title: Major artifacts encountered in studying biological samples containing ferric protoporphyrin IX.
abstract: Heme (ferric protoporphyrin IX, FP) dissolves very rapidly into the lipid phase of membranes, and a large number of studies have focused attention on its possible toxic effect in whole cells or isolated membranes. However, because of its molecular structure and reactivity, different problems can be encountered during the course of studying biological samples containing FP. In this article, we discuss important interferences by FP and artifacts that can affect the experimental values. First, FP interferes with the Lowry's protein determination; therefore, membranes containing FP are overestimated in their protein content determined by this procedure. Second, freezing membranes at -20 degrees C artifactually increases the local concentration of FP, thereby enhancing FP-induced lipid peroxidation. Third, in the presence of thiol compounds such as N-acetyl cysteine, FP is degraded to products that interfere with the thiobarbituric acid assay, one of the most widely used methods to measure the extent of lipoperoxidation.
authors.affiliation: Department of Pharmacy, Institute of General Physiology and Biochemistry G. Esposito, University of Milan, Milan 20134, Italy. fausta.omodeosale@unimi.it
authors.forename: Fausta
authors.initials: F
authors.lastname: Omodeo Salè
authors.forename: Elisa
authors.initials: E
authors.lastname: Vanzulli
authors.forename: Gigliola
authors.initials: G
authors.lastname: Montorfano
authors.forename: Diego
authors.initials: D
authors.lastname: Monti
mesh_terms: D000111:Acetylcysteine / Q000737:chemistry; D016718:Arachidonic Acid / Q000737:chemistry; D016477:Artifacts; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004910:Erythrocyte Membrane / Q000187:drug effects; D005615:Freezing; D006418:Heme / Q000032:analysis* / Q000737:chemistry / Q000494:pharmacology; D015227:Lipid Peroxidation / Q000187:drug effects; D008563:Membrane Lipids / Q000737:chemistry; D008823:Micelles; D011506:Proteins / Q000032:analysis; D012995:Solubility
chemical_list: D008563:Membrane Lipids; D008823:Micelles; D011506:Proteins; D016718:Arachidonic Acid; D006418:Heme; D000111:Acetylcysteine