The Interaction of Bioactive Peptides with an Immobilized Phosphatidylcholine Monolayer

Abstract

The interaction of three bioactive peptides, bombesin, beta-endorphin, and glucagon with a phosphatidylcholine monolayer that was immobilized to porous silica particles and packed into a stainless steel column cartridge, has been studied using dynamic elution techniques. This immobilized lipid monolayer provides a biophysical model system with which to study the binding of peptides to a lipid membrane. In particular, the influence of temperature and methanol concentration on the affinity of each peptide for the immobilized lipid surface was assessed. For all test peptides, nonlinear retention plots were observed at all temperatures that contrasted sharply with the simple linear plots observed for the small unstructured control molecules N-acetyltryptophanamide and diphenylalanine. An analysis of the thermodynamics of the interaction of peptides with the immobilized monolayer was also carried out. The results revealed that while the peptides interacted with the monolayer predominantly through hydrophobic interactions, the relative contribution of DeltaH(assoc)(O) and DeltaS(assoc)(O) to the overall free energy of association was dependent on the temperature and methanol concentration. In particular, it was evident that under most conditions, the binding of the peptides to the immobilized lipid monolayer was enthalpy-driven, i.e., mediated by nonclassical hydrophobic interactions. Significant band-broadening and asymmetric and split peaks were also observed for bombesin, beta-endorphin, and glucagon at different temperatures and methanol concentrations. These changes in affinity and peak shape are consistent with the formation of multiple conformational species during the interaction of these peptides with the lipid monolayer. In addition, the binding behavior of the three test peptides on an n-octylsilica surface that lacked the phospho headgroups of the phospholipid was significantly different from that observed with the immobilized phosphatidylcholine surface, indicating a specificity of interaction between the peptides and the lipid surface. Overall, these experimental results demonstrate that the biomimetic phosphatidylcholine monolayer provides a stable and sensitive system with which to explore the molecular mechanism of peptide conformational changes during membrane interactions.

Statins (HMG-coenzyme A reductase inhibitors)–biomimetic membrane binding mechanism investigated by molecular chromatography

“…Linear van't Hoff plots were obtained with correlation coefficients r higher than 0.98 for all fits. It was previously demonstrated that for some solute molecule, their binding with a phosphatidylcholine monolayer can lead to a phase transition of the IAM surface around 25 • C [44]. In this work, the observed linear relationships excluded a phase transition of the immobilized phosphatidylcholine in the stationary phase over the range of experimental temperatures as it was observed for bile salt-membrane interactions [45].…”

Not All Secretory Granules Are Created Equal: Partitioning of Soluble Content Proteins

“…PHM, mGFP, and DsRed each adopt a stable, folded structure and have been crystallized (www.rcsb.org/pdb: 1RRX; 1ZGO; 1OPM; Zacharias et al, 2002). In contrast, NPY and ACTH, which are unstructured (Mozsolits et al, 1999;Thomas et al, 2005), showed little segregation; neither pro-NPY nor POMC has been crystallized (www.rcsb.org/pdb). The simplest hypothesis consistent with our data is an old one, namely that individual proteins dictate the extent of their segregation in part through their ability to self-associate (Figure 10).…”

Surface plasmon resonance spectroscopy in the study of membrane‐mediated cell signalling

“…To understand peptide-membrane interactions in detail, the role of numerous physicochemical parameters including peptide charge, hydrophobicity, amphipathicity and the degree of secondary structure and the angle subtended by the polar face, in the physicochemical interaction between peptides and the membrane have been analysed. A wide variety of biophysical techniques such as circular dichroism, nuclear magnetic resonance, fluorescence spectroscopy, Fourier transform infrared spectroscopy, attenuated total reflection Fourier transform infrared spectroscopy, immobilized artificial membrane chromatography combined with model membrane systems have been used to study biomolecular-membrane interactions [12][13][14][15]. These techniques have provided important information on specific structure-function relationships associated with peptide-membrane interactions.…”