Table 1.
Molecular weight analysis by electrospray ionization mass spectrometry (ESI-MS) for purified proteins. The theoretical average molecular weight (Mtheor) of the His-tag perlecan constructs in dalton (Da) were calculated using ExPaSy ProtParam tool [41]. The experimental molecular weight (Mexp) was determined by mass spectrometry. Formation of one disulfide bond reduces the calculated theoretical molecular weight by approximately 2 Da. The same masses were obtained with NEM-treatment. The results suggest all cysteines are in disulfide bonds in the perlecan constructs analysed.
| Construct | # of Cysteine | Mtheor (Da) | Mexp (Da) | Δ mass |
|---|---|---|---|---|
| Perlecan MH6M-(G503-Q874) | 26 | 41713 | 41688 | 25 |
| Perlecan MH6M-(S762-R1158) | 30 | 43712 | 43681 | 31 |
| Perlecan MH6M-(R1158-T1672) | 48 | 56079 | 56030 | 49 |
| Perlecan MH6M-(G503-T1672) | 88 | 127264 | 127173 | 91 |