Time-resolved fluoroimmunoassay of 5-methyl-2'-deoxycytidine

We describe time-resolved fluoroimmunoassay of 5-methyl-2'-deoxycytidine (5MedCyd). The assay is based on the use of a highly specific antiserum raised in rabbits against BSA-conjugated 5-methylcytidine (5MeCyd). The tracer in the solid-phase time-resolved fluoroimmunoassay (TR-FIA) was antigen-selected anti-5MedCyd labeled with Europium. Thyroglobulin-linked 5MeCyd served as the solid-phase antigen. The measuring range for the fluoroimmunoassay was from less than 1 to 5000 pmol per assay of 5MedCyd. A good correlation between the results obtained with the TR-FIA and HPLC was demonstrated when the methods were applied to the measurement of methylation in human leukemic cells and other DNA samples. TR-FIA has several advantages over the more laborious techniques available so far: (i) high sensitivity, (ii) large assay ranges, (iii) rapidity and large number of simultaneous assays, (iv) simplicity, and (v) low cost provided that the laboratory has equipment for time-resolved fluorometry.

An improved radioimmunoassay for the quantitation of DNA methylation

A novel radioimmunoassay of 5MedCyd is described. The assay, employing a highly specific antiserum raised in rabbits against BSA-conjugated 5MeCyd, used 5-125iodo-2'-deoxycytidine as the tracer. The measuring range for the assay was found to be 1-1000 pmol per assay of 5MedCyd. When the methods were applied to the measurement of methylation in DNA samples a good correlation between the results obtained with the radioimmunoassay and HPLC was demonstrated. The method has several advantages over the more laborious and sophisticated techniques previously available: high sensitivity, large assay range, rapidity and potential for large number of simultaneous assays, simplicity, and low cost provided that the laboratory has equipment for gamma counting.

Radioimmunoassay of 5-methyl-2'-deoxycytidine. A method for the quantitation of DNA methylation

5-Methyl-2'-deoxycytidine (5MedCyd) is a minor constituent of mammalian cell DNA. We report the production and characterization of highly specific rabbit anti-5MedCyd antiserum. The antiserum was suitable for the radioimmunological measurement of 5MedCyd. This simple radioimmunoassay was capable of quantitating calf thymus DNA methylation at nanomolar levels of total DNA.