Search results for "bond."
showing 6 items of 3516 documents
Role of Weak Hydrogen Bonds and Halogen Bonds in 5-Halo-1,3-dimethyluracils and Their Cocrystals : A Combined Experimental and Computational Study
2016
Seven single crystals containing either N,N-dimethyluracil (DMHU) or one of its 5-halogenated derivatives (DMXU; X = F, Cl, Br, I) were prepared using N,N-dimethylformamide as the crystallization solvent. Single crystal X-ray diffraction and quantum chemical calculations carried out at the spin component scaled local MP2 level of theory were then used to study the intramolecular halogen and nonconventional hydrogen bonds present in the structures. The results were compared to and contrasted with the previously reported data for uracil and its halogenated derivatives. In particular, the intermolecular interactions in DMIU were compared to the halogen and hydrogen bonds in 5-iodouracil that, …
DNA-induced structural changes in the papillomavirus capsid.
2001
ABSTRACT Human papillomavirus capsid assembly requires intercapsomeric disulfide bonds between molecules of the major capsid protein L1. Virions isolated from naturally occurring lesions have a higher degree of cross-linking than virus-like particles (VLPs), which have been generated in eukaryotic expression systems. Here we show that DNA encapsidation into VLPs leads to increased cross-linking between L1 molecules comparable to that seen in virions. A higher trypsin resistance, indicating a tighter association of capsomeres through DNA interaction, accompanies this structural change.
Molecular Basis of SARS-CoV-2 Nsp1-Induced Immune Translational Shutdown as Revealed by All-Atom Simulations.
2021
The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic represents the most severe global health crisis in modern human history. One of the major SARS-CoV-2 virulence factors is nonstructural protein 1 (Nsp1), which, outcompeting with the binding of host mRNA to the human ribosome, triggers a translation shutdown of the host immune system. Here, microsecond-long all-atom simulations of the C-terminal portion of the SARS-CoV-2/SARS-CoV Nsp1 in complex with the 40S ribosome disclose that SARS-CoV-2 Nsp1 has evolved from its SARS-CoV ortholog to more effectively hijack the ribosome by undergoing a critical switch of Q/E158 and E/Q159 residues that perfects Nsp1's interactions…
Ortho -Functionalized Aryltetrazines by Direct Palladium-Catalyzed C−H Halogenation: Application to Fast Electrophilic Fluorination Reactions
2016
International audience; A general catalyzed direct C-H functionalization of s-tetrazines is reported. Under mild reaction conditions, N-directed ortho-C-H activation of tetrazines allows the introduction of various functional groups, thus forming carbon-heteroatom bonds: C-X (X=I, Br, Cl) and C-O. Based on this methodology, we developed electrophilic mono- and poly-ortho-fluorination of tetrazines. Microwave irradiation was optimized to afford fluorinated s-aryltetrazines, with satisfactory selectivity, within only ten minutes. This work provides an efficient and practical entry for further accessing highly substituted tetrazine derivatives (iodo, bromo, chloro, fluoro, and acetate precurso…
Relationaalinen itseys ja sosiaalinen side teoriassa ja empiriassa
2012
The relational self, the social bond and the dynamics of personal relationships : a sociological analysis / Kaisa Ketokivi. Helsinki : University of Helsinki, 2010.
Conformational investigation of alpha,beta-dehydropeptides. IX. N-Acetyl-(E)-alpha,beta-methylamide: stereoelectronic properties from infrared and th…
1998
The Fourier transform infrared spectra of Ac-(E)-deltaAbu-NHMe were analyzed to determine the predominant solution conformation(s) of this (E)-alpha,beta-dehydropeptide-related compound and the electron density perturbation in its amide groups. The measurements were performed in dichloromethane and acetonitrile in the region of mode vs (N-H), amide I, amide II and vs (C(alpha)=Cbeta). The equilibrium geometrical parameters, calculated by a method based on the density functional theory with the B3LYP functional and the 6-31G* basis set, were used to support spectroscopic interpretation and gain some deeper insight into the molecule. The experimental and theoretical data were compared with th…