A High Throughput Ambient Mass Spectrometric Approach to Species Identification and Classification from Chemical Fingerprint Signatures
Abstract
A high throughput method for species identification and classification through chemometric processing of direct analysis in real time (DART) mass spectrometry-derived fingerprint signatures has been developed. The method entails introduction of samples to the open air space between the DART ion source and the mass spectrometer inlet, with the entire observed mass spectral fingerprint subjected to unsupervised hierarchical clustering processing. A range of both polar and non-polar chemotypes are instantaneously detected. The result is identification and species level classification based on the entire DART-MS spectrum. Here, we illustrate how the method can be used to: (1) distinguish between endangered woods regulated by the Convention for the International Trade of Endangered Flora and Fauna (CITES) treaty; (2) assess the origin and by extension the properties of biodiesel feedstocks; (3) determine insect species from analysis of puparial casings; (4) distinguish between psychoactive plants products; and (5) differentiate between Eucalyptus species. An advantage of the hierarchical clustering approach to processing of the DART-MS derived fingerprint is that it shows both similarities and differences between species based on their chemotypes. Furthermore, full knowledge of the identities of the constituents contained within the small molecule profile of analyzed samples is not required.
Introduction
One of the manifestations of the genetic differences that distinguish one species from another is in the profile of constitutively present small molecules they contain, also known as the metabolome. Since the small-molecule profile of an organism ultimately reflects the genes that distinguish it, the information content of the metabolome might be just as well suited to genomic fingerprinting and assessment of genetic relatedness between species as the genomes themselves. There are several reasons why it would be useful to be able to accurately correlate the signature of small molecules observed within an organism to its overall systems biology. The observation of the composite of small-molecule biomarkers could provide a real-time view of gene expression activity, enable the monitoring of the status of cellular transcriptomes and proteomes, provide a means of assessing the evolutionary history of organisms and provide an avenue for the rapid monitoring of the success of gene knockouts and knockdowns, among other uses. Although these applications can be accomplished by phylogenetic methods, the paucity of mapped and/or annotated genes for the vast majority of fauna and flora in existence makes this approach impossible for all but a select group of mostly model systems.
For further information: https://www.nature.com/articles/srep11520