A method of high-performance liquid chromatography with evaporative light-scattering detector (HPLC-ELSD) has been optimalized for the determination of neutral and polar lipids. Column filled by silica with chemically bonded diol has been used as stationary phase. As mobile phase, a ternary gradient composed from A: hexan-tetrahydrofuran 99:1 (v/v), B: isopropanol-chloroform-acetic acid 82:20:0,01 (v/v/v), C: isopropanol-water-triethylamine 47:47:6 (v/v/v) was used. Calibration curves have been measured in the range 2-200 μg of the injected amount; for individual lipid classes, optimal interlay of experimental data corresponded to the following functions: triacylglycerols - third order polynom (R=0,998), cholesterol esters - exponential dependence (R=0,998), free cholesterol - third order polynom (R=0.9998), ceramid - exponential dependence (R=0,992), cardiolipin - square dependence (R=0,998), phosphatidylethanolamine - exponential dependence (R=0,999), phosphatidylcholine - square dependence (R=0,997), phosphatidylserine - third order polynom (R=0,9985), sphingomyelin - third order polynom (R=0,9997), lysophosphatidylcholine - exponential dependence (R=0,9986). Analysis of the synthetic control sample showed recovery in the range of 82-95%. On the basis od these measurements, concentration of...

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In Escherichia coli, the integral outer membrane (OM) enzyme PagP covalently modifies lipid A by incorporating a phospholipid-derived palmitate chain to fortify the OM permeability barrier. We perturbed the bacterial OM in order to activate PagP and examined if it exerts transcriptional regulation through either of its extracellular or periplasmic active sites. Data from RNA-seq revealed the differential expression of 50 genes upon comparing the E. coli imp4213 (lptD4213) strain NR760∆pagPλInChpagP (shortened to NR760λp in this work), in which PagP is constitutively activated, and the mutant NR760λpY87F carrying the periplasmic residue mutation Y87F. 40 genes were upregulated, and encoded proteins related to anaerobic processes, whereas 10 genes were downregulated, and encoded proteins related to aerobic processes. RNA-seq was followed by a study of differential gene expression using the NanoString nCounter system. Results confirmed a 2.7-fold upregulation of dmsA when we compared the strains NR760λp to NR760λpY87F. We also found a 2.5-fold repression of dmsA transcription when we compared the lptD+ parental strain NR754λp to NR754λpS77A carrying the mutation S77A in the extracellular active site of PagP. We then investigated dmsA transcription using a lacZ reporter gene in plasmid pRS551-lacZ. High basal β-galactosidase activity became attenuated in pagP null mutants. OM perturbation using pentamidine showed that dmsA transcription was repressed. Complementation of the chromosomal ∆pagP deletion with a single copy pBADGr plasmid, expressing PagP under the control of an arabinose-inducible promoter, restored dmsA β-galactosidase activity. We observed partial complementation with the downstream cspE gene, which identified a polar effect of the ∆pagP allele. Through deletion of rpoS, rcsB, cpxA, cpxR, pmrA, pmrB, and fadD in E. coli MC4100, we showed that β-galactosidase activity of pdmsA-lacZ was affected by all of these regulators. Our results indicate that these regulators are involved in PagP-mediated regulation of dmsA transcription under aerobic conditions. / Thesis / Doctor of Philosophy (PhD)

Previous work relating postmortem findings with cause of death have focused on the vitreous portion of the body. This research investigated the link between phospholipids in the brainstem and cause of death. The lipids were extracted by the Folch extraction method and then separated by High Performance Thin Layer Chromatography. These techniques gave excellent separation and resolution. Results showed no link between cause of death and the type of lipids found in the brainstem after death.

Thesis (Ph. D.)--Pennsylvania State University, 1968. / Includes bibliographical references.