AFM Projects

Atomic Force Microscopy in Protein Crystallization Graduate Student on Projects: Huayu Li

Surface Packing Arrangements on Protein Crystals

Any predicted molecular growth mechanism can now be experimentally verified by atomic force microscopy. While most AFM studies of protein crystal growth have been conducted in the low resolution mode (micron scale), we use the atomic force microscope in the high resolution mode, where the total scan size is in tens of nanometers. In this mode surface features are no longer visible, but individual molecules can now be discerned and surface packing information can be obtained. We have used such AFM scans to probe the relationship between the internal molecular packing arrangements in tetragonal lysozyme crystals and that on the crystal faces. Click here for a more detailed description. We also observed the surface reconstruction phenomenon on protein crystals for the first time.

Molecular AFM Image AFM image of individual lysozyme molecules on the (110) face of a tetragonal crystal.

Determining the Growth Units of Protein Crystals

In previous studies, the heights of growth steps were often measured but the addition of individual growth units to the crystal faces could not be observed due to the rapidity of the growth process at the molecular level. We have developed a new technique employing the AFM in the linescan mode to observe growth events on protein crystal faces in real time. This technique can be used to measure the growth unit sizes on protein crystal faces as well, allowing their molecular growth mechanisms to be determined experimentally. We have used it to probe the growth mechanism of the (110) face of tetragonal lysozyme crystals.

Real time observation of growth unit attachment on the (110) face of tetragonal lysozyme crystals from an AFM line scan.

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Huayu Li Macromolecular Crystallization Laboratory Chemical & Environmental Engineering UT College of Engineering The University of Toledo

Huayu Li	Macromolecular Crystallization Laboratory	Chemical & Environmental Engineering	UT College of Engineering	The University of Toledo