Use of shaped pulses for semi-selective excitation of imino 1H resonances in duplex DNA and RNA

✍ Scribed by William H. Gmeiner; Parag Sahasrabudhe; Richard T. Pon

• Publisher: John Wiley and Sons
• Year: 1995
• Tongue: English
• Weight: 385 KB
• Volume: 33
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1260330607

✦ Synopsis

Abstract

The application of shaped pulses, e.g. TOPHAT and hyperbolic secant, for the semi‐selective excitation of the imino ^1^H resonances of duplex DNA and RNA in aqueous solution is explored. The excitation profiles for the shaped pulses are calibrated on a sample containing a mixture of A:U base pairs in deuteriochloroform solution. The data obtained by performing a semi‐selective inversion‐recovery pulse sequence using a TOPHAT waveform for the 90° pulse and a hyperbolic secant waveform for the 180° pulse are fitted well by a single exponential function, are independent of transmitter offset over a 1 kHz bandwidth and are in good agreement with the value obtained with hard rectangular pulses. This approach for measuring T~1~ values was applied to a 2 mM sample of a self‐complementary oligoribonucleotide containing the nucleoside analogue 5‐fluorouridine in 90% H~2~O. The T~1~, values were calculated as a function of Tris concentration, a catalyst added to promote imino hydrogen exchange. The T~1~, values were obtained by good fits of single exponential functions to the inversion‐recovery data. The T~1~, values depend on the concentration of added Tris. Shaped pulses provide a convenient alternative to long rectangular pulses and hard pulse trains for the semi‐selective excitation of imino ^1^H resonances.