Synthetic model peptides for apolipoproteins. II. Characterization of the discoidal complexes generated between phospholipids and synthetic model peptides for apolipoproteins.

in Biochimica et Biophysica Acta (1993), 1170(1), 8-16

The structure, composition and physico-chemical properties of complexes generated between phospholipids and synthetic model peptides for the amphipathic helices of the plasma apolipoproteins were studied ... [more ▼]

The structure, composition and physico-chemical properties of complexes generated between phospholipids and synthetic model peptides for the amphipathic helices of the plasma apolipoproteins were studied. The sequences of the peptides were derived from that of the 18A peptide and designed to either enhance or decrease ionic interactions between pairs of peptides, as described in the accompanying paper. Complexes were prepared with dimyristoylphosphatidylcholine (DMPC), dipalmitoylphosphatidylcholine (DPPC), or with DPPC and cholesterol, and isolated on a Superose 6HR column. Association kinetics for the DMPC-peptides complexes were followed by measuring the turbidity as a function of the temperature. The diameters of the DPPC-peptide complexes, measured by gradient gel electrophoresis (GGE), were about 120 A. Fluorescence polarization measurements after labeling with diphenyl hexatriene (DPH) yielded transition temperatures of, respectively, 40.6, 41.5 and 41.8 degrees C for the DPPC/18AM1-, DPPC/18AM4- and DPPC/18A-peptide complexes. These values were confirmed by differential scanning calorimetry. Circular dichroism and infrared spectroscopy revealed that the peptides adopt an alpha-helical structure in solution and this percentage increased from 30-40% in the free peptides up to 50-60% in the complexes. Attenuated total reflection (ATR) infrared measurements of the complexes indicated that the peptides are oriented parallel to the acyl chains of the phospholipid bilayer. Denaturation of the peptides and of the peptide-lipid complexes was monitored by Trp fluorescence under addition of increasing amounts of GdmCl. The mid-points of the denaturation curves lie at, respectively, 0.05, 0.25 and 0.35 M GdmCl for the 18AM4, 18A and 18AM1 peptide and are shifted towards higher GdmCl concentrations after peptide-lipid binding. GdmCl denaturation decreased the alpha-helical content of the peptides and of the complexes, as monitored by circular dichroism measurement. The helix to random coil structure transition occurred at, respectively, 2.1, 2.2, and 2.0 M GdmCl for 18A, 18AM1 and 18AM4, compared to 5.1, 5.0, and 5.3 M in the corresponding complexes. These data suggest altogether that the structural properties, the mode of lipid-protein association and the stability of the phospholipid-peptide complexes are similar to those of native plasma apolipoproteins. The 18A and 18AM4 peptides which contain charged residues along the edge of the helix, leading to salt bridge formation between peptides were shown to mimic the amphipathic helices of the plasma apolipoproteins. [less ▲]

Synthetic Peptides Approach To Identification Of Epitopes On Bovine Leukemia-Virus Envelope Glycoprotein-Gp51

in Virology (1989), 169(1),

Synthetic, structural, magnetic, and Mossbauer spectral study of {Fe[HC(3,5-Me(2)pz)(3)](2)}I-2 and its spin-state crossover behavior

in European Journal Of Inorganic Chemistry (2002), (5), 1190-1197

The complex {Fe[HC(3,5-Me(2)pz)(3)](2)}I-2 (1) has been prepared from the reaction of FeI2 and HC(3,5-Me(2)pz)(3) (pz = pyrazolyl ring) in a 1:2 ratio. The complex is high-spin in both the solid state and ... [more ▼]

The complex {Fe[HC(3,5-Me(2)pz)(3)](2)}I-2 (1) has been prepared from the reaction of FeI2 and HC(3,5-Me(2)pz)(3) (pz = pyrazolyl ring) in a 1:2 ratio. The complex is high-spin in both the solid state and in solution at ambient temperature, In the solid state, magnetic susceptibility and Mossbauer spectral studies indicate that samples of the complex that have been crystallized and dried change completely from high-spin to low-spin upon cooling below 195 K, with a substantial two-step thermal hysteresis in the transition, The spin-crossover properties of I are sample dependent: powder samples do not change to low-spin at low temperatures. Two crystalline forms of I have been identified by X-ray crystallography, one form containing no solvent of crystallization and the other containing solvent, In both, there is only one iron site, with average Fe-N bond lengths of 2.18 and 2.17 Angstrom, values that confirm that the complex is high-spin. Single crystals of the nonsolvated form shatter at low temperatures whereas single crystals of the solvated form can be cooled to 110 K with no loss of crystallinity and remain fully high spin at this temperature, Crystallographic information: nonsolvated form is triclinic, P (1) over bar, a = 8,8062(2) Angstrom, b = 10.3549(2) Angstrom, c = 11.3549(2) Angstrom, a = 104.0768(10), beta = 110.2473(10)degrees, gamma = 92.6385(11)degrees, Z = 1; solvated form is monoclinic P2(1)/c, a 10.3214(5) Angstrom, b = 12.7753(7) Angstrom, c = 20.1995(11) Angstrom, alpha = 90degrees, beta = 97.5380(10)degrees, gamma = 90degrees, Z = 2. [less ▲]

Syphilis en 2008: controverses et attitudes pratiques.

in Revue Médicale Suisse (2008), 4(168), 1823-7

Rising incidence rate of syphilis is observed in economically advanced countries, particularly among homosexual men and subpopulation with low socioeconomic status. The various clinical presentations are ... [more ▼]

Rising incidence rate of syphilis is observed in economically advanced countries, particularly among homosexual men and subpopulation with low socioeconomic status. The various clinical presentations are divided into early and late stages, including neurosyphilis. The latter can occur during any stage of the disease, leading to the question "when to perform lumbar puncture", particularly in HIV positive patients. Penicillin continues to be the first-line therapy for all stages of syphilis. An alternative treatment should be considered as an exemption, after advice from a specialist. All patients require prolonged clinical and serological follow-up after treatment to rule out relapse or re-infection. The diagnosis of syphilis is an opportunity to search and treat other sexually transmitted diseases in patients and their sexual partner(s). [less ▲]

La syphilis, la grande simulatrice démasquée.

in Dermatologie Actualité (2007), 104

Syrie pré-hellénistique: Tell Beydar

in Annales d'Histoire de l'Art et d'Archéologie (1999), XXI

System and control theory furthers the understanding of biological signal transduction

in Queinnec, I.; Tarbouriech, S.; Garcia, G. (Eds.) et al Biology and Control Theory: Current Challenges (2008)

This article discusses why novel modelling and analysis methods are required for biological systems, presents recent advances and outlines some future challenges. In this respect, the main focus is placed ... [more ▼]

This article discusses why novel modelling and analysis methods are required for biological systems, presents recent advances and outlines some future challenges. In this respect, the main focus is placed upon methods for parameter estimation and sensitivity analysis as they are encountered in systems biology. [less ▲]

System for color fusion, processing, 3D visualization, and mining of EO,IR, & SAR images, and of other multisensor or multispectral images

Conference (2002, June)

System Identification and Modeling of Biochemical Systems

Conference (2007, November)

The system of kallikrein-kininogens-kinins (KKK) and the acute-phase reactant proteins (APRP) in human undergoing extracorporeal circulation (ECC)

in Arnaud, P.; Bienvenu, J.; Laurent, P. (Eds.) Marker proteins in inflammation (1984)