| Abstract
| - Poor detection limits and strong salt effects are two ofthemain problems encountered in the matrix-assisted laserdesorption/ionization time-of-flight (MALDI-TOF) massspectrometric analysis of DNA. This work demonstratesthat a probe tip with a paraffin wax film (Parafilm)surfaceimproves the MALDI performance in DNA analysis compared to the commonly used metal surface. First, theuseof Parafilm increases the detection sensitivity. Itwasfound that the detection limit achieved with Parafilm was5 times better than that obtained using stainless steelfora 85mer. More importantly, the Parafilm method couldimprove detection of larger DNA components in thepresence of a large excess of a smaller DNA componentor in a DNA mixture. This feature is important toanalysesof PCR and sequencing products. Second, we found thatthe use of Parafilm increased the salt tolerance limitsforthe 17-, 41-, and 85mers studied in this work and thatthe salt effect was less sensitive to the DNA size.Third,this method offers other analytical benefits, includingproducing a more homogeneous coverage of matrix/DNA,adding no extra cost and time to sample preparation, andeliminating the commonly required step for cleaning theprobe after analysis. In this paper, we will alsopresentour perspectives on why the use of Parafilm can improvethe MALDI-TOF performance in DNA analysis.
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