I did the protein (BSA) immobilization in acrylamide gel. After 7 days, I measured the protein content in the gel. And from the BSA standard curve equation I got negative value (- 0.115 mg/ml). What does it mean? Does it mean protein in the gel is gone/denatured?
Can you please give more details on your experiment ? It is likely that you do not use good reference
I am afraid that the simplest answer is that your protein concentration is too low and falls below your constructed curve. This has happened to me many times! I am unsure of your protein quantification assay, so I can't say whether denaturation is a factor here but at least in Bradford and BCA assays, denaturation will not affect the quantification of overall protein. However, as Arshad said, this could be an issue with background/blank subtraction, so indeed, testing a known protein's concentration will rule out any blank subtraction issues.
The Lowry method is sensitive to low concentrations of protein. Dunn [1992]
suggests concentrations ranging from 0.10 - 2 mg of protein per ml while
Price [1996] suggests concentrations of 0.005 - 0.10 mg of protein per ml. The
major disadvantage of the Lowry method is the narrow pH range within which
it is accurate.The Lowry method is sensitive to pH changes and therefore the pH of assay solution should be maintained at 10 - 10.5.
As we know, Y=mx+c, here if u got more value of 'c' then i suggest to do your BSA standard curve again till getting lower value as low as 0.01 or lower. The same was happened to me many times. Orelse you can go for Bradford method as said by Kelly N Chacón.
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