Question about phage library

[poloke]

Dear all,
I was reading about phage library and stumbled on this website (http://phagedisplay.net/).
Now, I understand how phage library works, but there is something in the explenation I do not get. Its about this part, and more specific the part in bold.

"Technical description of phage display

The starting point is usually a library of peptides, proteins or antibodies, which can be obtained commercially or constructed in house. The construction of a phage display library is accomplished by inserting DNA fragments into phage or phagemid genomes which proteins are expressed on the phage coat. This creates a direct physical link between the DNA sequences and their encoding proteins. All five capsid proteins from the phage (pIII, pVI, pVII, pVIII and pIX) have been used to display proteins, peptides or antibodies, to varying degrees. The choice of pVIII or pIII is related to the choice of the type of display, either polyvalent or monovalent display."


A direct physical link between DNA and protein?
Do they really mean the protein stays attached to the DNA ? Or what do they mean?

I was thinking that they mean that you can easly know what the corresponding DNA is for that protein since only the phages having the DNA coding for this particular protein will survive the enrichmentphases (they will stay attached, while others wont).

But I wouldnt state this as really being physically linked...
To me physically linked means that they are really link , meaning that the protein stays on the DNA or something like that.

[JackBean]

no, it's physical link between DNA sequences or physical link between encoded proteins and not physical link between DNA and protein, i.e. the DNA is connected and expressed as only one gene and thus there is only one protein composed of the capsid protein and your protein of interest.

[poloke]

no, it's physical link between DNA sequences or physical link between encoded proteins and not physical link between DNA and protein, i.e. the DNA is connected and expressed as only one gene and thus there is only one protein composed of the capsid protein and your protein of interest.

Ok, that does make sense!

But I found many websites/pdf files where they state it like this (eg.): "Physically link the protein to the DNA/RNA that encodes it" , and to me it sounds like the DNA is really linked with the protein...
Or: "maintain a physical link between the displayed protein and the DNA
sequence encoding it"

Perhaps its because I am not a native speaker...
But I dont find it clearly stated, to me it does sound that they mean that the DNA is indeed linked with the protein.



Altough, in this particucal case, the bold lines, it does indeed state linke between DNA sequences and a link between the proteins.

[JackBean]

Maybe if you've had it in a context