I am not sure whether I unterstand your setup correctly. I assume that you want to use the peptide as a catcher molecule. In this case, you have to be sure, that it is a) long enough to stick out from the surface and b) it is as polar as possible, otherwise the peptide will most probably interact with the BSA surface and will not be available for binding the analyte. You may use a polar spacer between peptide and BSA to solve this problem.

If your setup is completely different, please drop me a note.

Dear J.Hemberger.

Ocean of thanks for spending your precious time in resolving my puzzle. Actually I am developing Lateral flow test for HIV using peptide by conjugating it to gold particle as well as binding with Nitro cellulose membrane- A sandwich type immunoassay. 

Based on your suggestion, I had tried glutaraldehyde as spacer (recommended in an old research article) to bind with activated nitro cellulose(by diamino alkane) membrane and then used BSA coupled peptide to bind with NCM but still didn't showed any reactivity. probably, peptide coupled with BSA is not binding with analyte.

Therefore, I tried with biotin - streptavidin model without using BSA molecule and it starts showing reactivity with analyte. Yet sensitivity is not up to the desired intensity because its producing slight false positive results with negative samples but hopefully optimization of assay may resolve this issue. Therefore I am now looking for proper blocker for streptavidin gold conjugate to remove false positive results.

Thanks again for your suggestion.