Submitted to: Lipids
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/15/2015
Publication Date: 12/11/2015
Citation: Byrdwell, W.C. 2015. The simulacrum system as a construct for mass spectrometry of triacylglycerols and others. Lipids. 51:211-227.
Interpretive Summary: A new construct called a simulacrum is presented, which shows the framework behind recent publications that used "Critical Ratios" to describe structural characteristics of triacylglycerols (TAGs), also called triglycerides. A simulacrum, as defined by French philosopher Jean Baudrillard in the book Simulacrum and Simulation, is a simulation constructed to be so thorough at replacing the system it models that it renders the original system unnecessary. The simulacrum system presented provides direct information about the degree of unsaturation of TAGs and the locations and grouping of fatty acids in TAGs better than the raw abundances in mass spectra. Better yet, it provides a compact data set that allows a library of mass spectra to be reproduced using fewer values than the original abundances. Thus, it provides more information in fewer values.
Technical Abstract: A construct called a simulacrum is defined that provides all possible solutions to a sum of two mass spectral abundances, based on values (abundances) or ratios of those values. The defined construct is applied to atmospheric pressure chemical ionization (APCI) mass spectrometry (MS) of triacylglycerols (TAG). A simulacrum has precisely defined components, specifically a simulacrum sum, four Possibilities to Observe, two Cases, and eight solutions. A simulacrum with no restrictions is the First General Form of a Simulacrum (FGFS). When one value is specified to be 1 (as in mass spectrometry), the construct is called a Unit Simulacrum (US), also called the First Specified Form of a Simulacrum (FSFS). When one value is 1 and no value can be greater than 1 (the two specifications dictated by mass spectrometry), the construct is called the Second Specified Form of a Simulacrum (SSFS), or the Mass Spectrometry Simulacrum (MSS). Simulacra are used with three Critical Ratios calculated from raw abundances in mass spectra of TAG to provide structural information about the degree of unsaturation in TAG, the identity and quantity of regioisomers, and other structural characteristics. Three-level-deep nested simulacrum solutions yield the recently reported Updated Bottom Up Solution, from which the protonated molecule, [MH]+, and all diacylglycerol-like fragments, [DAG]+, of TAG can be reproduced from the Critical Ratios. Thus, the simulacrum solutions constitute a reduced data set in which more information is provided in fewer values than raw abundances, such that the Critical Ratios constitute a compact library of mass spectra.