Role of Hydrogen Bonding in Determining the Crystal Structures of the Adducts between Acetone and Urea Derivatives

1994 ◽  
Vol 6 (8) ◽  
pp. 1245-1249 ◽  
Author(s):  
Menahem Kaftory ◽  
Moshe Kapon ◽  
Mark Botoshansky
Keyword(s):  
Hydrogen Bonding ◽  
Crystal Structures ◽  
Urea Derivatives

scholarly journals Structures of furanosides: geometrical analysis of low-temperature X-ray and neutron crystal structures of five crystalline methyl pentofuranosides

2001 ◽  
Vol 57 (2) ◽  
pp. 213-220 ◽  
Author(s):  
Artem Evdokimov ◽  
A. Joseph Gilboa ◽  
Thomas F. Koetzle ◽  
Wim T. Klooster ◽  
Arthur J. Schultz ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Crystal Structures ◽  
Critical Role ◽  
Chair Conformation ◽  
Geometrical Analysis ◽  
X Ray ◽  
Wide Range ◽  
First Time ◽  
Ring Conformations

Crystal structures of all five crystalline methyl D-pentofuranosides, methyl α-D-arabinofuranoside (1), methyl β-D-arabinofuranoside (2), methyl α-D-lyxofuranoside (3), methyl β-D-ribofuranoside (4) and methyl α-D-xylofuranoside (5) have been determined by means of cryogenic X-ray and neutron crystallography. The neutron diffraction experiments provide accurate, unbiased H-atom positions which are especially important because of the critical role of hydrogen bonding in these systems. This paper summarizes the geometrical and conformational parameters of the structures of all five crystalline methyl pentofuranosides, several of them reported here for the first time. The methyl pentofuranoside structures are compared with the structures of the five crystalline methyl hexopyranosides for which accurate X-ray and neutron structures have been determined. Unlike the methyl hexopyranosides, which crystallize exclusively in the C 1 chair conformation, the five crystalline methyl pentofuranosides represent a very wide range of ring conformations.

Crystal structures of dicarboxy-2,2′-bipyridyl complexes: the role of hydrogen bonding and stacking interactions

2004 ◽  
pp. 492-497 ◽  
Author(s):  
Craig J. Matthews ◽  
Mark R. J. Elsegood ◽  
Gérald Bernardinelli ◽  
William Clegg ◽  
Alan F. Williams
Keyword(s):  
Hydrogen Bonding ◽  
Crystal Structures ◽  
Stacking Interactions

The Role of Hydrogen Bonding in the Crystal Structures of Zinc Phosphate Hydrates

2004 ◽  
Vol 10 (11) ◽  
pp. 2795-2803 ◽  
Author(s):  
Laurent Herschke ◽  
Volker Enkelmann ◽  
Ingo Lieberwirth ◽  
Gerhard Wegner
Keyword(s):  
Hydrogen Bonding ◽  
Crystal Structures ◽  
Zinc Phosphate

scholarly journals Deciphering the Role of π-Interactions in Polyelectrolyte Complexes Using Rationally Designed Peptides

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2074
Author(s):  
Sara Tabandeh ◽  
Cristina Elisabeth Lemus ◽  
Lorraine Leon
Keyword(s):  
Hydrogen Bonding ◽  
Phase Separation ◽  
Liquid Phase ◽  
Charge Density ◽  
Secondary Structures ◽  
Liquid Phase Separation ◽  
Polyelectrolyte Complexes ◽  
Π Interactions ◽  
Liquid Liquid Phase Separation

Electrostatic interactions, and specifically π-interactions play a significant role in the liquid-liquid phase separation of proteins and formation of membraneless organelles/or biological condensates. Sequence patterning of peptides allows creating protein-like structures and controlling the chemistry and interactions of the mimetic molecules. A library of oppositely charged polypeptides was designed and synthesized to investigate the role of π-interactions on phase separation and secondary structures of polyelectrolyte complexes. Phenylalanine was chosen as the π-containing residue and was used together with lysine or glutamic acid in the design of positively or negatively charged sequences. The effect of charge density and also the substitution of fluorine on the phenylalanine ring, known to disrupt π-interactions, were investigated. Characterization analysis using MALDI-TOF mass spectroscopy, H NMR, and circular dichroism (CD) confirmed the molecular structure and chiral pattern of peptide sequences. Despite an alternating sequence of chirality previously shown to promote liquid-liquid phase separation, complexes appeared as solid precipitates, suggesting strong interactions between the sequence pairs. The secondary structures of sequence pairs showed the formation of hydrogen-bonded structures with a β-sheet signal in FTIR spectroscopy. The presence of fluorine decreased hydrogen bonding due to its inhibitory effect on π-interactions. π-interactions resulted in enhanced stability of complexes against salt, and higher critical salt concentrations for complexes with more π-containing amino acids. Furthermore, UV-vis spectroscopy showed that sequences containing π-interactions and increased charge density encapsulated a small charged molecule with π-bonds with high efficiency. These findings highlight the interplay between ionic, hydrophobic, hydrogen bonding, and π-interactions in polyelectrolyte complex formation and enhance our understanding of phase separation phenomena in protein-like structures.

The role of hydrogen bonding on tuning hard-soft segments in bio-based thermoplastic poly(ether-urethane)s

2020 ◽  
Vol 274 ◽  
pp. 122678
Author(s):  
Paulina Kasprzyk ◽  
Hynek Benes ◽  
Ricardo Keitel Donato ◽  
Janusz Datta
Keyword(s):  
Hydrogen Bonding ◽  
Soft Segments

scholarly journals The crystal structures and mechanical properties of the uranyl carbonate minerals roubaultite, fontanite, sharpite, widenmannite, grimselite and čejkaite

2020 ◽  
Vol 7 (21) ◽  
pp. 4197-4221 ◽  
Author(s):  
Francisco Colmenero ◽  
Jakub Plášil ◽  
Jiří Sejkora
Keyword(s):  
Mechanical Properties ◽  
Hydrogen Bonding ◽  
Diffraction Pattern ◽  
Crystal Structures ◽  
First Principles ◽  
X Ray Diffraction ◽  
Carbonate Minerals ◽  
X Ray ◽  
Uranyl Carbonate

The structure, hydrogen bonding, X-ray diffraction pattern and mechanical properties of six important uranyl carbonate minerals, roubaultite, fontanite, sharpite, widenmannite, grimselite and čejkaite, are determined using first principles methods.

scholarly journals Spotlight on Alkali Metals: The Structural Chemistry of Alkali Metal Thallides

Crystals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1013
Author(s):  
Stefanie Gärtner
Keyword(s):  
Crystal Structure ◽  
Alkali Metal ◽  
Crystal Structures ◽  
Alkali Metals ◽  
Valence Electron ◽  
Oxidation States ◽  
Valence Electron Concentration ◽  
Base Metals ◽  
Charge Balancing

Alkali metal thallides go back to the investigative works of Eduard Zintl about base metals in negative oxidation states. In 1932, he described the crystal structure of NaTl as the first representative for this class of compounds. Since then, a bunch of versatile crystal structures has been reported for thallium as electronegative element in intermetallic solid state compounds. For combinations of thallium with alkali metals as electropositive counterparts, a broad range of different unique structure types has been observed. Interestingly, various thallium substructures at the same or very similar valence electron concentration (VEC) are obtained. This in return emphasizes that the role of the alkali metals on structure formation goes far beyond ancillary filling atoms, which are present only due to charge balancing reasons. In this review, the alkali metals are in focus and the local surroundings of the latter are discussed in terms of their crystallographic sites in the corresponding crystal structures.

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