The purpose of the CMSR facility is to provide state-of-the-art services and expertise for faculty and student researchers at Virginia Commonwealth University, as well as investigators at other institutes and private companies, for sample analysis with mass spectrometry. The resource has a growing number of mass spectrometers and ancillary equipment which allows us to design projects to meet the evolving needs of the investigator. We encourage investigators to contact the Mass Spec Resource regarding their experimental needs so that we can discuss how to get the best results for you.
Service is typically provided by the LTQ-Orbitrap for the confirmation of a known analyte or investigation of the elemental composition of an unknown. The sample is introduced by direct infusion to the ion source to obtain a high resolution/ low resolution mass spectrum of the analyte. Samples will need to be a minimum of 100 µL by volume with a concentration of 25-50 µM. The preferred solvent is pure water, but investigators may also choose to send samples dissolved in acetonitrile or methanol. It is important that the samples are salt free in order to get clear peaks of the analyte and avoid a clustered spectrum. Investigators who want to determine the molecular weight of an intact protein can also avail themselves of this service.
When an additional dimension is required to study a molecule, the ion mobility afforded by the Synapt G2-Si can be used. This separates molecules having the same m/z ratio based on their drift time, which is influenced by factors like molecular size and shape. The collisional cross section (CCS) of the ion can be determined using the IM-MS to study the chemical structure and three-dimensional conformation of the ions in gas phase. This is beneficial to study conformational changes of synthesized compounds, polymers, and heterogenous samples.
Fragmentation of the precursor ion, can be done to obtain additional and orthogonal information which may aid an investigator’s study of an unknown sample. A high collision energy produced by varying the Radio Frequency voltage, is applied to achieve the molecular dissociation of the precursor ion to product ions. The precursor ion can be pre-selected or may be the most abundant ion from the MS spectrum. The collision energy will be optimized by the facility staff to achieve the highest level of useful fragment ions.
Service can be utilized when the sample is a mixture requiring a separation or contains a high concentration of salts. The samples are analyzed by coupling a UPLC to the mass spectrometer, enhancing the concentration of each analyte as it enters the mass spectrometer and reducing the complexity of the sample. This allows the CPMSCF to accept sample concentrations as low as 10 fmol/µL and volumes of less than 10 µL. The elution flow from the UPLC is ionized and analyzed by the mass spectrometer.
The resulting spectra will be given as a series of printouts or emailed to the investigator.
Service is provided with the LTQ-Orbitrap Velos. The Orbitrap mass spectrometer detects the m/z of ions based on their frequency of oscillation in the orbitrap cell. This frequency is converted to m/z using Fourier transform. As frequency is the most accurately measureable property, mass measurements based on frequency have the highest mass accuracy. When exact mass measurement is requested, the sample measurement is carefully optimized by facility staff, including tuning the ion optics to reduce space-charge effect, which results in higher mass accuracy and lower mass error.
We encourage investigators to arrange a meeting with the to discuss their projects. Experiments not listed here, such as the elucidation of post-translational modifications or relative quantitation are viable projects for the Mass Spec Resource but may require a longer turnaround time or a higher quantity of sample.