Towards an analysis of the rice mitochondrial proteome

Purified rice (Oryza sativa) mitochondrial proteins have been arrayed by isoelectric focusing/polyacrylamide gel electrophoresis (PAGE), by blue-native (BN) PAGE, and by reverse-phase high-performance liquid chromatography (LC) separation (LC-mass spectrometry [MS]). From these protein arrays, we have identified a range of rice mitochondrial proteins, including hydrophilic/hydrophobic proteins (grand average of hydropathicity = -1.27 to +0.84), highly basic and acid proteins (isoelectric point = 4.0-12.5), and proteins over a large molecular mass range (6.7-252 kD), using proteomic approaches. BN PAGE provided a detailed picture of electron transport chain protein complexes. A total of 232 protein spots from isoelectric focusing/PAGE and BN PAGE separations were excised, trypsin digested, and analyzed by tandem MS (MS/MS). Using this dataset, 149 of the protein spots (the products of 91 nonredundant genes) were identified by searching translated rice open reading frames from genomic sequence and six-frame translated rice expressed sequence tags. Sequence comparison allowed us to assign functions to a subset of 85 proteins, including many of the major function categories expected for this organelle. A further six spots were matched to rice sequences for which no specific function has yet been determined. Complete digestion of mitochondrial proteins with trypsin yielded a peptide mixture that was analyzed directly by reverse-phase LC via organic solvent elution from a C-18 column (LC-MS). These data yielded 170 MS/MS spectra that matched 72 sequence entries from open reading frame and expressed sequence tag databases. Forty-five of these were obtained using LC-MS alone, whereas 28 proteins were identified by both LC-MS and gel-based separations. In total, 136 nonredundant rice proteins were identified, including a new set of 23 proteins of unknown function located in plant mitochondria. We also report the first direct identification, to our knowledge, of PPR (pentatricopeptide repeat) proteins in the plant mitochondrial proteome. This dataset provides the first extensive picture, to our knowledge, of mitochondrial functions in a model monocot plant.     

Proteomic analysis of hybrid poplar xylem sap

Xylem sap collected from Populus trichocarpa × Populus deltoides using root pressure was estimated to contain more than 100 proteins. Ninety-seven of these proteins were identified using liquid chromatography-tandem mass spectrometry (LC-MS/MS). These proteins were classified into 10 functional categories including metabolism, signaling, stress response and cell wall functions. The majority of xylem sap proteins were metabolic enzymes involved in processes including translation, proteolysis, and glycolysis. Stress-related proteins were also prevalent. In contrast to xylem sap proteins collected from annual plants, the majority of poplar xylem sap proteins do not appear to be classically secreted since only 33 proteins were predicted to have an N-terminal signal peptide targeting them to the secretory pathway. Of the remaining 64 proteins, 27 were predicted to be secreted non-classically. While a number of proteins identified here have been previously reported in xylem sap proteomes of annual plants, many xylem sap proteins were identified in poplar which may reflect functions specific to perennial plants.     

Comparison of SYPRO Ruby and Deep Purple using commonly available UV transilluminator: wide-scale application in proteomic research

Fluorescent stains are becoming increasingly useful in proteomics research involving protein expression as well as post-translational modification studies and are particularly useful for samples which are expensive and scarce. The fluorescent dyes Deep Purple and SYPRO Ruby are widely used in protein expression studies. Using UV transillumination and Charged Coupled Device (CCD) based imaging system, their relative sensitivity to detect proteins separated by two-dimensional polyacrylamide gel electrophoresis and downstream protein identification by liquid chromatography-tandem mass spectrometry (LC-MS/MS) was compared. Using mouse liver homogenate, we detected a greater number of spots using SYPRO Ruby over Deep Purple stain. However, the number of matched peptides and the percentage of amino acid residues identified for 21 different proteins were comparable suggesting their equivalency for LC-MS/MS identification. In spite of comparable MS compatibility, we recommend the use of SYPRO Ruby for expression proteomics due to its higher sensitivity in detecting protein spots.     

Separation and identification of soybean leaf proteins by two-dimensional gel electrophoresis and mass spectrometry

To establish a proteomic reference map for soybean leaves, we separated and identified leaf proteins using two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and mass spectrometry (MS). Tryptic digests of 260 spots were subjected to peptide mass fingerprinting (PMF) by matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) MS. Fifty-three of these protein spots were identified by searching NCBInr and SwissProt databases using the Mascot search engine. Sixty-seven spots that were not identified by MALDI-TOF-MS analysis were analyzed with liquid chromatography tandem mass spectrometry (LC-MS/MS), and 66 of these spots were identified by searching against the NCBInr, SwissProt and expressed sequence tag (EST) databases. We have identified a total of 71 unique proteins. The majority of the identified leaf proteins are involved in energy metabolism. The results indicate that 2D-PAGE, combined with MALDI-TOF-MS and LC-MS/MS, is a sensitive and powerful technique for separation and identification of soybean leaf proteins. A summary of the identified proteins and their putative functions is discussed.     

A systemic proteomic analysis of <Emphasis Type="Italic">Populus</Emphasis> chloroplast by using shotgun method

The chloroplast is one of the most important organelles in plants. Proteomic investigations of chloroplasts have been undertaken for many herb plant species, but to date no such investigation has been reported for woody plant chloroplasts. In the present study we initiated a systematic proteomic study of Populus chloroplasts using a shotgun proteomic method. After isolation of chloroplasts and tryptic digestion of the proteins, the protein fragments were separated via HPLC using an SCX column, and the peptides were analyzed by LC-MS/MS; 119 proteins were successfully identified. Based on annotation information in the UniProtKB/Swiss-Prot database, these proteins were identified as being localized in the chloroplast thylakoid membrane, chloroplast stroma, chloroplast thylakoid lumen, and plastoglobules. Over 50% of all identified proteins were confirmed as chloroplast thylakoid proteins, and 85 are encoded by the chloroplast genome with the remaining proteins encoded by the nuclear genome. Based on functional annotation, these proteins were classified into four functional categories, including photosynthesis, redox regulation and stress, primary and secondary metabolism, transport and signaling. These data provide a valuable basis for further studies on photosynthesis in poplar species.     

Characterisation of host defence proteins in milk using a proteomic approach

Besides providing nutrition to the newborn, milk also protects the neonate and the mammary gland against infection. As well as the six major proteins, bovine milk contains minor proteins, not all of which have been characterized. In this study, we have subjected bovine skim milk, whey, and milk fat globule membrane (MFGM) fractions to both direct liquid chromatography-tandem mass spectrometry (LC-MS/MS), and two-dimensional electrophoresis (2-DE) followed by matrix assisted laser desorption ionization-time-of-flight (MALDI-TOF) mass spectrometry (MS) of individual protein spots to better characterize the repertoire of minor milk proteins, particularly those involved with host defense. Milk from peak lactation as well as during the period of colostrum formation and during mastitis were analyzed to gain a more complete sampling of the milk proteome. In total, 2903 peptides were detected by LC-MS and 2770 protein spots by 2-DE. From these, 95 distinct gene products were identified, comprising 53 identified through direct LC-MS/MS and 57 through 2-DE-MS. The latter were derived from a total of 363 spots analyzed with 181 being successfully identified. At least 15 proteins were identified that are involved in host defense. These results demonstrate that the proteome of milk is more complex than has previously been reported and a significant fraction of minor milk proteins are involved in protection against infection.     

Two-dimensional proteome reference maps for the soybean cyst nematode Heterodera glycines

2-DE reference maps of Heterodera glycines were constructed. After in-gel digestion with trypsin, 803 spots representing 426 proteins were subsequently identified by LC-MS/MS. Proteins with annotated function were further categorized by Gene Ontology. The results showed that proteins involved in metabolic, developmental and biological regulation processes were the most abundant.     

Analysis of the pumpkin phloem proteome provides insights into angiosperm sieve tube function

Increasing evidence suggests that proteins present in the angiosperm sieve tube system play an important role in the long distance signaling system of plants. To identify the nature of these putatively non-cell-autonomous proteins, we adopted a large scale proteomics approach to analyze pumpkin phloem exudates. Phloem proteins were fractionated by fast protein liquid chromatography using both anion and cation exchange columns and then either in-solution or in-gel digested following further separation by SDS-PAGE. A total of 345 LC-MS/MS data sets were analyzed using a combination of Mascot and X!Tandem against the NCBI non-redundant green plant database and an extensive Cucurbit maxima expressed sequence tag database. In this analysis, 1,209 different consensi were obtained of which 1,121 could be annotated from GenBank and BLAST search analyses against three plant species, Arabidopsis thaliana, rice (Oryza sativa), and poplar (Populus trichocarpa). Gene ontology (GO) enrichment analyses identified sets of phloem proteins that function in RNA binding, mRNA translation, ubiquitin-mediated proteolysis, and macromolecular and vesicle trafficking. Our findings indicate that protein synthesis and turnover, processes that were thought to be absent in enucleate sieve elements, likely occur within the angiosperm phloem translocation stream. In addition, our GO analysis identified a set of phloem proteins that are associated with the GO term "embryonic development ending in seed dormancy"; this finding raises the intriguing question as to whether the phloem may exert some level of control over seed development. The universal significance of the phloem proteome was highlighted by conservation of the phloem proteome in species as diverse as monocots (rice), eudicots (Arabidopsis and pumpkin), and trees (poplar). These results are discussed from the perspective of the role played by the phloem proteome as an integral component of the whole plant communication system.     

Genome-wide identification of the subcellular localization of the Escherichia coli B proteome using experimental and computational methods

Escherichia coli K-12 and B strains have most widely been employed for scientific studies as well as industrial applications. Recently, the complete genome sequences of two representative descendants of E. coli B strains, REL606 and BL21(DE3), have been determined. Here, we report the subproteome reference maps of E. coli B REL606 by analyzing cytoplasmic, periplasmic, inner and outer membrane, and extracellular proteomes based on the genome information using experimental and computational approaches. Among the total of 3487 spots, 651 proteins including 410 non-redundant proteins were identified and characterized by 2-DE and LC-MS/MS; they include 440 cytoplasmic, 45 periplasmic, 50 inner membrane, 61 outer membrane, and 55 extracellular proteins. In addition, subcellular localizations of all 4205 ORFs of E. coli B were predicted by combined computational prediction methods. The subcellular localizations of 1812 (43.09%) proteins of currently unknown function were newly assigned. The results of computational prediction were also compared with the experimental results, showing that overall precision and recall were 92.16 and 92.16%, respectively. This work represents the most comprehensive analyses of the subproteomes of E. coli B, and will be useful as a reference for proteome profiling studies under various conditions. The complete proteome data are available online (http://ecolib.kaist.ac.kr).     

Proteomic analysis of human immunodeficiency virus using liquid chromatography/tandem mass spectrometry effectively distinguishes specific incorporated host proteins

A major challenge to studying virus-incorporated host proteins is the fact that they are not encoded by the viral genome. We used Liquid Chromatography/Tandem Mass Spectrometry (LC-MS/MS) on whole virions to obtain a snapshot of the HIV-1 proteome. We identified known viral and host-cellular proteins and also identified novel components of HIV-1 and confirm these by traditional biochemical methods. Our comparison of wild-type and mutant viruses demonstrates that LC-MS/MS has the specificity to distinguish the presence/absence of a single host protein in intact virions.     

Subproteomics analysis of phosphorylated proteins: application to the study of B-lymphoblasts from a patient with Scott syndrome

Proteomics based approaches, which examine the expressed proteins of a tissue or cell type, complement the genome initiatives and are increasingly used to address biomedical questions. Proteins are the main functional output, and post-translational modifications such as phosphorylation are very important in determining protein function. To address this question, we developed a method for specific immunoprecipitation using anti-phosphotyrosine antibodies. This method is directly compatible with two-dimensional gel electrophoresis (2-DE). In this report data are presented on B-lymphoblasts from a patient suffering of Scott syndrome. Scott syndrome is an orphan inherited hemorrhagic disorder due to a lack of exposure of procoagulant phosphatidylserine at the exoplasmic leaflet of plasma membrane of blood cells. We hypothesized that a consequence of the mutation is to alter phosphorylation of proteins involved in signal transduction leading to breakdown in cellular signaling pathways mediating phosphatidylserine exposure. An immunoprecipitation method combined with 2-DE was applied to search for modifications in the expression of phosphorylated polypeptides related to Scott syndrome phenotype. We report here the construction of a B-lymphoblast subproteomic map comprising of polypeptides observed after immunoprecipitation using antibodies to phosphotyrosine. The polypeptides were identified either by mass fingerprinting, by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and/or by matching with various lymphoid cell 2-DE maps included in the Laboratoire de Biochimie des Protéines et Protéomique 2-DE database. A differential analysis was further performed to explore several hundred proteins in Scott B-lymphoblasts in comparison with control B-lymphoblasts. Then, image analysis allowed detection of variations between control and Scott syndrome phenotype lymphoblasts. Five spots were specifically found on 2-DE from Scott syndrome phenotype lymphoblasts, and four only appeared on 2-DE from control cells. Protein identification was achieved using a combination of mass fingerprinting and peptide identification using LC-MS/MS.     

Tandem mass spectrometry for the detection of plant pathogenic fungi and the effects of database composition on protein inferences

LC-MS/MS has demonstrated potential for detecting plant pathogens. Unlike PCR or ELISA, LC-MS/MS does not require pathogen-specific reagents for the detection of pathogen-specific proteins and peptides. However, the MS/MS approach we and others have explored does require a protein sequence reference database and database-search software to interpret tandem mass spectra. To evaluate the limitations of database composition on pathogen identification, we analyzed proteins from cultured Ustilago maydis, Phytophthora sojae, Fusarium graminearum, and Rhizoctonia solani by LC-MS/MS. When the search database did not contain sequences for a target pathogen, or contained sequences to related pathogens, target pathogen spectra were reliably matched to protein sequences from nontarget organisms, giving an illusion that proteins from nontarget organisms were identified. Our analysis demonstrates that when database-search software is used as part of the identification process, a paradox exists whereby additional sequences needed to detect a wide variety of possible organisms may lead to more cross-species protein matches and misidentification of pathogens.     

Comparative proteomic analysis of chestnut blight fungus, Cryphonectria parasitica, under tannic-acid-inducing and hypovirus-regulating conditions

Chestnut blight fungus, Cryphonectria parasitica , and its hypovirus present a useful model system for investigating the mechanisms of hypoviral infection. To identify gene products associated with fungal pathogenicity and hypoviral regulation, we attempted a proteomic analysis of the virus-free EP155/2 strain and its isogenic virus-infected UEP1 strain in response to tannic acid (TA), which is abundant in the bark of chestnut trees. In this study, pretreatment of mycelia grown on TA-supplemented media was developed for proteomic analysis. Approximately 704 proteins from the mycelia of the EP155/2 strain were reproducibly present in 3 independent extractions. Among these, 111 and 79 spots were found to be responsive to hypovirus infection and TA supplementation, respectively. The TA-grown UEP1 strain yielded 28 spots showing an expression pattern different from that of untreated UEP1. Thirty protein spots showing considerable differences in spot density were selected for further analysis. Hybrid tandem LC-MS/MS spectrometry of the 30 selected protein spots revealed that 29 were identified while 1 was unidentified. Among the identified 29 proteins, 15 were metabolic enzymes; 5 were stress-related, of which 4 were heat-shock proteins and 1 was glutathione S-transferase; 5 were signaling and cellular process-related proteins; 2 were structural proteins; and 2 matched proteins of hypothetical genes.     

Protein identification from two-dimensional gel electrophoresis analysis of Klebsiella pneumoniae by combined use of mass spectrometry data and raw genome sequences

Separation of proteins by two-dimensional gel electrophoresis (2-DE) coupled with identification of proteins through peptide mass fingerprinting (PMF) by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) is the widely used technique for proteomic analysis. This approach relies, however, on the presence of the proteins studied in public-accessible protein databases or the availability of annotated genome sequences of an organism. In this work, we investigated the reliability of using raw genome sequences for identifying proteins by PMF without the need of additional information such as amino acid sequences. The method is demonstrated for proteomic analysis of Klebsiella pneumoniae grown anaerobically on glycerol. For 197 spots excised from 2-DE gels and submitted for mass spectrometric analysis 164 spots were clearly identified as 122 individual proteins. 95% of the 164 spots can be successfully identified merely by using peptide mass fingerprints and a strain-specific protein database (ProtKpn) constructed from the raw genome sequences of K. pneumoniae. Cross-species protein searching in the public databases mainly resulted in the identification of 57% of the 66 high expressed protein spots in comparison to 97% by using the ProtKpn database. 10 dha regulon related proteins that are essential for the initial enzymatic steps of anaerobic glycerol metabolism were successfully identified using the ProtKpn database, whereas none of them could be identified by cross-species searching. In conclusion, the use of strain-specific protein database constructed from raw genome sequences makes it possible to reliably identify most of the proteins from 2-DE analysis simply through peptide mass fingerprinting.     

Evaluation of multidimensional chromatography coupled with tandem mass spectrometry (LC/LC-MS/MS) for large-scale protein analysis: the yeast proteome

Highly complex protein mixtures can be directly analyzed after proteolysis by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). In this paper, we have utilized the combination of strong cation exchange (SCX) and reversed-phase (RP) chromatography to achieve two-dimensional separation prior to MS/MS. One milligram of whole yeast protein was proteolyzed and separated by SCX chromatography (2.1 mm i.d.) with fraction collection every minute during an 80-min elution. Eighty fractions were reduced in volume and then re-injected via an autosampler in an automated fashion using a vented-column (100 microm i.d.) approach for RP-LC-MS/MS analysis. More than 162,000 MS/MS spectra were collected with 26,815 matched to yeast peptides (7,537 unique peptides). A total of 1,504 yeast proteins were unambiguously identified in this single analysis. We present a comparison of this experiment with a previously published yeast proteome analysis by Yates and colleagues (Washburn, M. P.; Wolters, D.; Yates, J. R., III. Nat. Biotechnol. 2001, 19, 242-7). In addition, we report an in-depth analysis of the false-positive rates associated with peptide identification using the Sequest algorithm and a reversed yeast protein database. New criteria are proposed to decrease false-positives to less than 1% and to greatly reduce the need for manual interpretation while permitting more proteins to be identified.     

Identification of differentially expressed proteins in poplar leaves induced by Marssonina brunnea f. Sp. Multigermtubi

Black spot disease in poplar is a disease of the leaf caused by fungus. The major pathogen is Marssonina brunnea f. sp. multigermtubi. To date, little is known about the molecular mechanism of poplar （M. brunnea） interaction. In order to identify the proteins related to disease resistance and understand its molecular basis, the clone ＂NL895＂ （P. euramericana CL＂NL895＂）, which is highly resistant to M. brunnea f. sp. multigermtubi, was used in this study. We used two-dimensional gel electrophoresis （2-DE） and mass spectrometry （MS） to identify the proteins in poplar leaves that were differentially expressed in response to black spot disease pathogen, M. brunnea f. sp. multigermtubi. Proteins extracted from poplar leaves at 0, 12, 24, 48, and 72 h after pathogen-inoculation were separated by 2-DE, About 500 reproducible protein spots were detected, of which 40 protein spots displayed differential expression in levels and were subjected to Matrix assisted laser desorption/ionization time of flight mass spectrometry （MALDI-TOF MS） followed by database searching. According to the function, the identified proteins were sorted into five categories, that is, protein synthesis, metabolism, defense response and unclassified proteins.     

Two-dimensional electrophoretic profiling of normal human kidney glomerulus proteome and construction of an extensible markup language (XML)-based database

To contribute to physiology and pathophysiology of the glomerulus of human kidney, we have launched a proteomic study of human glomerulus, and compiled a profile of proteins expressed in the glomerulus of normal human kidney by two-dimensional gel electrophoresis (2-DE) and identification with matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) and/or liquid chromatography-tandem mass spectrometry (LC-MS/MS). Kidney cortices with normal appearance were obtained from patients under surgical nephrectomy due to renal tumor, and glomeruli were highly purified by a standard sieving method followed by picking-up under a phase-contrast microscope. The glomerular proteins were separated by 2-DE with 24 cm immobilized pH gradient strips in the 3-10 range in the first dimension and 26 x 20 cm sodium dodecyl sulfate polyacrylamide electrophoresis gels of 12.5% in the second dimension. Gels were silver-stained, and valid spots were processed for identification through an integrated robotic system that consisted of a spot picker, an in-gel digester, and a MALDI-TOF MS and / or a LC-MS/MS. From 2-DE gel images of glomeruli of four subjects with no apparent pathologic manifestations, a synthetic gel image of normal glomerular proteins was created. The synthetic gel image contained 1713 valid spots, of which 1559 spots were commonly observed in the respective 2-DE gels. Among the 1559 spots, 347 protein spots, representing 212 proteins, have so far been identified, and used for the construction of an extensible markup language (XML)-based database. The database is deposited on a web site (http://www.sw.nec.co.jp/bio/rd/hgldb/index.html) in a form accessible to researchers to contribute to proteomic studies of human glomerulus in health and disease.     

Strategic proteome analysis of Candida magnoliae with an unsequenced genome

Erythritol is a noncariogenic, low calorie sweetener. It is safe for people with diabetes and obese people. Candida magnoliae is an industrially important organism because of its ability to produce erythritol as a major product. The genome of C. magnoliae has not been sequenced yet, limiting the available proteome database. Therefore, systematic approaches were employed to construct the proteome map of C. magnoliae. Proteomic analysis with systematic approaches is based on two-dimensional electrophoresis, matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS), tandem mass spectrometry (MS/MS) and database interrogation. First, 24 spots were analyzed using peptide mass fingerprinting along with MALDI-TOF MS with high mass accuracy. Only four spots were reliably identified as carbonyl reductase and its isoforms. The reason for low sequence coverage seemed to be that these identification strategies were based on the presence of the protein database obtained from the publicly accessible genome database and the availability of cross-species protein identification. MS/MS (MS/MS ion search and de novo sequencing) in combination with similarity searches allowed successful identification of 39 spots. Several proteins including transaldolase identified by MS/MS ion searches were further confirmed by partial sequences from the expressed sequence tag database. In this study, 51 protein spots were analyzed and then potentially identified. The identified proteins were involved in glycolysis, stress response, other essential metabolisms and cell structures.     

Sequencing the genome of Marssonina brunnea reveals fungus-poplar co-evolution

ABSTRACT: BACKGROUND: The fungus Marssonina brunnea is a causal pathogen of Marssonina leaf spot that devastates poplar plantations by defoliating susceptible trees before normal fall leaf drop. RESULTS: \We sequence the genome of M. brunnea with a size of 52 Mb assembled into 89 scaffolds, representing the first sequenced Dermateaceae genome. By inoculating this fungus onto a poplar hybrid clone, we investigate how M. brunnea interacts and co-evolves with its host to colonize poplar leaves. While a handful of virulence genes in M. brunnea, mostly from the LysM family, are detected to up-regulate during infection, the poplar down-regulates its resistance genes, such as nucleotide binding site domains and leucine rich repeats, in response to infection. From 10,027 predicted proteins of M. brunnea in a comparison with those from poplar, we identify four poplar transferases that stimulate the host to resist M. brunnea. These transferas-encoding genes may have driven the co-evolution of M. brunnea and Populus during the process of infection and anti-infection. CONCLUSIONS: Our results from the draft sequence of the M. brunnea genome provide evidence for genomegenome interactions that play an important role in poplar-pathogen co-evolution. This knowledge could help to design effective strategies for controlling Marssonina leaf spot in poplar.     

Exploring proteins in Anopheles gambiae male and female antennae through MALDI mass spectrometry profiling

MALDI profiling and imaging mass spectrometry (IMS) are novel techniques for direct analysis of peptides and small proteins in biological tissues. In this work we applied them to the study of Anopheles gambiae antennae, with the aim of analysing expression of soluble proteins involved in olfaction perireceptor events. MALDI spectra obtained by direct profiling on single antennae and by the analysis of extracts, showed similar profiles, although spectra obtained through profiling had a richer ion population and higher signal to noise ratio. Male and female antennae showed distinct protein profiles. MALDI imaging experiments were also performed and differences were observed in the localization of some proteins. Two proteins were identified through high resolution measurement and top-down MS/MS experiments. A 8 kDa protein only present in the male antennae matched with an unannotated sequence of the An. gambiae genome, while the presence of odorant binding protein 9 (OBP-9) was confirmed through experiments of 2-DE, followed by MS and MS/MS analysis of digested spots. This work shows that MALDI MS profiling is a technique suitable for the analysis of proteins of small and medium MW in insect appendices, and allows obtaining data for several specimens which can be investigated for differences between groups. Proteins of interest can be identified through other complementary MS approaches.