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FAQ

Q1: What is the amount of protein required for intact mass determination?

A	40-50 µg of proteins will be enough for us to perform protein mass determination by MALDI-TOF or ESI-Q-TOF.

Q2: What is the amount of protein required for protein identification?

A	5-10 µg of proteins will be enough for us to get the consistent results by using our nanoLC-MS/MS.

Q3: What is the amount of protein required for protein post-translational modifications (PTMs) analysis?

A	5-10 µg of proteins will be enough for us to perform protein PTMs analysis by using our nanoLC-MS/MS.

Q4: Can you perform protein quantification analysis?

A	Yes, we provide protein quantification analysis by using various method including SILAC, iTRAQ/TMT and label-free.

Q5: What are the differences among SILAC, iTRAQ/TMT and label-free based quantification?

SILAC is the in vivo labeling method that can be used to process cell line samples; isotope labeled amino acid can be incorporated into the proteome by cell doubling. iTRAQ/TMT is the in vitro labeling method that can be used to handle protein samples that can’t be labeled in vivo. Label-free based quantification does not use a stable isotope containing compound to chemically bind to and thus label the protein. Also, it is suitable for less complex samples in a cost-effective way.

Q6: What is the amount of protein required for protein quantification analysis?

A	50-100 µg of proteins will be enough for us to perform protein quantification analysis.

Q7: How should I prepared samples?

A	As for the sample preparation, you may provide us the proteins in gels, in solution or lyophilized samples. If you want to provide us the samples in solution and follow up MS step, we would like to suggest that the buffer should be in low salt concentration and without any detergents.

Q8: How should I send my samples?

A	As for the shipment, you may send us the lyophilized powder or gel sample in ice pack or the solution sample in dry ice.

Q9: What are the advantages of nanoLC-MS/MS for protein identification?

By using nanoLC-MS/MS, some extremely low abundance proteins will also be identified (such as kinase and membrane proteins). It is more sensitive than other old versions of LC-MS/MS. Another important advantage of nanoLC-MS in protein identification is that it can be used to analyze more complex mixture.

Q10: What are the advantages of nanoLC-MS/MS for protein PTMs analysis?

Protein PTMs analysis, such as phosphorylation, glycosylation, methylation, acetylation, ubiqitination, and N-terminal/C-terminal processing, is often an essential step towards biopharmaceutical products analysis.As for protein PTMs analysis, nanoLC-MS/MS is naturally the most common-used tool. It also provides superior sensitivity, specificity and reliability in characterizing many types of protein post-translational modifications.

Q11: How to concentrate a protein sample?

Traditional protein concentrating methods, such as dialysis and membrane filtering are often unsuitble for microgram protein concentration, due to the large amount of sample loss. Therefore, we recommend using protein affinity concentration methods, in which proteins are bound to affinity beads, washed to remove salt, eluted with suitable elution buffer.

Q12: What type of gel should I use if I want to send you gel samples?

Many types of gels are compatible with MS analysis, such as traditional polyacrylamide gels and many commercially pre-cast gels including Thermo NuPAGE Bis-Tris and Tris-Acetate gel. For protein identification, we haven't observed any significant effect caused by different gels. However, we would like to suggest not to use Tricine gel for protein identification based on our experience.

Q13: How to cut a protein band out of a gel?

You should be careful, when you cut a protein band out of a gel. First, avoid direct contact with the gel in bare hands or with any potential dirty surface. Second, wear clean gloves during the whole process and put the gel on a ultra-clean plastic box. Third, cut out the interested protein band with a ultra-clean razor blade in an appropriate size. If you need to cut several bands out, please avoid mislabeling of different gel bands.

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