Jennifer Gidden

Laser Desorption/Ionization Time‐of‐Flight Mass Spectrometry of Triacylglycerols and Other Components in Fingermark Samples*

Abstract:  The chemical composition of fingermarks could potentially be important for determining investigative leads, placing individuals at the time of a crime, and has applications as biomarkers of disease. Fingermark samples containing triacylglycerols (TAGs) and other components were analyzed using laser desorption/ionization (LDI) time‐of‐flight mass spectrometry (TOF MS). Only LDI appeared to be useful for this application while conventional matrix‐assisted LDI‐TOF MS was not. Tandem MS was used to identify/confirm selected TAGs. A limited gender comparison, based on a simple t‐distribution and peaks intensities, indicated that two TAGs showed gender specificity at the 95% confidence level and two others at 97.5% confidence. Because gender‐related TAGs differences were most often close to the standard deviation of the measurements, the majority of the TAGs showed no gender specificity. Thus, LDI‐TOF MS is not a reliable indicator of gender based on fingermark analysis. Cosmetic ingredients present in some samples were identified.

A rapid separation technique for overcoming suppression of triacylglycerols by phosphatidylcholine using MALDI-TOF MS

Phospholipids and triacylglycerols (TAGs) are important classes of lipids in biological systems. Rapid methods have been developed for their characterization in crude samples, including MALDI time-of-flight MS. For mixtures, MALDI often selectively shows only some components. For example, phosphatidylcholine (PC) suppresses detection of other lipids. Most rapid MS methods detect either TAGs or phospholipids but not both. Herein, we demonstrate a simple approach to rapidly screen mixtures containing multiple lipid classes. To validate this approach, reference lipids [PC, tripalmitin (PPP), and phosphatidyl-ethanolamine (PE)] and real samples (beef, egg yolk) were used. In a binary mixture with a strong suppressor (PC), PPP was greatly suppressed. After a simple separation, suppression was virtually eliminated. A mixture of nominally nonsuppressing lipids (PE and PPP) was not adversely affected by separation. Ground beef and egg yolk were used to demonstrate detection of known lipid compositions where other methods have missed one or more lipids or lipid classes. Separation was performed using solid phase extraction with a PrepSep florisil column. A 10 min separation allows rapid screening for lipids and changes in lipids. It is sufficient to clearly detect all lipids and overcome suppression effects in complex lipid mixtures.

Switchgrass Water Extracts: Extraction, Separation and Biological Activity of Rutin and Quercitrin

Switchgrass (Panicum virgatum L.) has recently received significant attention as a possible feedstock for the production of liquid fuels such as ethanol. In addition, switchgrass may also be a source of valuable co-products, such as antioxidants, and our laboratory recently reported that switchgrass contains policosanols and alpha-tocopherol. Motivation for this work began when a switchgrass sample was extracted with water at 50 degrees C and was then tested for low-density lipoprotein (LDL) oxidation inhibition activity using the Thiobarbituric Acid Reactive Substances (TBARS) assay. The TBARS results showed that the switchgrass water extracts inhibited LDL oxidation by as much as 70% in comparison to the control. Liquid chromatography coupled with mass spectrometry (LC-MS) and high performance liquid chromatography (HPLC) were used to identify the compounds that were responsible for LDL oxidation inhibition activity as flavonoids: quercitrin (quercetin-3-O-rhamnoside) and rutin (quercetin-3-O-rutinoside). To maximize flavonoid concentrations, switchgrass was then extracted with water and 60% methanol at different temperatures. The 60% methanol treatment resulted in higher rutin and quercitrin yields when compared to water-only extraction; however, the use of this solvent would not be practical with current biorefinery technology. Centrifugal partition chromatography (CPC) was then used to purify rutin and quercitrin from the switchgrass water extract, which were then tested via the TBARS assay and shown to exhibit lipid peroxidation inhibition activity similar to that obtained with pure flavonoid standards. This is the first report on the presence of rutin and quercitrin in switchgrass. The results support the extraction of viable coproducts from switchgrass prior to conversion to liquid fuel.

Production and Fractionation of Xylose Oligomers from Switchgrass Hemicelluloses Using Centrifugal Partition Chromatography

Xylose oligomers are of interest to many fields of study and are intermediate reaction products of the hydrolysis of hemicelluloses. Protocols to generate xylose oligomers are reported, but these methods lead to the production of a pool of nonfractionated xylose oligomers with a wide range in degree of polymerization (DP). This work used switchgrass hemicelluloses as feedstock for production of purified xylose oligomers. Switchgrass hemicelluloses were autohydrolyzed at 160°C. Yields of xylobiose, xylotriose, xylotetraose, xylopentose, and xylohexose were 24, 34, 23, 19, and 38 mg, respectively, per g of hemicelluloses. The crude xylose oligomer mixture was fractionated using centrifugal partition chromatography (CPC) with a butanol:methanol:water (5:1:4, V:V:V) solvent system. Xylose oligomers with a DP from two to six were successfully purified. Purities obtained by CPC separation, as calculated by mass of a given oligomer divided by the total mass of detected oligomers and degradation products and then reported on a percent basis, were 75 ± 7%, 89 ± 1, 87% ± 2, 77 ± 6%, and 69 ± 12% for xylobiose, xylotriose, xylotetraose, xylopentose, and xylohexose, respectively. This work illustrates that a CPC-based process could be used to fractionate switchgrass xylose oligomers reference standards, which are currently not commercially available.