from internal peptide backbones of y-fragment ions are not unique to a single peptide and were observed in four of five model peptides studie...

Odd-electron a + 1 radical ions generated in the 157 nm photodissociation of peptide ions were investigated in an ion trap mass spectrometer. To localize the radical, peptide backbone amide hydrogens were replaced with deuterium. When the resulting radical ions underwent hydrogen elimination, no H/D scrambling was obvious, suggesting that without collisional activation, the radical resides on t...

The Poisson-Boltzmann approximation of the electrostatic interaction between two macro-ions, immersed in salt solution, assumes that the interactions between ions are very weak. For helical molecules, by using such considerations, one may derive the Kornyshev-Leikin theory of interaction [1] to describe the long-range behaviour of the forces between them. However, there may be certain cases whe...