Polymorphism of urea–barbituric acid co-crystals

2008 ◽  
Vol 64 (5) ◽  
pp. 623-632 ◽  
Author(s):  
Marlena Gryl ◽  
Anna Krawczuk ◽  
Katarzyna Stadnicka
Keyword(s):  
Barbituric Acid ◽  
Spatial Arrangement ◽  
Structural Components ◽  
Space Groups ◽  
The Third ◽  
Tautomeric Forms ◽  
Polymorphic Forms ◽  
Graph Set ◽  
Graph Set Analysis ◽  
Level Analysis

The crystal structures of three polymorphs found for the addition complex of urea and barbituric acid are described and compared. Two polymorphs are monoclinic, space groups P21/c and Cc, whereas the third is triclinic, P\bar 1. The displacement of electron density towards the mesomeric forms, corresponding to the tautomeric forms of higher stability, of the barbituric acid molecule seem to influence the type of hydrogen bonds formed, which in turn determines the different packing topology in the polymorphs. While the polymorphic forms can be easily differentiated at the first-level graph-set analysis of their hydrogen-bonding patterns, a higher-level analysis enables important features of the mutual spatial arrangement of the structural components to be revealed.

Sentiment Analysis of Comparative Sentences for Chinese Document

2012 ◽  
Vol 157-158 ◽  
pp. 1079-1082
Author(s):  
Guo Shi Wu ◽  
Xiao Yin Wu ◽  
Jing Jing Wei
Keyword(s):  
Sentiment Analysis ◽  
Opinion Mining ◽  
Sentiment Classification ◽  
The Third ◽  
Sentence Patterns ◽  
Simple Sentences ◽  
Document Level ◽  
Level Analysis

One of the most widely-studied sub-problems of opinion mining is sentiment classification, which includes three study levels: word, sentence and document. At the third level, most of the existing methods ignore comparative sentences which have particular sentence patterns and may lower the precision of the document-level analysis. This paper studies sentiment analysis of comparative sentences. The aim is to determine whether opinions expressed in a comparative sentence are positive or negative. Experiments of comparing with document-level sentiment analysis based on simple sentences shows the effectiveness of the proposed method.

Facing the Three Ds

2021 ◽  
pp. 25-41
Author(s):  
Clara Rachel Eybalin Casseus
Keyword(s):  
Local Development ◽  
The Bahamas ◽  
Urban Dynamics ◽  
The Third ◽  
Complex Process ◽  
The Third World ◽  
The City ◽  
Environmental Landscape ◽  
Epistemic Perspective ◽  
Level Analysis

In this chapter, the author provides a unique set of insights concerning the policy of urban dynamics that is part of a complex process. The focus is on how disasters and development are understood and experienced through the lens of decolonial thinking based on a discussion of the displaced issue in a complex global socio-economic context of the city. Because the third world is associated with development needs to be reformulated in terms of dialogues from different enunciation loci, it becomes pertinent to consider the decolonial epistemic perspective in a space that constantly faces disasters that jeopardize its development in the framework of the effects on the environmental landscape and local development initiatives of Hurricane Dorian. Based on an informative discussion of an institutional level analysis, the author concludes with important insights about the case of Haitians in the Bahamas to demonstrate some interesting implications for (mis)management through NGOs.

Conformational changes in the third PDZ domain of the neuronal postsynaptic density protein 95

2019 ◽  
Vol 75 (4) ◽  
pp. 381-391 ◽  
Author(s):  
Ana Camara-Artigas ◽  
Javier Murciano-Calles ◽  
Jose C. Martínez
Keyword(s):  
Binding Site ◽  
Conformational Changes ◽  
Pdz Domain ◽  
Postsynaptic Density ◽  
Crystal Form ◽  
Space Groups ◽  
The Third ◽  
Conformational Plasticity ◽  
Α Helix ◽  
Postsynaptic Density Protein

PDZ domains are protein–protein recognition modules that interact with other proteins through short sequences at the carboxyl terminus. These domains are structurally characterized by a conserved fold composed of six β-strands and two α-helices. The third PDZ domain of the neuronal postsynaptic density protein 95 has an additional α-helix (α3), the role of which is not well known. In previous structures, a succinimide was identified in the β2–β3 loop instead of Asp332. The presence of this modified residue results in conformational changes in α3. In this work, crystallographic structures of the following have been solved: a truncated form of the third PDZ domain of the neuronal postsynaptic density protein 95 from which α3 has been removed, D332P and D332G variants of the protein, and a new crystal form of this domain showing the binding of Asp332 to the carboxylate-binding site of a symmetry-related molecule. Crystals of the wild type and variants were obtained in different space groups, which reflects the conformational plasticity of the domain. Indeed, the overall analysis of these structures suggests that the conformation of the β2–β3 loop is correlated with the fold acquired by α3. The alternate conformation of the β2–β3 loop affects the electrostatics of the carboxylate-binding site and might modulate the binding of different PDZ-binding motifs.

scholarly journals Isomers and polymorphs of (E,E)-1,4-bis(nitrophenyl)-2,3-diaza-1,3-butadienes

2006 ◽  
Vol 62 (4) ◽  
pp. 666-675 ◽  
Author(s):  
Christopher Glidewell ◽  
John N. Low ◽  
Janet M. S. Skakle ◽  
James L. Wardell
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Three Dimensional ◽  
Stacking Interactions ◽  
Space Group ◽  
Stacking Interaction ◽  
Space Groups ◽  
Π Stacking ◽  
Π Stacking Interaction ◽  
Polymorphic Forms

The structures of five of the possible six isomers of (E,E)-1,4-bis(nitrophenyl)-2,3-diaza-1,3-butadiene are reported, including two polymorphs of one of the isomers. (E,E)-1,4-Bis(2-nitrophenyl)-2,3-diaza-1,3-butadiene, C14H10N4O4 (I), crystallizes in two polymorphic forms (Ia) and (Ib) in which the molecules lie across centres of inversion in space groups P21/n and P21/c, respectively: the molecules in (Ia) and (Ib) are linked into chains by aromatic π...π stacking interactions and C—H...π(arene) hydrogen bonds, respectively. Molecules of (E,E)-1-(2-nitrophenyl)-4-(3-nitrophenyl)-2,3-diaza-1,3-butadiene (II) are linked into sheets by two independent C—H...O hydrogen bonds. The molecules of (E,E)-1,4-bis(3-nitrophenyl)-2,3-diaza-1,3-butadiene (III) lie across inversion centres in the space group P21/n, and a combination of a C—H...O hydrogen bond and a π...π stacking interaction links the molecules into sheets. A total of four independent C—H...O hydrogen bonds link the molecules of (E,E)-1-(3-nitrophenyl)-4-(4-nitrophenyl)-2,3-diaza-1,3-butadiene (IV) into sheets. In (E,E)-1,4-bis(4-nitrophenyl)-2,3-diaza-1,3-butadiene (V) the molecules, which lie across centres of inversion in the space group P21/n, are linked by just two independent C—H...O hydrogen bonds into a three-dimensional framework.

Sebastian Moore’s Spiritual Vision and Christological Project

2018 ◽  
Vol 136 (3) ◽  
pp. 165-177
Author(s):  
Louis Roy OP
Keyword(s):  
Structural Components ◽  
The Third ◽  
Insight Into

This essay wants to examine the structural components and the viability of Sebastian Moore’s christological construction. The first section presents the origin of his insight into the redemptive role of Jesus. The second section reports his views on desire. In connection with desire, the third section details the experience that the followers of Jesus had of him, from the beginnings in Galilee, through his passion and death, ending with his appearances after his resurrection. The fourth justifies the validity of his Christology.

Mathematical aspects of molecular replacement. III. Properties of space groups preferred by proteins in the Protein Data Bank

2015 ◽  
Vol 71 (2) ◽  
pp. 186-194 ◽  
Author(s):  
G. Chirikjian ◽  
S. Sajjadi ◽  
D. Toptygin ◽  
Y. Yan
Keyword(s):  
Rigid Body ◽  
Protein Data Bank ◽  
Data Bank ◽  
Continuous Group ◽  
Molecular Replacement ◽  
Macromolecular Crystallography ◽  
Coset Space ◽  
Space Groups ◽  
The Third ◽  
Rigid Body Motions

The main goal of molecular replacement in macromolecular crystallography is to find the appropriate rigid-body transformations that situate identical copies of model proteins in the crystallographic unit cell. The search for such transformations can be thought of as taking place in the coset space Γ\Gwhere Γ is the Sohncke group of the macromolecular crystal andGis the continuous group of rigid-body motions in Euclidean space. This paper, the third in a series, is concerned with viewing nonsymmorphic Γ in a new way. These space groups, rather than symmorphic ones, are the most common ones for protein crystals. Moreover, their properties impact the structure of the space Γ\G. In particular, nonsymmorphic space groups contain both Bieberbach subgroups and symmorphic subgroups. A number of new theorems focusing on these subgroups are proven, and it is shown that these concepts are related to the preferences that proteins have for crystallizing in different space groups, as observed in the Protein Data Bank.

“Premit” System for Space Reticulated Structures

2003 ◽  
Vol 18 (1) ◽  
pp. 61-72
Author(s):  
Vincenzo Dipaola ◽  
Giuseppe Prete
Keyword(s):  
Static Analysis ◽  
Structural Characteristics ◽  
Parametric Modelling ◽  
Structural Components ◽  
Structural Process ◽  
The Third ◽  
Application Potential ◽  
Design Requirements ◽  
Technical Solutions

This is the third of three papers where we present the application potential of an original structural process for steel space grids, named PREMIT System. Here we explain the geometrical and structural characteristics of the welded version of the proposed System. Moreover we carry out the static analysis of structural components and we present a parametric modelling. Finally a codification and an inventory of technical solutions, useful to satisfy the design requirements of a wide applicative case study, are proposed. In the Appendix we present two System's variants, valid for both the bolted and the welded versions, with the aim to achieve appreciable economies in terms of materials and manufacturing.

scholarly journals Three isomeric 1-(2-chloronicotinoyl)-2-(nitrophenyl)hydrazines, including three polymorphs of 1-(2-chloronicotinoyl)-2-(2-nitrophenyl)hydrazine: hydrogen-bonded supramolecular structures in two and three dimensions

2007 ◽  
Vol 63 (1) ◽  
pp. 101-110 ◽  
Author(s):  
Solange M. S. V. Wardell ◽  
Marcus V. N. de Souza ◽  
James L. Wardell ◽  
John N. Low ◽  
Christopher Glidewell
Keyword(s):  
Hydrogen Bonds ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Framework Structure ◽  
Stacking Interaction ◽  
Space Groups ◽  
Isomeric Compound ◽  
Π Stacking ◽  
Π Stacking Interaction ◽  
Polymorphic Forms

1-(2-Chloronicotinoyl)-2-(2-nitrophenyl)hydrazine, C12H9ClN4O3, crystallizes in three polymorphic forms, two monoclinic forms in space groups Cc (Ia) and P21 (Ib), and an orthorhombic form in space group Pbcn (Ic). In the Cc polymorph (Ia) the molecules are linked into sheets by combinations of one N—H...O and two C—H...O hydrogen bonds, while in the P21 polymorph (Ib) the molecules are linked into sheets by combinations of three hydrogen bonds, one each of N—H...O, C—H...N and C—H...O types. In the orthorhombic polymorph (Ic) the molecules are linked into a complex three-dimensional framework structure by a combination of one N—H...O, one N—H...N and three C—H...O hydrogen bonds, and an aromatic π...π stacking interaction. In the isomeric compound 1-(2-chloronicotinoyl)-2-(3-nitrophenyl)hydrazine (II) the molecules are again linked into a three-dimensional framework, this time by a combination of three hydrogen bonds, one each of N—H...O, N—H...N and C—H...O types, weakly augmented by a π...π stacking interaction. The molecules of 1-(2-chloronicotinoyl)-2-(4-nitrophenyl)hydrazine (III) are linked into sheets by a combination of three hydrogen bonds, one each of N—H...O, N—H...N and C—H...O types.

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