The Effect of Ammonium Salt and Matrix in the Detection of DNA by Matrix-assisted Laser Desorption/Ionization Time-of-flight Mass Spectrometry

Abstract

The effect of ammonium salt in the detection of oligonucleotides by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry has been systematically investigated using several matrices with ammonium salt additives. The results show that the presence of ammonium salt in the matrix has a beneficial effect on protonation and deprotonation of oligonucleotides in addition to suppressing alkali-ion adducts. These observations indicate that a good matrix for DNA detection could be made from two components; i.e. one component for desorption, which has a relatively large absorption coefficient at the incident laser wavelength, and another component for ionization, which has good protonation and deprotonation ability. Experimental results show that ammonium citrate and ammonium tartrate are good ionization components. Experimental results also indicate that large numbers of chemicals can be used as desorption components. The concept of a two-component matrix system opens many possibilities in the search for a good matrix to be used in the detection of biopolymers. The selection criteria for good matrices in this two-component system are discussed.