Incorporation Of Polypeptides Research Articles

Effect of elastin-like polypeptide incorporation on the adhesion maturation of mineral trioxide aggregates.

The aim of this study was to investigate the effects of the incorporation of elastin-like polypeptide (ELP) on the adhesion maturation of mineral trioxide aggregates (MTA). Two types of ELPs (V125 and V125E8) were genetically synthesized. V125 consisted of 125 repeating pentapeptides (Val-Pro-Gly-Xaa-Gly) and V125E8 was functionalized with octaglutamic acid in the C-terminus of V125; both were diluted to 10 wt% in solution. Three 1.5 mm diameter holes in dentin discs were filled with MTA mixed with either a solution of ELP or deionized water. Push-out bond strength tests were performed following storage in simulated body fluid (SBF) for 1, 2, 4, and 8 weeks (n = 12). The interface between dentin and MTA was observed via scanning electron microscopy (SEM). The maturation of MTA was evaluated with a stereoscopic microscope and SEM. The incorporation of a specific ELP (V125E8) significantly increased the bond strength of MTA to dentin with regard to every maturation period (p < 0.05). The bond strength of MTA also significantly increased with a longer maturation time irrespective of ELP incorporation (p < 0.05). V125E8-incorporated MTA exhibited a more intimate interface with dentin compared to the other groups. More spindle-shaped crystal structures and thicker crystals were observed in all MTA mixtures as the storage duration increased even though V125E8 exhibited fewer crystal structures on the surface. Within the limitations of this study, the incorporation of V125E8 increased the adhesive properties of MTA and the maturation of MTA occurred regardless of ELP incorporation.

Effect of gramicidin addition upon the physicochemical properties of dipalmitoyl phosphatidyl choline large unilamellar vesicles

In this work, we report the results bearing on the effect of gramicidin incorporation upon the dynamic and structural properties of dipalmitoyl phosphatidyl choline (DPPC) large unilamellar vesicle (LUVs). Results were obtained at different depths in the bilayer, both in the bulk of the bilayer and the vicinity of the added pentadecapeptide. This analysis was performed employing a series of extrinsic fluorescent probes (1,6-diphenyl-1,3,5-hexatriene (DPH), 1-(4-trimethylammonium phenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH), 6-dodecanoyl-2-dimethyl aminenaphthalene (Laurdan), pyrenedodecanoic acid, pyrene butyric acid, 1-hexadecanoyl-2-(1-pyrenedecanoyl)-sn-glycero-3-phosphocholine (Py–C 10–PC) and 1,2-bis-(1-pyrenedecanoyl)-sn-glycero-3-phosphocholine (bis-Py–C 10–PC)). Fluorescence measurements were carried out after direct excitation of the probe or after its excitation by resonant energy transfer (RET) from the intrinsic tryptophan groups of the polypeptide. The last procedure allows an evaluation of the lipidic annulus properties in the vicinity of the incorporated polypeptide. In the gel state, gramicidin incorporation increases the order near the vesicle interface, as sensed by TMA-DPH. This increase is observed, above the phase transition temperature, over all the bilayer. This effect is probably related to a decrease in the lateral diffusion of the lipids, as evidenced by the reduced formation of intermolecular excimers following Py–C 10–PC excitation. Gramicidin incorporation also increases the penetration and/or mobility of water molecules located near the bilayer interface. In the gel phase, these changes are more relevant in the central part of the bilayer. When the LUVs are in the liquid crystalline state, the effect is observed through all the bilayer. In this state, the polypeptide incorporation also increases the diffusion/concentration of oxygen, irrespective of the probe localization. Resonance energy transfer between Trp residues and Laurdan, Py–C 10–PC or bis-Py–C 10–PC dyes was employed to evaluate the properties of the lipidic annulus surrounding the polypeptide. In the gel phase, gramicidin incorporation produces an increase in the penetration and/or dynamics of water molecules, while in the liquid crystalline state it leads to a decrease of the acyl chain mobility in the deepest parts of the bilayer.

Preparation and characterization of liposomes incorporating hydrophobic poly(amino acid)s with different secondary structure.

Incorporation of hydrophobic poly(amino acid) into liposomal membranes was achieved by the polymerization of N-carboxy anhydrides of amino acids in the egg yolk phosphatidylcholine (EyPC) bilayer under reduced pressure at 30 degrees C. The trapped volumes for the liposomes with and without polypeptides were 8.1-10.3 l mol-1 and 11.4 l mol-1, respectively. The permeability barrier abilities of liposomal membranes were lowered by the incorporation of polypeptides into the membrane bilayers. Water permeation across the membrane bilayer was more effective for the liposome with the alpha-helical polypeptide than for that with the beta-sheeted one.

Polymerization of Amino Acids in Liposomal Membrane under Reduced Pressure and Normal Pressure

Abstract Incorporation of polypeptides with hydrophobic side groups into lipid bilayers was achieved by the polymerization of N-carboxy anhydrides of γ-dodecyl l-glutamate and of γ-benzyl d-glutamate in DMPC liposomal membrane under reduced pressure and normal pressure. The effects of polypeptide conformations on the barrier properties of liposomal membrane incorporating polypeptide were examined. There was little difference in the trapping volume when liposomes prepared under reduced pressure and normal pressure were compared. The incorporation of polypeptides into the membrane bilayer had a tendency to decrease the volume trapping efficiencies. It was found that in the membrane-free aqueous phase, polymerization of N-carboxy amino acid anhydrides promoted formation of β-structure and in the membrane bilayer formation of α-helix structure was enhanced. The content of α-helical polypeptide was maximum for liposomes prepared under reduced pressure. The activation energies for water permeation across the liposomal membrane were lowered by the incorporation of polypeptdes into the membrane bilayer. The incorporation of α-helical polypeptide was more ceffective than that of β-structured one for the lowering of activation energies. The permeability barrier properties of liposomal membrane were larger for liposome incorporating poly(γ-dodecyl l-glutamate) (PDOLG) than for liposome incorporating poly(γ-benzyl d-glutamate)(PBDG). This seems to be due to a difference in miscibilities with lipid in the membrane bilayer.

Changes in segmental motion of the membrane‐composing molecules of dimyristoyl phosphatidyl choline liposomes by incorporation of polypeptides

AbstractThe interaction of glycoprotein and polypeptides with phospholipid liposomes was investigated by means of the fluorescence polarization technique. Poly(L‐glutamic acid) was incorporated into the bilayer of dimyristyol phosphatidyl choline liposomes by sonication. It reduces the segmental motion of the lipids especially in the hydrophobic region close to the hydrophilic surface. On the contrary, poly(L‐leucine), on incorporation into the lipids, strongly suppresses the molecular motion of hydrocarbon chains. Glycoprotein from bovine serum brings about a remarkable decrease in the molecular motion of hydrocarbon chains. In this case the molecular motion of the lipid for liposomes with 20% glycoprotein incorporation is comparable to that of the human erythrocyte ghost. The interaction of polypeptides with liposomes was also observed with an optical microscope by using gaint liposomes (∅︁ ca. 100 μm).

A simple theoretical model for the effects of cholesterol and polypeptides on lipid membranes

A simple theoretical model for the effects of impurities on biomembranes is proposed. The model accounts for the cholesterol-induced decrease of membrane phase transition temperature, membrane condensation above the gel to liquid crystalline phase transition, and increase in lateral compressibility. The model also predicts that addition of molecules such as cholesterol and polypeptides to membranes results in unmasking of a continuous phase transition. This results in a second broad peak in the calorimetric curves for melting of lipid-cholesterol mixtures, and the appearance of a second melting transition in membranes modified by the incorporation of polypeptides. The theory assumes that the membrane may be adequately described by a kink model, and that impurities are randomly distributed in the membrane. The difference in size and shape of impurity molecules, compared to membrane lipids, results in a spatial disordering in the membrane which in turn causes increased chain disorder and membrane condensation, as well as a decrease in the cooperativity of melting. The second transition results from a second expansion of the condensed, partially disordered membrane, which takes place over a several degree temperature range. This transition, although unmasked by boundary effects of non-lipid molecules, does not correspond to melting of a boundary annulus or phase separation.

On insertion of pigment-associated polypeptides during membrane biogenesis in Rhodopseudomonas capsulata

Early stages in the formation of membranes and photosynthetic units were studied under growth-limiting phototrophic and chemotrophic conditions in cells of Rhodopseudomonas capsulata. The incorporation of polypeptides, forming bacteriochlorophyll-carotinoid-protein complexes in the membrane, was followed by use of pulse-labeling and immunoprecipitation techniques. The newly synthesized polypeptides were inserted into two distinct membrane fractions at both different rates and proportions. The two membrane fractions differed in sedimentation behavior, absorption spectra and activities of the respiratory chain. The individual pigment-associated proteins did not exhibit precursor-product relationship between the two membrane fractions. The data suggest that newly synthesized polypeptides were integrated both into cytoplasmic and pre-existing intracytoplasmic membranes, where the proteins and pigments were assembled to form reaction centers and light-harvesting pigment-protein complexes.