Comparison of 125I-Labeled and 14C-Labeled Peptides of the Major outer Membrane Protein of Chlamydia Trachomatis Strain L2/434 separated by High-Performance Liquid Chromatography

Abstract

The objective of this study was to determine if in-gel chloramine-T radioiodination adequately labels OM proteins to allow for accurate and precise structural comparison of these molecules. Therefore, intrinsically ¹⁴C-amino acid labeled proteins and ¹²⁵I-labeled proteins were cleaved with two endopeptidic reagents and the peptide fragments separated by HPLC. A comparison of retention times of the fragments, as determined by differential radiation counting, thus indicated whether ¹²⁵I-labeling identified of all the peptide peaks seen in the ¹⁴C-labeled proteins. Results demonstrated that radioiodination yields complete and accurate information about the primary structure of outer membrane proteins. In addition, it permits the use of extremely small amounts of protein allowing for method optimization and multiple separations to insure reproducibility.