scholarly journals Nickel(II) complexes based on L-amino-acid-derived ligands: synthesis, characterization and study of the role of the supramolecular structure in carbon dioxide capture

2020 ◽  
Vol 76 (5) ◽  
pp. 825-838
Author(s):  
Andrea Rivas Marquina ◽  
Federico Movilla ◽  
Olga Carolina Sánchez Montilva ◽  
Eva Rentschler ◽  
Luca Carrella ◽  
...  
Keyword(s):  
Amino Acid ◽  
Supramolecular Structure ◽  
Crystal Packing ◽  
Carbon Dioxide Capture ◽  
Exchange Interactions ◽  
The Novel ◽  
Ferromagnetic Exchange ◽  
Magnetization Data ◽  
Structural Database

The formation of the symmetrical μ3-carbonate-bridged self-assembled trinuclear NiII complex Na2{[Ni(LO)2(H2O)]3(μ3-CO3)} (LO is the carboxylate anion of a L-tyrosine derivative), involves atmospheric CO2 uptake. The asymmetric unit of the complex comprises an octahedral coordination for the NiII with two L-tyrosine-based ligands, a water molecule and one O atom of the carbonate bridge. The Ni3–μ3-CO3 core in this compound is the first reported of this kind according to the Cambridge Structural Database (CSD). The supramolecular structure is mainly sustained by hydrogen bonds developed by the phenolic functionality of the L-tyrosine moiety of one ligand and the carboxylate group of a neighbouring ligand. The crystal packing is then characterized by three interpenetrated supramolecular helices associated with a diastereoisomer of the type R-sup P, which is essential for the assembly process. Magnetic susceptibility and magnetization data support weak ferromagnetic exchange interactions within the novel Ni3–μ3-CO3 core. The NiII complex obtained under the same synthetic conditions but using the analogous ligand derived from the amino acid L-phenylalanine instead of L-tyrosine gives rise to to a mononuclear octahedral system. The results obtained for the different complexes demonstrate the role of the supramolecular structure regarding the CO2 uptake property for these NiII–amino-acid-based systems.

scholarly journals On-off transition and ultrafast decay of amino acid luminescence driven by modulation of supramolecular packing

2021 ◽  
Author(s):  
Zohar A. Arnon ◽  
Topaz Kreiser ◽  
Boris Yakimov ◽  
Noam Brown ◽  
Ruth Aizen ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Crystal Packing ◽  
Optical Transition ◽  
Optically Active ◽  
Chemical Characteristics ◽  
Electronic Interactions ◽  
Visible Luminescence ◽  
Lifetime Decay

AbstractIt has been experimentally observed that various biomolecules exhibit clear luminescence in the visible upon aggregation, contrary their monomeric state. However, the physical basis for this phenomenon is still elusive. Here, we systematically examine all coded amino acids to provide non-biased insights into this phenomenon. Several amino acids, including non-aromatic, show intense visible luminescence. While lysine crystals display the highest signal, the very chemically similar non-coded ornithine does not, implying a role for molecular packing rather than the chemical characteristics of the molecule. Furthermore, cysteine show luminescence that is indeed crystal-packing-dependent as repeated rearrangements between two crystal structures result in a reversible on-off optical transition. In addition, ultrafast lifetime decay is experimentally validated, corroborating a recently raised hypothesis regarding the governing role of nπ* states in the emission formation. Collectively, our study supports the hypothesis that electronic interactions between molecules that are non-fluorescent and non-absorbing at the monomeric state may result in reversible optically-active states by the formation of supramolecular fluorophores.

scholarly journals A Novel, WidespreadqacAAllele Results in Reduced Chlorhexidine Susceptibility inStaphylococcus epidermidis

2019 ◽  
Vol 63 (6) ◽  
Author(s):  
Amin Addetia ◽  
Alexander L. Greninger ◽  
Amanda Adler ◽  
Shuhua Yuan ◽  
Negar Makhsous ◽  
...  
Keyword(s):  
Amino Acid ◽  
Staphylococcus Epidermidis ◽  
Sequence Data ◽  
Methicillin Resistance ◽  
Single Amino Acid ◽  
Data Sets ◽  
The Novel ◽  
Content Type

ABSTRACTChlorhexidine gluconate (CHG) is a topical antiseptic widely used in health care settings. InStaphylococcusspp., the pump QacA effluxes CHG, while the closely related QacB cannot due to a single amino acid substitution. We characterized 1,050 cutaneousStaphylococcusisolates obtained from 173 pediatric oncology patients enrolled in a multicenter CHG bathing trial. CHG susceptibility testing revealed that 63 (6%) of these isolates had elevated CHG MICs (≥4 μg/ml). Screening of all 1,050 isolates for theqacA/Bgene (the sameqacgene with A or B allele) by restriction fragment length polymorphism (RFLP) yielded 56 isolates with a novelqacA/BRFLP pattern,qacA/B273. The CHG MIC was significantly higher forqacA/B273-positive isolates (MIC50, 4 μg/ml; MIC range, 0.5 to 4 μg/ml) than for otherqacgroups:qacA-positive isolates (n = 559; MIC50, 1 μg/ml; MIC range, 0.5 to 4 μg/ml),qacB-positive isolates (n = 17; MIC50, 1 μg/ml; MIC range, 0.25 to 2 μg/ml), andqacA/B-negative isolates (n = 418, MIC50, 1 μg/ml; MIC range, 0.125 to 2 μg/ml) (P = 0.001). A high proportion of theqacA/B273-positive isolates also displayed methicillin resistance (96.4%) compared to the otherqacgroups (24.9 to 61.7%) (P = 0.001). Whole-genome sequencing revealed thatqacA/B273-positive isolates encoded a variant of QacA with 2 amino acid substitutions. This new allele, namedqacA4, was carried on the novel plasmid pAQZ1. TheqacA4-carrying isolates belonged to the highly resistantStaphylococcus epidermidissequence type 2 clone. By searching available sequence data sets, we identified 39 additionalqacA4-carryingS. epidermidisstrains from 5 countries. Curing an isolate ofqacA4resulted in a 4-fold decrease in the CHG MIC, confirming the role ofqacA4in the elevated CHG MIC. Our results highlight the importance of further studyingqacA4and its functional role in clinical staphylococci.

scholarly journals Crystal structure of tert-butyl 4-[4-(4-fluorophenyl)-2-methylbut-3-yn-2-yl]piperazine-1-carboxylate

2021 ◽  
Vol 77 (4) ◽  
pp. 360-365
Author(s):  
Ashwini Gumireddy ◽  
Kevin DeBoyace ◽  
Alexander Rupprecht ◽  
Mohit Gupta ◽  
Saloni Patel ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Crystal Packing ◽  
Chair Conformation ◽  
The Novel ◽  
Weak Hydrogen Bond ◽  
Dispersion Interactions ◽  
Fingerprint Analysis ◽  
Piperazine Ring ◽  
Structural Database

The title sterically congested piperazine derivative, C20H27FN2O2, was prepared using a modified Bruylants approach. A search of the Cambridge Structural Database identified 51 compounds possessing an N-tert-butyl piperazine substructure. Of these only 14 were asymmetrically substituted on the piperazine ring and none with a synthetically useful second nitrogen. Given the novel chemistry generating a pharmacologically useful core, determination of the crystal structure for this compound was necessary. The piperazine ring is present in a chair conformation with di-equatorial substitution. Of the two N atoms, one is sp 3 hybridized while the other is sp 2 hybridized. Intermolecular interactions resulting from the crystal packing patterns were investigated using Hirshfeld surface analysis and fingerprint analysis. Directional weak hydrogen-bond-like interactions (C—H...O) and C—H...π interactions with the dispersion interactions as the major source of attraction are present in the crystal packing.

scholarly journals Role of the Novel Peptide Phoenixin in Stress Response and Possible Interactions with Nesfatin-1

2021 ◽  
Vol 22 (17) ◽  
pp. 9156
Author(s):  
Tiemo Friedrich ◽  
Andreas Stengel
Keyword(s):  
Small Intestine ◽  
Amino Acid ◽  
Restraint Stress ◽  
The Novel ◽  
Stress Reactions ◽  
Brain Nuclei ◽  
Physiological Functions ◽  
Physiological Processes ◽  
Recent Developments

The novel peptide phoenixin was shown to be involved in several physiological processes ranging from reproduction to food intake. Interest in this protein has steadily increased over the last few years and its known implications have become much broader, playing a role in glucose homeostasis, anxiety, nociception, and pruritus. Phoenixin is expressed in a multitude of organs such as the small intestine, pancreas, and in the hypothalamus, as well as several other brain nuclei influencing numerous physiological functions. Its highly conserved amino-acid sequence amongst species leads to the assumption, that phoenixin might be involved in essential physiological functions. Its co-expression and opposing functionality to the extensively studied peptide nesfatin-1 has given rise to the idea of a possible counterbalancing role. Several recent publications focused on phoenixin’s role in stress reactions, namely restraint stress and lipopolysaccharide-induced inflammation response, in which also nesfatin-1 is known to be altered. This review provides an overview on the phoenixins and nesfatin-1 properties and putative effects, and especially highlights the recent developments on their role and interaction in the response to response.

scholarly journals Structural and biochemical characterization of the novel CTX-M-151 extended-spectrum β-lactamase and its inhibition by Avibactam

2021 ◽  
Author(s):  
Barbara Ghiglione ◽  
María Margarita Rodríguez ◽  
Florencia Brunetti ◽  
Krisztina M. Papp-Wallace ◽  
Ayumi Yoshizumi ◽  
...  
Keyword(s):  
Amino Acid ◽  
Biochemical Characterization ◽  
Sequence Divergence ◽  
Chair Conformation ◽  
Amino Acid Identity ◽  
The Novel ◽  
Proton Relay ◽  
Low Degree

The diazabicyclooctane (DBO) inhibitor, avibactam (AVI), reversibly inactivates most serine-β-lactamases including the CTX-M β-lactamases. Currently, more than 230 CTX-M unique members distributed in five clusters with less than 5% amino acid sequence divergence within each group are described. Recently, a variant named as CTX-M-151 was isolated from a Salmonella Choleraesuis strain in Japan. This variant possesses a low degree amino acid identity with the other CTX-Ms (63.2-69.7% with respect to the mature proteins), and thus it may represent a new sub-group within the family. CTX-M-151 hydrolyzes ceftriaxone better than ceftazidime (kcat/Km values 6,000-fold higher), as observed with CTX-Ms. CTX-M-151 is well inhibited by mechanism-based inhibitors like clavulanic acid (kinact/KI = 0.15 μM−1.s−1). For AVI, Ki app (0.4 μM) was comparable to KPC-2; k2/K (37,000 M−1s−1) was lower than for CTX-M-15, while the koff (0.0015 s−1) was 2-14-fold faster than other class A β-lactamases. The structure of the CTX-M-151/AVI complex (1.32 Å) reveals that AVI adopts a chair conformation with hydrogen bonds between the AVI carbamate and Ser70 and Ser237 at the oxyanion hole. Upon acylation, the side chain of Lys73 points towards Ser130 which is associated with the protonation of Glu166, supporting the role of Lys73 in the proton-relay pathway and Glu166 as the general base in deacylation. To our knowledge, this is the first chromosomally-encoded CTX-M in Salmonella Choleraesuis that shows similar hydrolytic preference towards cefotaxime/ceftriaxone when compared to ceftazidime.

scholarly journals Thiazole–amino acids: influence of thiazole ring on conformational properties of amino acid residues

Amino Acids ◽  
2021 ◽  
Author(s):  
Monika Staś ◽  
Małgorzata A. Broda ◽  
Dawid Siodłak
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Dft Method ◽  
Structural Motif ◽  
Thiazole Ring ◽  
Amino Acid Residues ◽  
Conformational Preferences ◽  
Macrocyclic Peptides ◽  
Structural Database

Abstract Post-translational modified thiazole–amino acid (Xaa–Tzl) residues have been found in macrocyclic peptides (e.g., thiopeptides and cyanobactins), which mostly inhibit protein synthesis in Gram + bacteria. Conformational study of the series of model compounds containing this structural motif with alanine, dehydroalanine, dehydrobutyrine and dehydrophenylalanine were performed using DFT method in various environments. The solid-state crystal structure conformations of thiazole–amino acid residues retrieved from the Cambridge Structural Database were also analysed. The studied structural units tend to adopt the unique semi-extended β2 conformation; which is stabilised mainly by N–H⋯NTzl hydrogen bond, and for dehydroamino acids also by π-electron conjugation. The conformational preferences of amino acids with a thiazole ring were compared with oxazole analogues and the role of the sulfur atom in stabilising the conformations of studied peptides was discussed.

ROLE OF THE NOVEL INTRODUCED PAN-INTESTINAL CAPSULE ENDOSCOPY SYSTEM IN CELIAC DISEASE

2019 ◽  
Author(s):  
F Foerster ◽  
K Mönkemüller ◽  
PR Galle ◽  
H Neumann
Keyword(s):  
Celiac Disease ◽  
Capsule Endoscopy ◽  
The Novel

Patterns: Rosamond Lehmann

2018 ◽  
Author(s):  
Vike Martina Plock
Keyword(s):  
Coming Of Age ◽  
Public Image ◽  
Market Forces ◽  
The Novel ◽  
Fashion Industry ◽  
To The Lighthouse ◽  
Fashion Magazines ◽  
Female Authorship ◽  
Rosamond Lehmann

This chapter analyzes the role of fashion as a discursive force in Rosamond Lehmann’s 1932 coming-of-age novel Invitation to the Waltz. Reading the novel alongside such fashion magazines as Vogue, it demonstrates Lehmann’s awareness that 1920s fashion, in spite of its carefully stylized public image as harbinger of originality, emphasized the importance of following preconceived (dress) patterns in the successful construction of modern feminine types. Invitation to the Waltz, it argues, opposes the production of patterned types and celebrates difference and disobedience in its stead. At the same time, the novel’s formal appearance is nonetheless dependent on the very same tenets it criticizes. On closer scrutiny, it is seen to reveal its resemblance to Virginia Woolf’s To the Lighthouse (1927). A tension between imitation and originality determines sartorial fashion choices. This chapter shows that female authorship in the inter-war period was subjected to the same market forces that controlled and sustained the organization of the fashion industry.

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