Jones, Mathew W., Strickland, Rachel A., Schumacher, Feliz F., Caddick, Stephen, Baker, James R., Gibson, Matthew I. and Haddleton, David M.. (2012) Polymeric dibromomaleimides as extremely efficient disulfide bridging bioconjugation and pegylation agents. Journal of the American Chemical Society, Vol.134 (No.3). pp. 1847-1852. ISSN 0002-7863

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Abstract

A series of dibromomaleimides have been shown to be very efficacious at insertion into peptidic disulfide bonds. This conjugation proceeds with a stoichiometric balance of reagents in buffered solutions in less than 15 min to give discrete products while maintaining the disulfide bridge and thus peptide conformation. The insertion is initiated by disulfide reduction using a water-soluble phosphine, tris(2-carboxyethyl)phosphine (TCEP) which allows for subsequent substitution of the two maleimide bromides by the generated thiols. Reaction of salmon calcitonin (sCT) with 2,3-dibromomaleimide (1.1 excess) in the presence of TCEP (1.1 equiv) in aqueous solution at pH 6.2 gives complete production of a single conjugate which requires no workup. A linear methoxy poly(ethylene glycol) (PEG) was functionalized via a Mitsunobu reaction and used for the successful site-specific and rapid pegylation of sCT. This reaction occurs in 15 min with a small stoichiometry excess of the pegylating agent to give insertion at the disulfide with HPLC showing a single product and MALDI-ToF confirming conjugation. Attempts to use the group in a functional ATRP polymerization initiator led to polymerization inhibition. Thus, in order to prepare a range of functional polymers an indirect route was chosen via both azide and aniline functional initiators which were converted to 2,3-dibromomaleimides via appropriate reactions. For example, the azide functional polymer was reacted via a Huisgen CuAAC click reaction to an alkyne functional 2,3-dibromomaleimide. This new reagent allowed for the synthesis of conjugates of sCT with comb polymers derived from PEG methacrylic monomers which in addition gave appropriate cloud points. This reaction represents a highly efficient polymer conjugation method which circumvents problems of purification which normally arise from having to use large excesses of the conjugate. In addition, the tertiary structure of the peptide is efficiently maintained.

Item Type:	Journal Article
Subjects:	Q Science > QD Chemistry
Divisions:	Faculty of Science > Chemistry
Journal or Publication Title:	Journal of the American Chemical Society
Publisher:	American Chemical Society
ISSN:	0002-7863
Date:	25 January 2012
Volume:	Vol.134
Number:	No.3
Number of Pages:	6
Page Range:	pp. 1847-1852
Identification Number:	10.1021/ja210335f
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
URI:	http://wrap.warwick.ac.uk/id/eprint/43752

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