			Home About us Contact

Monoclinic P21 (monoclinic + p21)

Distribution by Scientific Domains

Chemistry	100%

Selected Abstracts

Nine N -aryl-2-chloronicotinamides: supramolecular structures in one, two and three dimensions

ACTA CRYSTALLOGRAPHICA SECTION B, Issue 4 2006
Silvia Cuffini
Structures are reported here for eight further substituted N -aryl-2-chloronicotinamides, 2-ClC5H3NCONHC6H4X -4,. When X = H, compound (I) (C12H9ClN2O), the molecules are linked into sheets by N,H,N, C,H,,(pyridyl) and C,H,,(arene) hydrogen bonds. For X = CH3, compound (II) (C13H11ClN2O, triclinic with Z, = 2), the molecules are linked into sheets by N,H,O, C,H,O and C,H,,(arene) hydrogen bonds. Compound (III), where X = F, crystallizes as a monohydrate (C12H8ClFN2O·H2O) and sheets are formed by N,H,O, O,H,O and O,H,N hydrogen bonds and aromatic ,,, stacking interactions. Crystals of compound (IV), where X = Cl (C12H8Cl2N2O, monoclinic P21 with Z, = 4) exhibit inversion twinning: the molecules are linked by N,H,O hydrogen bonds into four independent chains, linked in pairs by C,H,,(arene) hydrogen bonds. When X = Br, compound (V) (C12H8BrClN2O), the molecules are linked into sheets by N,H,O and C,H,N hydrogen bonds, while in compound (VI), where X = I (C12H8ClIN2O), the molecules are linked into a three-dimensional framework by N,H,O and C,H,,(arene) hydrogen bonds and an iodo,N(pyridyl) interaction. For X = CH3O, compound (VII) (C13H11ClN2O2), the molecules are linked into chains by a single N,H,O hydrogen bond. Compound (VIII) (C13H8ClN3O, triclinic with Z, = 2), where X = CN, forms a complex three-dimensional framework by N,H,N, C,H,N and C,H,O hydrogen bonds and two independent aromatic ,,, stacking interactions. [source]

Emerging from pseudo-symmetry: the redetermination of human carbonic anhydrase II in monoclinic P21 with a doubled a axis

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 8 2010
Arthur H. Robbins
The crystal structure of human carbonic anhydrase II in the monoclinic P21 space group with a doubled a axis from that of the usually observed unit cell has recently been reported, with one of the two molecules in the asymmetric unit demonstrating rotational disorder [Robbins et al. (2010), Acta Cryst. D66, 628,634]. The structure has been redetermined, with the coordinates of both pseudo-symmetrically related molecules in the crystallographic asymmetric unit translated by x, = x± 1/4, and no rotational disorder is observed. This corresponds to a different choice of how the four molecules in the unit cell should be grouped into pairs that represent a single asymmetric unit. [source]

Pseudo-merohedral twinning in monoclinic crystals of wild-type human brain neuroglobin

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 4 2009
Djemel Hamdane
The purification, crystallization and successful structure determination by molecular replacement of wild-type human brain neuroglobin at 1.8,Å resolution is reported. The apparent space group was orthorhombic C2221, but the real space group was monoclinic P21, which resulted from twinning. Indeed, the unit-cell parameters, a = 31.2, b = 139.1, c = 31.2,Å, , = 102°, display a fortuitously close to c and twinning by the operator l, ,k, h occurs. Twinning was not evident from the initial analysis of intensity distribution, but pseudo-merohedral twinning was revealed by the Padilla and Yeates test based on local intensity differences. A twinning fraction of 0.5 was determined in SHELXL, indicating a perfect hemihedrally twinned crystal. To date, this type of twinning has been reported in more than ten structures, which makes it quite a common case in proteins. [source]

Platinum-induced space-group transformation in crystals of the platelet glycoprotein Ib, N-terminal domain

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 3 2004
Kottayil I. Varughese
The interaction between platelet glycoprotein (GP) Ib, and von Willebrand factor (VWF) is essential for thrombus formation, leading to the arrest of bleeding. The N-terminal domain of GP Ib,, which contains the binding sites for VWF and ,-thrombin, crystallized in the tetragonal space group P43 with one molecule in the asymmetric unit. When the crystals were treated with platinum, the crystals changed their symmetry from tetragonal to monoclinic P21 with two molecules in the asymmetric unit. The structure of the monoclinic form was solved using two-wavelength platinum anomalous dispersion data. The tetragonal crystal structure was subsequently solved using molecular-replacement techniques using the monoclinic structure as the search model and was refined with 1.7,Å resolution data. [source]