Detecting biological threats in five milliseconds might be the difference between life and death for modern soldiers.
The scenario is frightening. A terrorist group modifies clusters of anthrax bacteria so they resemble pollen grains. The life-threatening powder is deposited on the ground in anticipation of U.S. troops. The challenge to both scientists and military planners is to detect this camouflaged biological warfare agent in time so that soldiers could safely avoid the contaminated area.
Two ORNL researchers are confident their unique tandem mass spectrometry configuration, a type of hybrid mass analyzer, and its operating method could be further developed to sense such a threat. They also believe that the hybrid mass analyzer, developed with funding from ORNL's Laboratory Directed Research and Development Program, is a strong candidate for the next-generation technology needed by the U.S. military to detect known and unknown biological warfare agents.
"This instrument, which might be up to 1000 times faster than current tandem mass spectrometers, could be the basis for a next-generation detector of chemical and biological threats," says Doug Goeringer. "Proper use of the instrument by proteomics researchers would significantly speed up data acquisition for protein identification. Each protein is identified based on its molecular weight and its unique sequence of amino acids coded for by DNA. Bioinformatics software, by sorting through all the data, could then identify protein biomarkers of specific microbes."
The analyzer was conceived by Goeringer, a scientist in ORNL's Chemical Sciences Division, and Scott McLuckey, a former ORNL researcher. CSD's Marc Wise helped Goeringer build the instrument prototype. Wise led the development of the ion trap mass spectrometer at the heart of the Block II chemical biological mass spectrometer (CBMS) used by the U.S. Army on its ground reconnaissance vehicles to detect chemical warfare agents in war zones. This year the Army is testing the mass spectrometer's ability to detect biological warfare agents.
The hybrid mass analyzer, which separates ions based on their mass-to-charge ratio, consists of a radiofrequency ion trap, a gas-filled radiofrequency quadrupole collision chamber, and a time-of-flight mass spectrometer arranged in a tandem configuration. The instrument can be operated to generate a three-dimensional mass spectrum of parent ions and associated product ions, formed when the parent ions' internal energies are raised until they fragment into lighter-weight ions.
Unlike the CBMS, the new instrument can almost simultaneously analyze a heterogeneous population of ions whereas the CBMS focuses on analyzing one homogeneous population at a time. The CBMS ion trap repeatedly selects one type of parent ion to store, fragment into product ions, and mass analyze, while expelling all other types of parent ions from the sample. The trap is then refilled with another sample, and the process is repeated multiple times.
"In our device no parent ions are thrown away from the trap because it is used only to store and sort them," Goeringer says. "The ions dissociate in the collision chamber, and the resultant fragment ions are subsequently mass analyzed in the time-of-flight spectrometer, which is about 1000 times faster than the ion trap. Thus, the ion trap doesn't have to be refilled each time the next type of parent ion is analyzed."
"The CBMS ion trap requires 5 seconds to analyze ions of 25 different chemical warfare agents, toxic industrial chemicals, and environmental pollutants," Wise says. "Those same 25 different ions can be identified in only 5 milliseconds by the hybrid mass analyzer."
The CBMS can detect bacteria but not viruses because this instrument focuses on fatty acids found only in bacteria. The practical benefits of the hybrid mass analyzer stem from its ability to identify quickly harmful viruses, as well as bacteria, because the technology can detect proteins found in both types of biological threats.
In situations where the difference between life and death can be measured in seconds, the hybrid mass analyzer may prove as valuable to modern soldiers as the helmet was to their predecessors.
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