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A single crystal X-ray diffraction analysis of beta-amanitin, a bicyclic octapeptide toxin isolated from the poisonous mushroom Amanita phalloides, shows that the molecule has distinct regions of hydrophilic and hydrophobic residues and two 18-membered rings. The study confirms the proposed chemical sequence and the configuration of the residues. All eight peptide groups are in the trans conformation. Four intramolecular hydrogen bonds, two strong and two weak, occur in the structure. The toxin cocrystallizes with seven water and three ethanol molecules and participates in an extensive hydrogen-bonding network. The crystal structure was solved by direct methods. The space group is P2(1)2(1)2(1), and unit cell dimensions are a = 14.004(3), b = 14.943(3), and c = 30.794(7) A.

Latex paints contain several types of particles including polymer binder, primary pigment, extenders, and colorants. When the paints contain associative thickeners, control of particle dispersion can be very complicated due to the interaction of the particles with dispersants, surfactants, and the associative thickener itself. In particular, dispersion of the pigments can act independently of dispersion of the binder particles. The consequences of this situation are manifested in the physical properties of the paint and of the films it forms. This paper describes these interactions in terms of their colloid chemistry and shows the consequences of additive choices on the particle dispersion and also the optical properties of model paint films.

The 1 : 1 compound of urea and phosphoric acid, (NH2)2CO. HaPO4, has been studied by single-crystal neutron-diffraction techniques. All atoms, including the hydrogen atoms, have been accurately located. The carbonyl oxygen atom of urea is linked to the phosphoric acid moiety by a short hydrogen bond in which an acid hydrogen atom is nearly centered. Each of the remaining hydrogen atoms participates in an ordinary hydrogen bond. The space group is orthorhombic Pbca with lattice parameters a = 17.6492 (6), b= 7.4820 (3), and c= 9.0018 (4) A at 23 °C.

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