Molecular Mass Imaging with TOF-SIMS and Ink Jet Printing Technology

1. Quantitative Analysis of DNA Microarrays using Molecular Mass Signals. We have developed a method for producing DNA microarrays using our Ink Jet (IJ) printing technology. With this technology, a DNA (oligonucleotide) probe solution was printed onto a glass substrate, and covalently attached on the surface, enabling the production of highly reproducible microarrays at a low price. Visualization of probe DNA molecules (ca. 10⁷), which exist in a printed dot, has been realized using TOF-SIMS. We have shown that the probe molecules can be analyzed quantitatively using the reliable POx ions within an error of 10 %. Direct detection of target DNAs has also been investigated with TOF-SIMS using bromine labeled target DNAs. We have observed that an approximately linear relationship exists between the target DNA concentration and bromine ion intensity. <BR> 2. Protein Molecular Imaging with TOF-SIMS and IJ. We are also developing a tool capable of visualizing protein distribution at the sub-micrometer level with TOF-SIMS and IJ. MALDI and SELDI are the softest ionization methods of those currently known, but it is difficult to obtain a two-dimensional distribution image of a protein with a high spatial resolution. While TOF-SIMS gives a secondary ion image with a high spatial resolution, the protein is generally decomposed to small fragments. If we apply the TOF-SIMS to analysis of the two-dimensional distribution of proteins in a cell, there are further difficulties in soft ionization of proteins such as the existence of intermolecular forces. We will show a new method to visualize a protein as follows: (1) print of a digestive enzyme with IJ, (2) measurement of two-dimensional distributions of decomposed fragments with TOF-SIMS, and (3) analysis of two-dimensional distributions of proteins using results of proteome analysis. TOF-SIMS results on visualization of dot-patterned insulin using insulin molecular ion signals will be also presented.