Structure-dependent switchover of reaction modes: A laser flash photolysis and magnetic field effect study

Role of sugar in controlling reaction pathways: A study with thymine and thymidine

“…Addition of Thy (curve 2) has resulted in a sharp increase in intensity at 370 nm with a hump at 400 nm and another small peak at 500 nm. Earlier we had mentioned that peaks at 370 and 400 nm are combined effect of MQ dÀ and MQH d and MQ dÀ also exhibits a second peak around 490 nm [5,19]. Observation of a 400 nm hump is attributed to a facile H abstraction from Thy to MQ.…”

“…The MF effect (0.08 T) on the transient spectra has been studied by passing direct current through a pair of electromagnetic coils placed inside the sample chamber. There is a strong absorption maximum at 370 nm (curve 1) due to absorption of 3 MQ [19]. The 355 nm laser light can excite only quinones as their absorption maxima lies within this region [19,20].…”

“…There is a strong absorption maximum at 370 nm (curve 1) due to absorption of 3 MQ [19]. The 355 nm laser light can excite only quinones as their absorption maxima lies within this region [19,20]. DNA bases are not excited as they absorb below 300 nm [21,22].…”

“…Curve 1 depicts absorption due to MQ alone while curve 2 exhibits its field effect. The 370 nm peak is seen to increase in presence of an external MF thus associating it to a radical species, which can be assigned to MQH d [5,19]. The peak due to MQ and Thy (curve 3) presents broad maxima around 370 nm with appreciable absorption around 400 and 500 nm.…”

“…Our earlier works have shown H abstraction to be negligible in homogeneous medium [5,6,19]. H abstraction is assumed to be preceded by H bonding type interaction between the participating molecules.…”