Talk:Phage display
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I read that phage can be eluted with trypsin, but if you do that, and it cuts off the displayed protein, then how can you repeat the panning? Coat protein III which is usually what binds the displayed protein to the phage only occurs in one place with upto five units, and rounds of panning are often completed more than five times..? --Username132 16:19, 26 January 2006 (UTC)
The coding information for the expressed protein is contained within the phage particle. When the eluted phage are re-infected into host bacteria the displayed protein is expressed once more and displayed on the newly produced phage. Phil Scrutinator (talk) 17:41, 14 March 2008 (UTC)
KM13 is a popular helper phage that allows for elution using trypsin (although my experience suggests that elution be performed using TEA first, then trypsin treatment). Although this cuts the displayed protein, the genetic information is still contained within the phage. Once you infect bacteria with the eluted phage and amplify, the protein becomes displayed on the coat protein of the amplified phage for subsequent rounds of panning. Hope this helped. 216.199.242.34 17:47, 14 February 2006 (UTC) Warren D. Marcus
I think that it is wrong to say that phage display is a method to study (protein/protein or protein/DNA) interactions. I would say that it is a method for selecting for a particular protein or peptide phenotype while maintaining the link for the genotype. Thus, it also allows for multiple rounds of selection and (possibly error-prone) replication, mimicking evolution in the lab. One straightforward means of selection is indeed to use the interaction of the protein or peptide with some other protein, or DNA. But it's also possible to select for other features. For example, you can select for protease resistance (with an affinity tag which is or is not cleaved off). This is indeed mentioned at the end of the article (protein engineering), but the wrong definition at the beginning masks that more general meaning of the term.
In that context, one interesting information is missing: Which Phage display systems can be used for which sizes, what's the largest protein to be possibly displayed? Unfortunately, I don't know the answer (actually that was the reason why I visited the entry).
Frank Küster —Preceding unsigned comment added by 217.228.15.199 (talk) 15:04, 5 February 2008 (UTC)
I don't think there is a simple answer to this. The two predominantly used phage - T7 and filamentous M13 derivatives - differ in their size limits and it also depends on the nature of the protein and the coat protein used. Certainly both cpIII and cpVIII can display Fab heavy chain - approximately 800 bp of coding sequence. Another factor is whether the phage uses a mixture of wild type and fusion coat protein or just fusion coat protein - this can affect the infection process. The pJuFo system of Reto Crameri can potentially express whole cDNAs by using fos and jun leucine zipper fragments as intermediaries to cpIII. Phil Scrutinator (talk) 17:41, 14 March 2008 (UTC)
The article does seem to focus on filamentous phage display and accentuates the need for helper phage. This ignores methods based not on phagemids but on engineered M13 phage - the approach taken at the outset by Smith. Phil Scrutinator (talk) 17:44, 14 March 2008 (UTC)
T7 phage display should be mentioned also. Phil Scrutinator (talk) 11:29, 15 March 2008 (UTC)
