Characterization of polylactides with different stereoregularity using electrospray ionization ion mobility mass spectrometry

Kihyun Kim, Jong Wha Lee, Taihyun Chang, Hugh I. Kim

Research output: Contribution to journalArticlepeer-review

20 Citations (Scopus)

Abstract

We investigated the effect of stereoregularity on the gas-phase conformations of linear and cyclic polylactides (PLA) using electrospray ionization ion mobility mass spectrometry (ESI-IM-MS) combined with molecular dynamics simulations. IM-MS analysis of PLA ions shows intriguing difference between the collision cross section (ΩD) value of poly-L-lactide (PLLA) and poly-LD-lactide (PLDLA) ions with respect to their chain architecture and stereoregularity. In the singly sodiated linear PLA (l-PLA∗Na+) case, both l-PLLA and l-PLDLA up to 11mer have very similar ΩD values, but the ΩD values of l-PLLA are greater than that of l-PLDLA ions for larger ions. In the case of cyclic PLA (c-PLA), c-PLLA∗Na+ is more compact than c-PLDLA∗Na+ for short PLA ions. However, c-PLLA exhibits larger ΩD value than c-PLDLA for PLA ions longer than 13mer. The origin of difference in the ΩD values was investigated using theoretical investigation of PLAs in the gas phase. The gas-phase conformation of PLA ions is influenced by Na+-oxygen coordination and the weak intramolecular hydrogen bond interaction, which are more effectively formed in more flexible chains. Therefore, the less flexible PLLA has a larger ΩD value than PLDLA. However, for short c-PLA, concomitant maximization of both Na+-oxygen coordination and hydrogen bond interaction is difficult due to the constricted chain freedom, which makes the ΩD value of PLAs in this range show a different trend compared with other PLA ions. Our study facilitates the understanding of correlation between stereoregularity of PLAs and their structure, providing potential utility of IM-MS to characterize stereoisomers of polymers.

Original languageEnglish
Pages (from-to)1771-1779
Number of pages9
JournalJournal of the American Society for Mass Spectrometry
Volume25
Issue number10
DOIs
Publication statusPublished - 2014 Jan 1
Externally publishedYes

Keywords

  • Chiral polymer
  • Electrospray ionization
  • Ion mobility
  • Polylactide

ASJC Scopus subject areas

  • Structural Biology
  • Spectroscopy

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