New insights in the formation of deoxynucleoside adducts with the heterocyclic aromatic amines PhIP and IQ by means of ion trap MSⁿ and accurate mass measurement of fragment ions

Abstract

The formation of adducts by reaction of active metabolites of two heterocyclic aromatic amines (NHOH-PhIP and NHOH-IQ) at nucleophilic sites of deoxynucleosides has been studied by LC-MS n analyses of the obtained reaction mixtures. Sequential MS 3 experiments were carried out on an ion trap mass spectrometer to gain extensive structural information on each adduct detected in the first MS step. Attribution of ions was supported by accurate mass measurements performed on an Orbitrap mass analyzer. Particular attention was given to ions diagnostic of the linking between the heterocyclic aromatic amine (HAA) and the deoxynucleoside. By this way, the structures of five adducts have been characterized in this study, among which two are new compounds: dG-N7-IQ and dA-N 6 -IQ. No depurinating adduct was found in the reactions investigated therein. As expected, the C8 and N 2 p p atoms of dG were found as the most reactive sites of deoxynucleosides, resulting in the formation of two different adducts with IQ and one adduct with PhIP. An unusual non-depurinating dG-N7-IQ adduct has been characterized and a mechanism is proposed for its formation on the basis of the reactivity of arylamines. A dA-N 6 -IQ adduct has been identified for the first time in this work, showing that HAAs can generate DNA adducts with bases other than dG. (J Am Soc

Mass spectrometric investigation of the sequence selectivity for adduction of heterocyclic aromatic amines on single‐strand oligonucleotides

“…Finally, no depurination induced by the adduct formation was detected on any modified sequence. This result is in agreement with previous results obtained from reactions of PhIP and IQ with deoxynucleosides, 38 which showed that the alkylation process of nucleobases by these HAAs did not involve the destabilization of their sugar-base bond.…”

“…40 On the other hand, IQ is known to be able to generate three isomeric adducts with dG, namely dG-C8-IQ, which is the major one, dG-N 2 -IQ and dG-N7-IQ. 38 However, only one adduct has been observed under our synthetic conditions. Here again, taking into account data obtained on deoxynucleosides, this modification of oligonucleotides by IQ likely corresponds to the formation of a G-C8-IQ adduct.…”

“…Oligonucleotides were modified from N-hydroxyl HAA derivatives according to a previously described protocol. 38 Briefly, NHOH-PhIP was synthesized by dissolving 0. …”

“…37 We present hereafter an investigation of the chemioselectivity of the adduct formation on DNA bases, consisting of a systematic study of the neighbouring base effect on the adduction by the two heterocyclic aromatic amines, PhIP and IQ. These two HAAs are known to react with the C8 carbon atom of G to form a major G-C8 adduct, 11 and IQ is also known to generate minor adducts with the N 2 and N7 nitrogen atoms of G. 11,38 We have shown in a recent work …”

Orbitrap mass spectrometry: Instrumentation, ion motion and applications

“…The LTQOrbitrap has also been used to analyze intact small (3-10 kDa) (Bredehöft, Schänzer, & Thevis, 2008;Thevis et al, 2006a;Thevis, Thomas, & Schänzer, 2008b), medium (10-25 kDa) (Macek et al, 2006;Waanders, Hanke, & Mann, 2007) and large ($150 kDa) (Zhang & Shah, 2007) proteins where the MS n capability of the LIT coupled with the high performance features of the orbitrap can facilitate unambiguous determination of the charge states of fragment ions, as well as identification of PTMs by database searching. The high performance attributes of this hybrid mass spectrometer have also found applications in environmental chemistry (Barceló & Petrovic, 2007;Krauss & Hollender, 2008), drug and metabolite analysis (Breitling, Pitt, & Barrett, 2006;Cuyckens et al, 2008;Ding et al, 2007;Karu et al, 2007;Li et al, 2007a;Lim et al, 2007Lim et al, , 2008Madalinski et al, 2008;Nielen et al, 2007;Peterman et al, 2006;Ruan et al, 2008;Thevis et al, 2005;Thevis, Kamber, & Schänzer, 2006b;Thevis, Krug, & Schänzer, 2006c;Thevis et al, 2006dThevis et al, ,e, 2007aThevis et al, , 2008aZhu et al, 2007), lipidomics (Davis et al, 2008;Ejsing et al, 2006;Schwudke et al, 2007;Silipo et al, 2008), small-molecule (Chen et al, 2007b) and reaction product (Jamin et al, 2007) identification, as well as molecular structure characterization using hydrogen/deuterium exchange measurements (Chen et al, 2007a;...…”