Mj. Greig et al., NEGATIVE IONIZATION MICRO ELECTROSPRAY MASS-SPECTROMETRY OF OLIGONUCLEOTIDES AND THEIR COMPLEXES, Rapid communications in mass spectrometry, 10(1), 1996, pp. 47-50
The utility of negative ionization micro electrospray (microspray) mas
s spectrometry is demonstrated for detection of oligonucleotides and t
heir non-covalent complexes. A simple microspray ionization source is
fabricated from an outer stainless-steel needle and an inner fused-sil
ica capillary. Under these conditions, the liquid flow rate can be red
uced 15-fold from 7.5 mu L/min to 0.5 mu L/min. Studies of a 14-mer DN
A oligonucleotide show no change in the charge-state distribution and
quantity of adducted salt ions during the microspray process compared
to pneumatically assisted electrospray mass spectrometry. The microspr
ay ion source is less sensitive to the presence of solution buffers, a
nd an 11-fold increase in integrated ion abundance from oligonucleotid
e analyte is observed with a 10 mM concentration of ammonium acetate,
compared to pneumatically assisted nebulization (PAN). A >100-fold inc
rease in the duplex:single strand ratio for a 14-mer oligodeoxynucleot
ide and its complementary strand is observed using the microspray ion
source relative to experiments performed with PAN. Studies of duplexes
between DNA and a peptide nucleic acid suggest that this effect may b
e related to the degree of adduction of counterions to the DNA during
ionization.