Sample MALDI

MALDI-TOF was done on a Kratos Kompact Maldi III mass spectrometer fitted with a standard 337 nm nitrogen laser and operated in the linear mode at an accelerating voltage of 20 kV. The matrix used was a-cyano-4-hydroxyciimamic acid (33mM in acetonitrile/methanol, premade from BRS) at a ratio of 1 1 with purified peptide samples. MALDI sample slides were loaded with O.S-1.0 uL of matrix/sample mixture (estimated 1-10 pmol peptide). The data was reprocessed using the Kratos software provided with the instrument. Theoretical masses were determined by utilizing a spreadsheet in which individual peptide masses were added to all possible caibohycfrate forms these masses were then compared to the observed masses to identify structures consistent with the mass results obtained. 

UV, or evaporative light-scattering detection (ELSD). In a related approach, Schmid et al. described an automated robotics system based on SPE [45]. This system uses 1-3 fractionation steps, followed by a concentrahon step to generate semipurihed samples. MALDI-TOE was used to assess the purity and identity of the resulhng fractions. The complexity of the hnal frachons was dramatically reduced, resulting in better compatibility with their biological screens. These developments in automated fractionation have been used to generate a purihed central natural product pool, as described by Koch et al. [46]. 

Specimen Sample MALDI Sample preparation Refs... 

MALDI MS is an analytical approach suitable for obtaining molecular weights of peptides and proteins from complex samples. MALDI MS can profile the peptides and proteins from single-cell and small tissue samples without the need for extensive sample preparation, except for cell isolation and matrix preparation. Strategies for peptide identification and characterization of post-translational modifications are versatile and broadly applicable. " ... 

Finally, the transcripts were completely digested by RNase Ti at 37°C for 10 min with MALDI matrix (3-HPA) added as a denaturant. Briefly, 5 pL of RNA transcript (up to 20 pg) is added to 4 pL 3-HPA in 50% ACN/water and 1 pL of RNase Tj (1000 units) and reacted for 10 min and then placed on ice for MALDI preparation. For highest quality spectra, samples are desalted by reverse-phase purification in ZipTips according to manufacturer s directions for nucleic acid purification [96]. The final step in this process is elution of purified RNA oligonucleotide fragments onto the MALDI target using 2 pL of the MALDI matrix itself. Samples (MALDI spots ) are allowed to air dry or may be rapidly dried under vacuum. 

Initiate the image process with the oMALDI Server software. The sample MALDI plate will be moved from one spot to the other spot under a stationary laser automatically, creating a raster of desorbed areas over the tissue surface. 

MALDI is used to transform non-absorbing samples into absorbing samples. MALDI works best if the matrix is a strong absorber at the chosen laser wavelength. Nictonic acid, the first useful matrix for polymer molecules, absorbs at the 266 nm laser wavelength. Threshold irradiances for ion formation is 10 -10 W cm . ... 

---