The solid-phase microextraction (SPME) followed by gas chromatography-mass spectrometry (GC-MS) was used for the analysis of phenolic and other aromatic compounds in honey samples from different floral origin. Different parameters affecting the efficiency of the extraction, such as the type of the stationary phase of the fiber, NaCl and acetic acid addition, and extraction time, were optimized for the detection of the maximum number of compounds in the shortest analysis time. A total of 31 compounds were detected, with most of them identified and quantified by GC-MS. The principal component analysis (PCA) was applied to the data matrix; the results allowed for the differentiation between honeydew and nectar honeys on the basis of the salicylic acid concentration. It was found that this acid has a high contribution in the honeydew group (71.2-705.9 microg/100 g of honey) compared to the nectar honey group (0-47.6 microg/100 g of honey). The comparison of data in each honey group enabled us to characterize the floral source of some honeys using some aromatic compounds as markers.

Macrophage infectivity potentiator (MIP) was originally reported to be a chlamydial lipoprotein from experiments showing incorporation of radiolabeled palmitic acid into native and recombinant MIP; inhibition of posttranslational processing of recombinant MIP by globomycin, known to inhibit signal peptidase II; and solubility of native MIP in Triton X-114. However, the detailed structural characterization of the lipid moiety on MIP has never been fully elucidated. In this study, bioinformatics and mass spectrometry analysis, as well as radiolabeling and immunochemical experiments, were conducted to further characterize MIP structure and subcellular localization. In silico analysis showed that the amino acid sequence of MIP is conserved across chlamydial species. A potential signal sequence with a contained lipobox was identified, and a recombinant Chlamydiae are obligately intracellular gram negative bacteria that are major human pathogens capable of causing a wide range of diseases (11,12,24,34,43). All chlamydiae share a characteristic biphasic cycle of development with infectious, spore-like elementary bodies (EB) and intracellular dividing reticulate bodies (RB) that are metabolically active and inhabit a nonfusogenic inclusion (46). The mechanisms by which chlamydiae induce diseases are poorly understood but may include a proinflammatory immune response to chlamydial antigen (22), even if this antigen has yet to be unequivocally revealed (62). In many bacterial diseases, lipoproteins play a prominent role in pathogenesis, with a ubiquitous presence as major constituents of the bacterial cell wall. However, little is known about the actual existence and role of lipoproteins in chlamydiae. One of the few lipoproteins characterized so far, in Chlamydia trachomatis, is macrophage infectivity potentiator (MIP), which was identified as a lipoprotein by incorporation of radiolabeled palmitic acid into the native and recombinant proteins (41), inhibition of posttranslational processing of recombinant MIP (rMIP) by globomycin (a specific inhibitor of signal peptidase II [31]), and solubility of native MIP in Triton X-114 (42). Other studies have shown that C. trachomatis MIP is a 27-kDa membrane protein located in both EB and RB (38), with a COOH-terminal region showing high homology with eukaryotic and prokaryotic FK506 binding proteins (FKBP) (41) and exhibiting peptidyl-prolyl cis/trans isomerase (PPIase) activity (40). However, no evidence supporting the presence of a classical lipoprotein feature in MIP, similar to the murein lipoprotein from Escherichia coli (25), the best characterized bacterial lipoprotein, has been shown.Since chlamydiae are notably very atypical bacteria, phylogenetically separated from other eubacteria (48), we have conducted a detailed structural characterization of MIP. The probable signal sequence was determined by in silico analysis, and the cysteine in position 20 (cysteine 20 ) was predicted to be the lipobox cysteine (33,44). To assess the involvement of cysteine 20 in lipid modifi...

To determine the limitations of electrospray mass spectrometry for the study of condensed-phase chemistry, it is important to understand the origin of cases for which the electrospray mass spectra, which are a measure of the relative abundances of gas-phase ions, do not reflect the equilibrium ion abundances in the solution electrosprayed. One such divergent case is that of free-base octaethylporphyrin. Under conditions for which this porphyrin is present in solution predominantly as the doubly charged, diprotonated molecule, the predominant ionic species observed in the electrospray mass spectrum is the singly charged, monoprotonated molecule. In this paper, direct optical spectroscopic measurements of the ions in solution (absorption spectra) and in the electrospray plume (fluorescence excitation spectra) are correlated with the ion distribution observed in the gasphase (as reflected in the electrospray mass spectra) to determine at what point in the electrospray process and by what mechanism(s) the transformation from dication to monocation occurs. The data indicate that the major portion of the doubly protonated porphyrin species originally present in solution are converted to singly protonated species relatively late in the electrospray process, during the latter stages of droplet desolvation in the atmospheric/vacuum interface of the mass spectrometer, via the loss of a charged solvent molecule/cluster.An electrospray ion source is an electrostatic spray device that assists the transfer of analyte species in a liquid solution to the gas-phase where they can be detected by a mass Spectrometer.' This analysis technique, termed electrospray mass spectrometry (ES-MS), has rapidly become the mass spectrometry method of choice for the analysis of a wide range of polar, nonvolatile and thermally labile compounds, ranging from elemental species'. to very high molecular weight biop~lymers.~.~ Best analytical results with ES-MS are usually obtained for analytes that are ionic in solution and, in general, it is believed that the ions observed in the gas phase are, at a minimum, a qualitative reflection of the equilibrium ion concentrations in the original liquid sample solution.' A number of experimental studies support this general view."I5 However, an increasing number of reports have shown that the distribution of gas-phase ions observed can be quite different from the distribution known to be in the solution on the basis of calculated solution equilibria.IG2' As a result of these conflicting observations, an important area of fundamental ES-MS research today is an exploration of the various factors that determine the correspondence (or lack thereof) among the ionic species in the original sample solution and the ions ultimately observed in the gas phase. The findings of this research will have ramifications in many ES-MS applications, including, among others, general qualitative and quantitative analys~s ?~ the study of noncovalent solution interactions of biomolecular specie^,'^ and the use of ES-MS for elemental...

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