Forensic scientists may soon have another tool in their arsenal that can help them identify criminals. DNA profiling currently helps investigators identify perpetrators of crime but hair protein analysis could one day make it more difficult for criminals to evade justice.
Researchers from the Lawrence Livermore National Laboratory (LLNL) in the United States found that analysis of proteins that are found in human hair can be as effective as using DNA in identifying unique individuals.
The problem with using hair shafts in criminal investigations is that these these do not have nuclear DNA, the chemical blueprint that a person inherits from both parents, and while hair shafts may have mitochondrial DNA, this is passed down matrilineally (through the mother) so there are limits as to how it can be used as a means for investigation.
DNA is unique to each person so it is commonly used for identification in forensic science. However, environmental and chemical processes pose problems in DNA profiling because these can degrade DNA and limit its usefulness over time. Proteins, however, are more stable compared with DNA and have variations that are unique to the individual.
Each strand of hair is composed of proteins and DNA provides the blueprint for these proteins. In a research published in the journal PLOS ONE, Brad Hart from the LLNL and colleagues established that DNA mutations in a person cause small changes in the building blocks of proteins.
The frequency of these tiny changes can be measured and since the number and pattern of each individual's hair protein markers are unique, protein analysis can be used in a similar manner DNA is used to identify a person.
"Coding quirks found in an individual's DNA (called single nucleotide polymorphisms, or SNPs) will translate into recognizable variants in the proteins, known as single amino acid polymorphisms (SAPs)," Melissa Healy of Los Angeles Times explained. "These SAPs are the protein markers that could guide future forensic scientists in identifying an individual even when DNA is not available."
Researchers said that while individual protein markers that can be utilized to differentiate people can be as many as 1,000, about 185 protein markers appear enough to distinguish a person from a population of 1 million.
"This study demonstrates that quantifiable measures of identity discrimination and biogeographic background can be obtained from detecting genetically variant peptides in hair shaft protein, including hair from bioarchaeological contexts," the researchers reported in their study.
