Hi Trinath,

I would go for a protein that is readily available and can be purchased easily in sufficient purity. The only protein that matches that description in my opinion is insulin. Depending on the source (bovine, porcine, human) it may have slightly different molar mass, but the average is about 5.8 kD.

I hope this helps, kind regards, Leo

There is a commercial marker which I have used before, it is the Precision Plus marker from BioRad which ranges from 2kD to 20kD. Since your targeted product is 2.5kD, it may fit your criteria. Not sure if my suggestion will be helpful, but you can explore the possibilities.

Thanks Soo for your recommendation of choosing the right marker. I will definitely try to go with your suggestions.