Identification and classification of seafood‐borne pathogenic and spoilage bacteria: 16S rRNA sequencing versus MALDI‐TOF MS fingerprinting

The present study aims to compare two molecular technologies, 16S rRNA sequencing and MALDI‐TOF MS, for bacterial species identification in seafood. With this aim, 70 reference strains from culture collections, including important seafood‐borne pathogenic and spoilage bacterial species, and 50 strains isolated from commercial seafood products, were analysed by both techniques. Genomic analysis only identified the species of 50% of the isolated strains, proving to be particularly poor at identifying members of the Pseudomonas and Bacillus genera. In contrast, MALDI‐TOF MS fingerprinting identified 76% of the strains at the species level. The mass spectral data were submitted to the SpectraBank database ( http://www.spectrabank.org ), making this information available to other researchers. Furthermore, cluster analysis of the peak mass lists was carried out with the web application SPECLUST and the calculated groupings were consistent with results determined by a phylogenetic approach that is based on the 16S rRNA sequences. However, the MALDI‐TOF MS analysis demonstrated more discriminating potential that allowed for better classification, especially for the Pseudomonas and Bacillus genera. This is of importance with respect to the varying pathogenic and spoilage character at the intragenus and intraspecies level. In this sense, MALDI‐TOF MS demonstrated to be a competent bacterial typing tool that extends phenotypic and genotypic approaches, allowing a more ample classification of bacterial strains.     

Direct identification of trypanosomatids by matrix‐assisted laser desorption ionization–time of flight mass spectrometry (DIT MALDI‐TOF MS)

Accurate and rapid determination of trypanosomatids is essential in epidemiological surveillance and therapeutic studies. Matrix‐assisted laser desorption ionization/time of flight mass spectrometry (MALDI‐TOF MS) has been shown to be a useful and powerful technique to identify bacteria, fungi, metazoa and human intact cells with applications in clinical settings. Here, we developed and optimized a MALDI‐TOF MS method to profile trypanosomatids. trypanosomatid cells were deposited on a MALDI target plate followed by addition of matrix solution. The plate was then subjected to MALDI‐TOF MS measurement to create reference mass spectra library and unknown samples were identified by pattern matching using the BioTyper software tool. Several m/z peaks reproducibly and uniquely identified trypanosomatids species showing the potentials of direct identification of trypanosomatids by MALDI‐TOF MS. Moreover, this method discriminated different life stages of Trypanosoma cruzi, epimastigote and bloodstream trypomastigote and Trypanosoma brucei, procyclic and bloodstream. T. cruzi Discrete Typing Units (DTUs) were also discriminated in three clades. However, it was not possible to achieve enough resolution and software‐assisted identification at the strain level. Overall, this study shows the importance of MALDI‐TOF MS for the direct identification of trypanosomatids and opens new avenues for mass spectrometry‐based detection of parasites in biofluids. Copyright © 2016 John Wiley & Sons, Ltd.     

Characterization of braun’s lipoprotein and determination of its attachment sites to peptidoglycan by 252Cf-PD and MALDI time-of-flight mass spectrometry

A strategy for the characterization of bacterial lipoprotein-in this case Braun’s lipoprotein (an outer membrane 7-ku lipoprotein) isolated from Escherichia coli—is described by time-of-flight mass spectrometric (TOF/MS) techniques [²⁵²Cf plasma desorption (PD) TOF/MS and matrix-assisted laser desorption-ionization (MALDI) TOF/MS]. Covalent linkage of lipid at the N-terminal cysteine (posttranslationally modified to a S-[2,3-bis(acyloxy)-propyl]-N-acylcysteine) and, therefore, strict insolubility in aqueous solution constitute common features for this class of proteins. Relative molecular mass determination of the major molecular species of Braun’s lipoprotein was obtained by selection of an appropriate mixture of organic solvents compatible with matrix/support materials useful for the mass spectrometric techniques applied. Minor components of this lipoprotein that differ only in the fatty acid composition of the lipid anchor were detected by PD TOF/MS after enzymatic release of the extremely hydrophobic N-terminal amino acid followed by selective extraction with chloroform. Part of the primary sequence of this lipoprotein was confirmed based on peptide fragment ions observed in the positive ion PD mass spectra of cyanogen bromide-generated peptide fragments that had been isolated previously by reverse phase high-performance liquid chromatography (HPLC). Peptidoglycan fragments that represent the attachment sites of lipoprotein to peptidoglycan were enzymatically released, separated by reverse phase HPLC, and finally characterized by time-of-flight mass spectrometric techniques (²⁵²Cf-PD TOF/MS, MALDI TOF/MS). The results obtained with both techniques differed only in the better sensitivity obtained with MALDI TOF/MS, which consumed a factor of 100 to 1000 less material than with PD TOF/MS.     

Impact of updating the MALDI‐TOF MS database on the identification of nontuberculous mycobacteria

Conventional identification of mycobacteria species is slow, laborious and has low discriminatory power. Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) has proved highly effective for identifying conventional bacteria, and it may also be useful for identifying mycobacteria. The aim of this study was to evaluate and compare MALDI‐TOF MS with currently recommended molecular methods for the identification of nontuberculous mycobacteria (NTM), applying Mycobacteria Libraries v3.0 (ML3.0) and v2.0 (ML2.0). A total of 240 clinical isolates of 41 NTM species grown on solid media were analysed: 132 isolates of slow‐growing mycobacteria and 108 of rapid‐growing mycobacteria. MALDI‐TOF MS, using ML3.0, identified 192 (80%) NTM isolates with a score ≥1.7, encompassing 35 (85.4%) different species, that is, 17 (7.1%; p  = 0.0863) isolates and 15 (36.6%; p  = 0.0339) species more than currently recommended molecular techniques (polymerase chain reaction reverse hybridization). All these isolates were correctly identified according to molecular identification methods. The application of ML3.0 also identified 15 (6.2%) NTM isolates more than ML2.0 (p  < 0.01). The scores obtained with MALDI‐TOF MS using ML3.0 (mean score: 1.960) were higher in 147 (61.2%) isolates than when using ML2.0 (mean score: 1.797; p  < 0.01). Three of the species analysed were not included in either database, so they were not recognized by this system. In conclusion, MALDI‐TOF MS identified more isolates and species than the recommended polymerase chain reaction reverse hybridization assays. Although the new ML3.0 is not the definitive database, it yielded better results than ML2.0. This shows that the updating of the MALDI‐TOF MS database plays an essential role in mycobacterial identification. Copyright © 2017 John Wiley & Sons, Ltd.     

Need for database extension for reliable identification of bacteria from extreme environments using MALDI TOF mass spectrometry

The ability of MALDI TOF MS (matrix-assisted laser desorption ionisation time-of-flight mass spectrometry) to identify cultivable microflora from two waste disposal sites from non-ferrous metal industry was analysed. Despite the harsh conditions (extreme pH values and heavy metal content in red mud disposal site from aluminium production or high heavy metal content in nickel sludge), relatively high numbers of bacteria were recovered. In both environments, the bacterial community was dominated by Gram-positive bacteria, especially by actinobacteria. High-quality MALDI TOF mass spectra were obtained but most of the bacteria isolates could be not identified using MALDI Biotyper software. The overall identification rate was lower than 20 %; in two of the environments tested identification rates were lower than 10 %. As a dominant bacterial species, Microbacterium spp. in drainage water from an aluminium red mud disposal site near ?iar nad Hronom, Bacillus spp. in red mud samples from the same site, and Arthrobacter spp. from nickel smelter sludge near Sereï were identified by a combination of the Biolog system and 16S rRNA sequence analysis. As the primary focus of the MALDI TOF MS-based methodology is directed towards medically important bacteria, reference database spectra expansion and refinement are needed to improve the ability of MALDI TOF MS to identify environmental bacteria, especially those from extreme environments.     

Enhanced matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometric analysis of bacteriophage major capsid proteins with β‐mercaptoethanol pretreatment

Bacteriophage (phage) proteins have been analyzed previously with matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS). However, analysis of phage major capsid proteins (MCPs) has been limited by the ability to reproducibly generate ions from MCP monomers. While the acidic conditions of MALDI‐TOF MS sample preparation have been shown to aid in disassembly of some phage capsids, many require further treatment to successfully liberate MCP monomers. The findings presented here suggest that β‐mercaptoethanol reduction of the disulfide bonds linking phage MCPs prior to mass spectrometric analysis results in significantly increased MALDI‐TOF MS sensitivity and reproducibility of Yersinia pestis‐specific phage protein profiles. Copyright © 2009 John Wiley & Sons, Ltd.     

Detection of pathogenic Verticillium spp. using matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry

Verticillium spp. have been listed by the European and Mediterranean Plant Protection Organization (EPPO) and China as plant quarantine pests. Although attempts have been made to develop a simple routine laboratory assay to detect these organisms, none are routinely used. We describe for the first time a robust assay for reliable identification of Verticillium spp. using protein fingerprinting data obtained by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry(MALDI‐TOF‐MS). Several sample preparation methods and matrices were investigated to improve mass spectra for the routine identification of six species of Verticillium spp.(Verticillium dahiliae, V. alboatrum, V. fungicola, V. nigrescens, and V. lecanii) by MALDI‐TOF‐MS. Using the optimized experimental method, we constructed a protein fingerprint database for six species of Verticillium and established a analysis criteria of log(Score). This MALDI‐TOF‐MS protocol should prove useful as a rapid and reliable assay for distinguishing different Verticillium spp. Copyright © 2009 John Wiley & Sons, Ltd.     

MALDI‐TOF‐Massenspektrometrie: Risikoanalyse im Flug

The high accuracy, molecular resolution and sensitivity of matrix‐assisted laser desorption/ionisation time‐of‐flight mass spectrometry (MALDI‐TOF‐MS) make it an efficient method for analysing all kinds of biomolecules including nucleic acids, proteins/peptides, carbohydrates and lipids. MALDI‐TOF‐MS based high‐throughput genotyping of genetic heterogeneities possesses the potential of becoming a routine method. MAL‐DI‐TOF‐MS can be used for the identification of proteins and posttranslational modifications. Taken together, MALDI‐TOF‐MS represents a integrated platform technology in bioanalytics and molecular medicine.     

Application of matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry for the study of Helicobacter pylori

The characteristics of matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectrometry based investigation of extremely variable bacteria such as Helicobacter pylori were studied. H. pylori possesses a very high natural variability. Accurate tools for species identification and epidemiological characterization could help the scientific community to better understand the transmission pathways and virulence mechanisms of these bacteria. Seventeen clinical as well as two laboratory strains of H. pylori were analyzed by the MALDI Biotyper method for rapid species identification. Mass spectra collected were found containing 7–13 significant peaks per sample, and only six protein signals were identical for more than half of the strains. Four of them could be assigned to ribosomal proteins RL32, RL33, RL34, and RL36. The reproducible peak with m/z 6948 was identified as a histidine‐rich metal‐binding polypeptide by tandem mass spectrometry (MS/MS). In spite of the evident protein heterogeneity of H. pylori the mass spectra collected for a particular strain under several cultivations were highly reproducible. Moreover, all clinical strains were perfectly identified as H. pylori species through comparative analysis using the MALDI Biotyper software (Bruker Daltonics, Germany) by pattern matching against a database containing mass spectra from different microbial strains (n = 3287) including H. pylori 26695 and J99. The results of this study allow the conclusion that the MALDI‐TOF direct bacterial profiling is suited for H. pylori identification and could be supported by mass spectra fragmentation of the observed polypeptide if necessary. Copyright © 2010 John Wiley & Sons, Ltd.     

Use of electrophoretic techniques and MALDI–TOF MS for rapid and reliable characterization of bacteria: analysis of intact cells, cell lysates, and “washed pellets”

In this study electrophoretic and mass spectrometric analysis of three types of bacterial sample (intact cells, cell lysates, and “washed pellets”) were used to develop an effective procedure for the characterization of bacteria. The samples were prepared from specific bacterial strains. Five strains representing different species of the family Rhizobiaceae were selected as model microorganisms: Rhizobium leguminosarum bv. trifolii, R. leguminosarum bv. viciae, R. galegae, R. loti, and Sinorhizobium meliloti. Samples of bacteria were subjected to analysis by four techniques: capillary zone electrophoresis (CZE), capillary isoelectric focusing (CIEF), gel IEF, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI–TOF MS). These methods are potential alternatives to DNA-based methods for rapid and reliable characterization of bacteria. Capillary electrophoretic (CZE and CIEF) analysis of intact cells was suitable for characterization of different bacterial species. CIEF fingerprints of “washed pellets” and gel IEF of cell lysates helped to distinguish between closely related bacterial species that were not sufficiently differentiated by capillary electrophoretic analysis of intact cells. MALDI–TOF MS of “washed pellets” enabled more reliable characterization of bacteria than analysis of intact cells or cell lysates. Electrophoretic techniques and MALDI–TOF MS can both be successfully used to complement standard methods for rapid characterization of bacteria.     

Characterization of different food‐isolated Enterococcus strains by MALDI‐TOF mass fingerprinting

Enterococcus is a controversial genus due to its great variability; this genus includes pathogenic strains, spoilage strains, and apparently safe strains including some probiotic strains. Previous studies focused on the characterization of strains of Enterococcus spp. involved in nosocomial infections. However, little research has been conducted on Enterococcus strains in foodstuffs. In the present work, 36 strains of different species of Enterococcus have been characterized by means of MALDI‐TOF MS, resulting in highly specific mass spectral fingerprints. Characteristic peak masses common to certain bacterial species of Enterococcus have been identified. Thus, a peak at m/z 4426 ± 1 was assigned as a genus‐specific biomarker. In addition, phyloproteomic relationships based on the mass spectral data were compared to the results of a phylogenetic analysis based on the 16S rRNA gene sequence. A better grouping at the species level was observed in the phyloproteomic tree, especially for the Enterococcus faecium group. Presumably, the assortment of some strains or ecotypes could be related to their ecological niche specialization. The approach described in this study leads the way toward the rapid and specific identification of different strains and species of Enterococcus in food based on molecular protein markers, aiming at the early detection of pathogenic strains and strains implicated in food poisoning or food spoilage.     

Identification of proteins from membrane preparations by a combination of MALDI TOF-TOF and LC-coupled linear ion trap MS analysis of an Antarctic bacterium Pseudomonas syringae Lz4W, a strain with unsequenced genome

Multidimensional protein identification technology helps in identifying a large number of proteins with ESI by sequencing several peptides with MS/MS methods. When ionization and separation of different hydrophobic and hydrophilic peptides in a single process are difficult, a combination of LC-coupled linear ion trap MS and MALDI TOF/TOF can be used for identification of proteins as shown in the present study. We have used this combinational approach to identify membrane proteins of the Antarctic bacterium Pseudomonas syringae Lz4W, which are separated by SDS gel electrophoresis. Although the genome of P. syringae Lz4W has not been sequenced, the known genome sequences of mesophilic Pseudomonas species have been used for the identification of the proteins. Broadly, many membrane proteins, proteins with a wide range of molecular weight and pI including some integral membrane proteins could be identified using this procedure. Some of the identified proteins are involved in low temperature adaptation.     

Anthocyanin identification and composition of wild Vitis spp. accessions by using LC–MS and LC–NMR

The composition and concentration of anthocyanins of grape berry skins were analyzed in order to assess phenotypic variation between four grape wine varieties belonging to 4 different species: Vitis vinifera, Vitis amurensis, Vitis cinerea and Vitis X champinii. High-performance liquid chromatography coupled to mass spectrometry (LC–MS) and NMR spectroscopy (LC–NMR) were used to separate and identify the structure of anthocyanins present in these species. Combination of LC–MS and LC–NMR data resulted in the identification of 33 anthocyanins. In particular, newly reported cis isomers of p-coumaric-derivatives were identified (petunidin-, peonidin- and malvidin-3-(6-p-coumaroyl)-5-diglucoside). In V. cinerea and V. vinifera, anthocyanins were monoglucoside derivatives whereas in V. amurensis and V. X champinii, both mono- and diglucoside derivatives were identified. Malvidin-, delphinidin- and petunidin-derivatives were, respectively, the most abundant components in V. cinerea and V. vinifera, V. amurensis and V. X champinii.     

Comparison of MALDI‐TOF mass spectra with microsatellite length polymorphisms in Candida albicans

Candida albicans is the most frequent yeast involved in human infections. Its population structure can be divided into several genetic clades, some of which have been associated with antifungal susceptibility. Therefore, detecting and monitoring fungal clones in a routine laboratory setting would be a major epidemiological advance. Matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectra results are now widely used as bar codes to identify microorganisms in clinical microbiology laboratories. This study aimed at testing MALDI‐TOF mass spectra bar codes to identify clades among a set of C. albicans isolates. Accordingly, 102 clinical strains were genotyped using 10 microsatellite markers and analyzed via MALDI‐TOF mass spectrometry. The mass spectra were compared with a reference spectral library including 33 well‐characterized collection strains, using a Microflex^TM system and Biotyper^TM software, to test the capacity of the spectrum of a given isolate to match with the reference mass spectrum of an isolate from the same genetic clade. Despite high confidence species identification, the spectra failed to significantly match with the corresponding clade (p = 0.74). This was confirmed with the MALDI‐TOF spectra similarity dendrogram, in which the strains were dispersed irrespective of their genetic clade. Various attempts to improve intra‐clade spectra recognition were unsuccessful. In conclusion, MALDI‐TOF mass spectra bar code analysis failed to reliably recognize genetically related C. albicans isolates. Further studies are warranted to develop alternative MALDI‐TOF mass spectra analytical approaches to identify and monitor C. albicans clades in the routine clinical laboratory. Copyright © 2015 John Wiley & Sons, Ltd.     

Modeling bacteriophage amplification as a predictive tool for optimized MALDI‐TOF MS‐based bacterial detection

Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) is a valuable tool for rapid bacterial detection and identification but is limited by the need for relatively high cell count samples, which have been grown under strictly controlled conditions. These requirements can be eliminated by the natural infection of a viable bacterial species of interest with a host‐specific phage. This produces a rapid increase in phage protein concentrations in comparison to bacterial concentrations, which can in turn be exploited as a method for signal amplification during MALDI‐TOF MS. One drawback to this approach is the requirement for repetitive, time‐consuming sample preparation and analysis applied over the course of a phage infection to monitor phage concentrations as a function of time to determine the MALDI‐TOF MS detection limit. To reduce the requirement for repeated preparation and analysis, a modified phage therapy model was investigated as a means for predicting the time during a given phage infection when a detectable signal would occur. The modified model used a series of three differential equations composed of predetermined experimental parameters including phage burst size and burst time to predict progeny phage concentrations as a function of time. Using Yersinia pestis with plague diagnostic phage ?A1122 and Escherichia coli with phage MS2 as two separate, well‐characterized model phage–host pairs, we conducted in silico modeling of the infection process and compared it with experimental infections monitored in real time by MALDI‐TOF MS. Significant agreement between mathematically calculated phage growth curves and those experimentally obtained by MALDI‐TOF MS was observed, thus verifying this method's utility for significant time and labor reduction. Copyright © 2012 John Wiley & Sons, Ltd.     

Differential characterization of biogenic amine‐producing bacteria involved in food poisoning using MALDI‐TOF mass fingerprinting

Histamine poisoning is caused by the consumption of fish and other foods that harbor bacteria possessing histidine decarboxylase activity. With the aim of preventing histamine formation, highly specific mass spectral fingerprints were obtained from the 16 major biogenic amine‐producing enteric and marine bacteria by means of MALDI‐TOF MS analysis. All bacterial strains analyzed exhibited specific spectral fingerprints that enabled its unambiguous differentiation. This technique also identified peaks common to certain bacterial groups. Thus, two protein peaks at m/z 4182±1 and 8363±6 were found to be present in all Enterobacteriaceae species analyzed except for Morganella morganii. Peaks at m/z 3635±1 and 7267±2 were specific to both M. morganii and Proteus spp. Biogenic amine‐forming Proteus spp. exhibited three genus‐specific peaks at m/z 3980, 7960±1 and 9584±2. The genus Photobacterium also showed three genus‐specific peaks at m/z 2980±1, 4275±1 and 6578±1. The two histamine‐producing Gram‐positive bacteria Lactobacillus sp. 30A and Staphylococcus xylosus exhibited a few protein peaks in the 2000–7000 m/z range and could be easily distinguished from biogenic amine‐forming Gram‐negative bacteria. Clustering based on MALDI‐TOF MS also exhibited a good correlation with phylogenetic analysis based on the 16S rRNA gene sequence, validating the ability of the MALDI‐TOF technique to establish relationships between microbial strains and species. The approach described in this study leads the way toward the rapid and specific identification of major biogenic amine‐forming bacteria based on molecular protein markers with a goal to the timely prevention of histamine food poisoning.     

Surface-modified TiO(2) nanoparticles as affinity probes and as matrices for the rapid analysis of phosphopeptides and proteins in MALDI-TOF-MS

We utilized three different types of TiO₂ nanoparticles (NPs) namely TiO₂‐dopamine, TiO₂‐CdS and bare TiO₂ NPs as multifunctional nanoprobes for the rapid enrichment of phosphopeptides from tryptic digests of α‐ and β‐casein, milk and egg white using a simplified procedure in MALDI‐TOF‐MS. Surface‐modified TiO₂ NPs serve as effective matrices for the analysis of peptides (gramicidin D, HW6, leucine‐enkephalin and methionine‐enkephalin) and proteins (cytochrome c and myoglobin) in MALDI‐TOF‐MS. In the surface‐modified TiO₂ NPs‐based MALDI mass spectra of these analytes (phosphopetides, peptides and proteins), we found that TiO₂‐dopamine and bare TiO₂ NPs provided an efficient platform for the selective and rapid enrichment of phosphopeptides and TiO₂‐CdS NPs efficiently acted as the matrix for background‐free detection of peptides and proteins with improved resolution in MALDI‐MS. We found that the upper detectable mass range is 17 000 Da using TiO₂‐CdS NPs as the matrix. The approach is simple and straightforward for the rapid analysis of phosphopeptides, peptides and proteins by MALDI‐MS in proteome research.     

Picolinamidination of phosphopeptides for MALDI-TOF-TOF mass spectrometric sequencing with enhanced sensitivity

Two orders of magnitude matrix-assisted laser desorption/ionization (MALDI) signal enhancement of phosphopeptides has been achieved by picolinamidination of N-terminal amine group and ε-amine group of lysine residues. Due to the presence of picolinamidination tag at the N-terminal amine of peptides, MS/MS spectra with a strong b-ion series was obtained, which greatly facilitated sequencing and identification of the phosphorylation site. Phosphorylation site of a phosphopeptide could be identified from MALDI TOF/TOF spectrum obtained from a tryptic or a chymotryptic phosphopeptide, which was not even detected in the positive ion mode, without signal enhancement by picolinamidination, due to the negative charge of the phosphate group in the presence of other peptides.     

Qualitative and quantitative analysis of diterpenoids in Salvia species by liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry

An on-line ultra-high-performance liquid chromatography (UHPLC) coupled with photodiode-array detection and quadrupole time-of-flight tandem mass spectrometry (QTOF-MS/MS) method has been optimized and established for the qualitative and quantitative analysis of the important diterpenoids in the methanol extracts of 12 Salvia species. Specific marker components were identified for the classification of the Salvia samples by principal component analysis. The accurate mass measurement within 3 ppm error for all the protonated molecules and subsequent fragment ions offers higher quality structural information for interpretation of fragmentation pathways of various groups of diterpenoids. Thus, a total of 21 diterpenoids from different Salvia species were separated within 10 min, and were unequivocally or tentatively identified via comparisons with authentic standards and literature. This UHPLC-QTOF-MS/MS method was validated to be sensitive, precise and accurate with the limit of detections at 3.0–16 ng/ml, and the overall intra-day and the inter-day variations less than 3%. The recovery of the method was in the range of 96.2–101.8%, with relative standard deviation (RSD) less than 3.0%. The results demonstrated that the qualitative and quantitative differences in diterpenoids were not only useful for chemotaxonomy in some Salvia species but also for the standardization and differentiation of large numbers of similar samples.     

MALDI-TOF-TOF鉴定IPG IEF分离的蛋白质

K562细胞是一株分化差、恶性程度高的人白血病细胞。研究表明,在一些分化诱导剂的作用下,细胞可以向红细胞系、粒细胞系和巨K562核细胞系方向分化成熟,并表现出相应血细胞类型的成熟标志。用一维固相pH梯度等电聚焦电泳(IPGIEF)分离K562细胞总蛋白质,其每一条带常包含多个蛋白质,难以用肽指纹谱技术来鉴定。有人探索过基于液相色谱的串联质谱技术来鉴定混合蛋白质,但灵敏度上存在一些问题。本文尝试采用基质辅助激光解吸附电离-串联飞行时间质谱(MALDI-TOF-TOF)分析一维电泳条带,鉴定了K562细胞中部分可能与白血病相关的蛋白质。