Global relationship between <i>TC</i> and <i>HYD</i> in MMPs of metazoan animals.

<p>Solid circles represent the average values of <i>HYD</i> and <i>TC</i> in each animal group, with the hydrophobic score S>0 (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0098188#s2" target="_blank">Materials and Methods</a>). The red circles show the <i>STC</i> values, which well describe the vertebrate lineage <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0098188#pone.0098188-Kitazoe1" target="_blank">[16]</a>. Such a strong correlation was also obtained by analyzing all 13 proteins (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0098188#pone.0098188.s001" target="_blank">Figure S1</a>). The correlation is totally well reproduced by a non-linear function (<b>A</b>: <i>TC</i> = 0.429•<i>HYD</i>^−4.2045 with R² = 0.901), but it can be separately expressed by 2 regression lines with different slopes (<b>B</b>: the dotted line for the deuterostomes with R² = 0.918) and (<b>C</b>: the dotted line for the other groups with R² = 0.890). The error range of the x-axis (<i>HYD</i>) in an animal group can be estimated by moving the regression curve <b>A</b> in parallel along the y-axis so that the y-value of this curve may be equal to that of the solid circle of the group, since this error range of <i>HYD</i> may be roughly given by the x-axis values of the curve corresponding to the error range of the y-axis (<i>STC</i>).</p

Evolution of Mitochondrial Power in Vertebrate Metazoans

<div><p>Background</p><p>Basal metabolic rate (<i>BMR</i>) has a very strong body-mass (<i>M</i>) dependence in an individual animal group, and <i>BMR</i> per unit mass (<i>msBMR</i>) converges on a markedly narrow range even across major taxonomic groups. However, it is here a basic question in metazoan biology how much <i>BMR</i> per unit mitochondrion (<i>mtBMR</i>) changes, and then whether <i>mtBMR</i> can be related to the original molecular mechanism of action of mt-encoded membrane proteins (MMPs) playing a central role in cellular energy production.</p><p>Methodology/Principal Findings</p><p>Analyzing variations of amino-acid compositions of MMPs across 13 metazoan animal groups, incorporating 2022 sequences, we found a strong inverse correlation between Ser/Thr composition (<i>STC</i>) and hydrophobicity (<i>HYD</i>). A majority of animal groups showed an evolutionary pathway of a gradual increase in <i>HYD</i> and decrease in <i>STC</i>, whereas only the deuterostome lineage revealed a rapid decrease in <i>HYD</i> and increase in <i>STC</i>. The strongest correlations appeared in 5 large subunits (ND4, ND5, ND2, CO1, and CO3) undergoing dynamic conformational changes for the proton-pumping function. The pathway of the majority groups is well understood as reflecting natural selection to reduce <i>mtBMR</i>, since simply raising <i>HYD</i> in MMPs (surrounded by the lipid bilayer) weakens their mobility and strengthens their stability. On the other hand, the marked decrease in <i>HYD</i> of the deuterostome elevates <i>mtBMR</i>, but is accompanied with their instability heightening a turnover rate of mitochondria and then cells. Interestingly, cooperative networks of interhelical hydrogen-bonds between motifs involving Ser and Thr residues can enhance MMP stability.</p><p>Conclusion/Significance</p><p>This stability enhancement lowers turnover rates of mitochondria/cells and may prolong even longevity, and was indeed founded by strong positive correlations of <i>STC</i> with both <i>mtBMR</i> and longevity. The lowest <i>HYD</i> and highest <i>STC</i> in Aves and Mammals are congruent with their very high <i>mtBMR</i> and long longevity.</p></div

Relationships of <i>STC</i> with <i>mtBMR</i> (A), <i>mtBMR</i>·<i>MLS</i> (B), and <i>MLS</i> (C).

<p>Relationships of <i>STC</i> with <i>mtBMR</i> (A), <i>mtBMR</i>·<i>MLS</i> (B), and <i>MLS</i> (C).</p

<i>HYD</i>-<i>TC</i> and <i>TC</i>-<i>CC</i> correlations (R²) within respective proteins.

<p>The * symbol denotes 2 subunits with weak correlations (ATP6 and ND6) and 4 subunits with small numbers (3 or less in humans) of helices (ND3, ATP8, ND4L, and CO2). The analysis includes the following 13 metazoan animal groups: Porifera, Cnidaria, Mollusca, Crustacea, Hexapoda, Chelicerata, Nematoda, Platyhelminthes, Echinodermata, Fishes, Amphibia, Eutheria, and Aves.</p

<i>HYD</i> and <i>TC</i> distributions in the mt inner membrane of ND2, ND4 and ND5.

<p>Four animal groups were selected as providing extreme situations of the hydrophobic distribution. This result was obtained by using SOSUI WWW server <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0098188#pone.0098188-SOSUI1" target="_blank">[19]</a> and TMHMM Server <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0098188#pone.0098188-TMHMM1" target="_blank">[20]</a> for the prediction of the secondary structure of proteins.</p

<i>HYD</i> and <i>TC</i> versus <i>TSN</i>.

<p>The regression lines for Deuterostomes and those for Protostomes were estimated separately. <i>HYD</i> and <i>TC</i> are expressed on the left and right ordinates, respectively.</p

Vapor-Phase Growth and Structural Characterization of Single Crystals of Magnesium Doped Two-Dimensional Fullerene Polymer Mg₂C₆₀

Single crystals of magnesium doped fullerene polymer Mg₂C₆₀ can be directly grown via a binary vapor-phase mixture of Mg and C₆₀, in sealed glass tubes at elevated temperatures. This is the first single crystal, in metal-doped two-dimensional fullerene polymers, which enables precise X-ray structural refinement. The Mg₂C₆₀ crystallizes in a monoclinic space group, <i>I</i>2/<i>m</i>, with lattice parameters of <i>a</i> = 9.324(2) Å, <i>b</i> = 9.041(2) Å, <i>c</i> = 14.817(3) Å, and β = 91.699(10)°. A Mg atom is located at each tetrahedral fullerene ball interstice, where the shortest Mg–C distance is 2.341(2) Å, suggesting that the Mg cation is in van der Waals contact with carbon p orbitals. The precise structure of the two-dimensional fullerene polymer network is characterized by comparison with structural data reported previously on powder samples

Correlations (R²) between the pairs of variables (<i>HYD</i>, <i>TC</i>, <i>STC</i>, <i>CC</i>, <i>TSN</i>, <i>mtBMR</i>, <i>msBMR</i> and <i>MLS</i>).

<p> denotes that <i>TSN</i> of each protein set occupies the n % of that of the complete amino acid sequence in Human. P and N stand for the positive and negative correlations, respectively. The best results in the respective correlation croups are denoted by italics.</p

High-Pressure Synthesis and Superconductivity of the Laves Phase Compound Ca(Al,Si)₂ Composed of Truncated Tetrahedral Cages Ca@(Al,Si)₁₂

The Zintl compound CaAl₂Si₂ peritectically decomposes to a new ternary cubic Laves phase Ca­(Al,Si)₂ and an Al–Si eutectic at temperatures above 750 °C under a pressure of 13 GPa. The ternary Laves phase compound can also be prepared as solid solutions Ca­(Al_1–<i>x</i>Si_<i>x</i>)₂ (0.35 ≤ <i>x</i> ≤ 0.75) directly from the ternary mixtures under high-pressure and high-temperature conditions. The cubic Laves phase structure can be regarded as a type of clathrate compound composed of face-sharing truncated tetrahedral cages with Ca atoms at the center, Ca@(Al,Si)₁₂. The compound with a stoichiometric composition CaAlSi exhibits superconductivity with a transition temperature of 2.6 K. This is the first superconducting Laves phase compound composed solely of commonly found elements

High Pressure Synthesis and Superconductivity of the Ternary Compounds Mg(Mg_1–<i>x</i>Al_<i>x</i>)Si with the Anticotunnite Structure

Ternary compounds Mg­(Mg_1–<i>x</i>Al_<i>x</i>)Si (0.3 < <i>x</i> < 0.8) have been prepared under high pressure and high temperature conditions of 5 GPa at 800–1100 °C. The single crystal study revealed that the compound (<i>x</i> = 0.45) is isomorphous with the anticotunnite, or the TiNiSi structure, and crystallizes with space group <i>Pnma</i>, with lattice parameters <i>a</i> = 6.9242(2), <i>b</i> = 4.1380(1), <i>c</i> = 7.9618(2) Å, and <i>Z</i> = 4. The compound with <i>x</i> > 0.5 shows superconductivity with a transition temperature (<i>T</i>_c) ∼ 6 K. The compound is a peritectic solid solution associated with other phases such as Mg₉Si₅, Al, and Si, depending on cooling protocols in the preparation. The band structure calculation on the composition MgAlSi suggests that the Al and Mg orbitals mainly contribute to the density of states near the Fermi level, and the substitution of Mg with Al favors the superconductivity