Epik software

The three-dimensional structures of β-D-mannopyranuronate (M) and α-L-gulopyranuronate (G) were obtained based on previous work conducted in our laboratory [26 (link)]. Similarly, the structure of abscisic acid (ABA) was obtained from a protein structure co-crystallized with ABA (PDB code: 3JRQ), and the chitosan polymer structure was obtained from a study by Valdes et al. (2021) [27 (link)]. The pKa values for M (approximately 3.4) and G (approximately 3.6) were obtained from Bustos et al. (2022) [26 (link)], while the pKa value for ABA was evaluated using the Epik software from the Maestro-Schrödinger program [28 (link)].
To generate the molecular systems, both alginate and chitosan polymers were used according to the methodology described by Valdes et al. (2021) [27 (link)]. The alginate:chitosan ratio was varied to create three different systems (1:1, 1:2, and 2:1). In these systems, the alginate and chitosan blocks were formed using G8-block/M8-block and GM8-block structures, respectively, with chains of chitosan consisting of 16 monomers (Figure 1). The polymer chains were randomly distributed within a sphere with a radius of 60 Å using PACKMOL software v.16.070.0 [29 ]. Finally, 20 ABA molecules were randomly placed in a smaller sphere with a radius of 50 Å.