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The crystal structure of native salmon pancreatic elastase (SPE) has been solved by molecular-replacement methods, and refined by conventional conjugate-gradient methods and simulated-annealing techniques. The final R value is 17.2% for 21 389 reflections between 8.0 and 1.61 A, and the corresponding free R value is 23.9%. The overall tertiary structure of SPE is remarkably similar to that of porcine pancreatic elastase I (PPE), to which it shows about 67% sequence identity. The primary structure of SPE is determined from the electron-density maps, and only about 15 side chains are somewhat uncertain. Interesting differences between SPE and PPE, are one sequence deletion assigned to position 186, the residue 192 at the entrance of the specificity pocket is substituted from a Gln in PPE to Asn in SPE, and one of the calcium ligands is different. Furthermore, electron density is missing in SPE for the last three residues of the C-terminal helix. A comparison of the present amino-acid sequence of SPE with other sequences available indicates that SPE belongs to the class 1 pancreatic elastases.

Anionic salmon trypsin in a second crystal form (ST-IIB) has been refined at 1.83 A, resolution. The crystals are orthorhombic and belong to space group P2(1)2(1)2 with lattice parameters a = 77.09, b = 82.33 and c = 31.16 A. The present structure has been compared to salmon trypsin as it appears in a previously reported crystal form (ST-IIA) with cell dimensions a = 61.95, b = 84.33 and c = 39.11 A [Smalas & Hordvik (1993). Acta Cryst. D49, 318-330]. The presence of a sulfate group involved in several hydrogen bonds to active-site residues, and the location of an additional benzamidine site in the crystal lattice, are the most striking differences between the present and the previous structure. Superposition of main-chain atoms in the two structures give an overall r.m.s. difference of 0.26 A, with the main differences located to areas with different molecular packing. The overall coordinate error is estimated to be between 0.20 and 0.25 A, by the method of Luzzati.

The crystal structure of an anionic form of salmon trypsin has been determined at 1.82 A resolution. We report the first structure of a trypsin from a phoikilothermic organism in a detailed comparison to mammalian trypsins in order to look for structural rationalizations for the cold-adaption features of salmon trypsin. This form of salmon trypsin (ST II) comprises 222 residues, and is homologous to bovine trypsin (BT) in about 65% of the primary structure. The tertiary structures are similar, with an overall displacement in main chain atomic positions between salmon trypsin and various crystal structures of bovine trypsin of about 0.8 A. Intramolecular hydrogen bonds and hydrophobic interactions are compared and discussed in order to estimate possible differences in molecular flexibility which might explain the higher catalytic efficiency and lower thermostability of salmon trypsin compared to bovine trypsin. No overall differences in intramolecular interactions are detected between the two structures, but there are differences in certain regions of the structures which may explain some of the observed differences in physical properties. The distribution of charged residues is different in the two trypsins, and the impact this might have on substrate affinity has been discussed.

Purification of hemoglobin from North Atlantic salmon (Salmo salar) gave three different types. The CO-complexes of types I and III have been crystallized by the batch method at 4 degrees C from solutions 18% (w/v) in polyethylene glycol 2000, 50 mg/ml in hemoglobin and 0.05 M in phosphate buffer (pH 8.3). Orthorhombic crystals, space group P2(1)2(1)2(1), were obtained for both, with cell dimensions a = 53.9 A, b = 80.4 A, c = 132.4 A, and a = 58.7 A, b = 95.0 A, c = 107.4 A, for types I and III, respectively.

Crystals of benzamidine-inhibited trypsin from the North Atlantic salmon ( Salmo salar ) have been grown from ammonium sulphate solution at pH 5.0. Two crystal forms suitable for X-ray structure analysis, obtained from a hanging-drop experiment, have been characterized. Both belong to space-group P 22 1 2 1 with cell dimensions a = 39.2 A, b = 62.4 A, c = 84.6 Aanda = 31.4 A, b = 74.8 A, c = 83.5 A, for forms I and II, respectively. Intensity data to 1.82 Ahave been collected for crystal form I on a CAD4 diffractometer, and initial phases have been obtained by molecular replacement methods. The conventional R -factor after two rounds of model building and subsequent refinement is 0.25 for data between 6.0 and 2.0 A. So far no water molecules have been included in the model.

La reaction d'ynamines avec des aryl-5 dithiazole-1,2,4ones-3 et -thiones-3 conduit respectivement aux diethylamino-5 thioaroylimino-2 oxathioles-1,3 et dithioles-1,3

Structural data have been obtained by X-ray crystallography for three 4-thiazoline derivatives, 2-benzoylimino-3, 4-diphenyl-4-thiazoline, 3-methyl-4-phenyl-2-thiobenzoylimino-4-thiazoline, and 3,4-diphenyl-4-thiazolin-2-ylidene thioacetophenone. In these compounds the separations between the sulphur atoms of the thiazoline rings and the adjacent oxygen or sulphur atoms of the carbonyl or thiocarbonyl groups approximate to the Huggins “constant energy” distances, suggesting that there is little or no bonding between them.

C 33 H 23 S 4 I 3 cristallise avec le groupe d'espace I2/c, et C 9 H 7 S 2 I 3 avec le groupe d'espace Ia. Affinement de la structure jusqu'a 0,05 pour les deux composes

Etudes theoriques relatives a une reaction d'electrode A±e⇄B, suivie par des reactions homogenes de B

Des gem-dibromo- et bromocyclopropanes sont solvolyses dans le methanol a 20-65°C en presence de trifluoroacetate d'argent. Les dibromures acyl- et alcoxycarbonyl-substitues ne reagissent pas alors que leurs analogues alcenyl-substitues subissent une decyclisation et donnent principalement des dibromo-1,3 et -1,4 dienes et de petites quantites d'allenes. Les monobromures sont plus reactifs que les dibromures

The results from structure studies on 6a-thiathiophthenes show that different substituent groups perturb the bonding in the three-sulphur sequence to different degrees. Both equal and unequal SS bonds occur in symmetrically as well as in unsymmetrically substituted derivatives. The specific effect of methyl and phenyl substituents on the sulphur-sulphur bonding may be described by the results from CNDO/2 calculations on mono-methyl and mono-phenyl substituted 6a-thiathiophthenes. Molecular packing and intermolecular close contacts also seem to affect the SS bonding. The structures of equally substituted 6a-thiathiophthene analogues with and show, when compared with the equivalent 6a-thiathiophthene, that and cause a pronounced change in the SS bonding, while the perturbation caused by is negligible. In symmetrical 6a-thiathiophthene analogues with and , the average bond length in the linear three-atom sequence is 9 – 12% longer than the respective single bond.