Covalent binding of biological structures to derivatized glass substrates has enabled high resolution imaging of some samples that are not stable on untreated glass substrates. Bacteriophage T4 polyheads do not seem to adhere tightly to glass coverslips. In another example, the lattice structure of the HPI layer of D. Radiodurans can clearly be imaged using this technique. The AFM's ability to provide accurate height measurements demonstrated that the native HPI layer was preserved with close correlation to freeze-dried unstained HPI layer data generated by electron microscopy. New approaches such as these have provided a solid foundation from which research is expanding into more complex analyses.
Higher resolution imaging of a variety of small molecules continues to improve at a rapid pace.
In most cases it is as simple as spotting a few microliters of solution on mica or glass. The AFM then generates images in real-time at speeds from one to four frames per minute. The addition of a fluid cell allows immersion imaging in buffer or solvent. The fluid cell is an open system which allows the exchange of fluids so the local ionic environment can be changed, proteins, peptides or catalysts can be added - any in vitro manipulation is possible. Binding force is also quantified when a small number of molecular interactions are taking place, providing piconewton binding measurements for individual molecular pairs.