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Analysis of the crystal structure of 9-ethyl-8-hydroxyguanine using X-ray diffraction showed that it is in C-8 keto form. As compared with 9-ethylguanine, significant differences were observed in bond lengths and bond angles of the imidazole ring.

In this paper we report on the crystal structure of 4-methyl-4′,5′-dihydropyrrolocoumarin (MDPC, see Figs. 1 and 2). The tricyclic chromophore is formed on ring-closure by bridging amino nitrogen (N(1)) and ring carbon (C(6)) with two methylene groups (C(7) and C(8)). The tricyclic compound is regarded as a coumarin-indoline hybrid in which a pyrrolidine moiety is condensed with a coumarin skeleton.A previous spectroscopic study 1 suggests that the methylene bridge makes the amino moiety more pyramidal than simple Nalkylation without ring formation. Pyramidalization at the nitrogen atom may be responsible for the observed blue shift and the slight decrease in the molar extinction coefficient or oscillator strength in comparison with the more planar Nalkylaminocoumarin. 1 MDPC was synthesized according to a procedure described by Quanten et al. X-ray Structure Analysis Online Crystal Structure of a Coumarin-Indoline Hybrid DyeNoriko KITAMURA,* Yoshiharu TORIUMI,** Shigeru KOHTANI,* , *** and Ryoichi NAKAGAKI* , *** † *Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan **Toray Research Center, Inc, 3-3-7 Sonoyama, Otsu 520-8567, Japan ***Faculty of Pharmaceutical Sciences, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan The crystal structure of 4-methyl-4′,5′-dihydropyrrolocoumarin (MDPC) has been determined by X-ray diffraction. The crystal, C12H11NO2, belongs to space group P21/c with cell dimensions of a = 7.539(2)Å, b = 19.230(2)Å, c = 6.9395(9)Å, β = 103.89(1)˚. The final R value is 0.036. The methylene bridge in the indoline moiety makes the amino moiety more pyramidal than simple N-alkylation.

The crystallization and preliminary crystallographic study of phycocyanin from the thermophilic cyanobacterium Synechococcus elongatus is reported. Phycocyanin is composed of alpha- and beta-subunits consisting of 162 and 172 amino-acid residues, respectively. These associate to form an alphabeta heterodimer, which further associates to give a ring-shaped trimer (alphabeta)(3). Two trimers bind head-to-head to form a hexamer (alphabeta)(6). Phycocyanin crystals have been obtained by the sitting-drop vapour-diffusion method with a precipitant solution containing 30%(w/v) PEG 4000 and 100 mM MES pH 7.5-8.0. Using synchrotron radiation, the crystals diffract to 2.0 A resolution. They belong to the trigonal space group R32, with unit-cell parameters a = b = 186.75 (3), c = 59.75 (4) A, alpha = beta = 90, gamma = 120 degrees. Assuming that the crystallographic triad is identical to the threefold axis of the hexamer and with three (alphabeta)(6) molecules in a unit cell, the calculated molar volume (V(M)) is 2.64 A(3) Da(-1). This value corresponds to a solvent content of approximately 53%, with one alphabeta heterodimer occupying the asymmetric unit.