title: Different interfacial behaviors of peptides chemically immobilized on surfaces with different linker lengths and via different termini.
abstract: Molecular structures such as conformation and orientation are crucial in determining the activity of peptides immobilized to solid supports. In this study, sum frequency generation (SFG) vibrational spectroscopy was applied to investigate such structures of peptides immobilized on self-assembled monolayers (SAMs). Here cysteine-modified antimicrobial peptide cecropin P1 (CP1) was chemically immobilized onto SAM with a maleimide terminal group. Two important characteristics, length of the poly(ethylene glycol) (PEG) segment in the SAM and location of the cysteine residue in the peptide, were examined using SFG spectroscopy to determine the effect of each on surface immobilization as well as peptide secondary structure and its orientation in the immobilized state. Results have shown that while each length of PEG chain studied promotes chemical immobilization of the target peptide and prevents nonspecific adsorption, CP1 immobilized on long-chain (PEG2k) maleimide SAMs shows random coil structure in water, whereas CP1 demonstrates α-helical structure when immobilized on short-chain (with four ethylene glycol units - (EG4)) maleimide SAMs. Placement of the cysteine residue at the C-terminus promotes the formation of α-helical structure of CP1 with a single orientation when tethered to EG4 maleimide SAM surfaces. In contrast, immobilization via the N-terminal cysteine of CP1 results in a random coil or lying-down helical structure. The bacteria capturing/killing capability was tested, showing that the surface-immobilized CP1 molecules via C- and N- terminal cysteine exhibit only slight difference, even though they have different secondary structures and orientations.
authors.affiliation: Department of Chemistry, ‡Department of Biophysics, and §Department of Environmental Health Sciences, University of Michigan , Ann Arbor, Michigan 48109, United States.
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Han
authors.forename: Yuwei
authors.initials: Y
authors.lastname: Liu
authors.forename: Fu-Gen
authors.initials: FG
authors.lastname: Wu
authors.forename: Joshua
authors.initials: J
authors.lastname: Jansensky
authors.forename: Taehoon
authors.initials: T
authors.lastname: Kim
authors.forename: Zunliang
authors.initials: Z
authors.lastname: Wang
authors.forename: Charles L
authors.initials: CL
authors.lastname: Brooks
authors.forename: Jianfeng
authors.initials: J
authors.lastname: Wu
authors.forename: Chuanwu
authors.initials: C
authors.lastname: Xi
authors.forename: Charlene M
authors.initials: CM
authors.lastname: Mello
authors.forename: Zhan
authors.initials: Z
authors.lastname: Chen
mesh_terms: D000327:Adsorption; D055767:Immobilized Proteins / Q000737:chemistry*; D008301:Maleimides / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D010455:Peptides / Q000737:chemistry*; D017433:Protein Structure, Secondary; D013499:Surface Properties
chemical_list: D055767:Immobilized Proteins; D008301:Maleimides; D010455:Peptides; C043592:maleimide; C070016:cecropin P1-LI