Introduction

    Conjugation of a peptide to a larger molecule is necessary for anti-peptide antibody production.  It is because that a peptide is too small to be antigenic.  A larger protein, such as KLH or BSA, is usually a good carrier.  In order to get a good result, a careful design of conjugation is critical, in addition to selecting a suitable antigenic peptide sequence.       

    Typically, a peptides is conjugated to a carrier protein through a stable covalent.   At Princeton BioMolecules, we will examine the peptide sequences, linker functional groups, points of conjugation, reaction conditions, and many other factors to ensure that the efficiency of conjugation is reach certain degree. 

Carrier Protein

    A carrier protein is a high molecular weight protein, which may carries a small peptide so it can be recognized in the process of antibody production in vivo.  In general, KLH or BSA is a good carrier protein.   Obviously, either KLH or BSA can not be used as it is.  It is treated so that the self intra-molecular linkage can be avoided.  

Linker

    A linker is a six carbon straight chain, such as BS-3 which is a homo bifunctional linker or MSH which is a hetero-bifunctional linker.  Both of them contain an hexamethylene, -CH₆-, group to form a space of 7.5 A between peptide and carrier protein.  The advantage of those linker are.

1. The distance of 7.5 A spacer allows the conjugated peptide to stick out form the surface of carrier protein, compared with traditional methods of using glutaldehyde which does not have any space.  The peptide is therefore more accessible to be antigenic.  

2. The covalent bond between the peptide and the carrier protein is very stable, making detachment unlikely during normal immunization procedure.   

3. The spacer is a six methylene chain.  No other functional groups are presented.  It will help to reduce unwanted immunological response and to create a cleaner background.

    The site of conjugation can be at N- or C- terminus or in the middle of the sequence.  The point of conjugation can be a sulfhydryl (SH) group or amino group (NH₂).  A homo-bifunctional linker is to link a peptide and a protein through Lys on both sides.  While a hetero-bifunctional linker is to link a peptide through Cys and a protein through Lys or N-terminus.

Conjugated Sites

    The point of conjugation can be at N- or C- terminus or in the middle of a peptide, depending on the design of sequence.  Some peptide needs to be conjugated at N- terminus, other may be at C-terminal, or even in the middle of sequence.

Product Package   

Conjugated product is free of un-conjugated peptide.  It is shipped as lyophilized powder.

 

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