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Good afternoon, Thank you for your fast response to my e-mail. First aswering to the last two questions: I've been using Streptavidin protein (HRP) (ab7403) as for thedilution of the secondary antibody is 1/250 Nowwith regard to the form sent: 1) Abcam product code ab469 3) Description of the problem: Need more intense staining 4) Sample preparation: Species: Rat Type of sample:PFA/formalin fixed paraffin embedded sections Negative control: Removal of primary antibody 5) Fixation step Yes If yes: Fixative agent and concentration:paraformaldehyde 4% Fixation time: at least 48 hours Fixation temperature 4ºC 6) Antigen retrieval method: Heat-induced with 10mM Sodium Citrate Buffer 7) Permeabilization method: Not done 8) Blocking agent (eg BSA, serum…):Normal Goat serum Concentration 5% in TBST Blocking time: 1h Blocking temperature: room temperature 9) Endogenous peroxidases blocked? Yes (3% Hydrogen Peroxide) Endogenous biotins blocked? Yes (Endogenous avidin + biotin blocking system ab3387) 10) Primary antibody (If more than one was used, describe in “additional notes”) : Anti-Survivin (ab469) Concentration or dilution 1/500 Diluent buffer1xTBST Incubation time Overnight 11) Secondary antibody: Goat Polyclonal Secondary antibody to Rabbit IgG - H&L (Biotin) (ab6720) Concentration or dilution 1/250 Diluent buffer1xTBST Incubation time 2h 12) Washing after primary and secondary antibodies: Yes Buffer: 1x TBST Number of washes at least 3 times 13) Detection method: Streptavidin Protein (HRP) (ab7403) DAB substrate kit (ab94665) 14) How many times have you run this staining? Several Times Do you obtain the same results every time?yes almost every time What steps have you altered to try and optimize the use of this antibody? Altering the dilution of primary antibody, altering the time of incubation of the primary antibody, altering the time of incubation of the cromogen. Best regards,
Asked on Jan 04 2012
Thank you for providing that extra information. It has helped greatly to understand what you have been doing and what may help to improve the signal of the staining. There are a few areas that I would suggest would be worth optimising (if you have not already done so) which may lead to an improved signal. 1. Fixation You have stated that you are fixing the tissue for a minimum of 48 hours. The ideal fixation time will depend on the size of the tissue block and type of tissue but usually 18-24 hours seems ideal for most applications. Over-fixation can lead to the epitope being masked. 2. Antigen retrieval Antigen retrieval can be used to overcome the masking mentioned for the fixation. Depending on the level of masking, different conditions of antigen retrieval may be required. For example, if using a microwave we would usually suggest trying retrieval for 5, 10, 15 and 20 minutes to see which produces the optimal results. 3. Hydrogen peroxide blocking I would suggest performing the hydrogen peroxide blocking following the incubation of the primary antibody if you have not already tried this. The hydrogen peroxide can sometimes affect sensitive epitopes and by performing the step following the incubation with the primary antibody this will not affect the staining. 4. Primary antibody incubation You mention that you have optimised this step by changing the dilution and incubation time. If you have not already done so I would suggest attempting the incubation for 1-1.5 hours at room temperature with agitation. 5. Detection method Different techniques can be used to directly amplify the signal. Currently you are using streptavidin-HRP conjugate which is labelled in a 1:1 ratio. It is possible to employ avidin which has been labelled in a 3:1 ratio with HRP using kits such as Piercenet product 32020. Although avidin can cause greater background compared to using streptavidin. Alternatively HRP polymer can be employed. This consists of using a secondary antibody which is attached to a polymer-HRP complex. Abcam has the following product to offer, ab2891, however this is a little pricey. I would suggest trying to optimise the steps 1-4 and if sufficient progress is not made contemplate employing one of signal amplification methods mentioned. We have quite a detailed guide to IHC which may be of help to you. This outlines many of the different experimental parameters which need to be considered when performing IHC and suggestions to improve experiments: https://www.abcam.com/ps/pdf/protocols/ihc_p.pdf I hope this information has been of help and your staining improves. If you want any further information or help please do not hesitate to contact us again.
回复于 Jan 04 2012