Services Offered

Proteomics

Accurate Mass

Accurate mass is used to determine the molecular weight of a sample to within 10 ppm or in other words, accurate to the third decimal point. It is used to verify a predicted molecular formula of a pure compound. The analyte is mixed with an internal standard to use as a "lock mass" or internal calibration. The Q-TOF with ESI, and LCT are available for accurate mass determination.

Molecular Weight Analysis

A simple molecular weight analysis can determine the presence or absence of a compound, purity, relative concentration and molecular weight. We can measure molecular weights as low as 50 Da and as high as 150,000 Da (and higher, no one has submitted anything bigger). ESI, EI and MALDI can all be used for this type of sample. Polymers, peptides, proteins, oligonucleotides are typically analyzed by simple molecular weight analysis. Most of our instruments are high resolution, so you can still get isotope information with the simple molecular weight analysis.

Polymer Distribution

Polymer distribution of polar and non-polar polymers can be determined using MALDI-TOF MS. Polymers must be soluble in water or organic solvent for analysis. Our software package on the MALDI allows for calculation of Mn, Mw.

Protein/Peptide Analysis

Protein and peptides can be analyzed by both MALDI and ESI. Peptides and proteins are desalted prior to analysis, all buffers and salts must be removed for mass spec analysis as it suppresses ionization and many buffers are observed as background in the mass spectrum. As a guideline, we would need approximately 0.5 ug of a 10 KDa protein, 2.5 ug of a 50 KDa protein and 5 - 10 ug of a 100 KDa protein for good results. Please include the sequence if known at the time of sample submission.

Oligonucleotide Analysis

Oligonucleotides (DNA and RNA) can be analyzed by both MALDI and ESI. As with peptides and proteins, oligos are desalted prior to analysis, all buffers and salts must be removed for mass spec analysis as it suppresses ionization and many buffers are observed as background in the mass spectrum.

LC/MS

LC/MS is a very effective technique to combine peak detection with peak identification. Combining chromatography with mass spectrometry allows the chromatographer to "see inside" the chromatographic peak and to resolve co-eluting compounds of different molecular weights. Molecular weight information can identify predicted unknowns with better certainty and identify true unknowns by obtaining a "fingerprint' mass spectrum or fragmentation from CID and searching against commercial databases of spectra.

MS/MS

MS/MS or CID is used to determine structural or sequence information. The Esquire, and Q-TOF (ESI) can give fragment information. For ESI applications, the target molecule is isolated in the mass spectrometer and then collided with a gas to induce fragmentation. Due to the inherent nature of EI, molecules fragment as part of the ionization process. Here is an example of a tryptic peptide sequenced using the QTOF from Dr Micheal Freitas' research group.

GC-MS

Gas chromatography (GC) and mass spectrometry (MS) make an effective combination for chemical analysis. Among its uses are drug testing and environmental contaminant identification. The sample is injected through an injection port of the GC device, the GC instrument vaporizes the sample and then separates and analyzes the various components. MS identifies the separated substances by using an electron impact ionization source (EI) which breaks the molecules into charged fragments and detected by the mass analyzer. A spectral plot displays the mass of each fragment under each peak in the GC plot. The compound can be identified by the GC retention time, the parent ion and fragmentation pattern as searched by a database of known compounds. The retention time can help to differentiate between some compounds.

IR-MS

A sample's isotopic composition is measured by determining the ratios of the stable isotope masses being examined the current configuration of our instrument measures 15N/14N or 13C/12C, as appropriate. These ratios are measured on an isotope ratio mass spectrometer, a device that separates ions of the element of interest on the basis of their differing mass/charge ratio (m/z). Biological materials analyzed for stable isotope content include leaves, roots, soil, plasma and other solid and liquid substances. Before samples can be analyzed, they must be converted into the simple gases N2 or CO2. A Carlo Erba NA 1500 Series II NC elemental analyzer is used to combust solid and viscous liquid samples containing organic matter.