Classical and Nonclassical Nucleation Mechanisms of Biomolecules

Area of Science:

• Biophysics
• Crystallography
• Materials Science

Background:

• Classical nucleation theory (CNT) has limitations in explaining protein crystallization.
• Nonclassical nucleation mechanisms, including two-step nucleation (TSN) and composite cluster models, offer alternative frameworks.
• Liquid-liquid phase separation (LLPS) is increasingly recognized as a critical factor influencing nucleation.

Purpose of the Study:

• To critically review classical and nonclassical nucleation mechanisms in protein crystallization.
• To emphasize the role of LLPS as a modulator of the local environment and a precursor state.
• To discuss the spatial location of nucleation events and influencing factors.

Main Methods:

• Review of existing literature on nucleation mechanisms.
• Analysis of experimentally documented case studies.
• Discussion of theoretical models, including multidimensional free energy landscapes and simulation approaches.

Main Results:

• TSN and composite cluster models provide better descriptions for nucleation involving intermediate disordered phases.
• The spatial location of nucleation (dense phase, interface, lean phase) impacts structural and kinetic parameters.
• Intermolecular interactions and phase behavior are crucial determinants of nucleation outcomes.

Conclusions:

• Integrated experimental and computational strategies are essential for understanding and controlling nucleation in complex biological systems.
• Current models and measurement techniques have limitations that require further investigation.
• LLPS plays a significant role in modulating the local environment and acting as a potential precursor state for nucleation.