Hydrogen bonds and twist in cellulose microfibrils

Area of Science:

• Biophysics
• Materials Science
• Computational Chemistry

Background:

• Cellulose microfibrils are key structural components in plant cell walls.
• Evidence suggests cellulose microfibrils can adopt a stable twisted conformation.
• Understanding the forces driving this twist is crucial for materials science applications.

Purpose of the Study:

• To investigate the role of intrachain hydrogen bonds in driving the twist of cellulose microfibrils.
• To determine if specific hydrogen bonds, like O2-O6', are essential for microfibril twisting.
• To explore alternative mechanisms that may induce twist in cellulose.

Main Methods:

• Atomistic molecular dynamics (MD) simulations were employed.
• Intrachain hydrogen bond formation was systematically manipulated by constraining dihedral angles and altering charges.
• Simulations were run independently to ensure reproducibility of results.

Main Results:

• A consistent right-handed twist was observed in most simulations.
• Blocking the O2-O6' intrachain hydrogen bond in two simulation sets resulted in no consistent twist, suggesting its role in driving twist.
• However, right-handed twist still developed even when exocyclic group rotation was blocked, indicating intrachain hydrogen bonds are not solely responsible for driving twist.

Conclusions:

• Intrachain hydrogen bonds, particularly the O2-O6' bond, appear to play a significant role in driving the twist of cellulose microfibrils.
• However, intrachain hydrogen bonds are not strictly necessary for twist development, as other factors can also induce twisting.
• Further research is needed to fully elucidate the complex mechanisms governing cellulose microfibril twist.