Search results for "structure analysis"
showing 10 items of 65 documents
Binding of water and solvent molecules in a 25-membered-ring host compound
1993
The macrocyclic 15- and 25-membered-ring pyridine oligomers 1 and 2 containing three and five methoxy substituents in the 4-position of the pyridine rings were prepared by Muller-Roscheisen cyclization and then isolated by chromatography. They are attractive as synthetic endobasic receptor molecules. X-ray structure analysis exhibits the inclusion of hydrogen-bonded solvent molecules (water and trichloromethane) inside the pentameric macrocycle 2.
A Hooke's law-based approach to protein folding rate
2014
Kinetics is a key aspect of the renowned protein folding problem. Here, we propose a comprehensive approach to folding kinetics where a polypeptide chain is assumed to behave as an elastic material described by the Hooke[U+05F3]s law. A novel parameter called elastic-folding constant results from our model and is suggested to distinguish between protein with two-state and multi-state folding pathways. A contact-free descriptor, named folding degree, is introduced as a suitable structural feature to study protein-folding kinetics. This approach generalizes the observed correlations between varieties of structural descriptors with the folding rate constant. Additionally several comparisons am…
5-Carbonyl-1,3-oxazine-2,4-diones from N-Cyanosulfoximines and Meldrum’s Acid Derivatives
2020
At elevated temperatures, N-cyanosulfoximines react with Meldrum's acid derivatives to give sulfoximines with N-bound 5-carbonyl-1,3-oxazine-2,4-dione groups. A representative product was characterized by single-crystal X-ray structure analysis. The product formation involves an unexpected molecular reorientation requiring several sequential bond-forming and -cleaving processes.
Automated electron diffraction tomography – development and applications
2019
Electron diffraction tomography, a potential method for structure analysis of nanocrystals, and, in more detail, the strategies to use automated diffraction tomography (ADT) technique are described. Examples of ADT application are discussed according to the material class.
Synthesis and reactivity of P-ferrocenylalkylidenephosphanes and related iminophosphanes and diphosphenes
1997
P-Ferrocenyl-substituted alkylidenephosphanes have been prepared and characterized spectroscopically. Their ready conversion to the corresponding acylphosphanes and 1,2-diacyldiphosphanes, as well as a new type of phosphirene synthesis are presented. The X-ray structure of the tetraferrocenyl-substituted diacyldiphosphane has been investigated. Furthermore, P-ferrocenyl iminophosphanes and their complexation behaviour are described. Diferrocenyldiphosphene, which is known to be unstable, has been stabilized by complexation; this has been confirmed by NMR-spectroscopy and X-ray structure analysis.
Topical Depth and Writing Quality in Student EFL Compositions
1992
ABSTRACT This study tests a method to describe the relationship between coherence and writing quality by using topical structure analysis. Originally the method was used to examine short professional texts written in the mother tongue (L1) but in the present study it is applied to short compositions written in English by students learning this foreign language (EFL). The analyses showed that what characterized good writers was the ability to develop the topics in their compositions more evenly across several topic levels than mid‐quality writers and especially the poor writers. Good writers were more homogeneous (measured by the size of standard deviation) as a group in handling topics at h…
Synthesis of new cationic donor-stabilized phosphenium adducts and their unexpected P-substituent exchange reactions
2008
The reaction between two 1,3-dialkylimidazolium-2-carboxylates 1a and 1b and two different dichlorophosphines (RPCl(2), with R = Ph and NEt(2)) led to new donor-stabilized phosphenium adducts. When the reaction was performed with the 1,3-dimethylimidazolium-2-carboxylate 1a and PhPCl(2) in a 2:1 ratio, the phosphine 4a, bearing two imidazolium moieties, was obtained and led to 5a, after an anion exchange reaction with KPF(6), the latter being fully characterized by an X-ray structure analysis. In similar conditions, the bis-imidazolium phosphine or phosphene-di-ium, 4b, which is analogous to 4a, has been obtained by the addition of PhPCl(2) to the 1-dodecyl-3-methylimidazolium-2-carboxylate…
Chromatin modifiers and recombination factors promote a telomere fold-back structure, that is lost during replicative senescence.
2020
Telomeres have the ability to adopt a lariat conformation and hence, engage in long and short distance intra-chromosome interactions. Budding yeast telomeres were proposed to fold back into subtelomeric regions, but a robust assay to quantitatively characterize this structure has been lacking. Therefore, it is not well understood how the interactions between telomeres and non-telomeric regions are established and regulated. We employ a telomere chromosome conformation capture (Telo-3C) approach to directly analyze telomere folding and its maintenance in S. cerevisiae. We identify the histone modifiers Sir2, Sin3 and Set2 as critical regulators for telomere folding, which suggests that a dis…
Synthesis and structural characterization of titanium complexes containing a sulfinyl-bridged bis(phenolato) ligand
1998
Abstract Titanium complexes containing the novel tridentate 2,2′-sulfinylbis(6-tert-butyl-4-methylphenoxo) ligand (sibmp) were synthesized and characterized. Treatment of titanium tetra-iso-propoxide with 2,2′-sulfinylbis(6-tert-4-methylphenol) (sibmpH2) in 1:1 molar ratio afforded red-orange, sparingly soluble di-iso-propoxo derivative [Ti(sibmp)(O-i-Pr)2]2·0.5 Et2O. The single-crystal structure analysis was performed and revealed a dimeric centrosymmetric structure with a planar Ti2O2 core. The titanium center is approximately octahedral with a SO function intramolecularly coordinated at the titanium center. Treatment of sibmpH2 with titanium tetra-iso-propoxide in 2:1 molar ratio gave y…
Identifying and validating the presence of guanine-quadruplexes (G4) within the blood fluke parasite schistosoma mansoni
2021
Schistosomiasis is a neglected tropical disease that currently affects over 250 million individuals worldwide. In the absence of an immunoprophylactic vaccine and the recognition that mono-chemotherapeutic control of schistosomiasis by praziquantel has limitations, new strategies for managing disease burden are urgently needed. A better understanding of schistosome biology could identify previously undocumented areas suitable for the development of novel interventions. Here, for the first time, we detail the presence of G-quadruplexes (G4) and putative quadruplex forming sequences (PQS) within the Schistosoma mansoni genome. We find that G4 are present in both intragenic and intergenic regi…