M/Z: 287.2177

By writing the four English letters “PNMK” on white paper with a marker pen, and then scanning with a DESI ion source to obtain the scanning result. The signal of the chemical substances on the marker pen used appears on the channel with an m/z value of 322.1918, 323.1953, 546.4010, and etc, from the single cell deconvolution sampling layer class_4. This test data was tested by chuxiaoping from PANOMIX’s R&D laboratory.

1 male adult wild-type rat was obtained from Inserm U1085 - Irset Research Institute (University of Rennes1, France). Animals were age 60 days and were reared under ad-lib conditions. Care and handling of all animals complied with EU directive 2010/63/EU on the protection of animals used for scientific purposes. The whole epididymis was excised from each animal immediately post-mortem, loosely wrapped rapidly in an aluminum foil and a 2.5% (w/v) carboxymethylcellulose (CMC) solution was poured to embed the epididymis to preserve their morphology. To remove air bubbles, the filled aluminum molds was gently freezed by depositing it on isopentane or dry ice, then on the nitrogen vapors and finally by progressively dipping the CMC/sample coated with aluminum foil into liquid nitrogen (or only flush with liquid nitrogen). Frozen tissues were stored at -80 °C until use to avoid degradation.