2011 Volume 16 Issue 2 Pages 119-124
We have developed preliminary test of forensic saliva identification method to locate saliva adhesion position on a wide area such as clothing and floor using coloration reagent. We used 2-chloro-4-nitrophenyl-4-O-β-D-galactopyranosylmaltoside (Gal-G2-CNP), which yields 2-chloro-4-nitrophenyl (CNP) by α-amylase and turns yellow. Detection of α-amylase activity was performed by dropping or spraying Gal-G2-CNP reaction reagent on a sample, and then the sample stained with Gal-G2-CNP reaction reagent was incubated at room temperature. We defined a positive result as yellow coloration within 10 min by the naked eye. The CNP produced by α-amylase was clearly observed as yellow coloration in saliva stain. This method was able to detect stains of 10∼100-fold diluted saliva and 10 U/ml α-amylase. The results of detection of α-amylase from 112 forensic samples by this method completely corresponded with the results of the blue starch-agarose method. All of the saliva stains stored for 6 years on filter paper showed positive reaction. Also in wide area such as the shirt and the mask, saliva adhesion position was easily identified using this method. This reaction reagent did not influence DNA extraction and DNA typing. When Gal-G2-CNP reaction reagent stored at 4°C, deterioration of sensitivity was not observed at least 6 months. This method has many merits that are able to overcome demerits of traditional saliva detection methods because this method is suitable for locating saliva adhesion position on a wide area, rapid and simple. Therefore, this method is very useful as forensic preliminary coloration test of saliva.
