No abstract

Infrared and Raman spectra of solid and matrix isolated diimide, HNNH Hydrazoic acid labeled with deuterium and IoN was photolyzed in solid nitrogen at 20oK. The IoN multiplet splitting positively identifies absorptions of photolysis products as those of trans-N2H2 (at 1286 cm-I ) , trans-HNND (at 1481 and 1058 em-I), trans-N2D2 (at 946 cm-I ), and cis-N2H2 (at 3074 and 1279 em-I).The spectrum of trans-N2H2 is in agreement with a planar symmetric structure and the vibrational frequencies are quite close to corresponding vibrations of ethylene.Imidogen, NH, was also observed in both solid argon and in solid nitrogen as another photolysis product. The IoN splitting in the ammonia absorptions shows that the ammonia dimer in solid nitrogen has a cyclic structure.

Mambalgins are a novel class of snake venom components that exert potent analgesic effects mediated through the inhibition of acid-sensing ion channels (ASICs). The 57-residue polypeptide mambalgin-2 (Ma-2) was synthesized by using a combination of solid-phase peptide synthesis and native chemical ligation. The structure of the synthetic toxin, determined using homonuclear NMR, revealed an unusual three-finger toxin fold reminiscent of functionally unrelated snake toxins. Electrophysiological analysis of Ma-2 on wild-type and mutant ASIC1a receptors allowed us to identify a-helix 5, which borders on the functionally critical acidic pocket of the channel, as a major part of the Ma-2 binding site. This region is also crucial for the interaction of ASIC1a with the spider toxin PcTx1, thus suggesting that the binding sites for these toxins substantially overlap. This work lays the foundation for structure-activity relationship (SAR) studies and further development of this promising analgesic peptide.

Synopsis If coarse grained marble is heated to around 6OO°C the anisotropy of thermal expansion of calcite causes almost complete separation at grain boundaries. The resulting material retains its shape and consists of a mass of crystals in contact, with a porosity of about 4%, very small direct tensile strength and the mechanical analysis and permeability to water of a sand. It may be regarded as a laboratory model of randomly jointed rock and perhaps of bad and broken rock in general. It has frequently been suggested that soil mechanics theory may be applied to such rock. This Paper examines the mechanical properties of the heated marble and shows that they different from those of soils. A small amount of confining pressure varies the triaxial strength rapidly, the initial slope of the Mohr envelope being of the order of 65° and the strength finally increasing to over 80% of that of the original rock. Young's modulus also increases with confining pressure but only to about 30% of that of original rock. Even if one principal stress is tensile, a perpendicular compressive stress greatly increases the strength. Model ‘plate bearing’ tests give the same value of Young's modulus as compression of cylinders, suggesting that this may be true for full scale tests on bad rock. Permeability is found to decrease rapidly with confining pressure and slightly with uniaxial stress. Pronounced effects of size on strength are observed which appear to deviate from the usual power or Protodyakonov laws at small sizes. Si du marbre à grains grossiers est chauffè á environ 600°C l'anisotropie de la dilatation thermique de la calcite provoque une séparation presque complète à la limite de composition des grains. La matière qui en résulte conserve sa forme et est formée d'une masse de cristaux en contact, d'une porosité d'environ 4%, d'une très petite résistance directe à la traction et possédant les qualités d'analyse mécanique et de perméabilité à l'eau d'un sable. On peut la considérer comme un exemple de laboratoire d'une roche assemblée au hasard et peut-être d'une roche de mauvaise qualité et brisée d'une façon générale. Il a été fréquemment suggéré que la théorie de la mécanique du sol pourrait peut-être être appliquée á une telle roche. Cet exposé examine les propriétés mécaniques du marbre chauffté et montre qu'elles sont différentes de celles des sols. Une petite quantité de pression dans une enceinte rigide fait rapidement varier la résistance triaxiale, la pente initiale de la courbe intrinsèque étant de l'ordre de 65° et la résistance augmentant jusqu'à plus de 80% de celle de la roche d'origine. Le module d'Young augmente aussi avec une pression dans une enceinte rigide mais seulement jusqu'à une valeur d'environ 30% de celle de la roche d'origine. Même si une contrainte principale est à la traction, une contrainte de compression perpendiculaire augmente beaucoup la résistance. Des essais de ‘charge sur plaque’ sur maquette donnent la même valeur que le module d'Young qu'une compression de cylindres, suggérant que ceci pourrait étre vrai pour des essais in situ sur des roches de mauvaise qualité On trouve que la perméabilité diminue rapidement avec la pression dans une enceinte rigide, et légèrement avec une contrainte selon un axe. On observe des effets prononcés de la taille sur la résistance qui paraissent ne pas se conformer aux lois de puissance habituelles ou de Protodyakonov pour les petites tailles.

Gas-phase and N2 matrix vibrational spectra of HN3, DN3, H15NNN, 15NNNH, D15NNN, and 15NNND are reported. The pure rotation spectrum of HN3 is given as well. Strong vibration—rotation interaction is evident in the v5, v6 spectra, in the changes of the A rotational constant by 4%−8% in the hydrogen stretching and bending fundamentals, and in the pure rotation spectrum of HN3. Normal coordinates and eight force constants are determined using 22 vibrational frequencies from six molecules. A large (HNN bend)—(HN–N stretch) interaction force constant is found. Its magnitude and sign are readily understood in terms of the electronic structure of hydrazoic acid.