Faculty of Biological Sciences

Mass Measurements

Useful for:

  • Confirming correct synthesis/expression
  • Establishing purity
  • Detecting PTMs
  • Checking chemical derivitisation
   
Intact protein mass measurement

Using LC-MS, protein samples are deslated immeditately prior to mass measurment. With this approach, in most cases, buffer exchange prior to analysis is no longer required (N.B. any PEG or glycerol must still be removed before analylsis). Minimum sample volume is 20 uL at 20 uM concentration . Users must also submit an aliquot of sample buffer (min. 100 uL for each sample) to enable dilution of samples if required. Details of method used to measure concentration should be provided. Internal users have the option of using the VersaWave spectrophotometer in the MS Facility to determine concentration.

 

Some sensitive proteins are not amenable to LC-MS degrading during analysis. In these cases samples should be buffer exchanged into a volatile ammonium buffer by dialysis or using a buffer exchange spin column. Buffer exchange columns, spin dialysis filters and button dialysis options are avaiable in the Facility if required.

   

Oligonucleotide mass measurement

Oligos require extensive purification before analysis to remove metal ions particularly sodium. The most successful methods of purification are dialysis against 200 mM ammonium acetate or using precipitation methods. Minimum sample volume is 20 uL at 50-100 uM concentration.
   
Accurate mass measurment
Molecules below 2000 Da in mass can be determined to within 5 ppm. Small organic molecules and peptides can be submitted in lyophilised form or in solution using an acceptable solvent system. Acceptable solvent systems can be formulated from: water, acetonitrile, methanol, propan-2-ol, hexafluoropropan-2-ol and chloroform. Solvents to be avoided are the less volatile ones such as dimethylformamide, and less stable ones such as tetrahydrofuran. DMSO is acceptable only if present at below 1% v/v.

Sample submission

Samples can be submitted to the service at any time by bringing them to the Mass Spec Facility in lab 9.107 of the Astbury building. You should download and complete a sample submission form to bring along with your sample (Please note that results of anlaysis cannot be made available until a grant code has been received). Results for molecular mass analysis are usually available and emailed to you within 48 hous of submission depending on current demand.

Users external to the University can find additional information here.

Notes

The concentrations and volumes stated above are provided as a guide only. We will still accept and attempt MS analysis on samples of lower (or unknown) concentration and/or volume. Where analytes are only stable outside of their preferred buffer for short periods of time, buffer exchange can be performed in the mass spec lab immediatley prior to analysis. Please contact us in advance to arrange this if required.