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The appearance of voltage-gated, sodium-selective channels with rapid gating kinetics was a limiting factor in the evolution of nervous systems. Two rounds of domain duplications generated a common 24 transmembrane segment (4 × 6 TM) template that is shared amongst voltage-gated sodium (Nav1 and Nav2) and calcium channels (Cav1, Cav2, and Cav3) and leak channel (NALCN) plus homologs from yeast, different single-cell protists (heterokont and unikont) and algae (green and brown). A shared architecture in 4 × 6 TM channels include an asymmetrical arrangement of extended extracellular L5/L6 turrets containing a 4-0-2-2 pattern of cysteines, glycosylated residues, a universally short III-IV cytoplasmic linker and often a recognizable, C-terminal PDZ binding motif. Six intron splice junctions are conserved in the first domain, including a rare U12-type of the minor spliceosome provides support for a shared heritage for sodium and calcium channels, and a separate lineage for NALCN. The asymmetrically arranged pores of 4x6 TM channels allows for a changeable ion selectivity by means of a single lysine residue change in the high field strength site of the ion selectivity filter in Domains II or III. Multicellularity and the appearance of systems was an impetus for Nav1 channels to adapt to sodium ion selectivity and fast ion gating. A non-selective, and slowly gating Nav2 channel homolog in single cell eukaryotes, predate the diversification of Nav1 channels from a basal homolog in a common ancestor to extant cnidarians to the nine vertebrate Nav1.x channel genes plus Nax. A close kinship between Nav2 and Nav1 homologs is evident in the sharing of most (twenty) intron splice junctions. Different metazoan groups have lost their Nav1 channel genes altogether, while vertebrates rapidly expanded their gene numbers. The expansion in vertebrate Nav1 channel genes fills unique functional niches and generates overlapping properties contributing to redundancies. Specific nervous system adaptations include cytoplasmic linkers with phosphorylation sites and tethered elements to protein assemblies in First Initial Segments and nodes of Ranvier. Analogous accessory beta subunit appeared alongside Nav1 channels within different animal sub-phyla. Nav1 channels contribute to pace-making as persistent or resurgent currents, the former which is widespread across animals, while the latter is a likely vertebrate adaptation.

The energetic and structural relationships among various C2H2NM isomers (M = Li, Na, MgH, and the anion) are explored by theoretical calculations. The cyanomethyl anion, CH2CN-, is predicted to have a pyramidal structure but with a very low inversion barrier of 0.3 kcal/mol (MP2/6-3l+G*//6-3l+G*). At the same level of ab initio theory, a significantly higher barrier of 2.8 kcal/mol is found for the isocyanomethyl anion, CH2NC-. r-Delocalization in CH2CN-results in a large stabilization relative to CH3-(calculated 45.3, experimental 44.4 kcal/mol). In contrast, the CH2NC-anion is stabilized (by 36.3 kcal/mol relative to CH3-) largely inductively by the sp-hybridized nitrogen. Extensive ab initio examination of the lithium, sodium, and magnesyl (MgH) derivatives of these anions (as well as those of isomeric structures) found lithium-bridged and, to a somewhat lesser extent, sodium-bridged geometries 7 and 12 to be favored. The magnesyl derivatives, 1 and 12, have more covalent character and nearly classical structures. The metallated ketenimine forms, M-N=C=CH2( 2 , M = Li, Na, MgH), are next lowest in energy. The metallated nitrile ylides, M-C=N=CH2, are substantially higher in energy than the bridged forms but also show the geometrical variations associated with increasing ionic character. Other C2H2NM isomers, including metallated aminoacetylenes and carbene complexes, are energetically unfavorable. The energy orderings of the acyclic C2HlNM isomers also reflect the relative stabilities of the parent systems (in kcal/mol), e.g., CH3CN (O.O), CH3NC (+20.8), H2C=C=NH (+35.3), HCC-NH2 (+51.4), HC=N==CH2 (+69.0), at the 6-31G*//6-31G* level. More revealing are the stabilization energies relative to CH3M or to NH2M, depending on the principal site of metal attachment of the metal derivatives based on the parent C2H3N structures. Thus, the amino (vs. NH2M) stabilization energies, 40.9 kcal/mol for Na-N=C=CH2 and 32.4 kcal/mol for Li-N=C=CH2 (3-21G//3-21G), are 70% and 56% those of the free anion; the value for M=MgH (23.3 kcal/mol) is decreased even further. Likewise, the methyl stabilization energies (vs. CH3M) of the CH,(M)CN forms (Li, 21.5; Na, 23.2; and MgH, 8.7 kcal/mol) are all substantially less than that of the free anion, 45.3 kcal/mol (CHICN-vs. CH3-). Similar attenuation is found for the CH2(M)NC species vs. the CHINC-anion. Aggregation and solvation effects were probed by MNDO calculations. The most stable unsolvated dimers of both LiCH2CN and LiCH2NC are indicated to prefer eight-membered-ring structures, but solvation favors the alternative four-membered-ring N-lithiated ketenimine dimer form of the former, which may be the structure in the solid state.The importance of cyano-stabilized carbanions as synthetic intermediates is underscored by Volume 31 of "Organic Reactions", the latest in a series of reviews devoted to this topic1 The sodium salt of propionitrile was first described almost a 100 years ago.2 Lithium derivatives of aliphatic nitriles were reported by Ziegler in 19323 and the corresponding...

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Various calcium hydroxyapatites [Calo~z(HP04)z( PO,)6 -,(OH), -,; z = 0, stoichiometric apatite (Ca/P = 1.67; atomic ratio); 0 < z 6 1, non-stoichiometric apatites ( 1.67 > Ca/P > 1.50)], together with the apatites of Ca/P = 1.72, were analysed by powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and extended X-ray absorption fine structure (EXAFS) spectroscopy and their catalytic properties in the oxidation of methane at 973 K were examined in the presence and absence of tetrachloromethane as a gas-phase additive. The XRD patterns of each hydroxyapatite were the same. However, the nearestneighbour distances of the Ca-0 bond of stoichiometric and non-stoichiometric hydroxyapatites as estimated by EXAFS were 2.41,2.37,2.38 and 2.39 A for each catalyst of Ca/P = 1.72, 1.68, 1.64 and 1.58, respectively. In the oxidation of methane on each hydroxyapatite in the absence of CCl,, the conversion of methane was little influenced by the value of Ca/P but the selectivities to C2H6 and CO showed a maximum and minimum, respectively, at Ca/P = 1.68. On addition of CCl, into the feedstream, the selectivity to C 0 2 on Ca/P = 1.68 and 1.72 decreased as the time on-stream increased while sharp decreases in conversion were observed with time on-stream on non-stoichiometric hydroxyapatites of Ca/P = 1.64 and 1.53, respectively, without suppression of the selectivity to C 0 2 .