Prestructured MALDI-MS sample supports

Improved detection of higher molecular weight proteins by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry on polytetrafluoroethylene surfaces

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) of proteins was performed on a range of polytetrafluoroethylene (PTFE) surfaces. Sinapinic acid and alpha-cyano-4-hydroxycinnamic acid matrices were compared and the order of application varied to identify the best combination for each surface. It is demonstrated that the use of a PTFE surface improves the intensity of signals obtained for higher molecular weight proteins.

Genotyping single-nucleotide polymorphisms by matrix-assisted laser-desorption/ionization time-of-flight mass spectrometry

In recent years matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI) has emerged as a very powerful method for genotyping single nucleotide polymorphisms. The accuracy, speed of data accumulation, and data structure are the major features of MALDI. Several SNP genotyping methods have been implemented with a high degree of automation and are being applied for large-scale association studies. Most methods for SNP genotyping using MALDI mass spectrometric detection and their potential application for high-throughput are reviewed here.

Sample depletion of the matrix-assisted laser desorption process monitored using radionuclide detection

To investigate analyte consumption during the laser desorption process, matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) is combined with radionuclide detection. Radionuclide detection provides highly sensitive and quantitative information on the amount of radiolabeled analytes in a MALDI MS sample spot. 14C-Labeled cytochrome c is deposited with 2,5-dihydroxybenzoic acid in 10-nL volume spots. By comparing radioactivity levels of the labeled cytochrome c both before and after spectral acquisition, the reduction in labeled analyte molecules on the target allows monitoring of the moles of desorbed sample. Through a depletion study on this sample, the amount of analyte consumed for MALDI time-of-flight spectral acquisition and the average number of molecules desorbed per laser ablation are determined. When [14C]-cytochrome c is no longer detected by MALDI MS, approximately 70% of the original analyte remains in the sample spots. Redissolving the spots produced further desorption, indicating that the analyte before dissolution was in a physical environment that did not facilitate the desorption process. As a technique with a response that does not depend on the environment of the analyte, radionuclide detection allows characterization of mass-limited sampling methods to better understand the MALDI process.

Protein array technology: the tool to bridge genomics and proteomics

The generation of protein chips requires much more efforts than DNA microchips. While DNA is DNA and a variety of different DNA molecules behave stable in a hybridisation experiment, proteins are much more difficult to produce and to handle. Outside of a narrow range of environmental conditions, proteins will denature, lose their three-dimensional structure and a lot of their specificity and activity. The chapter describes the pitfalls and challenges in Protein Microarray technology to produce native and functional proteins and store them in a native and special environment for every single spot on an array, making applications like antibody profiling and serum screening possible not only on denatured arrays but also on native protein arrays.

Protein array technology. Potential use in medical diagnostics

The human genome is sequenced, but only a minority of genes have been assigned a function. Whole-genome expression profiling is an important tool for functional genomic studies. Automated technology allows high-throughput gene activity monitoring by analysis of complex expression patterns, resulting in fingerprints of diseased versus normal or developmentally distinct tissues. Differential gene expression can be most efficiently monitored by DNA hybridization on arrays of oligonucleotides or cDNA clones. Starting from high-density filter membranes, cDNA microarrays have recently been devised in chip format. We have shown that the same cDNA libraries can be used for high-throughput protein expression and antibody screening on high-density filters and microarrays. These libraries connect recombinant proteins to clones identified by DNA hybridization or sequencing, hence creating a direct link between gene catalogs and functional catalogs. Microarrays can now be used to go from an individual clone to a specific gene and its protein product. Clone libraries become amenable to database integration including all steps from DNA sequencing to functional assays of gene products.

Continuous sample deposition from reversed-phase liquid chromatography to tracks on a matrix-assisted laser desorption/ionization precoated target for the analysis of protein digests

Peptide mass fingerprinting by matrix-assisted laser desorption/ionization (MALDI)-mass spectrometry (MS) is one of the standard high-throughput methods for protein identification today. Traditionally this method has been based on spotting peptide mixtures onto MALDI targets. While this method works well for more abundant proteins, low-abundance proteins mixed with high-abundance proteins tend to go undetected due to ion suppression effects, instrumental dynamic range limitations and chemical noise interference. We present an alternative approach where liquid chromatography (LC) effluent is continuously collected as linear tracks on a MALDI target. In this manner the chromatographic separation is spatially preserved on the target, which enables generation of off-line LC-MS and LC-MS/MS data by MALDI. LC-MALDI sample collection provides improved sensitivity and dynamic range, spatial resolution of peptides along the sample track, and permits peptide mass mapping of low-abundance proteins in mixtures containing high-abundance proteins. In this work, standard and ribosomal protein digests are resolved and captured using LC-MALDI sample collection and analyzed by MALDI-TOF-MS.

On-probe digestion of bacterial proteins for MALDI-MS

On-probe digestion combined with MALDI mass spectrometry is studied as a rapid method for the analysis and identification of bacterial proteins. The use of trypsin adsorbed to the probe surface reduces the digestion time from hours to minutes. A high amount of trypsin must be applied to the probe for the successful digestion of bacterial proteins. Mass spectra of the digest contain a number of low-mass digest fragments. Several components of a B. subtilis bacterial digest can be identified through postsource decay and database searching.

MALDI-TOF mass spectrometry-based SNP genotyping

In recent years a growing demand for simple and robust SNP genotyping platforms has arisen from the widespread use of SNPs in industrial and public research. The resulting knowledge about genotype/phenotype correlations is of special interest for the identification of potential new drug targets and in the field of pharmacogenomics. However, full exploitation of the available genomic information requires vast numbers of SNP analyses, as large cohorts of patients have to be screened for a large number of markers. Only very few of the current SNP genotyping techniques can cope with the resulting demands concerning sample throughput, automation, accuracy and cost-effectiveness. MALDI-TOF mass spectrometry has the potential to develop into a 'Gold Standard' for high-throughput SNP genotyping - if it has not already done so. This review will focus on the latest developments of this technology.

High-throughput genetic screening using matrix-assisted laser desorption/ionization mass spectrometry

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has become a powerful and widespread analytical tool in all fields of life science. Compared with other techniques, its high accuracy and sensitivity makes it a superior method, especially for the analysis of nucleic acids. Recent problems in the analysis of nucleic acids by MALDI-TOF MS can be solved using an automated MALDI-compatible sample-preparation system. Together with the reliable minisequencing assay, high-throughput genotyping of single nucleotide polymorphisms by MALDI-TOF MS is able to become a routine method in research, clinical genetics and diagnostics.

Protein identification with Teflon as matrix-assisted laser desorption/ionization sample support

Protein identification is a critical step in proteomics, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) plays an important role in that identification. Polytetrafluoroethylene (Teflon) was tested as a new MALDI sample support to improve protein identification. The tryptic peptides obtained from a model protein were bound to the surface of a modified MALDI sample holder via the hydrophobic interactions that occur between the Teflon surface and the peptide ion-pairs, and the affinity of alpha-cyano-4-hydroxycinnamic acid for the peptides. During that surface-binding step, the peptide mixture was also desalted and concentrated. A greater number of matched peptides and a larger sequence coverage were obtained for the proteins when Teflon was used as the sample support compared with conventional sample preparation methods and a stainless-steel surface. In addition, the characterization of a small amount of protein was improved with Teflon. Nine silver-stained protein spots obtained from 2-D gel of a human cerebrospinal fluid (CSF) proteome were identified by this method. Among the nine protein spots, peptide 6:c3c fragment and procollagen c-proteinase enhancer were not annotated in any published 2-D map of human CSF. A Teflon MALDI sample support is a low-cost, simple, and effective method that can be used to improve the quality of the MALDI mass spectrum of a complex tryptic peptide mixture, and to achieve a higher level of reliability and success in protein identification.

Optimization of guanidination procedures for MALDI mass mapping

Improved procedures for guanidination of lysine-containing peptides, a derivatization that results in increased MALDI mass spectral signal intensities are presented. The complete conversion of lysines to homoarginines can be accomplished in as little as 5 min. The method is demonstrated on a model peptide and on tryptic digests of three proteins. To demonstrate the applicability to proteomics samples, it is successfully applied to the digest of 50 fmol of a protein. Approaches for concentrating and purifying low-quantity protein digests following guanidination are evaluated. Experiments with the model peptide GRGDSPK enable investigation of the specificity of the guanidination reaction.

Large-scale genotyping by mass spectrometry: experience, advances and obstacles

Single nucleotide polymorphism (SNP) genotyping has become a key technology for genetic studies. In recent years, matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry has emerged as a very powerful method for SNP genotyping. Here, we discuss our experience in implementing a high-throughput SNP genotyping facility based on MALDI, and the issues encountered in adapting this to large-scale genetic studies. Most of these issues are not specific to using MALDI approaches, and they will also serve as valuable pointers for establishing high-throughput genotyping with other methods.

MALDI-TOF-MS analysis of droplets prepared in an electrodynamic balance: "wall-less" sample preparation

Methodology enabling mass spectral analysis of the composition of droplet(s) prepared in an electrodynamic balance (EDB) by matrix-assisted laser desorption/ionization (MALDI) is described. The dc field surrounding the electrodynamic balance was manipulated to eject single droplets at a time from the EDB thereby causing their deposition onto a MALDI sample plate precoated with matrix. When the laser was directed onto the droplet(s) and held stationary, marked gains in the signal-to-noise and signal-to-background ratios were realized with each subsequent mass spectrum due to the suppression of matrix cluster ion formation. Optical microscopy of the plate, after 1024 laser shots were fired at eight droplets that had been deposited one on top of the other, revealed a residual island of droplet matter (area approximately 3.1 x 10(-9) m2) inside the region where the crystalline matrix had been ablated away within the laser spot (area approximately 1.6 x 10(-8) m2). Removing the predried crystalline matrix layer and, instead, adding matrix into the starting solution was found to be a more effective means of suppressing matrix cluster ion formation. The chemical composition of the droplet(s) prepared in the EDB is discussed with regard to sample preconcentration, the images of the laser spot after MALDI, matrix cluster ion suppression, and the possibility for improved quantitation and detection limits by MALDI-TOF-MS.

Recent developments in quantification methods for metallothionein

The metallothioneins (MT), a family of proteins with relatively low molecular weight (6-7 kDa), are characterised by the intrinsic presence of 20 cysteinyl groups in their structure, which confers unique metal binding properties to the molecule. Since MT are involved in biological roles, quantification of MT remains an important task. To date, a large number of determination methods have been developed. In this paper recent developments, from 1995 to the present, in methodology employed in quantification studies of total MT and MT polymorphism are described. Different fields were taken into consideration, such as (i) separation techniques and hyphenated systems, (ii) electrochemical methods, (iii) immunological methods and (iv) quantification of MT mRNA. The data presented are based on our own and published results. A brief overview of the use of metallothionein as a biomarker is included as a relevant example of the importance of MT quantification. Finally, general problems associated with determination and evaluation of obtained results within the above four topics are mentioned.

Ready-made matrix-assisted laser desorption/ionization target plates coated with thin matrix layer for automated sample deposition in high-density array format

The methodology for ready-made matrix-assisted laser desorption/ionization (MALDI) target plates covered with an optimized thin layer consisting of matrix and nitrocellulose has been developed. Piezoelectric microdispensing enabled sample depositions in a high-density array format of 2000 sample depositions on a conventionally sized target plate (45 x 47 mm). The sample depositions were made reproducibly in a fully automated mode by using an in-house developed computer-controlled piezoelectric flow-through microdispenser. Additionally, the piezoelectric technique facilitated significant analyte enrichment that increased the detection sensitivity. The MS signal was obtained rapidly, generally within ten laser pulses. An airbrush device was used to generate a fine spray of matrix and nitrocellulose dissolved in acetone. The acetone evaporated instantly when reaching the target plate leaving the entire surface with a thin and uniform matrix/nitrocellulose coating consisting of very small crystals of matrix embedded in the nitrocellulose. These crystals acted as a seed-layer on subsequent analyte depositions, rendering homogeneous sample spots when using alpha-cyano-4-hydroxycinnamic acid (CHCA) as matrix. The relative standard deviation of the signal intensity between spots was (20-30)% (n = 30). The detection sensitivity was improved by restricting the sample spot diameter to 300 microm. The spot size was affected by the deposition rate and the evaporation rate of the dispensed sample volume. Mass spectra of a 25-amol peptide mixture deposition were successfully recorded.

On-target fraction collection for the off-line coupling of capillary isoelectric focusing with matrix-assisted laser desorption/ionization mass spectrometry

In the present work, we describe a collection system for the off-line coupling of capillary isoelectric focusing (CIEF) with matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. In this system, the capillary effluent is directly deposited in fractions onto the MALDI target via the use of a sheath liquid. The collected fractions are subsequently supplemented with matrix and further analysed by MALDI-TOF mass spectrometry for mass assignment. The experimental set-up includes a fiber optic based UV detector operating at 280 nm, which allows the study of the influence of the sheath liquid composition on the CIEF separation. The influence of the carrier ampholyte concentration on the protein MALDI spectra was also evaluated and the feasibility of the collection method was finally demonstrated with a mixture of four standard proteins.

Disposable polymeric high-density nanovial arrays for matrix assisted laser desorption/ionization-time of flight-mass spectrometry: I. Microstructure development and manufacturing

In order to meet the expected enormous demand for mass spectrometry (MS) throughput as a result of the current efforts to completely map the human proteome, this paper presents a new concept for low-cost high-throughput protein identification by matrix assisted laser desorption/ionization-time of flight-(MALDI-TOF)-MS peptide mapping using disposable polymeric high-density nanovial MALDI target plates. By means of microfabrication technology precision engineered nanovial arrays are fabricated in polymer substrates such as polymethylmethacrylate (PMMA) and polycarbonate (PC). The target plate fabrication processes investigated were precision micromilling, cold embossing and injection moulding (work in progress). Nanovial dimensions were 300, 400 or 500 microm. Typical array densities were 165 nanovials/cm2, which corresponds to 3,300 vials on a full Applied Biosystems MALDI target plate. Obtained MALDI data displayed equal mass resolution, accuracy, signal intensity for peptide standards as compared to high-density silicon nanovial arrays previously reported by our group [7], as well as conventional stainless steel or gold targets.

Sugar additives for MALDI matrices improve signal allowing the smallest nucleotide change (A:T) in a DNA sequence to be resolved

Sample preparation for matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) of DNA is critical for obtaining high quality mass spectra. Sample impurity, solvent content, substrate surface and environmental conditions (temperature and humidity) all affect the rate of matrix-analyte co-crystallization. As a result, laser fluence threshold for desorption/ionization varies from spot to spot. When using 3-hydroxypicolinic acid (3-HPA) as the matrix, laser fluence higher than the threshold value reduces mass resolution in time-of-flight (TOF) MS as the excess energy transferred to DNA causes metastable decay. This can be overcome by either searching for 'hot' spots or adjusting the laser fluence. However, both solutions may require a significant amount of operator manipulation and are not ideal for automatic measurements. We have added various sugars for crystallization with the matrix to minimize the transfer of excess laser energy to DNA molecules. Fructose and fucose were found to be the most effective matrix additives. Using these additives, mass resolution for DNA molecules does not show noticeable deterioration as laser energy increases. Improved sample preparation is important for the detection of single nucleotide polymorphisms (SNPs) using primer extension with a single nucleotide. During automatic data acquisition it is difficult to routinely detect heterozygous A/T mutations, which requires resolving a mass difference of 9 Da, unless a sugar is added during crystallization.

Large-gel two-dimensional electrophoresis-matrix assisted laser desorption/ionization-time of flight-mass spectrometry: an analytical challenge for studying complex protein mixtures

The large-gel two-dimensional electrophoresis (2-DE) technique, developed by Klose and co-workers over the past 25 years, provides the resolving power necessary to separate crude proteome extracts of higher eukaryotes. Matrix assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS) provides the sample throughput necessary to identify thousands of different protein species in an adequate time period. Spot excision, in situ proteolysis, and extraction of the cleavage products from the gel matrix, peptide purification and concentration as well as the mass spectrometric sample preparation are the crucial steps that interface the two analytical techniques. Today, these routines and not the mass spectrometric instrumentation determine how many protein digests can be analyzed per day per instrument. The present paper focuses on this analytical interface and reports on an integrated protocol and technology developed in our laboratory. Automated identification of proteins in sequence databases by mass spectrometric peptide mapping requires a powerful search engine that makes full use of the information contained in the experimental data, and scores the search results accordingly. This challenge is heading a second part of the paper.

Determination of beta-2 microglobulin levels in plasma using a high-throughput mass spectrometric immunoassay system

A high-throughput mass spectrometric immunoassay (MSIA) system for the analysis of proteins directly from biological fluids is reported. A 96-well-format robotic workstation equipped with antibody-derivatized affinity pipet tips was used for the parallel extraction of specific proteins from samples and subsequent deposition onto 96-well arrayed matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) targets. Interferences from nonspecifically bound proteins were minimized through choice of appropriate affinity pipet tip derivatization chemistries. Sample preparation for MALDI-TOFMS was enhanced through the use of hydrophobic/hydrophilic contrasting targets, which also presented functionalities found to promote matrix/analyte crystal growth. Automated mass spectrometry was used in the unattended acquisition of data, resulting in an analysis rate of approximately 100 samples/h (biological fluid-->data). The quantitative MSIA of beta2m levels present in human plasma samples is given as illustration.

Measurements of protein stability by H/D exchange and matrix-assisted laser desorption/ionization mass spectrometry using picomoles of material

Recently, we reported on a new H/D exchange- and matrix-assisted laser desorption/ionization (MALDI)-based technique, termed SUPREX, that can be used to measure the thermodynamic stability of a protein (Ghaemmaghami, S.; Fitzgerald, M. C.; Oas, T. G. Proc. Natl. Acad. Sci. U.S.A. 2000, 97, 8296-8301). In the work described here, we report on our efforts to optimize the sensitivity of SUPREX analyses. We describe a new sample handling protocol for SUPREX that involves the use of batch chromatography methods with reversed-phase chromatographic media for the microconcentration and desalting of SUPREX samples. Using ribonuclease A as a model protein system, we demonstrate that our new protocol permits the SUPREX analysis of as little as 10 pmol of protein. This amount of protein is 100-fold less than the amount of material required in our initial SUPREX protocol, and it is 1-2 orders of magnitude less than the amount of material required in conventional spectroscopy-based methods for measuring the thermodynamic stability of a protein.

Protein identification based on matrix assisted laser desorption/ionization-post source decay-mass spectrometry

Due to its very short analysis time, its high sensitivity and ease of automation, matrix-assisted laser desorption/ionization (MALDI)-peptide mass fingerprinting has become the preferred method for identifying proteins of which the sequences are available in databases. However, many protein samples cannot be unambiguously identified by exclusively using their peptide mass fingerprints (e.g., protein mixtures, heavily posttranslationally modified proteins and small proteins). In these cases, additional sequence information is needed and one of the obvious choices when working with MALDI-mass spectrometry (MS) is to choose for post source decay (PSD) analysis on selected peptides. This can be performed on the same sample which is used for peptide mass fingerprinting. Although in this type of peptide analysis, fragmentation yields are very low and PSD spectra are often very difficult to interpret manually, we here report upon our five years of experience with the use of PSD spectra for protein identification in sequence (protein or expressed sequence tag (EST)) databases. The combination of peptide mass fingerprinting and PSD and analysis described here generally leads to unambiguous protein identification in the amount of material range generally encountered in most proteome studies.

A CE-MALDI interface based on the use of prestructured sample supports

We have developed an off-line coupling of capillary electrophoresis (CE) to matrix-assisted laser desorption/ionization time-of-flight mass spectrometry(MALDI-TOF-MS) based on CE fraction collection onto prestructured MALDI sample supports. Analyte carryover and detection sensitivity were investigated using a standard peptide mixture. Low femtomole amounts were detected, and no noticeable carryover was discovered. The performance of the method was evaluated with a mixture of tryptic digests of proteins from a human fetal brain cDNA expression library. The total number of identified peptides was increased from 47 to 211 when the CE-MALDI interface was used compared to direct MALDI-MS analysis. Sequence coverage with CE-MALDI was in the 25-60% range for the different proteins, corresponding to an increase of 1.3-4.9 times relative to that obtained with MALDI-MS of the crude mixture. Fractionation of sample components also facilitated protein identification by MALDI postsource decay analysis. Our initial results suggest this CE-MALDI interface can be used for the analysis of complex peptide mixtures isolated from biological tissues.

Identification and characterization of asporin. a novel member of the leucine-rich repeat protein family closely related to decorin and biglycan

Asporin, a novel member of the leucine-rich repeat family of proteins, was partially purified from human articular cartilage and meniscus. Cloning of human and mouse asporin cDNAs revealed that the protein is closely related to decorin and biglycan. It contains a putative propeptide, 4 amino-terminal cysteines, 10 leucine-rich repeats, and 2 C-terminal cysteines. In contrast to decorin and biglycan, asporin is not a proteoglycan. Instead, asporin contains a unique stretch of aspartic acid residues in its amino-terminal region. A polymorphism was identified in that the number of consecutive aspartate residues varied from 11 to 15. The 8 exons of the human asporin gene span 26 kilobases on chromosome 9q31.1-32, and the putative promoter region lacks TATA consensus sequences. The asporin mRNA is expressed in a variety of human tissues with higher levels in osteoarthritic articular cartilage, aorta, uterus, heart, and liver. The deduced amino acid sequence of asporin was confirmed by mass spectrometry of the isolated protein resulting in 84% sequence coverage. The protein contains an N-glycosylation site at Asn(281) with a heterogeneous oligosaccharide structure and a potential O-glycosylation site at Ser(54). The name asporin reflects the aspartate-rich amino terminus and the overall similarity to decorin.

Application of nonporous polyurethane (PU) membranes and porous PU thin films as sample supports for MALDI-MS of wheat proteins

Non-porous polyurethane (PU) membranes and porous PU thin films are used as sample supports for MALDI-TOFMS. Mass spectra obtained are compared with those acquired using metal targets and the crushed matrix method. The compounds characterized are wheat proteins which consist of moderately water-soluble gliadins, and of water-insoluble low molecular weight (LMW) and high molecular weight (HMW) glutenins. Mass spectra obtained using the PU supports are in general of good quality, and this method of sample preparation is the most convenient for sample handling. In the case of gliadins and LMW glutenins, the spectra obtained on PU are comparable with those obtained using metal supports. Isolation of the LMW and HMW wheat proteins characterized in this study requires the use of buffers incompatible with MALDI. Spectra of samples containing buffer components on PU supports are of better quality than those obtained using the crushed matrix method. This effect is attributed to stronger protein binding onto the PU supports, which allows for extensive washing and removal of water soluble buffer components. The PU film, when cast onto a MALDI probe, is porous and flat in topology. The differences in surface characteristics between the PU film and the PU membrane result in slight variations in the mass spectra. The extent of surface charging, observed significantly using 50 µm thick PU membranes, decreases with 25 µm membranes and becomes insignificant with PU thin films. An important advantage of using the PU supports is the possibility of preparing samples on the film or membrane in the field and of analysing them at a later time. This is especially important when samples are susceptible to chemical degradation in solution. These proteins are known to degrade while stored in solution. We have thus incorporated the use of PU membrane–film supports into our routine analysis of these proteins.Key words: gliadins, glutenins, MALDI, membrane supports, polymeric supports, time-of-flight analysis.

Alpha-cyano-4-hydroxycinnamic acid affinity sample preparation. A protocol for MALDI-MS peptide analysis in proteomics

We present a new MALD1 sample preparation technique for peptide analysis using the matrix alpha-cyano-4-hydroxy-cinnamic acid (CHCA) and prestructured sample supports. The preparation integrates sample purification, based on the affinity of microcrystalline CHCA for peptides, thereby simplifying the analysis of crude peptide mixtures. Enzymatic digests can thus be prepared directly, without preceding purification. Prepared samples are homogeneous, facilitating automatic spectra acquisition. This method allows preparation of large numbers of samples with little effort and without the need for automation. These features make the described preparation suitable for cost-efficient high-throughput protein identification. Performance of the sample preparation is demonstrated with in situ proteolytic digests of human brain proteins separated by two-dimensional gel electrophoresis.

Meeting Review: The 48th ASMS conference on mass spectrometry and allied topics

The general theme of the meeting was the application of mass spectrometry to pharmaceutical and biotechnological research. The majority of the oral presentations and posters were concerned with the development and application of all mass spectrometric techniques related to proteomics.