The crystal structure of cytochrome c, from Rhodopseudomonas viridts has been refined using molecular dynamics and restrained least-squares methods to a crystallographic R-factor of 0.216 at 2.7 A resolution. A structural comparison between Rps. vi&s cytochrome c, and the other bacterial cytochromes c2 or mitochondrial cytochromes c indicates that the overall protein foldings are very similar to each other with the exception of the surface loop and terminal region of the polypeptide chain. However, the position and hydrogen-bond pattern of the evolutionarily conserved water molecule buried within the heme binding pocket in Rps. viridis cytochrome c, are common to those in the mitochondrial cytochromes c. This fact indicates that Bps. viridis cytochrome c1 is structurally more similar to mitochondrial cytochromes c than to the other bacterial cytochromes c,.

C-Phycocyanin from a red alga, Porphyra tenera, has been crystallized by the vapor-diffusion procedure. Both orthorhombic and hexagonal forms were obtained from ammonium sulfate solutions, whereas only the orthohombic form was selectively grown from sodium citrate solutions. The orthorhombic crystals are more suitable for further crystallographic work; their space group is P2(1)2(1)2(1), with unit-cell dimensions of a = 105, b = 121, and c = 184 A. The asymmetric unit comprises two (alpha beta)3 trimer molecules of C-phycocyanin. These crystals diffract X-rays up to about 3 A resolution.

An automatic molecular-replacement procedure has been applied to solve the crystal structure of cytochrome c(2) from Rhodopseudomonas viridis. The structure was solved on the basis of the structure of tuna cytochrome c as a search model using an automatic processing program system, AUTOMR. The refinements by molecular dynamics and restrained least-squares methods result in a current crystallographic R factor of 0.219 for diffraction data at 3 A resolution.

Yb(OTf ) 3 -Catalyzed 1,3-Dipolar Cycloaddition of Nitrone with Alkene; Switch in Diastereoselectivity by Solvent and Bidentate Auxiliary.-The ytterbium triflate catalyzed 1,3-dipolar cycloaddition of diphenylnitrone (I) with the crotylamides (II) is investigated. The diastereoselectivity is found to depend on the nature of the amide auxiliary and the solvent. -(MINAKATA, S.; EZOE, T.; NAKAMURA, K.; RYU, I.; KOMATSU, M.; Tetrahedron Lett. 39 (1998) 29, 5205-5208; Dep. Appl. Chem., Fac. Eng.,