Molecular construction of HIV-gp120 discontinuous epitope mimics by assembly of cyclic peptides on an orthogonal alkyne functionalized TAC-scaffold

Abstract

Mimics of discontinuous epitopes of for example bacterial or viral proteins may have considerable potential for the development of synthetic vaccines, especially if conserved epitopes can be mimicked. However, due to the structural complexity and size of discontinuous epitopes molecular construction of these mimics remains challeging. We present here a convergent route for the assembly of discontinuous epitope mimics by successive azide alkyne cycloaddition on an orthogonal alkyne functionalized scaffold. Here the synthesis of mimics of the HIV gp120 discontinuous epitope that interacts with the CD4 receptor is described. The resulting protein mimics are capable of inhibition of the gp120-CD4 interaction. The route is convergent, robust and should be applicable to other discontinuous epitopes.

Highly potent antimicrobial peptide derivatives of bovine cateslytin

“…Therefore, the serum stability of cateslytin (1) and the most potent peptide synlytin (7) was determined by a method used previously in our group. 38 Human serum was used to evaluate the stability of the peptides for up to 24h at 37 °C (Figure 1). …”

Polar Hinges as Functionalized Conformational Constraints in (Bi)cyclic Peptides

“…Next, these azide‐containing hinges 17 and 18 were used in the cyclization of a peptide containing C‐ and N‐terminal cysteine residues. It was decided to use a peptide sequence corresponding to one of the three loops present in the HIV‐gp120 discontinuous epitope interaction with CD4 (peptide 19 , CLTRDGGKC, cysteine residues are underlined), which in the past gave considerable solubility problems when cyclized with the original aromatic dibromide hinge 4 , leading to N 3 ‐DBMB‐gp120 ( 22 ) . Both hinges 17 and 18 reacted cleanly and quickly with the crude linear peptide to form the cyclized peptides N 3 ‐TADB‐gp120 ( 20 ) and N 3 ‐DBMT‐gp120 ( 21 ) in good overall yields of 26 % for cyclic peptide 20 and 28 % for cyclic peptide 21 (Figure ).…”

“…gp120 (19) : The peptide was synthesized according to the protocol described above on a 0.25 mmol scale. This gave crude peptide 19 (269.8 mg), which was used without any purification in the cyclization step.…”

“…N 3 ‐DBMB‐gp120 (22) : Crude gp120 ( 19 , 48.8 mg, 40 μmol, 1 equiv) was treated with the previously described azido benzylic dibromide hinge 4 (12.8 mg, 40 μmol, 1 equiv) according to the cyclization method described above. The resulting crude cyclic peptide was dissolved in DMSO (500 μL), HPLC buffer B (2.5 mL) and HPLC buffer A (2 mL) and subjected to purification by preparative HPLC.…”

“…In the past we used a derivative of benzylic tribromide hinge 1 to tackle the complicated PPIs involved in discontinuous epitopes in, for example, antibody–antigen interactions . Through the chemical creation of cyclic peptides corresponding to the amino acid sequence of the epitopes by use of azido di(bromomethyl)benzene ( 4 , N 3 ‐DBMB) and attachment of these to a molecular scaffold, PPI modulators of the HIV‐gp120–CD4 interaction were obtained . Although cyclization of the peptides with the benzylic dibromide hinge 4 was very efficient and clean, solubility problems with the resulting cyclic peptides were encountered, probably caused by the apolar hinge used.…”