Self-assembled peptides exposing epitopes recognizable by human lymphoma cells

A bifunctional N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer containin g nitrilotriacetic acid (NTA) and benzophenone (BP) groups was synthesized by free-radical copolymerization of HPMA, 2-methacrylamidobutyl nitrilotria cetic acid (MABNTA), and 4-methacrylamido benzophenone (MABP) using 2,2'-az obisisobutyronitrile (AIBN) as initiator. A His-tagged coiled coil stem loo p peptide containing a tridecapeptide (TDP) epitope (GFLGEDPGFFNVE) in the loop region (CCSL-TDP) was designed and synthesized genetically by expressi ng an artificial gene in Escherichia coli BL21 (DE3). The peptide was chara cterized by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), size-exclusion chromatography (SEC), and circ ular dichroism (CD) spectroscopy. Surfaces containing self-assembled CCSL-T DP peptide were prepared by first covalently grafting poly(HPMA-co-MABNTA-c o-MABP) onto polystyrene (PS) surface by UV irradiation, then charging the surface with nickel through NTA groups, and finally attaching the CCSL-TDP peptide through Ni-histidine chelation. The modified PS surfaces with and w ithout self-assembled CCSL-TDP peptide were characterized by X-ray photoele ctron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS). Cell attachment studies with human Burkitt's lymphoma Raji B c ells showed that the cells selectively bound to the self-assembled CCSL-TDP peptide surfaces, but not to the surfaces of PS, PS with grafted copolymer , and PS with grafted copolymer and self-assembled coiled coil peptide with similar structure but without the epitope. This indicates that the cell at tachment was mediated by the CCSL-TDP peptide; most probably by the TDP epi tope region. The CCSL peptide self-assembly presented here may represent a feasible model of exposing epitopes for biorecognition studies.