Mass Spec Standard FAQs

1. What are the heavy labeled amino acids used for the production of MS standard proteins?

They are L-Arginine: HCL (U-13C6; U-15N4) and L-Lysine: 2HCL (U-13C6; U-15N2).

2. For HEK293T cells, how many doublings were passed in heavy amino acid containing medium?

The HEK293T cells were grown in heavy isotope supplemented medium for at least 10 doubling times to ensure complete incorporation of heavy labeled amino acids.

3. What kind of protein expression system does OriGene use for the production of heavy labeled MS standard proteins?

OriGene expresses and purifies from only mammalian cells and we primarily use HEK293T cells, a line derived from human embryonic kidney. The production cells have been incorporated with heavy labeled L-Arginine and L-Lysine through SILAC approach

4. What is the OriGene guarantee for the purified MS standard proteins?

OriGene guarantees that the purified MS standard proteins will show at least 80% purity by SDS-PAGE/Coomassie staining, will exhibit at least over 90% incorporation efficiency for heavy labeled isotopic amino acids, will contain <0.1EU/ug of endotoxin, will be fully soluble at a minimum concentration of 50ug/ml, and will not contain any detectable protease, DNase, or RNase activity

5. Where can I find the concentration of the purified protein that I received?

The concentration of the purified protein is determined by BCA assay (Pierce) and is on the tube and the Certificate of Analysis.

6. The MS standard size offered is 10µg and this is not enough for my assays. Can I order a larger amount?

Yes, you can contact OriGene technical support team to inquire large quantity service.

7. What is the stability of OriGene’s purified MS standard protein?

OriGene guarantees that the protein will remain stable for up to three months after receipt pending appropriate storage and handling.

8. What are the recommended storage and handling conditions for MS standard protein samples?

Store at –80C. Thaw on ice, aliquot to individual single-use tubes, and then re-freeze immediately. Only 2-3 freeze thaw cycles are recommended.

9. What buffer is the protein provided in?

The final buffer composition is:100mM glycine, 24mM Tris-HCl, pH 7.3.

10. What method does OriGene use to purify the MS standard proteins?

All proteins are purified using our standard anti-DDK immunoaffinity column.