Gold nanoparticle-powered screening of membrane protein-specific lipids from complex lipid mixtures.

Membrane proteins (MPs) are affected by binding of specific lipids. We previously developed a methodology for systematically analyzing MP-lipid interactions leveraging surface plasmon resonance (SPR). In this method, the gold sensor chip surface was modified with a self-assembled monolayer (SAM), which allowed for a larger amount of MP-immobilization.

Truncated derivatives of amphidinol 3 reveal the functional role of polyol chain in sterol-recognition and pore formation.

Here we examined the membrane binding and pore formation of amphidinol 3 (AM3) and its truncated synthetic derivatives. Importantly, both of the membrane affinity and pore formation activity were well correlated with the reported antifungal activity. Our data clearly demonstrated that the C1-C30 moiety of AM3 plays essential roles both in sterol recognition and stable pore formation.

Impact of sphingomyelin acyl chain heterogeneity upon properties of raft-like membranes.

Sphingomyelin (SM) is a main component of lipid rafts and characteristic of abundance of long and saturated acyl chains. Recently, we reported that fluorescence-labeled lipids including C16:0 and C18:0SMs retained membrane behaviors of inherent lipids. Here, we newly prepared fluorescent SMs with longer acyl chains, C22:0 and C24:1, for observing their partition and diffusion in SM/cholesterol (chol)/dioleoylphosphatidylcholine (DOPC) bilayers.

The influence of ceramide and its dihydro analog on the physico-chemical properties of sphingomyelin bilayers.

The influence of ceramide and its dihydro analog (Cer and DHCer, respectively; inclusively termed Cers) on sphingomyelin (SM) bilayers was examined. Fluorescent microscopy showed that SM/Cers binary bilayers undergo phase separation between Cers-rich and Cers-poor phases. Based on calorimetry, the content of Cers in the Cers-rich phase was estimated and the results show that DHCer in the DHCer-rich phase (17.

Mechanism of local anesthetic-induced disruption of raft-like ordered membrane domains.

Background: Because ordered membrane domains, called lipid rafts, regulate activation of ion channels related to the nerve pulse, lipids rafts are thought to be a possible target for anesthetic molecules. To understand the mechanism of anesthetic action, we examined influence of representative local anesthetics (LAs); dibucaine, tetracaine, and lidocaine, on raft-like liquid-ordered (L)/non-raft-like liquid-disordered (L) phase separation.

Methods: Impact of LAs on the phase separation was observed by fluorescent microscopy.

A concise method for quantitative analysis of interactions between lipids and membrane proteins.

Although interactions between lipids and membrane proteins (MPs) have been considered crucially important for understanding the functions of lipids, lack of useful and convincing experimental methods has hampered the analysis of the interactions. Here, we developed a surface plasmon resonance (SPR)-based concise method for quantitative analysis of lipid-MP interactions, coating the sensor chip surface with self-assembled monolayer (SAM) with C-chain. To develop this method, we used bacteriorhodopsin (bR) as an MP, and examined its interaction with various types of lipids.

Evidence of lipid rafts based on the partition and dynamic behavior of sphingomyelins.

Sphingomyelin (SM)-rich membrane nano-domains, called lipid rafts, have attracted the interest of researchers due to their potential involvement in the formation of signaling platform. Although there are many studies on lipid rafts, the direct observation of lipid rafts is still challenging owing to two critical reasons. One is the lack of an appropriate fluorescent probe mimicking the native behavior of raft lipids; fluorescent labeling often alters the intrinsic disposition of raft lipids.

Marine sponge cyclic peptide theonellamide A disrupts lipid bilayer integrity without forming distinct membrane pores.

Theonellamides (TNMs) are antifungal and cytotoxic bicyclic dodecapeptides derived from the marine sponge Theonella sp. These peptides specifically bind to 3β-hydroxysterols, resulting in 1,3-β-D-glucan overproduction and membrane damage in yeasts. The inclusion of cholesterol or ergosterol in phosphatidylcholine membranes significantly enhanced the membrane affinity of theonellamide A (TNM-A) because of its direct interaction with 3β-hydroxyl groups of sterols.

Orientation and Order of the Amide Group of Sphingomyelin in Bilayers Determined by Solid-State NMR.

Sphingomyelin (SM) and cholesterol (Chol) are considered essential for the formation of lipid rafts; however, the types of molecular interactions involved in this process, such as intermolecular hydrogen bonding, are not well understood. Since, unlike other phospholipids, SM is characterized by the presence of an amide group, it is essential to determine the orientation of the amide and its order in the lipid bilayers to understand the nature of the hydrogen bonds in lipid rafts. For this study, 1'-(13)C-2-(15)N-labeled and 2'-(13)C-2-(15)N-labeled SMs were prepared, and the rotational-axis direction and order parameters of the SM amide in bilayers were determined based on (13)C and (15)N chemical-shift anisotropies and intramolecular (13)C-(15)N dipole coupling constants.

Deuterium NMR of raft model membranes reveals domain-specific order profiles and compositional distribution.

In this report, we applied site-specifically deuterated N-stearoylsphingomyelins (SSMs) to raft-exhibiting ternary mixtures containing SSM, 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), and cholesterol (Chol) and successfully acquired deuterium quadrupole coupling profiles of SSM from liquid-ordered (Lo) and liquid-disordered (Ld) domains. To our knowledge, this is the first report that shows detailed lipid chain dynamics separately and simultaneously obtained from coexisting Lo and Ld domains. We also found that the quadrupole profile of the Lo phase in the ternary system was almost identical to that in the SSM-Chol binary mixture, suggesting that the order profile of the binary system is essentially applicable to more complicated membrane systems in terms of the acyl chain order.