I´m trying to measure the concentration of a salivary glycoprotein. Though ELISA results are positive, I can not obtain meaningful serial dilutions. The problem is that the OD readings are very similar between dilutions. So, I make 1/2, 1/4, 1/8... etc. but the results usually come up equal or within 5-10% difference from the undiluted sample. I tried various centrifugation, vortexing and diff. pH buffer protocols. I also used reverse pipetting and prewetting the tips, but no meaningful results yet.
Any help or advice would be much appreciated.
I'm doing a research on porcine GP2 (glycoprotein 2, pancreatic zymogen granule membrane protein), and I want to localize it in the intestine and pancreas. The parts of porcine intestine that I research are duodenum, jejunum, ileum and colon. Beside intestine, I want to check it on pancreas. I am doing frozen tissue IHC (immunofluorescent detection), and if someone could recommend good markers for the tissues above, that would be wonderful.