Atomic level analysis of dipeptide biomolecules by a scanning atom probe

The biomolecules of dipeptide, alpha-L-glutamyl-L-glutamic acid and alpha-L-lysyl-L-lysine, were analyzed by a scanning atom probe (SAP). Single walled carbon nanotubes grown by the high-pressure carbon monoxide process were used to prepare a small ball of tangled carbon nanotubes. Then, the ball was attached to a tungsten tip using silver paste and was dipped into a sample solution of each biomolecule. The air dried specimens were analyzed by SAP at the room temperature applying voltage pulses to trigger field evaporation of the molecules. The number of clusters corresponding to structural functional groups in each of the major mass peaks were counted and compared to the number known to be in the molecule. The results indicate that the SAP analysis is reasonably quantitative. (C) 2016 American Vacuum Society.