title: Phenolphthalein false-positive reactions from legume root nodules.
abstract: Presumptive tests for blood play a critical role in the examination of physical evidence and in the determination of subsequent analysis. The catalytic power of hemoglobin allows colorimetric reactions employing phenolphthalein (Kastle-Meyer test) to indicate "whether" blood is present. Consequently, DNA profiles extracted from phenolphthalein-positive stains are presumed to be from blood on the evidentiary item and can lead to the identification of "whose" blood is present. Crushed nodules from a variety of legumes yielded phenolphthalein false-positive reactions that were indistinguishable from true bloodstains both in color quality and in developmental time frame. Clothing and other materials stained by nodules also yielded phenolphthalein false-positive reactivity for several years after nodule exposure. Nodules from leguminous plants contain a protein (leghemoglobin) which is structurally and functionally similar to hemoglobin. Testing of purified leghemoglobin confirmed this protein as a source of phenolphthalein reactivity. A scenario is presented showing how the presence of leghemoglobin from nodule staining can mislead investigators.
authors: Oregon State Police Forensic Services Division, Portland Metro Forensic Laboratory, 13309 SE 84th Avenue, Suite 200, Clackamas, OR 97015.
authors: Daniel
authors: D
authors: Petersen
authors: Frank
authors: F
authors: Kovacs
mesh_terms: D001801:Blood Stains; D003124:Colorimetry; D004247:DNA / Q000302:isolation & purification; D016172:DNA Fingerprinting; D019075:Electrophoresis, Capillary; D007887:Fabaceae / Q000737:chemistry*; D005189:False Positive Reactions; D006454:Hemoglobins / Q000737:chemistry; D006801:Humans; D007874:Leghemoglobin / Q000737:chemistry / Q000302:isolation & purification*; D020113:Phenolphthalein; D016133:Polymerase Chain Reaction; D011934:Reagent Strips; D053204:Root Nodules, Plant / Q000737:chemistry*
chemical_list: D006454:Hemoglobins; D007874:Leghemoglobin; D011934:Reagent Strips; D020113:Phenolphthalein; D004247:DNA
keywords: CSF1PO; D13S317; D16S539; D18S51; D19S433; D21S11; D2S1338; D3S1358; D5S818; D7S820; D8S1179; DNA extraction; DNA typing; FGA; Hemastix; Kastle-Meyer; TH01; TPOX; amelogenin; blood test; bloodstain; capillary electrophoresis; false-positive; forensic science; hemoglobin; leghemoglobin; legume; phenolphthalein; polymerase chain reaction; presumptive; short tandem repeats; vWA