Atomic force microscopy of biological samples at low temperature

The atomic force microscope (AFM) has been successful imaging rigid samples with atomic resolution, but this resolution has not been matched on soft biological samples at room temperature. On many biological samples even tracking forces as small as 10−9 N distort the sample during a scan.At low temperatures proteins freeze into a single conformational state and become much more rigid. In this paper we demonstrate that it should be feasible to get atomic resolution on frozen biological samples with a low-temperature AFM. We also show some preliminary low-temperature AFM images of one biological sample, purple membrane.