Controlling the Fine Structure of Glycogen-like Glucan by Rational Enzymatic Synthesis

Glycogen-like glucan (GnG), a hyperbranched glucose polymer, has been receiving increasing attention to generate synthetic polymers and nanoparticles. Importantly, different branching patterns strongly influence the functionality of GnG. To uncover ways of obtaining different GnG branching patterns, a series of GnG with radius from 22.03 to 27.06 nm were synthesized using sucrose phosphorylase, alpha-glucan phosphorylase (GP), and branching enzyme (BE). Adjusting the relative activity ratio of GP and BE (GP/BE) made the molecular weight (MW) distribution of intermediate GnG products follow two different paths. At a low GP/BE, the GnG developed from small to large during the synthetic process, with the MW increasing from 6.15 x 10(6) to 1.21 x 10(7) g/mol, and possessed a compact structure. By contrast, a high GP/BE caused the large to small model, with the MW reduction of GnG from 1.62 x 10(7) to 1.21 x 10(7) g/mol, and created a loose external structure. The higher GP activity promoted the elongation of external chains and restrained chain transfer by the BE to the inner zone of GnG, which would modulate the loose-tight structure of GnG. These findings provide new useful insights into the construction of structurally well-defined nanoparticles.

Automated summary

By adjusting the ratio of enzyme activities, researchers were able to synthesize GnG with different branching patterns, leading to either a compact or loose structure depending on the ratio of GP/BE. Low GP/BE ratios resulted in larger and more tightly packed GnG molecules, while high GP/BE ratios produced smaller and more loosely structured GnG molecules.