. The interfacial activation of Pseudomonas lipases involves conformational rearrangements of surface loops and appears to conform to models of activation deduced from the structures of fungal and mammalian lipases. Factors controlling the conformational rearrangement are not understood, but a comparison of crystallization conditions and observed conformation suggests that the conformation of the protein is determined by the solution conditions, perhaps by the dielectric constant.

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NaZn(C6H6NO6).H20: Mr =295"44, orthorhombic, P212121, a = 7.869 (4), b =9.783 (6), c = 12.292 (6) A,, V = 946-3 A, 3, Z = 4, Dx = 2.07 gcm -3, A (So Kc~) = 0.71073A,, /z=27.4cm -I Final R=0.052 for 859 unique reflections. The nitrilotriacetate ion is coordinated to the Zn 2+ ion in a tetradentate fashion. The remaining two octahedral sites about the Zn 2÷ ion are occupied by O atoms of different nitrilotriacetate ions. A comparison of the structure with other published structures identifies a common geometry, termed the 'butterfly' geometry, for transition-metal complexes with nitrilotriacetate ligands. The Na ÷ ions bridge the nitrilotriacetatozinc ions thereby holding the structure intact. The water molecule is coordinated to the five-coordinate Na ÷ ion.

Aqualysin I, a thermostable protease found in the culture medium of Thermus aquaticus YT-1, has been purified to homogeneity using a combination of ion-exchange and affinity chromatography. It is a polypeptide with a molecular weight of 28 350 . Eur. J. Biochem. 173, 491497]

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