The controversial discussion about the role of Chlamydia pneumoniae in atherosclerosis cannot be solved without a reliable diagnosis that allows discrimination between past and persistent infections. Using a proteomic approach and immunoblotting with human sera, we identified 31 major C. pneumoniae Ags originating from 27 different C. pneumoniae proteins. More than half of the proteins represent Chlamydia Ags not described previously. Using a comparative analysis of spot reactivity Pmp6, OMP2, GroEL, DnaK, RpoA, EF-Tu, as well as CpB0704 and CpB0837, were found to be immunodominant. The comparison of Ab-response patterns of sera from subjects with and without evidence for persisting C. pneumoniae, determined by multiple PCR analysis of PBMC and vasculatory samples, resulted in differential reactivity for 12 proteins, which is not reflected by reactivity of the sera in the microimmunofluorescence test, the current gold standard for serodiagnosis. Although reactivity of sera from PCR-positive donors was increased toward RpoA, MOMP, YscC, Pmp10, PorB, Pmp21, GroEL, and Cpaf, the reactivity toward YscL, Rho, LCrE, and CpB0837 was decreased, reflecting the altered protein expression of persisting C. pneumoniae in vitro. Our data provide the first evidence of a unique Ab-response pattern associated with persistent C. pneumoniae infections, which is a prerequisite for the serological determination of persistently infected patients.

The liver is the most central organ and the largest gland of the body that influences and controls a variety of metabolic and catabolic processes. It produces inconceivable many essential proteins, is responsible for the recovery of various food components, degrades toxins, mediates the bile production, and is involved in the excretion of unwanted metabolites. Several of these anabolic or catabolic functions of the liver depend on trace elements. These are either integral part of enzymes, cofactors, or act as chemical catalysts. Therefore, a lack of trace elements can lead to organ failure or systemic illness. Conversely, excessive hepatic trace element deposition resulting from genetic disorders, intoxication, extensive dietary supply, or long-term parenteral nutrition may cause hepatic inflammation, fibrosis, cirrhosis, and even hepatocellular carcinoma. Although specific serum parameters currently allow rough assessment of metal deficit and excess, the precise quantification of hepatic metal content in liver is presently only possible by different titration or staining techniques of biopsy specimens. Recently, novel innovative metal imaging techniques were developed that are on the way to replace these traditional methods. In the present review, we summarize the function of different trace elements in liver health and disease and discuss the present knowledge on how quantitative biometal imaging techniques such as synchrotron X-ray fluorescence microscopy, secondary ion mass spectrometry, and laser ablation inductively coupled plasma mass spectrometry enrich diagnostics in the detection and quantification of hepatic metal disorders. We will further discuss sample preparation, sensitivity, spatial resolution, specificity, quantification strategies, and potential future applications of metal bioimaging in experimental research and clinical daily routine. © 2015 Wiley Periodicals, Inc. Mass Spec Rev 35:666-686, 2016.

Structure and dynamics of membrane-bound light-harvesting pigment-protein complexes (LHCs), which collect and transmit light energy for photosynthesis and thereby play an essential role in the regulation of photosynthesis and photoprotection, were identified and characterized using high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). LHCs from photosystem n (LHCn) were isolated from the thylakoid membrane of Arabidopsis thaliana leaves after light stress treatment using sucrose density gradient centrifugation, and separated by gel-filtration into LHCn subcomplexes. Using reversed-phase high-performance liquid chromatography and two-dimensional (2D) gel electrophoresis, the LHCn proteins, Lhcbl-6 and fibrillins, were efficiently separated and identified by FIICR-MS. Some of the LHcn subcomplexes were shown to migrate from photosystem n to photosystem I as a result of short-term adaptation to changes in light intensity. In the mobile LHCn subcomplexes, decreased levels of fibrillins and a modified composition of LHCn protein isoforms were identified compared to the tightly bound LHcn subcomplexes. In addition, FTICR-MS analysis revealed several oxidative modifications of LHCn proteins. A number of protein spots in 2D gels were found to contain a mixture of proteins, illustrating the feasibility of high-resolution mass spectrometry to identify proteins that remain unseparated in 2D gels even upon extended pH gradients. (J

The primary visual cortex (area V1) is an extensively studied part of the cerebral cortex with well-characterized connectivity, cellular and molecular architecture and functions (for recent reviews see Amunts and Zilles, Neuron 88:1086–1107, 2015; Casagrande and Xu, Parallel visual pathways: a comparative perspective. The visual neurosciences, MIT Press, Cambridge, pp 494–506, 2004). In humans, V1 is defined by heavily myelinated fibers arriving from the radiatio optica that form the Gennari stripe in cortical layer IV, which is further subdivided into laminae IVa, IVb, IVcα and IVcβ. Due to this unique laminar pattern, V1 represents an excellent region to test whether multimodal mass spectrometric imaging could reveal novel biomolecular markers for a functionally relevant parcellation of the human cerebral cortex. Here we analyzed histological sections of three post-mortem brains with matrix-assisted laser desorption/ionization mass spectrometry imaging and laser ablation inductively coupled plasma mass spectrometry imaging to investigate the distribution of lipids, proteins and metals in human V1. We identified 71 peptides of 13 different proteins by in situ tandem mass spectrometry, of which 5 proteins show a differential laminar distribution pattern revealing the border between V1 and V2. High-accuracy mass measurements identified 123 lipid species, including glycerolipids, glycerophospholipids and sphingolipids, of which at least 20 showed differential distribution within V1 and V2. Specific lipids labeled not only myelinated layer IVb, but also IVa and especially IVc in a layer-specific manner, but also and clearly separated V1 from V2. Elemental imaging further showed a specific accumulation of copper in layer IV. In conclusion, multimodal mass spectrometry imaging identified novel biomolecular and elemental markers with specific laminar and inter-areal differences. We conclude that mass spectrometry imaging provides a promising new approach toward multimodal, molecule-based cortical parcellation.Electronic supplementary materialThe online version of this article (10.1007/s00429-018-1660-y) contains supplementary material, which is available to authorized users.

In the present study. the metal-containing proteins in the roots ofCu-tole rant plant ElsllOltzia splendens were investigated. The proteins from the plant roots were extracted and separated by two-dimensional gel electrophoresis (2D GE). Las er ablation inductively coupl ed plasma mass spectrometry (LA-ICP-MS) was used to screen metal-containing proteins on the dried 2D gels. Images of Cu. Zn. Na. Mg. K. Ca. Mn , Fe. P and S. and also of Ag. were obtained by scanning the gel (line by line) using the LA-ICP-MS techniques deve loped in our laboratory. Cu-. Zn-and Mg-containing proteins were found in the gel sections ofinterest via LA-ICP-MS imaging. These protein spots were then in-gel digested with trypsin and analyzed by liquid chromatography tandem mass spectrometry (LC-MS/MS) for identification. The mechanisms involved in Cu tolerance and accumulation were also discussed.

The combination of MALDI-TOF-mass spectrometry with gel electrophoretic separation using protein visualization by staining procedures involving such as Coomassie Brilliant Blue has been established as a widely used approach in proteomics. Although this approach has been shown to present high detection sensitivity, drawbacks and limitations frequently arise from the significant background in the mass spectrometric analysis. In this chapter we describe an approach for the application of MALDI-MS to the mass spectrometric identification of proteins from one-dimensional (1D) and two-dimensional (2D) gel electrophoretic separation, using stain-free detection and visualization based on native protein fluorescence. Using the native fluorescence of aromatic protein amino acids with UV transmission at 343 nm as a fast gel imaging system, unstained protein spots are localized and, upon excision from gels, can be proteolytically digested and analyzed by MALDI-MS. Following the initial development and testing with standard proteins, applications of the stain-free gel electrophoretic detection approach to mass spectrometric identification of biological proteins from 2D-gel separations clearly show the feasibility and efficiency of this combination, as illustrated by a proteomics study of porcine skeleton muscle proteins. Major advantages of the stain-free gel detection approach with MALDI-MS analysis are (1) rapid analysis of proteins from 1D- and 2D-gel separation without destaining required prior to proteolytic digestion, (2) the low detection limits of proteins attained, and (3) low background in the MALDI-MS analysis.

We describe here an approach for the mass spectrometric identification of proteins in proteome analysis from 10-and 2D-gel electrophoretic separation, using stain-free detection and visualization based on native fluorescence, Staining procedures such as by Coomassie Brilliant Blue, silver salts and fluorescent dyes are typically employed to visualize gel-separated protein bands with high detection sens itivity, however all of these staining procedures produce significant background in mass spectrometric analysis. Using the native fluorescence of aromatic protein amino acids with UV transmission at 343 nm as a fast gel imaging system, unstained visualized protein spots were localised. Upon excision from gels using precise spot picking tools, gel spots were proteolytically digested and analysed by matrix-assisted laser desorption-ionisation mass spectrometry (MALDI-MSl. After initial development and testing using 10gel separated standard proteins, the stain-free detection approach was successfu lly applied to MALDI-MS protein identifications in (il, bacterial proteomics of Desul!otignum phosphitoxidans, and (iil, in porcine skeleton muscle proteomics. Major advantages of the stain-free gel detection approach are (il, rapid analysis of proteins from 10-and 2D-gel separations without desta ining required before proteolytic digestion; (iil, low detection limits of proteins in gels; and (iiil, low background in the mass spectrometric analysis of proteins.

We report here an affinity-proteomics approach that combines 2D-gel electrophoresis and immunoblotting with high performance mass spectrometry to the identification of both full length protein antigens and antigenic fragments of Chlamydophila pneumoniae (C. pneumoniae). The present affinity-mass spectrometry approach effectively utilized high resolution FTICR mass spectrometry and LC-tandem-MS for protein identification, and enabled the identification of several new highly antigenic C. pneumoniae proteins that were not hitherto reported or previously detected only in other Chlamydia species, such as Chlamydia trachomatis. Moreover, high resolution affinity-MS provided the identification of several neo-antigenic protein fragments containing N-and C-terminal, and central domains such as fragments of the membrane protein Pmp21 and the secreted chlamydial proteasome-like factor (Cpaf), representing specific biomarker candidates.