Peptide-lipid complex

There have been many papers reporting the biological applications of solid-state 170 NMR.89-100 This section briefly describes several notable examples of 170 NMR for biological solids, including 13C-170 Rotational Echo Adiabatic Passage Double Resonance (REAPDOR) experiments,100 the ONIOM methods for NMR calculations27 and 170 NMR studies of carbohydrates98 and a peptide-lipid complex.92... 

Efficient Gene Transfer by Lipid/Peptide Transfection Complexes... 

IR spectroscopy of the X-receptor protein signal peptide in phospholipid monolayers shows that the peptide affects the packing of the lipid hydrocarbon tails (M. S. Briggs, R. A. Dluhy, D. G. Cornell, and L. M. Gierasch, unpublished results). In samples formed at the same surface pressure, the lipid tails are oriented differendy in the presence and absence of signal peptide. A phospholipase assay for structural defects in phospholipid bilayers (Jain et al., 1984) indicates that the X-receptor protein signal peptide interacts with vesicles to induce such defects. The peptides perturb the lipid structure at lower mole fractions than do various lysophospholipids. These data provide yet another indication that signal peptides interact with and perturb lipid complexes. 

Natural organic matter in aquatic media are complex mixture of substances such as polysaccharides, proteins, peptides, lipids, and humic substances (Duursmu and Dawson, 1981 Buffie, 1984). Humic material is itself a mixture of polymers of a wide range of molecular weights (Buffle, 1988). Besides naturally occurring substances, various artificial compounds are introduced in natural water as the result of human activities. 

In another strategy developed by Legendre and Szoka (65), the cationic peptides gramicidin S and tyrocidine are combined with DOPE (5 1 lipid peptide ratio). Complex formation was promoted by simple mixing of the peptide (2 mg/mL) with DNA (20 pg in 300 pL) in 30 mM Tris-HCl (pH 8.5), followed by addition... 

How molecular motions of the protein and lipid chains are correlated with each other is a very important issue. The interaction between the protein and the lipid is strongly related to the mechanism of transportation of the protein molecules which are floated in the bilayer membrane. Figure 8.23 shows the conventional ESR spectra of spin labeled stearic acid, 14-SASL, in complexes of a 26-residue peptide (K26)) with DMPC of different lipid/peptide ratios [24]. The spectra consist of two components one corresponding to the fluid bilayer regions of the lipid complexes and the other, with the larger hyperflne anisotropy (visible in the outer wings of the spectra), corresponding to the motionally restricted lipid environment at the intra-membranous surface of the incorporated peptide. 

The cationic lipopolymer is biodegradable, the polymers may form complexes with biomolecules and thus are useful as carriers for the delivery of biomolecules to cells. Examples of biomolecules that form complexes with cationic Upopolymers include nucleic acids, proteins, peptides, lipids, and carbohydrates. 

Several interesting review articles have been recently published focusing on the use of NMR methods to study peptide-lipid and small molecular weight molecule interactions in model and natural membranes. Maler as well as Kang and Li highlighted the unique possibilities of solution-state NMR to investigate the structure, dynamics and location of proteins and peptides in artificial bilayers and peptide-lipid interactions. On the other hand, Renault et reviewed recent advances in cellular solid-state nuclear magnetic resonance spectroscopy (SSNMR) to follow the structure, function, and molecular interactions of protein-lipid complexes in their cellular context and at atomic resolution. 

Due to the structural complexity of membrane proteins in lipid environments, protein-lipid interactions and structures of protein-lipid complexes are frequently studied using recombinant peptides, representing transmembrane domains of membrane integral proteins, and artificial lipids and/ or detergents. 

Fig. 4. Density gradient ultracentrifugation of apolipoprotein A-IV/phospholipid/cholesterol complexes. Apo A-IV-1 (wild type) and Apo A-IV-2 (variant) /lipid complexes were prepared by the dialysis detergent procedure and subjected to density-gradient ultracentrifugation as outlined in Fig. 2. Note that the variant Apo A-IV-2 peptide forms stable complexes with lipids as the wild type, Apo A-IV-1...

In recent years, several classes of biomolecules (peptides, lipids, nucleic acids, and sugars) have been studied as building blocks for self-assembled nanostructures, yielding complex therapeutic agents and nanoscale vectors (Kuzuya and Komiyama 2010 Namiki et al. 2011 Matson and Stupp 2012 Reichardt et al. 2013). 

Synthetic peptides have also been developed that enhance the release of the peptide/DNA complexes from the endosome following endocytosis. Without a means of escaping the endosome, the endosomal-lysosomal pathway presents a major barrier to transfection via receptor mediated endocytosis. The use of endosomal lysis agents, such as membrane active lipids or peptides, is important in non-viral gene delivery systems. 

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