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Phenolphthalein False‐Positive Reactions from Legume Root Nodules
Author(s) -
Petersen Daniel,
Kovacs Frank
Publication year - 2014
Publication title -
journal of forensic sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.715
H-Index - 96
eISSN - 1556-4029
pISSN - 0022-1198
DOI - 10.1111/1556-4029.12352
Subject(s) - phenolphthalein , legume , root (linguistics) , root nodule , chemistry , biology , botany , philosophy , linguistics , organic chemistry , nitrogen fixation , nitrogen
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 ( K astle‐ M eyer 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.