Design, synthesis, and characterization of peptide nanostructures having ion channel activity

Insights on the interactions of synthetic amphipathic peptides with model membranes as revealed by 31P and 2H solid-state NMR and infrared spectroscopies

We studied the interaction between synthetic amphipathic peptides and model membranes by solid-state NMR and infrared spectroscopies. Peptides with 14 and 21 amino acids composed of leucines and phenylalanines modified by the addition of crown ethers were synthesized. The 14-mer and 21-mer peptides both possess a helical amphipathic structure. To shed light on their membrane interaction, (31)P and (2)H solid-state NMR experiments were performed on both peptides in interaction with dimyristoylphosphatidylcholine vesicles in the absence and presence of cholesterol, dimyristoylphosphatidylglycerol vesicles, and oriented bicelles. (31)P NMR experiments on multilamellar vesicles reveal that the dynamics and/or orientation of the polar headgroups are weakly yet markedly affected by the presence of the peptides, whereas (31)P NMR experiments on bicelles indicate no significant changes in the morphology and orientation of the bicelles. On the other hand, (2)H NMR experiments on vesicles reveal that the acyl chain order is affected differently depending on the membrane lipidic composition and on the peptide hydrophobic length. Finally, infrared spectroscopy was used to study the interfacial region of the bilayer. Based on these studies, mechanisms of membrane perturbation are proposed for the 14-mer and 21-mer peptides in interaction with model membranes depending on the bilayer composition and peptide length.

Neural membrane microdomains as computational systems: Toward molecular modeling in the study of neural disease

Several studies indicate that the lipid biological membrane contains discrete regions known as rafts or microdomains. These structures range in size from approximately 50 to 70nm to nearly a mum and play important roles in cell signaling. In the neuron, computational models suggest that transiently polarized microdomain ethenes may regulate ion-channel dynamics and control impulse propagation. Thus the microdomain is nominated as the fundamental unit of nervous system signaling. Based on this model, the article proposes a first-approximation design for a supported-membrane device which would mimic microdomain properties. The basic architecture would consist of an electrically addressable biotemplated nanowire crossing an artificial membrane corralled in a vertical carbon nanofiber barrier. Advantages and disadvantages of model components are discussed at length. It is proposed that artificial devices of this type would be medically useful in simulating membrane states correlated with neural disease. This possibility is examined with reference to the A-current potassium channel, implicated in epilepsy.

Chloride ion efflux from liposomes is controlled by sidechains in a channel-forming heptapeptide

A suite of amphiphilic heptapeptides incorporating a glutamic acid derivative on the C-terminal side of a (Gly)(3)Pro sequence gives dramatically lower chloride ion release from liposomes when present in free carboxyl form rather than as an ester or amide.