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51.
Tsikouris O Bartl T Tousek J Lougiakis N Tite T Marakos P Pouli N Mikros E Marek R 《Magnetic resonance in chemistry : MRC》2008,46(7):643-649
Substituted pyrazolopyridines are potent inhibitors of phosphodiesterases and cyclin-dependent kinases. In this study, NMR was used to investigate the potential N1-H and N2-H tautomerism of 5-substituted pyrazolo[3,4-c]pyridine derivatives. Six compounds were fully characterized by using (1)H, (13)C, and (15)N chemical shifts and indirect (1)H--(13)C and (1)H--(15)N coupling constants. The (1)H NMR spectra were measured over a broad range of temperatures. All of the compounds were shown to exist predominantly in the N1-H tautomeric form. Complementary quantum-chemical calculations of the chemical shieldings and indirect spin-spin couplings support the structural conclusions drawn. 相似文献
52.
Gliko O Pan W Katsonis P Neumaier N Galkin O Weinkauf S Vekilov PG 《The journal of physical chemistry. B》2007,111(12):3106-3114
Dense liquid phases, metastable with respect to a solid phase, but stable with respect to the solution, have been known to form in solutions of proteins and small-molecule substances. Here, with the protein lumazine synthase as a test system, using dynamic and static light scattering and atomic force microscopy, we demonstrate submicron size clusters of dense liquid. In contrast to the macroscopic dense liquid, these clusters are metastable not only with respect to the crystals, but also with respect to the low-concentration solution: the characteristic cluster lifetime is limited to approximately 10 s, after which they decay. The cluster population is detectable only if they occupy >10(-6) of the solution volume and have a number density >105 cm-3 for 3 to 11% of the monitored time. The cluster volume fraction varies within wide limits and reaches up to 10(-3). Increasing protein concentration increases the frequency of cluster detection but does not affect the ranges of the cluster sizes, suggesting that a preferred cluster size exists. A simple Monte Carlo model with protein-like potentials reproduces the metastable clusters of dense liquid with limited lifetimes and variable sizes and suggests that the mean cluster size is determined by the kinetics of growth and decay and not by thermodynamics. 相似文献
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Marina A. Tzani Dimitra K. Gioftsidou Michael G. Kallitsakis Nikolaos V. Pliatsios Natasa P. Kalogiouri Panagiotis A. Angaridis Ioannis N. Lykakis Michael A. Terzidis 《Molecules (Basel, Switzerland)》2021,26(24)
Emission of light by matter can occur through a variety of mechanisms. When it results from an electronically excited state of a species produced by a chemical reaction, it is called chemiluminescence (CL). The phenomenon can take place both in natural and artificial chemical systems and it has been utilized in a variety of applications. In this review, we aim to revisit some of the latest CL applications based on direct and indirect production modes. The characteristics of the chemical reactions and the underpinning CL mechanisms are thoroughly discussed in view of studies from the very recent bibliography. Different methodologies aiming at higher CL efficiencies are summarized and presented in detail, including CL type and scaffolds used in each study. The CL role in the development of efficient therapeutic platforms is also discussed in relation to the Reactive Oxygen Species (ROS) and singlet oxygen (1O2) produced, as final products. Moreover, recent research results from our team are included regarding the behavior of commonly used photosensitizers upon chemical activation under CL conditions. The CL prospects in imaging, biomimetic organic and radical chemistry, and therapeutics are critically presented in respect to the persisting challenges and limitations of the existing strategies to date. 相似文献
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Xiao‐Ping Wang Panagiotis Angaridis Carlos A. Murillo F. Albert Cotton 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(2):m109-m111
The title compound, [Ru2(C2H3O2)4(C15H16N2O2)2], lies on a crystallographic inversion center and exhibits an Ru—Ru bond length of 2.2847 (8) Å. There are weak intramolecular hydrogen‐bonding interactions between the N1,N2‐di‐p‐anisylformamidine (HDAniF) ligands and the bridging acetate ligands. The molecule is one of the few examples of a crystallographically characterized axial bis‐adduct of a {Ru2}4+ complex with two N‐donor ligands. 相似文献
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We give necessary and sufficient conditions under which an HNN-extension with abelian base group or an amalgamated free product
of abelian groups is a Howson group (that is the intersection of any two finitely generated subgroups is finitely generated).
We describe HNN-extensions and amalgamated free products which are Howson groups without satisfying the Burns–Cohen statements. 相似文献
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