X-ray studies on crystalline complexes involving amino acids and peptides: Part XVIII. Crystal structure of a new form of L-arginine D-glutamate and a comparative study of amino acid crystal structures containing molecules of the same and mixed chirality

1989 ◽  
Vol 14 (2) ◽  
pp. 111-125 ◽  
Author(s):  
Jayashree Soman ◽  
M. Vijayan
Keyword(s):  
Crystal Structure ◽  
Amino Acids ◽  
Amino Acid ◽  
Comparative Study ◽  
Crystal Structures ◽  
X Ray ◽  
Acid Crystal ◽  
New Form ◽  
Amino Acid Crystal

X-ray studies on crystalline complexes involving amino acids and peptides. XL. Conformational variability, recurring and new features of aggregation, and effect of chirality in the malonic acid complexes of DL- and L-arginine

2002 ◽  
Vol 58 (6) ◽  
pp. 1051-1056 ◽  
Author(s):  
N. T. Saraswathi ◽  
M. Vijayan
Keyword(s):  
Amino Acids ◽  
Hydrogen Bonding ◽  
Amino Acid ◽  
Crystal Structures ◽  
Malonic Acid ◽  
Conformational Flexibility ◽  
X Ray ◽  
Conformational Variability ◽  
Aggregation Pattern ◽  
Positively Charged

The crystal structures of the complexes of malonic acid with DL- and L-arginine, which contain positively charged argininium ions and negatively charged semimalonate ions, further demonstrate the conformational flexibility of amino acids. A larger proportion of folded conformations than would be expected on the basis of steric consideration appears to occur in arginine, presumably because of the requirements of hydrogen bonding. The aggregation pattern in the DL-arginine complex bears varying degrees of resemblance to patterns observed in other similar structures. An antiparallel hydrogen-bonded dimeric arrangement of arginine, and to a lesser extent lysine, is a recurring motif. Similarities also exist among the structures in the interactions with this motif and its assembly into larger features of aggregation. However, the aggregation pattern observed in the L-arginine complex differs from any observed so far, which demonstrates that all the general patterns of amino-acid aggregation have not yet been elucidated. The two complexes represent cases where the reversal of the chirality of half the amino-acid molecules leads to a fundamentally different aggregation pattern.

The Anion [Co(C8H12)2]–. A Comparative Study of the Crystal Structures of [{K(18-crown-6)}2(C5H5)][Co(C8H12)2] and Co(C8H12)(C8H13)

2009 ◽  
Vol 64 (8) ◽  
pp. 985-988 ◽  
Author(s):  
Jian-Qiang Wang ◽  
Thomas F. Fässler
Keyword(s):  
Crystal Structure ◽  
Crown Ether ◽  
Comparative Study ◽  
Single Crystal ◽  
Crystal Structures ◽  
Structure Determination ◽  
Cobalt Complex ◽  
Crystal Structure Determination ◽  
X Ray ◽  
Cyclopentadienyl Anion

The cobalt complex [{K(18-crown-6)}2(C5H5)]- [Co(C8H12)2]・(THF)2 (3) has been synthesized and characterized by X-ray single-crystal structure determination. The crystal structure of Co(C8H12)(C8H13) (2) has been reinvestigated and compared with the structure of 3. The 1,5-cyclooctadiene (C8H12) and C8H13 ligands are coordinated in an η4 and η3 fashion, respectively. The cyclopentadienyl anion in [{K(18-crown-6)}2(C5H5)]+ in 3 is η5-coordinated to the two crown ether-encapsulated potassium cations

Transformation of the Carboxyl Group of an Amino Acid to Variously Substituted Imidazoles through a Davidson-Type Heterocyclization

Synthesis ◽  
2019 ◽  
Vol 51 (09) ◽  
pp. 1961-1968 ◽  
Author(s):  
Jim Küppers ◽  
Michaela Hympánová ◽  
Tim Keuler ◽  
Andreas Schneider ◽  
Gregor Schnakenburg ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Amino Acids ◽  
Amino Acid ◽  
Carboxylic Acid ◽  
Building Blocks ◽  
Carboxyl Group ◽  
Amino Group ◽  
Combinatorial Approach ◽  
X Ray ◽  
Imidazole Derivatives

The modification of amino acids leads to valuable building blocks for the synthesis of bioactive compounds. By keeping the amino group protected, the carboxylic acid functionality can be converted in two steps into an imidazole moiety via a Davidson-like heterocyclization. This reaction allows for a combinatorial approach, in which two positions at the heterocycle can be modified. Herein, we report the synthesis of such imidazole derivatives by employing N-protected cyclohexylalanine as the starting material. Different α-halo ketones were used and two points of diversity, positions 4 and 5, were examined. The structure of the final imidazole derivatives was confirmed by three X-ray crystal structure analyses and their protease inhibiting activities were evaluated.

Topological analysis of experimental electron densities

1999 ◽  
Vol 32 (2) ◽  
pp. 210-217 ◽  
Author(s):  
Mohamed Souhassou ◽  
Robert H. Blessing
Keyword(s):  
Amino Acid ◽  
Crystal Structures ◽  
Electron Density ◽  
Topological Analysis ◽  
Three Dimensional ◽  
Electron Densities ◽  
Acid Crystal ◽  
Density Distributions ◽  
Amino Acid Crystal ◽  
Experimental Electron Density

Practical computing algorithms are described for analysing the topology of experimental electron density distributions represented as either three-dimensional grid densities or multipolar pseudoatom superpositions. The algorithms are implemented in the programNEWPROP, results from which are illustrated with applications to twoN-acetyl,C-methylamide blocked amino acid crystal structures.

X-ray studies on crystalline complexes involving amino acids and peptides. XXXVIII. Crystal structures of the complexes of L-arginine and L-histidine with glutaric acid and a comparative study of amino acid–glutaric acid complexes

2001 ◽  
Vol 57 (6) ◽  
pp. 842-849 ◽  
Author(s):  
N. T. Saraswathi ◽  
M. Vijayan
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Comparative Study ◽  
Dicarboxylic Acid ◽  
Glutaric Acid ◽  
Ionization State ◽  
Crystal Forms ◽  
X Ray ◽  
Aggregation Pattern ◽  
Fully Extended Conformation

The complexes of glutaric acid with L-arginine and L-histidine (two crystal forms) exhibit different stoichiometries and ionization states. The aggregation patterns in two of the crystals are remarkably similar to those observed earlier in similar structures, while the pattern in the remaining one has not been seen earlier. The variability in the ionization state and stoichiometry observed in amino acid–dicarboxylic acid complexes appears to represent subtle differences in the response of a molecule to the presence in its neighbourhood of another type of molecule. The glutaric acid molecules (or glutarate or semiglutarate ions) in their complexes and in other crystals favour a fully extended conformation, albeit with frequent departures from it. The change in the chirality of the component molecules in the complex could lead to drastic changes in the aggregation pattern; alternatively, the effects of the change are accommodated through small adjustments in essentially the same pattern.

Crystal structures of non-proteinogenic amino acid peroxosolvates: rare example of H-bonded hydrogen peroxide chains

CrystEngComm ◽  
2018 ◽  
Vol 20 (46) ◽  
pp. 7413-7416 ◽  
Author(s):  
Mger A. Navasardyan ◽  
Dmitry A. Grishanov ◽  
Tatiana A. Tripol'skaya ◽  
Lyudmila G. Kuz'mina ◽  
Petr V. Prikhodchenko ◽  
...  
Keyword(s):  
Amino Acids ◽  
Hydrogen Peroxide ◽  
Amino Acid ◽  
Crystal Structures ◽  
Proteinogenic Amino Acid ◽  
X Ray ◽  
X Ray Crystallography

Novel peroxosolvates of the non-proteinogenic amino acids sarcosine C3H7NO2·H2O2 (1) and phenylserine C9H11NO3·H2O2 (2) were prepared and their structures were determined by X-ray crystallography.

HYDROGEN-BONDED COMPLEX BETWEEN NUCLEOTIDE BASE AND AMINO ACID, CRYSTAL STRUCTURE OF 5-BROMOCYTOSINE:N-TOSYL-L-GLUTAMIC ACID

1974 ◽  
Vol 3 (6) ◽  
pp. 551-554
Author(s):  
Minoru Ohki ◽  
Akio Takenaka ◽  
Hirotaka Shimanouchi ◽  
Yoshio Sasada
Keyword(s):  
Crystal Structure ◽  
Amino Acid ◽  
Glutamic Acid ◽  
Acid Crystal ◽  
Nucleotide Base ◽  
Amino Acid Crystal ◽  
Hydrogen Bonded

scholarly journals Ancestral L-amino acid oxidases for deracemization and stereoinversion of amino acids

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Shogo Nakano ◽  
Kohei Kozuka ◽  
Yuki Minamino ◽  
Hiroka Karasuda ◽  
Fumihito Hasebe ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Protein Engineering ◽  
Crystal Structures ◽  
Reaction Mechanisms ◽  
Molecular Level ◽  
Substrate Recognition ◽  
Engineering Method ◽  
Substrate Selectivity ◽  
X Ray

AbstractL-amino acid oxidases (LAAOs) can be applied to convert racemic amino acids to D-isomers, which are potential precursors of pharmaceuticals. However, this application is hampered by the lack of available stable and structure-determined LAAOs. In this study, we attempt to address this limitation by utilizing two ancestral LAAOs: AncLAAO-N4 and AncLAAO-N5. AncLAAO-N4 has the highest thermal and temporal stabilities among the designed LAAOs that can be used for deracemization and stereoinversion. AncLAAO-N5 can provide X-ray crystal structures, which are helpful to reveal substrate recognition and reaction mechanisms of LAAOs at the molecular level. Next, we attempted to improve activity of AncLAAO-N4 toward L-Val through a semi-rational protein engineering method. Three variants with enhanced activity toward L-Val were obtained. Taken together, we believe that the activity and substrate selectivity of AncLAAOs give them the potential to be key enzymes in various chemoenzymatic reactions.

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