High performance RNA separation by in-capillary denaturing gel electrophoresis with carboxylic acid as RNA denaturant

For RNA size separation in a small sample volume (<10 nL), a strong denaturant to cleave the intramolecular hydrogen bonds that maintain the high-order structures of RNA and optimization for a small sample volume are required. We suggested, “in-capillary denaturing gel electrophoresis” as the RNA separation based on capillary gel electrophoresis, that realizes the denaturation and separation simultaneously in a capillary tube. We found that carboxylic acids were strong denaturants for in-capillary denaturing gel electrophoresis, and the performance of RNA separation was dramatically improved with a running buffer containing acetic acid. Based on the decrease of DNA melting temperature, we estimated that the denaturing ability of 2.0 M acetic acid was stronger than that of either 2.5 M formaldehyde or 7.0 M urea. The baseline separation of RNA with a size of 100−10,000 nt was achieved in only 25 min by in-capillary denaturing gel electrophoresis containing 2.0 M acetic acid. The resolution and number of plates of RNA separation were higher and larger than those obtained in a conventional capillary gel electrophoresis with sample preparation with 7.0 M urea.