enzymes (PsiD, PsiH, PsiK, and PsiM) in P. cubensis and P. cyanescens, although it is possible that the biosynthetic pathway differs between species. These enzymes are encoded in gene clusters in Psilocybe, Panaeolus, and Gymnopilus. Escherichia coli has been genetically modified to manufacture large amounts of psilocybin. Psilocybin can be produced de novo in yeast. Analytical methods Several relatively simple chemical tests—commercially available as reagent testing kits—can be used to assess the presence of psilocybin in extracts prepared from mushrooms. The drug reacts in the Marquis test to produce a yellow color, and a green color in the Mandelin reagent. Neither of these tests, however, is specific for psilocybin; for example, the Marquis test will react with many classes of controlled drugs, such as those containing primary amino groups and unsubstituted benzene rings, including amphetamine and methamphetamine. Ehrlich's reagent and DMACA reagent are used as chemical sprays to detect the drug after thin layer chromatography. Many modern techniques of analytical chemistry have been used to quantify psilocybin levels in mushroom samples. Although the earliest methods commonly used gas chromatography, the high temperature required to vaporize the psilocybin sample prior to analysis causes it to spontaneously lose its phosphoryl group and become psilocin—making it difficult to chemically discriminate between the two drugs. In forensic toxicology, techniques involving gas chromatography coupled to mass spectrometry (GC–MS) are the most widely used due to their high sensitivity and ability to separate compounds in complex biological mixtures. These techniques include ion mobility spectrometry, capillary zone electrophoresis, ultraviolet spectroscopy, and infrared spectroscopy. High-performance liquid chromatography (HPLC) is used with ultraviolet, fluorescence, electrochemical, and electrospray mass spectrometric detection methods. Various chromatographic methods have been developed to detect psilocin in body fluids: the rapid emergency drug identification system (REMEDi HS), a drug screening method based on HPLC; HPLC with electrochemical detection; GC–MS; and liquid chromatography coupled to mass spectrometry. Although the determination of psilocin levels in urine can be performed without sample clean-up (i.e., removing potential contaminants that make it difficult to accurately assess concentration), the analysis in plasma or serum requires a preliminary extraction, followed by derivatization of the extracts in the case of GC–MS. A specific immunoassay has also been developed to detect psilocin in whole blood samples. A 2009 publication reported using HPLC to quickly separate forensically important illicit drugs including psilocybin and psilocin, which were identifiable within about half a minute of analysis time.