Synthesis of charged amphipathic nitroxide lipid spin labels and an example of their application in membrane studies
✍ Scribed by John F.W. Keana; Steven A. Boyd; Debra A. McMillen; Edward M. Bernard; Patricia C. Jost
- Publisher
- Elsevier Science
- Year
- 1982
- Tongue
- English
- Weight
- 607 KB
- Volume
- 31
- Category
- Article
- ISSN
- 0009-3084
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✦ Synopsis
The synthesis of a series of amphipathic nitroxide lipid spin labels is reported. Thus, 12-proxylhexadecanol has been converted into the versatile fatty acid spin label 14-proxylstearic acid. This substance was used to prepare 14-proxylstearyltrimethylammonium methanesulfonate, a positively charged label, and 14-proxylstearylmethyl phosphate sodium salt, a negatively charged label. Also prepared in the doxyl series were quaternary ammonium salts derived from 16-doxyl- and 7-doxylstearic acid. The positively charged and negatively charged proxyl labels were used in a preliminary experiment to investigate the role of charge in their interaction with reconstituted cytochrome oxidase. The average binding affinity of the negatively charged label is approximately 2-fold higher than that of the positively charged label at pH 7.4. At pH 5.5 the average relative affinity for negatively charged label is about 3.5-fold higher than that of positively charged label, suggesting that the ionizable group(s) on the protein can interact with the lipid headgroup.