Prasad AV, Ju JM, Plantner JJ, Kean EL. Reductively methylated, tritiated rhodopsin of high specific activity; a convenient sensitive tracer for use in the radioimmunoassay of rhodopsin.
Curr Eye Res 1992;
11:267-73. [PMID:
1587149 DOI:
10.3109/02713689209001778]
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Abstract
Bovine rhodopsin was subjected to reductive methylation in the dark using formaldehyde and high specific activity sodium borotritide. After purification by gel filtration and affinity chromatography on Concanavalin A-Sepharose, the product retained its immunoreactive properties. [3H]-Reductively methylated rhodopsin (specific activity, 32 Ci/mmole) was suitable for use in radioimmunoassays for rhodopsin, having many advantages over radioiodinated rhodopsin for this purpose. The site of the reductive methylation was shown to be the non-active site lysines with the production of tritiated N-epsilon-dimethyllysine and tritiated N-epsilon-methyllysine in a molar ratio of about 1.3:1, respectively. In terms of stability, ease of preparation, and specificity, tritiated, reductively methylated rhodopsin presents itself as a preferable ligand to radioiodinated rhodopsin in many applications, such as the radioimmunoassay.
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