Thermal desorption effects on fragment ion production from multi-photon ionized uridine and selected analogues

Abstract

This work reveals the first experimental evidence supporting isomer-dependence in the radiation response of a nucleoside.

Comparing pulsed and continuous laser-induced acoustic desorption (LIAD) as sources for intact biomolecules

“…3b we show the associated fragment-to-parent ratios. At lower desorption laser intensities up to 4-5 W/cm 2 the ratio is very stable and constant, showing that also for cw-LIAD the desorption laser at these incident intensities does not lead to fragmentation of the target molecule, as has been previously found for other systems studied using the cw-LIAD approach [10]. Increasing the desorption intensity further, however, leads to a steep increase in the observed fragmentation.…”

“…In the case of cw-LIAD, it seems clear that desorption cannot be based on a mechanical or acoustic process, since the continuous laser does not induce any shock waves within the substrate. Desorption here must be due to a thermal process from a controlled and localised heating of the foil substrate, as has been previously discussed [10,26].…”

“…In this approach the target molecule is deposited on a thin a e-mail: d.horke@science.ru.nl (corresponding author) metal substrate, which is irradiated by a desorption laser from the backside, thus avoiding any direct contact between the laser and the target system. The LIAD approach has now been adopted by a number of groups, and demonstrated with both continuous-wave [9,10] and nanosecond pulsed lasers used for desorption [11][12][13][14][15]. However, open questions remain about whether or not the LIAD process introduces fragmentation of target systems in the produced molecular plume [16].…”

“…Moreover, the nature of the desorption mechanism behind LIAD still remains actively discussed [16][17][18], and likely depends not only on the desorption laser source (continuous or nanosecond pulsed), but also on further experimental parameters such as the thickness of the sample layer or the material of the metal substrate. Previously employed substrate materials include stainless steel [10,19], tantalum [9,20] and titanium [14,21], typically chosen for their high melting point and low thermal conductivity.…”

High-throughput UV-photofragmentation studies of thymine and guanine

“…27 Hence the desorption mechanism in LBTD cannot be impulse-driven, but is considered purely thermal. It is a unique technique that allows efficient and soft desorption of a sample into the gas phase as intact neutral molecules, [28][29][30] in contrast to conventional desorption/ionisation techniques for nonvolatiles such as matrix-assisted laser desorption ionisation, 31 electrospray ionisation, 32 or desorption electrospray ionisation 33 which produce ions. LBTD is also significantly 'softer' than conventional laser desorption involving direct irradiation of the sample matrix, 34 which can often lead to significant fragmentation and contamination of the molecular sample.…”