New forensic method identifies people using human hair proteins
The researchers believe that the number of individual protein markers that can be used to differentiate people could go as high as 1,000. Protein markers also can be found in other tissue types, such as shed skin cells, bones and teeth, and the scientists have started studying how people can be identified using the latter two tissues.
Using their current sample sizes, the researchers are able to find enough markers to provide a unique pattern for an individual that would distinguish that person among a population of one million.
The new method, in effect, addresses a 2009 National Research Council report on forensic science that detailed the weaknesses of many current approaches and reported an urgent need for new science-based forensic methods.
“Nuclear DNA is the gold standard for human identification, but it is quite fragile,” Hart said. “When the DNA molecule degrades from light, heat exposure or other environmental conditions, it becomes useless for identification.”
Proteins more robust than DNA
Proteins are chemically more robust than nuclear DNA. That point was illustrated by the team’s work as the researchers found protein markers in human hair from six skeletal remains taken from cemeteries in the greater London area dating back about 150 to 250 years.
Proteins are long molecular chains formed from amino acids — the basic building blocks of life. DNA is the pattern or template the body uses to produce proteins.
In the research, the protein markers used by the scientists have been variants in the proteins resulting from amino acid substitutions that stem from DNA mutations, and are known as single amino acid polymorphisms (SAPs).
The team’s research kicked into high gear in March 2013 when biochemist Glendon Parker, the inventor of the protein identification concept and then an associate professor at Utah Valley University, came to work at LLNL. Parker is the lead author of the PLOS ONE paper.
“Glendon’s clever invention was to realize that the uniqueness of SAPs could be used to identify individual people, and the robustness of the technique relies on its link back to DNA,” said Deon Anex, an LLNL chemist and co-author.
Although people do not inherit proteins, they do inherit the DNA that produces their proteins.
“As a result, there is a link between the protein markers that we find and a person’s DNA. There are two reasons why this is particularly important: the DNA is unique to each individual and it is inherited from a person’s parents,” Anex said.
Currently, the sample preparation, instrument run time and analysis period for the protein identification method requires about 2 1/2 days, Anex said, noting the team expects the cost to be competitive with other similar technologies.
“The discovery phase has been quite complex, but once the technique is established, we believe it can be made into a routine procedure for use in crime labs.”
The researchers are seeking to establish a set of 90-100 protein markers that would be sufficient to distinguish an individual among the world’s population using a single hair.
LLNL notes the current research funding comes from LLNL’s Laboratory Directed Research & Development program, which supports high-risk, potentially high-payoff projects at the forefront of science and technology.
— Read more in Glendon J. parker et al., “Demonstration of Protein-Based Human Identification Using the Hair Shaft Proteome,” PLOS One (7 September 2016) (doi: org/10.1371/journal.pone.0160653)
