Antibodies specific for psoralen-modified RNA were developed and characterized. These antibodies were produced by immunizing rabbits with psoralen-modified RNA complexed with methylated bovine serum albumin. The antibodies showed strong reactivity with psoralen-modified RNA and DNA, particularly when AMT-uridine was present. The binding of these antibodies was not significantly affected by high ionic strength, suggesting that ion pair formation is not involved. Psoralen modification of RNA altered its recognition by anti-dsRNA antibodies, indicating that psoralen modification affects the ribose-phosphate backbone of RNA. The antibodies were useful for detecting and localizing psoralen adducts in RNA and for studying the secondary and tertiary structure of RNA in vitro and in intact cells. The study also showed that psoralen modification of RNA in intact cells can lead to detectable base-pairing and secondary structure, suggesting that viral and cellular RNA in intact cells possess the necessary structures for psoralen intercalation and photoaddition. The results demonstrate that both cellular and EMCV RNA were covalently modified with AMT in intact cells, indicating that viral and cellular RNA in intact cells possess the base-pairing/secondary structure required for AMT intercalation and photoaddition. The antibodies will be useful for studying RNA structure, including the detection of psoralen adducts and mapping the position of psoralen-modified nucleotides.Antibodies specific for psoralen-modified RNA were developed and characterized. These antibodies were produced by immunizing rabbits with psoralen-modified RNA complexed with methylated bovine serum albumin. The antibodies showed strong reactivity with psoralen-modified RNA and DNA, particularly when AMT-uridine was present. The binding of these antibodies was not significantly affected by high ionic strength, suggesting that ion pair formation is not involved. Psoralen modification of RNA altered its recognition by anti-dsRNA antibodies, indicating that psoralen modification affects the ribose-phosphate backbone of RNA. The antibodies were useful for detecting and localizing psoralen adducts in RNA and for studying the secondary and tertiary structure of RNA in vitro and in intact cells. The study also showed that psoralen modification of RNA in intact cells can lead to detectable base-pairing and secondary structure, suggesting that viral and cellular RNA in intact cells possess the necessary structures for psoralen intercalation and photoaddition. The results demonstrate that both cellular and EMCV RNA were covalently modified with AMT in intact cells, indicating that viral and cellular RNA in intact cells possess the base-pairing/secondary structure required for AMT intercalation and photoaddition. The antibodies will be useful for studying RNA structure, including the detection of psoralen adducts and mapping the position of psoralen-modified nucleotides.