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MALDI Matrix (maldi + matrix)

Distribution by Scientific Domains

Chemistry	91%

Selected Abstracts

A Novel MALDI Matrix for Analyzing Peptides and Proteins: Paraffin Wax Immobilized Matrix,

CHINESE JOURNAL OF CHEMISTRY, Issue 1 2009
Yuanlong WEI
Abstract A new kind of MALDI matrix, termed paraffin wax immobilized matrix, was used to study peptide mixtures and proteins. During the preparation process, the paraffin wax was heated and coated on the stainless-steel target plate, and then 2,5-dihydrobenzoic acid (DHB) was deposited on the paraffin layer and stainless-steel target plate to obtain different kinds of matrix spots. The morphology of matrices on different supports and peptide-matrix co-crystallization were observed by a high resolution digital-video microscopy system. Peptide mixtures and bovine serum albumin (BSA) digests were used to investigate the performance of the immobilized matrices on the paraffin target. The MALDI-FTMS analysis results also showed that the detection sensitivity of matrices immobilized in the paraffin sample support was better than that on other sample supports. [source]

Metal ion attachment to the matrix meso-tetrakis(pentafluorophenyl)porphyrin, related matrices and analytes: an experimental and theoretical study,

JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 11 2009
Jeroen J. A. van Kampen
Abstract In a previous study [van Kampen et al.Analytical Chemistry 2006; 78: 5403], we found that meso-tetrakis (pentafluorophenyl)porphyrin (F20TPP), in combination with lithium salts, provides an efficient matrix to cationize small molecules by Li+ attachment and that this combination can be successfully applied to the quantitative analysis of drugs, such as antiretroviral compounds using matrix-assisted laser desorption ionization in conjunction with a time-of-flight analyzer (MALDI,TOF). In the present study, we further explore the mechanism of metal ion attachment to F20TPP and analytes by MALDI,FTMS(/MS). To this end, we have studied the interaction of F20TPP and analytes with various mono-, di- and trivalent metal ions (Li+, Na+, K+, Rb+, Cs+, Co2+, Cu2+, Zn2+, Fe2+, Fe3+ and Ga3+). For the alkali cations, we find that F20TPP forms complexes only with Li+ and Na+; in addition, model analyte molecules such as poly(ethyleneglycol)s, mixed with F20TPP and the alkali cations, also only form Li+ and Na+ adducts. This contrasts sharply with the commonly used matrix 2,5-dihydroxybenzoic acid, where analytes are most efficiently cationized by Na+ or K+. Reasons for this difference are delineated. Ab initio calculations on porphyrin itself reveal that even the smallest alkali cation, Li+, does not fit in the porphyrin cavity, but lies on top of it, pushing the 21H and 23 H hydrogen atoms out of and below the plane with concomitant bending of the porphyrin skeleton in the opposite direction, i.e. toward the cation. Thus, the Li+ ion is not effectively sequestered and is in fact exposed and thus accessible for donation to analyte molecules. Interaction of F20TPP with di- and trivalent metal ions leads to protoporphyrin,metal ions, where the metal ion is captured within the protoporphyrin dianion cavity. The most intense signal is obtained when F20TPP is reacted with CuCl2 and then subjected to laser ablation. This method presents an easy general route to study the metal containing protoporphyrin molecules, which could all act as potential MALDI matrices. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Glycoproteomics of N -glycosylation by in-gel deglycosylation and matrix-assisted laser desorption/ionisation-time of flight mass spectrometry mapping: Application to congenital disorders of glycosylation

PROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 10 2005
Dijana
Abstract A general strategy for the structural evaluation of N -glycosylation, a common post-translational protein modification, is presented. The methods for the release of N -linked glycans from the gel-separated proteins, their isolation, purification and matrix-assisted laser desorption/ionisation-mass spectrometry (MALDI-MS) analysis of their mixtures were optimised. Since many glycoproteins are available only at low quantities from sodium dodecyl sulphate-polyacrylamide gel electrophoresis or two-dimensional gels, high attention was paid to obtain N -glycan mixtures representing their actual composition in human plasma by in-gel deglycosylation. The relative sensitivity of solid MALDI matrices for MS analysis of acidic N -glycans was compared. The most favourable results for native acidic N -glycans were obtained with 2,4,6-trihydroxyacetophenone monohydrate/diammoniumcitrate as a matrix. This matrix provided good results for both neutral and acidic mixtures as well as for methylated N -glycans. In the second part of this paper the potential of such an optimised MS strategy alone or in combination with high pH anion-exchange chromatography profiling for the clinical diagnosis of congenital disorders of glycosylation is presented. [source]

Serum biomarker profiling by solid-phase extraction with particle-embedded micro tips and matrix-assisted laser desorption/ionization mass spectrometry,

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 7 2008
Arti Navare
One of the main challenges in high-throughput serum profiling by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is the development of proteome fractionation approaches that allow the acquisition of reproducible profiles with a maximum number of spectral features and minimum interferences from biological matrices. This study evaluates a new class of solid-phase extraction (SPE) pipette tips embedded with different chromatographic media for fractionation of model protein digests and serum samples. The materials embedded include strong anion exchange (SAX), weak cation exchange (WCX), C18, C8, C4, immobilized metal affinity chromatography (IMAC) and zirconium dioxide particles. Simple and rapid serum proteome profiling protocols based on these SPE micro tips are described and tested using a variety of MALDI matrices. We show that different types of particle-embedded SPE micro tips provide complementary information in terms of the spectral features detected for , -casein digests and control human serum samples. The effect of different sample pretreatments, such as serum dilution and ultrafiltration using molecular weight cut-off membranes, and the reproducibility observed for replicate experiments, are also evaluated. The results demonstrate the usefulness of these simple SPE tips combined with offline MALDI-TOF MS for obtaining information-rich serum profiles, resulting in a robust, versatile and reproducible open-source platform for serum biomarker discovery. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Serum protein profiling by miniaturized solid-phase extraction and matrix-assisted laser desorption/ionization mass spectrometry

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 12 2005
Anne K. Callesen
Serum profiling by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) holds promise as a clinical tool for early diagnosis of cancer and other human diseases. Sample preparation is key to achieving reproducible and well-resolved signals in MALDI-MS; a prerequisite for translation of MALDI-MS based diagnostic methods to clinical applications. We have investigated a number of MALDI matrices and several miniaturized solid-phase extraction (SPE) methods for serum protein concentration and desalting with the aim of generating reproducible, high-quality protein profiles by MALDI-MS. We developed a simple protocol for serum profiling that combines a matrix mixture of 2,5-dihydroxybenzoic acid and , -cyano-4-hydroxycinnamic acid with miniaturized SPE and MALDI-MS. Functionalized membrane discs with hydrophobic, ion-exchange or chelating properties allowed reproducible MALDI mass spectra (m/z 1000,12,000) to be obtained from serum. In a proof-of-principle application, SPE with chelating material and MALDI-MS identified protein peaks in serum that had been previously reported for distinguishing a person diagnosed with breast cancer from a control. These preliminary results indicate that this simple SPE/MALDI-MS method for serum profiling provides a versatile and scalable platform for clinical proteomics. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Sample preparation effects in matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry of partially depolymerised methyl cellulose

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 11 2003
Dane Momcilovic
Methyl cellulose (MC) was partially depolymerised and the oligomers thus obtained were studied by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOFMS). The depolymerisation was either enzymatic or acidic. Fractions of enzymatically depolymerised MC were collected from size-exclusion chromatography and subjected to a sample preparation investigation. Several MALDI matrices and solvents were evaluated. The results showed that the solvent choice had a significant effect on the measured degree of substitution (DS). Aprotic solvents produced higher DS values, which was most likely due to poor solubility of species with low DS. The obtained signal intensity, however, did not correlate with the solubility but seemed to be more dependent on certain matrix/solvent combinations. All the matrices attempted produced mass spectra with sufficient signal intensity for accurate peak area calculation. The choice of matrix did not have any significant effect on the measured DS. Sample spots obtained from organic solvents had a more homogeneous distribution of the analyte and smaller crystals than those obtained from water. This increased both the reproducibility and peak resolution and in addition the analysis time was shorter. DS measurements were performed on two acidically depolymerised MCs with different nominal DS values. It was easy to distinguish between the two MCs, and the measured DS values agreed well with the values supplied by the manufacturers. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Facilitating the hyphenation of CIEF and MALDI-MS for two-dimensional separation of proteins

ELECTROPHORESIS, Issue 15 2010
Chang Cheng
Abstract Both CIEF and MALDI-MS are frequently used in protein analysis, but hyphenation of the two has not been investigated proportionally. One of the major reasons is that the additives (such as carrier ampholytes and detergent) in CIEF severely suppress the MALDI-MS signal, which hampers the hyphenation of the two. In this paper, we develop a simple means to alleviate the above signal-suppressing effect. We first deposit 1,,L of water onto a MALDI-MS target, deliver a fraction of CIEF-separated protein (,0.1,,L) to the water droplet, evaporate the solvent, add 0.5,,L of MALDI matrix to the sample spot, dry the matrix and move the target plate to a MALDI-TOF-MS for mass spectrum measurement. We optimize the droplet volume and the laser-ablation region. Under the optimized conditions, we improve the S/N by two- to tenfold. We also apply this method for 2-D separations of standard proteins and apolipoprotein A,I, a membrane protein expressed in Escherichia coli cells. [source]

Molecular mass determination of plasma-derived glycoproteins by ultraviolet matrix-assisted laser desorption/ionization time-of-flight mass spectrometry with internal calibration

JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 11 2002
Omar Belgacem
Abstract Human plasma-derived antithrombin III (AT-III), factor IX (FIX) and vitronectin (VN) were characterized as native glycoproteins and in their de- N -glycosylated form by means of MALDI mass spectrometry. The average molecular masses of the three complex glycoproteins were determined applying internal calibration with high-mass, well-defined protein calibrants. Internal calibration generated for the 47 kDa yeast protein enolase a mass precision in the continuous and delayed extraction mode of ±0.12 and ±0.022%, respectively. The achievable mass accuracy for such a high-mass, unmodified protein was in the range of 0.02% in the continuous mode, which turned out to be better than in the delayed extraction mode. Purification of all (glyco) proteins (even the calibration proteins) by means of ZipTip® technology and direct elution with a solvent system containing the appropriate MALDI matrix turned out to be a prerequisite to measure the exact molecular masses with an internal calibration. The average molecular masses of the two different forms of AT-III, namely AT-III, and AT-III,, were shown to be 57.26 and 55.04 kDa, respectively. The 2.22 kDa mass difference is attributed to the known difference in carbohydrate content at one specific site (Asn-135). After exhaustive de- N -glycosylation (by means of PNGase F) of the ,- and ,-form and subsequent MALDI-MS analysis, average molecular masses of 48.96 and 48.97 kDa, respectively, were obtained. These values are in good agreement (,0.15%) with the calculated molecular mass (49.039 kDa) of the protein part based on SwissProt data. The molecular mass of the heavily post-translational modified glycoprotein FIX was found to be 53.75 kDa with a peak width at 10% peak height of 4.5 kDa, because of the presence of many different posttranslational modifications (N - and O -glycosylation at multiple sites, sulfation, phosphorylation, hydroxylation and numerous ,-carboxyglutamic acids). MALDI-MS molecular mass determination of the native, size-exclusion chromatography-purified, VN sample revealed that the glycoprotein was present as dimer with molecular mass of 117.74 kDa, which could be corroborated by non-reducing SDS-PAGE. After sample treatment with guanidine hydrochloride and mass spectrometric analysis, a single, new main component was detected. The molecular mass turned out to be 59.45 kDa, representing the monomeric form of VN, known as V75. The determined molecular mass value was shown to be on one hand lower than from SDS-PAGE and on the other higher than the calculated amino acid sequence molecular mass (52 277 Da), pointing to the well-known SDS-PAGE bias and to considerable post-translational modifications. Further treatment of the sample with a reducing agent and subsequent MALDI-MS revealed two new components with molecular masses of 49.85 and 9.41 kDa, corresponding to V65 and V10 subunits of VN. PNGase F digest of the V75 and V65 units and MS analysis, exhibiting a molecular mass reduction of 6.37 kDa in both cases, verified the presence of a considerable amount of N -glycans. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Study of human neutrophil peptides in saliva by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 19 2009
Ming-Hui Yang
Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry is used to rapidly characterize the human neutrophil peptides , HNP 1, 2, and 3 , in saliva. The saliva excreted from the parotid and sublingual/submandibular glands of 70 individuals were collected and examined using MALDI-TOF. The MALDI approach requires no sample pretreatment other than mixing the saliva-absorbing material with the matrix and drying under ambient conditions. Tissue paper was the best material for collecting the saliva samples because of its strong texture and high absorbance, and sinapinic acid was the best MALDI matrix for the analysis of the HNPs. HNPs were detected in almost all the samples collected from the parotid glands, with no obvious differences among age or gender. In contrast, the distribution of the HNPs in the samples collected from the sublingual/submandibular glands was age-dependent: no HNPs were detected for those collected from individuals younger than 30, but the HNPs were present in all of the samples collected from those older than 60 years. The increased probability of detecting saliva HNPs with age suggests that HNPs may function as a biomarker for aging. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry of 4-sulfophenyl isothiocyanate-derivatized peptides on AnchorChipÔ sample supports using the sodium-tolerant matrix 2,4,6-trihydroxyacetophenone and diammonium citrate

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 6 2005
Leon P. Oehlers
The reagent 4-sulfophenyl isothiocyanate (SPITC) is an effective, stable, and inexpensive alternative to commercially available reagents used in the N-terminal sulfonation of peptides for enhanced postsource decay (PSD) in matrix-assisted laser desorption/ionization time-of-flight mass spectrometric (MALDI-TOFMS) analyses. However, suppression of ionization of sulfonated peptides due to sample and matrix contaminants such as sodium can be a problem when using prestructured MALDI target sample supports, such as the Bruker Daltonics AnchorChipÔ. We show that use of the salt-tolerant matrix 2,4,6-trihydroxyacetophenone containing diammonium citrate (THAP/DAC) as an alternative to , -cyanohydroxycinnamic acid (HCCA) reduces the need for extensive washing of ZipTip-bound peptides or additional on-target sample clean-up steps. Use of the THAP/DAC matrix results in selective ionization of sulfonated peptides with greater peptide coverage, as well as detection of higher mass derivatized peptides, than was observed for HCCA or THAP alone. The THAP/DAC matrix is quite tolerant of sodium contamination, with SPITC-peptides detectable in preparations containing up to 50,mM NaCl. In addition, THAP/DAC matrix was found to promote efficient PSD fragmentation of sulfonated peptides. We demonstrated the utility of using the THAP/DAC MALDI matrix for peptide sequencing with DNA polymerase , tryptic peptide mixture, as well as tryptic peptides derived from Xiphophorus maculatus brain extract proteins previously separated by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). Copyright © 2005 John Wiley & Sons, Ltd. [source]

Evaluation of pyridoindoles, pyridylindoles and pyridylpyridoindoles as matrices for ultraviolet matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 23 2001
Hiroshi Nonami
In an effort to gain an understanding of the processes governing ultraviolet matrix-assisted laser desorption/ionization (UV-MALDI), direct comparison was made of the mass spectra of proteins, carbohydrates and synthetic polymers (polyethylene glycol, polyester and polyamide) by using pyridylindoles, pyridoindoles and pyridylpyridoindoles as UV (337,nm)-MALDI-TOFMS matrices in positive and negative ion mode. In order to study the combined effect of the indole N-H and the pyridine nitrogen of the MALDI matrix on the desorption/ionization process in MALDI, compounds were selected that include either or both of these functions in their structure. Within the compounds studied only those that possess simultaneously both functions in a 1,4-relation behave as very good matrices for proteins. These compounds also work as matrices for some carbohydrates and synthetic polymers used as analytes in the present study. Some of the compounds were also found to be useful for the post-source decay (PSD) analysis of cyclodextrins in positive and negative ion mode. In several cases we also examined the matrix behavior of the corresponding N-methylindole derivatives. Copyright © 2001 John Wiley & Sons, Ltd. [source]