Spin-label assay for metal ion chelation and complex formation

Journal Article · Mon Oct 15 04:00:00 EDT 1979 · Anal. Biochem.; (United States)

DOI:https://doi.org/10.1016/0003-2697(79)90060-5· OSTI ID:5388078

Wagner, S J; Keith, A D; Strong, K; Snipes, W

The electron spin resonance (ESR) lines of nitroxide spin labels are broadened by electron spin exchange reactions that take place during collisions with paramagnetic ions. The degree of line broadening is greatly reduced when the paramagnetic ion forms a coordination bond with certain functional groups on organic molecules. These observations form the basis for a spin-label assay for metal ion chelation and complex formation. This paper describes the characteristics of such an assay for divalent nickel ions and the spin label TEMPONE (2,2,6,6-tetramethylpiperidone-N-oxyl). The chelation of Ni/sup 2 +/ by cysteine and the interaction of Ni/sup 2 +/ with sodium dodecyl sulfate micelles and phospholipid vesicles are demonstrated. In addition to monitoring interactions of paramagnetic ions, the assay also allows the detection of interactions of nonparamagnetic ions that compete with the paramagnetic ions for binding sites. A kinetic analysis of competition between Ni/sup 2 +/ and Zn/sup 2 +/ ions for binding sites on phospholipid vesicles is presented. There are several advantages of the spin-label line-broadening assay compared to other conventional assays for metal chelation and complex formation. The line-broadening assay does not require that the sample be optically clear or chemically defined, it requires only very small quantities of material, it can detect as little as 0.4 to 1 ..mu..mol of complexing agent, and it may be utilized in complex biological systems including subcellular organelles and macromolecules.

• Research Organization: Pennsylvania State Univ., University Park
• OSTI ID: 5388078
• Journal Information: Anal. Biochem.; (United States), Journal Name: Anal. Biochem.; (United States) Vol. 99:1; ISSN ANBCA
• Country of Publication: United States
• Language: English

Related Subjects

550200 -- Biochemistry
560301* -- Chemicals Metabolism & Toxicology-- Cells-- (-1987)
59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
BIOLOGICAL MATERIALS
CHELATING AGENTS
CHEMICAL ANALYSIS
CHEMICAL COMPOSITION
CHEMICAL REACTION KINETICS
COMPLEXES
ELECTRON SPIN RESONANCE
ESTERS
KINETICS
LIPIDS
MAGNETIC RESONANCE
MATERIALS
NICKEL COMPLEXES
ORGANIC COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
PHOSPHOLIPIDS
QUALITATIVE CHEMICAL ANALYSIS
REACTION KINETICS
RESONANCE
TRANSITION ELEMENT COMPLEXES
ZINC COMPLEXES