Then we placed DNA probes (K 562, Serac) containing proteinase K (Merck) on cellulose and dried them. After that, we cut the DNA spots into equal pieces and dyed one of them with ninhydrin spray according to the manufacturer's instructions. Both pieces where set to DNA analysis. After the DNA extraction was performed as described for fingerprints below, the DNA was quantified by real-time PCR using a TaqMan™ DNA probe on a GeneAmp® 5700 sequence-detection system (Applied Biosystems). We did five measurements on every sample, whereby three measurements where made to define the DNA quantities and two measurements took place to reveal inhibitory effects. In these two probes we added a known DNA amount (2 ng) so that, if ninhydrin did not inhibit PCR, these probes should show there own DNA amount plus the added 2 ng.
Finally, blood of several persons (n=10) was placed on cellulose and dried. Then two portions (size: 2 × 2 mm) of each where cut out. One was directly set to DNA isolation and the other was treated beforehand with ninhydrin according to the manufacturer's instructions. Subsequently, the intensively dyed probes where dried and DNA analysis was carried out. The DNA isolation and analysis was performed as described for fingerprints below.