Combining Electrophoretic and Fluorescence Method for Screening Fine Structural Variations Among Lignin Model Polymers Differing in Monomer Composition

Abstract

Due to the challenges of cell walls (biomass) and its applications in various new technologies, there is a need of rapid and reliable screening of fine variations in lignin structure. The in vitro synthesized lignin model polymers are good experimental system to relate lignin structure/properties with its applications. We used iso-electric focusing electrophoresis (IEF) and fluorescence spectroscopy for screening fine structural variations in lignin model polymers, synthesized from the three lignin monomers, coniferyl alcohol, ferulic acid and p-coumaric acid, mixed in various ratios. The results were related with the thermal behavior of the polymers, revealed by differential scanning calorimetry. Each polymer had characteristic IEF pattern that can be used as its fingerprint. On the basis of the number and intensity of particular bands, it is possible to detect fine differences between polymer patterns, associated with the charge distribution on the polymer fractions. The blue shift of the main fluorescence maximum position of the polymers increased in the same order as temperature of glass transition, i. e. (polymer from coniferyl alcohol)>[polymer from coniferyl alcohol and ferulic acid 9: 1 (w/w)>[(polymer from coniferyl alcohol, ferulic acid and p-coumaric acid 8: 1: 1)>(polymer from coniferyl alcohol and p-coumaric acid 9: 1). The results show that the proposed combination of the fluorescence method and IEF may be used to gain complementary information on fine structural differences among the polymers, and influence of the types and ratios of the monomers building the polymer structure.