Metal Complexation with Langmuir Monolayers of Histidyl Peptide Lipids

Abstract

Langmuir monolayers made from peptide-lipid molecules represent a novel direction in the research areas of biomimetic interfaces and two-dimensional supramolecular chemistry. Peptide structures and molecular recognition activities toward other guest molecules have been the focus of previous study. This study reports the investigation of metal complexation to histidine-containing peptide lipids in the organized Langmuir, Langmuir-Schaefer, or Langmuir-Blodgett films. Three peptide lipids PEP1-PEP3, with a histidine amino acid incorporated in the middle of the peptide, were designed and synthesized. The monolayer structures and metal-binding activities of each peptide lipid and their 1:1:1 molar ratio mixture were studied by thermodynamic and spectroscopic techniques. It was found that hard Lewis acid type metal cations such as K+ and Mg2+, and borderline or soft metal cations such as Zn2+, Cu2+, and Cd2+ exhibit clearly different binding activity toward peptide-lipid monolayers. The conformational changes of peptides upon binding with Cu2+ and Zn2+ were partially revealed by FT-IR spectroscopic studies. Furthermore, by adding a fluorescent-probe lipid to the peptide monolayer, dramatic fluorescence change was observed when Cu2+ or Zn2+ bound to the Langmuir and Langmuir-Schaefer films of peptide-lipid monolayers. Metal-protein complexation plays a crucial role in the function and activity of proteins and enzymes. Investigation of metal complexation to organized peptide Langmuir monolayers may provide an alternative approach for the development of artificial metalloproteins and novel supramolecular systems or materials.

Self-assembly and applications of biomimetic and bioactive peptide-amphiphiles

“…31,[62][63][64][65][66][67] In addition, LB isotherms of peptide-amphiphiles can be affected by different conformations of the peptide headgroup induced by the hydrophobic tail, 31 by ions present in the aqueous subphase, 68,69 or by metals that complexate with the polar headgroup. 70 Atomic force microscopy (AFM) of peptide-amphiphile/ lipid LB films, shows the appropriate height ''differential'' for peptide-amphiphiles and lipids. 32,34,59,71 Fourier-transform infrared spectroscopic data for RGD-containing peptideamphiphiles 33 and neutron reflectivity data for triplehelical peptide-amphiphiles 32,72 demonstrated that peptide headgroups are oriented perpendicular to the air-water interface and retain the same conformation as in solution.…”

Nanoaggregate shapes at the air/water interface

“…11 A variety of artificial host-guest assemblies has been planned to comprehend molecular recognition systems with new properties and functions. Recognition of various aqueous guest molecules, such as nucleic acids, their bases, nucleosides, and nucleotides, [12][13][14][15] barbituric acid and related derivatives, [16][17][18][19] amino acids, saccharides, [20][21][22][23][24][25][26] etc., 27,28 as well as chiral recognition within membrane components [29][30][31][32][33] and/or between amphiphile and aqueous guests [34][35][36][37][38][39][40][41] at the air/water interface have been studied.…”

Peptide based amphiphiles

“…Huo et al have incorporated N-acylated peptide lipids into a Langmuir monolayer to form receptors for both sugars 22 and metal ions. 23 The dynamic character of such monolayers was exploited to create dynamic combinatorial libraries of receptors that displayed substrate specificity. Langmuir monolayers made of peptide libraries (stearoyl-modified tri-and hexapeptides, see Table 2) were constructed and their surface behaviour was studied on an aqueous subphase, containing different solutes.…”

“…10. In a second study 23 the ability of similar peptide lipids to form complexes with metal ions like Cu 2+ and Zn 2+ was investigated. In this case binding performance was not affected by going from single peptide lipids to a mixture.…”