title: Genotyping single nucleotide polymorphisms using intact polymerase chain reaction products by electrospray quadrupole mass spectrometry.
abstract: Both single nucleotide polymorphisms (SNPs) and mutations are commonly observed in the gene encoding the tumor suppressor protein, p53. SNPs occur at specific locations within genes whereas mutations may be distributed across large regions of genes. When determining nucleotide differences, mass spectrometry is the only method other than Sanger sequencing which offers direct structural information. Electrospray ionization (ESI) quadrupole mass spectrometry (MS) analysis of intact polymerase chain reaction (PCR) products was performed following a simple purification and on-line heating to limit ion adduction. The PCR products were amplified directly from genomic DNA rather than plasmids, as in our previous work. Two known polymorphisms of the p53 gene were genotyped. A cytosine (C) or guanine (G) transversion, designated C <--> G (G <--> C on the opposite strand), were each detected by a 40.0 Da change upon ESI quadrupole MS analysis. Using known PCR products as standards, the genotypes determined for 10 human samples corresponded with restriction fragment length polymorphism (RFLP) analysis. Cytosine/thymine (T) transitions, designated C <--> T (G <--> A on the opposite strand), were also genotyped by ESI-MS. This SNP is discriminated by a 15.0 Da change on one strand (C <--> T) and a 16.0 Da change on the other (G <--> A). Appropriate sample preparation and instrumental configuration (including heated sample inlet syringe and MS source), to limit adducts, are both vital for successful ESI quadrupole MS analysis of intact PCR products.
authors.affiliation: Department of Microbiology and Immunology, University of South Carolina, School of Medicine, Columbia, SC 29208, USA.
authors.forename: J J
authors.initials: JJ
authors.lastname: Walters
authors.forename: W
authors.initials: W
authors.lastname: Muhammad
authors.forename: K F
authors.initials: KF
authors.lastname: Fox
authors.forename: A
authors.initials: A
authors.lastname: Fox
authors.forename: D
authors.initials: D
authors.lastname: Xie
authors.forename: K E
authors.initials: KE
authors.lastname: Creek
authors.forename: L
authors.initials: L
authors.lastname: Pirisi
mesh_terms: D004247:DNA / Q000737:chemistry / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D016158:Genes, p53 / Q000235:genetics; D005838:Genotype; D006801:Humans; D009711:Nucleotides / Q000737:chemistry* / Q000235:genetics; D010957:Plasmids / Q000235:genetics; D011110:Polymorphism, Genetic / Q000235:genetics*; D012150:Polymorphism, Restriction Fragment Length; D020133:Reverse Transcriptase Polymerase Chain Reaction; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D009711:Nucleotides; D004247:DNA