Andrea Cinnirella, Andrea L. Aloia, Elena C.L. Rigante, Tommaso R. I. Cataldi, Antonio Monopoli, Cosima Damiana Calvano

Dipartimento di Chimica, Università degli Studi di Bari Aldo Moro, 70126 Bari, Italy

The application of matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) to low molecular weight compounds has stayed challenging due to the spectral interferences produced by conventional organic matrices in the low m/z range. To overcome this issue, alternative approaches based on rationally designed organic matrices have been proposed [1]. The purpose of this study was to synthesize a new functionalized MALDI matrix able to react with small amines and alcohols with the aim of analyzing these low-mass compounds avoiding interfering matrix background. The functionalization was carried out by nucleophilic substitution of two different p-hydroxy compounds, 4-hydroxybenzoic acid (4-HBA) and alpha-cyano-4-hydroxycinnamic acid (CHCA), with a 2,4,6-trichloro-1,3,5-triazine (TCT) in the presence of a base [2]. Trichloro-triazine, also known as cyanuric chloride, has reported a marked reactivity toward hydroxyl and amine groups [3]. 

In our experiments, we first carried out the reaction between CHCA or HBA and TCT exploiting the presence of -OH residue on the matrix; the resulting product was characterized by ATR-IR and NMR spectroscopies and MS analysis. Thus, the other two chlorines on TCT-CHCA or TCT-HBA can further react with amines or alcohols allowing to increase the molecular weight of these small compounds towards higher m/z ratio. The newly obtained compounds, TCT-CHCA or TCT-HBA, were tested with different amino acids, such as phenylalanine, glycine, isoleucine and cysteine. Preliminary results are reported in this communication.

Keywords: MALDI-ToF, Matrix, Triazine, Amino acids

References

1. Calvano C.D, Monopoli A. et al. Anal Bioanal Chem, 410, (2018), pp. 4015-4038. DOI: 10.1007/s00216-018-1014-x 

2. Funfuenha W., Phakhodee  et al., Tetrahedron 70, (2014), pp. 5415–5419. DOI: 10.1016/j.tet.2014.06.127 

3. Giacomelli G., Porcheddu, et al., Current Organic Chemistry. 8, (2014), pp. 1497–1519. DOI: 10.2174/1385272043369845