Matrix-assisted laser desorption/ionization, fast atom bombardment and plasma desorption mass spectrometry of polyethylene glycol esters of (2-benzothiazolon-3-yl) acetic acid

Fast atom bombardment (FAB), matrix-assisted laser desorption/ionization ti me-of-flight (MALDI-TOF) and plasma desorption (PD) mass spectra of newly s ynthesized polyethylene glycols (PEGs), (M-w 600-4000 Da) chemically modifi ed with biologically active (2-benzothiazolon-3-yl)acetyl end-groups are de scribed (products 1-6). The spectra were also used for the determination of the molecular mass characteristics (number average (M,) and weight average (M,) molecular masses) of the initial and modified PEGs. As expected, M, a nd M, of the modified samples are higher than those of the nonmodified samp les. However, it is shown that molecular mass dispersity (determined by the comparison of the polydispersity indices (PDI = M-w/M-n) of both types of PEGs) essentially do not change during this modification. The FAB mass spec tra, together with molecular species, show the presence of abundant [M + Na ](+) ions of product 1 and [M + Na + H](+) species of 2 and 3, and [M + Na + 2H](+) of product 4. Two main series of fragment ions, derived from the c leavage of the ether bonds, are observed. The number fractions of the molec ular adduct ions and fragment adduct ions, determined from the FAB and PD m ass spectra of the modified PEGs, are compared. The MALDI-TOF mass spectra of compounds 1-6 show the presence of two series of polymers. The most abun dant peaks are due to [M + Na](+) and [M + K](+) ions originating from the polymers, in which the two terminal hydroxyl groups of PEGs are esterified with (2-benzothiazolon-3-yl)acetic acid. The less abundant peaks are due to the monosubstituted polymers. Copyright (C) 2001 John Wiley & Sons, Ltd.