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

Abstract

Fast atom bombardment (FAB), matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) and plasma desorption (PD) mass spectra of newly synthesized polyethylene glycols (PEGs), (M(w) 600-4000 Da) chemically modified with biologically active (2-benzothiazolon-3-yl)acetyl end-groups are described (products 1-6). The spectra were also used for the determination of the molecular mass characteristics (number average (M(n)) and weight average (M(w)) molecular masses) of the initial and modified PEGs. As expected, M(n) and M(w) of the modified samples are higher than those of the non-modified samples. 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 spectra, 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 cleavage of the ether bonds, are observed. The number fractions of the molecular adduct ions and fragment adduct ions, determined from the FAB and PD mass 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 abundant 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.

Mass Spectrometry of Step-Growth Polymers

“…Polypeptides and proteins showing an accurate mass up to 100 kDa were studied by using the PD-MS technique. 4 The introduction of MALDI-ToF-MS in 1985 5,6 was a break-trough technique for polymer mass analysis exceeding 10 kDa 7,8 and 100 kDa. 4 Tanaka recorded mass spectra of some commercially available proteins (mol.…”

Molecular Mass Characteristics of (2-Benzothiazolon-3-yl)acetic Acid-Telechelic Poly(ethylene oxide)s Determined by MALDI-TOF Mass Spectrometry and SEC

“…Poly-(ethylene glycol) esters of BTAA were synthesized with high degree of esterification (77-100%) according to 1 H NMR using PEGs with molecular mass of 600-4 000 Da under mild conditions. [37] The corresponding BTAA derivatives of PEGs 600 -4000 , denoted as PEG.bt 600 -4000 . PEG.bt 600 -2000 , are highly viscous liquids at room temperature.…”

“…[37] In the following, the molecularmass characteristics of these polymers, determined by SEC and MALDI-TOF MS, are compared. It is shown that a low molecular part of the polymer MMD is cut off during PEG esterification and its subsequent purification and isolation.…”

Ion/Molecule Attachment Reactions: Mass Spectrometry

“…[279,280]. MALDI-MS, FAB-MS, and PDI-MS data for PEG-esters of (2-benzothiazolon-3-yl)acetic acid have been reported as well [281] as are data on PEGylated peptides and other (bio) molecules [282]. Similarly, [M + NH 4 ] + -and [M + Na] + -ions are frequently observed for PEG-esters of relatively nonpolar molecules, e.g., nonylphenol ethoxylates that are used as surfactants [283].…”