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Biomedical subjects

Karl J Wallace

Publications and source records attributed to Karl J Wallace.

4 recordsLinked to original sources
PubMed2005

An artificial siderophore for the detection of iron(III).

An artificial siderophore in the form of a squaraine dye (1) has been synthesized. The bidentate ligand chelates to Fe(III) between the deprotonated hydroxyl group on the ortho position of the ring adjacent to the carbonyl group of the cyclobutadiene ring. The optical response is due to a subtle geometry change of 1 on chelation to Fe(III). This artificial siderophore forms a 2 ratio 1 ligand ratio metal complex, as indicated by a sigmoidal isotherm (K(a)= 10(7) M(-1)). The optical response on the addition of Fe(III) is observed at low concentrations in comparison to other metal salts. The X-ray crystal structure and calculated structures of dye (1) are also included, and will be discussed.

Cations↗
PubMed2003

Slow anion exchange, conformational equilibria, and fluorescent sensing in venus flytrap aminopyridinium-based anion hosts.

The synthesis, anion binding, and conformational properties of a series of 3-aminopyridinium-based, tripodal, tricationic hosts for anions are described. Slow anion and conformational exchange on the (1)H NMR time scale at low temperature, coupled with NMR titration, results in a high level of understanding of the anion-binding properties of the compounds, particularly with respect to significant conformational change resulting from induced fit complexation. Peak selectivity for halides, particularly Cl(-), is observed. The approach has been extended to dipodal and tripodal podands based on 3-aminopyridinium "arms" containing photoactive anthracenyl moieties. The 1,3,5-tripodal host shows a remarkable selectivity for acetate over other anions, in contrast to the analogous unsubstituted tris(3-aminopyridinium) analogue, despite the fact that low-temperature (1)H NMR experiments reveal a total of four acetate-binding conformations. Photodimerization of anthracene units results in the formation of potential fluorescent anion sensors.

Journal Article↗
PubMed2002

Cooperative anion binding and electrochemical sensing by modular podands.

A series of podands based on two or three hydrogen bonding "arms" situated in mutually ortho, meta, or para relationships about an aryl core have been prepared, and their affinities for simple inorganic anions were measured. Of the two-arm hosts the meta compound and to a lesser extent the ortho host exhibit a cooperative anion binding effect. The two arms function essentially independently in the para derivative. The mutually meta three-arm host shows dramatically enhanced cooperative binding. Conformational changes within the meta two-arm host result in significantly enhanced electrochemical anion sensing compared with the more conformationally rigid three-arm host.

Anions↗