Qualitative analysis and quantitative assessment of changes in neutral glycerol lipid molecular species within cells.

Triacylglycerols (TAGs) and diacylglycerols (DAGs) are present in cells as a complex mixture of molecular species that differ in the nature of the fatty acyl groups esterified to the glycerol backbone. In some cases, the molecular weights of these species are identical, confounding assignments of identity and quantity by molecular weight. Electrospray ionization results in the formation of [M+NH4]+ ions that can be collisionally activated to yield an abundant product ion corresponding to the loss of ammonia plus one of the fatty acyl groups as a free carboxylic acid.

N-(3-hydroxyhexanoyl)-l-homoserine lactone is the biologically relevant quormone that regulates the phz operon of Pseudomonas chlororaphis strain 30-84.

Phenazine production by Pseudomonas fluorescens 2-79 and P. chlororaphis isolates 30-84 and PCL1391 is regulated by quorum sensing through the activator PhzR and acyl-homoserine lactones (acyl-HSLs) synthesized by PhzI. PhzI from P.

Detection of the abundance of diacylglycerol and triacylglycerol molecular species in cells using neutral loss mass spectrometry.

Triacylglycerols (TAGs) are neutral lipids present in all mammalian cells as energy reserves, and diacylglycerols (DAGs) are present as intermediates in phospholipid biosynthesis and as signaling molecules. The molecular species of TAGs and DAGs present in mammalian cells are quite complex, and previous investigations revealed multiple isobaric species having molecular weights at virtually every even mass between 600 and 900 Da, making it difficult to assess changes of individual molecular species after cell activation. A method has been developed, using tandem MS and neutral loss scanning, to quantitatively analyze changes in those glyceryl ester molecular species containing identical fatty acyl groups.

Specificity of acyl-homoserine lactone synthases examined by mass spectrometry.

Many gram-negative bacteria produce a specific set of N-acyl-L-homoserine-lactone (AHL) signaling molecules for the purpose of quorum sensing, which is a means of regulating coordinated gene expression in a cell-density-dependent manner. AHLs are produced from acylated acyl-carrier protein (acyl-ACP) and S-adenosyl-L-methionine by the AHL synthase enzyme. The appearance of specific AHLs is due in large part to the intrinsic specificity of the enzyme for subsets of acyl-ACP substrates.