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Stable equidistant step trains during crystallization of insulin
Olga Gliko1, Ilya Reviakine, Peter G Vekilov
1Department of Chemical Engineering, University of Houston, Houston, Texas 77204, USA.
Physical Review Letters
|July 15, 2003
Summary
Stable, equidistant step trains were observed during insulin crystallization, challenging previous theories. This finding was enabled by screw dislocations and transport-controlled growth, offering new insights into crystal formation.
Area of Science:
- Crystallization science
- Materials science
- Surface science
Background:
- Bunching of growth steps is a common problem in layerwise crystallization across various fields.
- Theoretical models predict that equidistant step trains are inherently unstable under many conditions.
Purpose of the Study:
- To investigate the generation and evolution of step trains during material crystallization.
- To search for and characterize stable, equidistant step trains, challenging existing theories.
Main Methods:
- Utilized atomic force microscopy (AFM) and phase-shifting interferometry.
- Monitored step train dynamics over length scales from 100 nm to 1 mm.
- Focused on the crystallization process of insulin.
Main Results:
- Observed the generation of near-equidistant step trains.
- Identified single and cooperating screw dislocations as the source of these step trains.
- Demonstrated that the absence of step-step interactions and a transport-controlled growth regime stabilize the equidistant arrangement.
Conclusions:
- Stable, equidistant step trains can form during crystallization, contrary to some theoretical predictions.
- Screw dislocations play a crucial role in forming regular step structures.
- Understanding these mechanisms can inform controlled crystallization processes for materials.