Increased dynamics in the 40-57 Ω-loop of the G41S variant of human cytochrome c promote its pro-apoptotic conformation

Thrombocytopenia 4 is an inherited autosomal dominant thrombocytopenia, which occurs due to mutations in the human gene for cytochrome c that results in enhanced mitochondrial apoptotic activity. The Gly41Ser mutation was the first to be reported. Here we report stopped-flow kinetic studies of azide binding to human ferricytochrome c and its Gly41Ser variant, together with backbone amide H/D exchange and 15N-relaxation dynamics using NMR spectroscopy, to show that alternative conformations are kinetically and thermodynamically more readily accessible for the Gly41Ser variant than for the wild-type protein. Our work reveals a direct conformational link between the 40-57 Ω-loop in which residue 41 resides and the dynamical properties of the axial ligand to the heme iron, Met80, such that the replacement of glycine by serine promotes the dissociation of the Met80 ligand, thereby increasing the population of a peroxidase active state, which is a key non-native conformational state in apoptosis

Formation of cooperative amidoaminocalixresorcinarene – methotrexate nanosized aggregates in an aqueous solution and on the surface of gold nanoparticles

<p>Cooperative nanoscale associates of amido(dimethylamino) calixresorcinarenes with pentyl (<b>C5</b>) and undecyl (<b>C11</b>) substituents on lower rim with antitumor drug-methotrexate (<b>MTX</b>) in aqueous solution and on the surface of gold nanoparticles <b>C5</b>@Au and <b>C11</b>@Au were formed. The formation of nanoparticles was investigated by ¹H NMR, NMR FT-PGSE, 2D NOESY, DLS, TEM, spectrophotometry, fluorimetry. It was found that during the interaction of <b>C5</b> or <b>C11</b> macrocycles with <b>MTX</b> in aqueous solution, the latter generates dissociation of macrocycles self-associates with formation of cooperative macrocycle–<b>MTX</b> associates of smaller size due to multiple non-covalent interactions, which leads to increase in fluorescence intensity of <b>MTX</b>. In contrast, binding of <b>MTX</b> by macrocyclic associates preorganized as bilayer on surface of gold nanoparticles through electrostatic interactions induces aggregation of <b>C5</b>@Au-<b>MTX</b> or <b>C11</b>@Au-<b>MTX</b> associates, which results in quenching of <b>MTX</b> fluorescence in solution. Such particles have possible potential in the field of binding and delivery of antitumor drugs.</p

Structure and transport properties of La0.5Sr0.5 (-) xCaxFeO3 (-) (delta)

Effects of calcium doping on the structure, dimensional stability, and mixed oxygen-ion and electron conductivity of perovskite-like La0.5Sr0.5 - xCaxFeO3 - delta(x = 0-0.3) were studied in light of potential membrane applications. The incorporation of relatively small Ca2+ cations into the lanthanum-strontium ferrite lattice decreases unit cell volume, oxygen nonstoichiometry variations and chemical contribution to the thermal expansion in air. These changes correlate with rising tendency to local oxygen-vacancy ordering and the formation of nano-sized domains with the brownmillerite and LaCa2Fe3O8-type lattices, as revealed by electron diffraction. The resultant vacancy trapping, changing domain structure and enlargement of the interfacial boundary area lead to non-linear relationships between the partial ion conductivity and cation composition, while the apparent activation energy for ion transport at temperatures below 900 degrees C remains almost constant, 0.6-0.7 eV. The n-type electron contribution to the total conductivity, measured in the oxygen pressure range 10(-20)-0.5 atm at 700-950 degrees C, is also essentially independent of the calcium concentration. (C) 2013 Elsevier B.V. All rights reserved