The Mass Spectrometry Facility is able to assist with a wide variety of projects such as:
Identification of purified peptides and proteins using peptide fingerprinting and sequencing
Identification of protein bands from Coomassie or silver stained gel
Accurate mass identification of proteins/peptide targets
Mass Spectrometry offers both high precision and high accuracy. These two very important characteristics are necessary for reliable identification of biological molecules such as proteins and peptides as well as small molecules. Exact mass can be accurately determined with the LC-MS Q-TOF to a 2ppm (2 x 10-6) range, eliminating false hits from databases or mis-matched molecular formula matching. The Mass Spectrometry Core MALDIs offer a 200ppm range of accuracy for quickly determining biological molecules or small molecules of interest typically without many hours of method development.
The targeted analysis of peptides is one of the most popular types of analysis with mass spectrometry. Specific precursor and fragment ions are monitored over a period of time, enabling the definitive detection of targeted compounds. Mass spectrometer instruments are capable of detecting very low concentrations (for peptides in the femtomole concentration levels) in mixtures. Quantitative data analysis methods may also be employed to ascertain concentrations within the linear range of the standard calibration curve.
Small molecule accurate mass identification
Identification of targeted small molecules in a variety of matrices (GC-MS or LC-MS)
Quantitation of targeted small molecules in a variety of matrices (GC-MS or LC-MS)
Small molecule ID by spectral match (GC-MS only)
Thermal desorption (Leco GC x GC MS)
This technique concentrates volatile organic carbon (VOC) compounds prior to injecting the sample on a GC column. It effectively lowers the detection limits and narrows peak widths. For example, one may use this technique to analyze what compounds are off gassing from a plastic sample at various storage temperatures.
2D GC experiments (Leco GC x GC MS)
This technique helps to resolve compounds that may not be well separated in one dimensional GC (i.e. complex mixtures such as petroleum). Two columns with different chemistries are joined in tandem. Thermal modulation is employed to trap the compounds from the first column and rapidly inject them onto the second column.
Method development and method validation
Mass spectrometry is a sensitive and selective technique. However, oftentimes in many applications the analyte of interest must be separated from a large number of other compounds contained in a specimen. Typically mass spectrometry alone is unable to meet this need as it can only differentiate compounds by their mass-to-charge ratio (m/z) which is insufficient in most practical applications of the technique. Complex sample matrices require additional separation techniques and sample extraction procedures prior to introduction into the mass spectrometer.
“Semi-quantitative” mass spectrometry can be performed with or without the addition of an internal standard. The peak intensity, or the peak area, from individual molecules is correlated to the amount of analyte in the sample or the known concentration of a high purity standard. However, the individual signal depends on how well the sample can be separated by GC and the ionizability of the compound.
Novel method development and special projects