MALDI-TOF analysis

Hurst, G. B. Weaver, K. Doktycz, M. I Buchanan, M. V. Costello, A. M. Lidstrom, M. E. MALDI-TOF analysis of polymerase chain reaction products from methan-otrophic bacteria. Anal. Chem. 1998, 70, 2693-2698. 

The peptide mixture on the MALDI target can be exposed to a chemical derivatization to confirm the identity of a peptide by the mass shift associated with the sequence-specific derivatization. A large number of possible derivatization reactions can be combined with the MALDI-TOF analysis. Their usefulness depends critically on the kinetics of the derivatization reaction, whether the reaction is complete with small amounts of peptides and whether only one product is generated. A visible MALDI signal can be generated from low atomole of peptide present under the laser beam (Vorm et al., 1994), but these amounts are often not sufficient... 

In 1988, Tanaka et al. first reported the use of ultrafine metal powder in protein analysis. Since then, many inorganic materials, including graphite particles, fine metal or metal oxide powder, silver thin-film substrates or particles,and silica gel, have been used in the MALDI-TOF analysis of low-mass molecules. 

Sugui, J.A. et al., MALDI-TOF analysis of mixtures of 3-deoxyanthocyanidins and anthocyanin. 

The most widely used mass spectrometric identification procedure is MALDI-Tof analysis of the entire peptide mixture. Gas-phase matrix interaction with peptide ions in MALDI-Tof results in singly charged ions, giving a mass profile that is highly characteristic of the protein from which the peptides are derived. These peptide masses (actually protonated peptide molecular ions, MH+) can be used to search databases (either protein or nucleic acid databases) to identify the proteins. The two most important factors in successfully identifying proteins by this approach are the number of matching peptide masses and the accuracy of the peptide mass determination. 

Table 1 Search of a Protein Sequence Database With Ions Resulting from a MALDI-Tof Analysis of a Tryptic Digest of a Rat Serum Protein Enriched by Cation-Exchange Chromatography a...

Transfer a small amount of resin to the test tube and perform test for the presence of free hydroxyl groups (see refs. (65) and (66)) or monitor the coupling by MALDI-TOF analysis. 

The two mainstays of modem mass spectrometry, electrospray MS and MALDI/ TOFMS, can both be used with adequate sensitivity for single-bead detection of molecular weight and structural information [37], Single-bead MS using TFA cleavage and MALDI/ TOF analysis is now a well-established technique [38 11], A Scripps group [42] reports... 

Soeryapranata, E., Powers, J.R., Fajarrini, F., Weller, K.M., Hill, H.H., and Siems, W.F. 2002. Relationship between MALDI-TOF analysis of (3-cn fl93-209 concentration and sensory evaluation of bitterness intensity of aged cheddar cheese. J. Agric. Food Chem. 50, 4900-4905. 

Fig. 35 a. SEC of oligo(caprolactone) and MALDI-TOF analysis of fractions (from [183] with permission)... 

We further characterized a sample by MALDI-TOF and SiNMR (run 5, Table 1). The MALDI TOF analysis shows the presence of multiple chain populations with different chain-ends, SiOH/SiOH (A), SiOH/SiOMe (B) and SiOMe/ SiOMe (C) (Fig. 5). A Si NMR spectrum of the same sample is given in Fig. 6, where it shows the presence of D, D, in addition to the linear polymer and the absence... 

To examine the ability of membranes to prepare samples with known contaminants, we contaminated the above peptide and protein solution with 5% glycerol and 500 mM NaCl. In addition to preventing effective crystallization of analyte samples with matrix on conventional stainless steel surfaces, glycerol and sodium contaminants are frequently present in biological samples. Doped samples were prepared for MALDI-TOF analysis by saturating the membrane with MeOH, immediately followed by the addition of 1 ul of the sample. The membrane was washed 3 times with 3-6 ml 70% methanol in water and allowed to dry after each wash. Once dry, lul saturated matrix solution was added to the sample spot. 

The only important limitation arises from the peptide mass fragment analysis. It appears to be completely unambiguous for single proteins (Thble 2). As the number of proteins in a mixture or in a complex increase the number of unambiguous M/Z values from the MALDI-TOF analysis decrease. An important observation is that when ambiguities arose in this study, only MGPs appeared in the C2N2 driven association. None of the other 3400 proteins showed up. 

Fig. 4 General approach of the bioreactive MALDI mass spectrometer probe tips. Goid piated probe tips are activated through the covalent attachment of enzymes (the general terminology of Au/enzyme is used to indicate the nature of the activated surfaces). The probe tips are then used for protein characterization by direct appiication of the analyte and time given for digestion. The digestions are stopped with the addition of a MALDI matrix, the reaction product-matrix mixture aiiowed to dry, and the probe tips are inserted into the mass spectrometer for MALDI-TOF analysis.

It is well known that at present MALDI-TOF analysis of broad MMD polymers represents a difficult task [282]. Typically, as the... 

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