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1.
Nat Commun ; 10(1): 5021, 2019 11 04.
Artigo em Inglês | MEDLINE | ID: mdl-31685819

RESUMO

The world's first superconducting megahertz repetition rate hard X-ray free-electron laser (XFEL), the European XFEL, began operation in 2017, featuring a unique pulse train structure with 886 ns between pulses. With its rapid pulse rate, the European XFEL may alleviate some of the increasing demand for XFEL beamtime, particularly for membrane protein serial femtosecond crystallography (SFX), leveraging orders-of-magnitude faster data collection. Here, we report the first membrane protein megahertz SFX experiment, where we determined a 2.9 Å-resolution SFX structure of the large membrane protein complex, Photosystem I, a > 1 MDa complex containing 36 protein subunits and 381 cofactors. We address challenges to megahertz SFX for membrane protein complexes, including growth of large quantities of crystals and the large molecular and unit cell size that influence data collection and analysis. The results imply that megahertz crystallography could have an important impact on structure determination of large protein complexes with XFELs.


Assuntos
Elétrons , Lasers , Proteínas de Membrana/química , Cristalografia , Cianobactérias/metabolismo , Modelos Moleculares , Complexo de Proteína do Fotossistema I/química , Complexo de Proteína do Fotossistema I/isolamento & purificação , Eletricidade Estática , Síncrotrons , Raios X
2.
Nat Commun ; 10(1): 4910, 2019 10 28.
Artigo em Inglês | MEDLINE | ID: mdl-31659163

RESUMO

AspH is an endoplasmic reticulum (ER) membrane-anchored 2-oxoglutarate oxygenase whose C-terminal oxygenase and tetratricopeptide repeat (TPR) domains present in the ER lumen. AspH catalyses hydroxylation of asparaginyl- and aspartyl-residues in epidermal growth factor-like domains (EGFDs). Here we report crystal structures of human AspH, with and without substrate, that reveal substantial conformational changes of the oxygenase and TPR domains during substrate binding. Fe(II)-binding by AspH is unusual, employing only two Fe(II)-binding ligands (His679/His725). Most EGFD structures adopt an established fold with a conserved Cys1-3, 2-4, 5-6 disulfide bonding pattern; an unexpected Cys3-4 disulfide bonding pattern is observed in AspH-EGFD substrate complexes, the catalytic relevance of which is supported by studies involving stable cyclic peptide substrate analogues and by effects of Ca(II) ions on activity. The results have implications for EGFD disulfide pattern processing in the ER and will enable medicinal chemistry efforts targeting human 2OG oxygenases.


Assuntos
Proteínas de Ligação ao Cálcio/química , Proteínas de Membrana/química , Oxigenases de Função Mista/química , Proteínas Musculares/química , Sequência de Aminoácidos , Asparagina/metabolismo , Proteínas de Ligação ao Cálcio/genética , Proteínas de Ligação ao Cálcio/metabolismo , Domínio Catalítico , Cristalografia , Dissulfetos/química , Dissulfetos/metabolismo , Fator de Crescimento Epidérmico/metabolismo , Compostos Ferrosos/química , Compostos Ferrosos/metabolismo , Humanos , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Oxigenases de Função Mista/genética , Oxigenases de Função Mista/metabolismo , Proteínas Musculares/genética , Proteínas Musculares/metabolismo , Conformação Proteica
3.
Nat Methods ; 16(10): 979-982, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31527838

RESUMO

We introduce a liquid application method for time-resolved analyses (LAMA), an in situ mixing approach for serial crystallography. Picoliter-sized droplets are shot onto chip-mounted protein crystals, achieving near-full ligand occupancy within theoretical diffusion times. We demonstrate proof-of-principle binding of GlcNac to lysozyme, and resolve glucose binding and subsequent ring opening in a time-resolved study of xylose isomerase.


Assuntos
Cristalografia/métodos , Síncrotrons , Acetilglucosamina/química , Aldose-Cetose Isomerases/química , Glucose/química , Muramidase/química , Estudo de Prova de Conceito
4.
Mater Sci Eng C Mater Biol Appl ; 104: 109966, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31499942

RESUMO

In this study we present the first crystal structure model for bone apatite based on the analysis of individual nanocrystals by high resolution transmission electron microscopy (HRTEM). Crystallographic image processing of the obtained HRTEM images from different projections indicates symmetry reduction with respect to P63/m stoichiometric apatites and the presence of threefold symmetry along the c axis. Based on HRTEM observations and the measured Ca/P = 2 ratio we propose a structural model with phosphate-to-carbonate substitution and O vacancies localized along c axis, which explains the observed loss of 63 screw axis parallel, and the shift of mirror plane perpendicular to the c axis. Also, the presence of non-equivalent (010) surfaces has been proven. These results on the atomic structure of bone apatite nanocrystals contribute to the understanding of their biochemically controlled nucleation processes.


Assuntos
Apatitas/química , Osso e Ossos/química , Nanopartículas/química , Carbonatos/química , Cristalografia/métodos , Microscopia Eletrônica de Transmissão/métodos
5.
Nat Commun ; 10(1): 3177, 2019 07 18.
Artigo em Inglês | MEDLINE | ID: mdl-31320619

RESUMO

Bacteriorhodopsin (bR) is a light-driven proton pump. The primary photochemical event upon light absorption is isomerization of the retinal chromophore. Here we used time-resolved crystallography at an X-ray free-electron laser to follow the structural changes in multiphoton-excited bR from 250 femtoseconds to 10 picoseconds. Quantum chemistry and ultrafast spectroscopy were used to identify a sequential two-photon absorption process, leading to excitation of a tryptophan residue flanking the retinal chromophore, as a first manifestation of multiphoton effects. We resolve distinct stages in the structural dynamics of the all-trans retinal in photoexcited bR to a highly twisted 13-cis conformation. Other active site sub-picosecond rearrangements include correlated vibrational motions of the electronically excited retinal chromophore, the surrounding amino acids and water molecules as well as their hydrogen bonding network. These results show that this extended photo-active network forms an electronically and vibrationally coupled system in bR, and most likely in all retinal proteins.


Assuntos
Bacteriorodopsinas/química , Halobacterium salinarum/metabolismo , Retinaldeído/química , Cristalografia , Isomerismo , Luz , Fótons , Conformação Proteica , Análise Espectral , Água/química
6.
Molecules ; 24(12)2019 Jun 20.
Artigo em Inglês | MEDLINE | ID: mdl-31226827

RESUMO

Isomers provide more possibilities for the structure of organic compounds. Molecular structures determine their corresponding properties, therefore the intrinsic relationship between structure and properties of isomers is of great research value. Isomers with a stable structure and excellent performance possess more potential for development and application. In this paper, we design and synthesize structural isomers with different molecular symmetries based on the asymmetric structure of imidazole and the symmetrical structure of pyrene. Isomers with stable molecular structures can be obtained by a simple and efficient "one-pot" reaction, involving axisymmetric configuration and centrosymmetric configuration. Using this "click-like" reaction, the structure of target molecules is controllable and adjustable. Furthermore, the effect of molecular configurations on molecular stacking of crystal is studied. The variation of the optical and thermal properties, the optimized structures, and orbital distributions of isomers depends on different molecular geometry with different symmetry, which are revealed by crystallographic analysis. This present strategy provides an efficient synthetic method for the design and synthesis of structural isomers based on pyrene-imidazole.


Assuntos
Imidazóis/química , Isomerismo , Pirenos/química , Cristalografia , Imidazóis/síntese química , Estrutura Molecular , Pirenos/síntese química
7.
Nucleic Acids Res ; 47(19): 10134-10150, 2019 11 04.
Artigo em Inglês | MEDLINE | ID: mdl-31199869

RESUMO

Tyrosyl DNA-phosphodiesterase I (TDP1) repairs type IB topoisomerase (TOP1) cleavage complexes generated by TOP1 inhibitors commonly used as anticancer agents. TDP1 also removes DNA 3' end blocking lesions generated by chain-terminating nucleosides and alkylating agents, and base oxidation both in the nuclear and mitochondrial genomes. Combination therapy with TDP1 inhibitors is proposed to synergize with topoisomerase targeting drugs to enhance selectivity against cancer cells exhibiting deficiencies in parallel DNA repair pathways. A crystallographic fragment screening campaign against the catalytic domain of TDP1 was conducted to identify new lead compounds. Crystal structures revealed two fragments that bind to the TDP1 active site and exhibit inhibitory activity against TDP1. These fragments occupy a similar position in the TDP1 active site as seen in prior crystal structures of TDP1 with bound vanadate, a transition state mimic. Using structural insights into fragment binding, several fragment derivatives have been prepared and evaluated in biochemical assays. These results demonstrate that fragment-based methods can be a highly feasible approach toward the discovery of small-molecule chemical scaffolds to target TDP1, and for the first time, we provide co-crystal structures of small molecule inhibitors bound to TDP1, which could serve for the rational development of medicinal TDP1 inhibitors.


Assuntos
Inibidores Enzimáticos/química , Ligantes , Diester Fosfórico Hidrolases/química , Conformação Proteica , Sequência de Bases , Domínio Catalítico/genética , Cristalografia , Reparo do DNA/genética , Histidina/análogos & derivados , Histidina/química , Histidina/isolamento & purificação , Humanos , Modelos Moleculares , Diester Fosfórico Hidrolases/genética , Transdução de Sinais , Bibliotecas de Moléculas Pequenas/química
8.
Biochim Biophys Acta Gene Regul Mech ; 1862(11-12): 194390, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31202783

RESUMO

Spliceosomal introns and self-splicing group II introns share a common mechanism of intron splicing where two sequential transesterification reactions remove intron lariats and ligate exons. The recent revolution in cryo-electron microscopy (cryo-EM) has allowed visualization of the spliceosome's ribozyme core. Comparison of these cryo-EM structures to recent group II intron crystal structures presents an opportunity to draw parallels between the RNA active site, substrate positioning, and product formation in these two model systems of intron splicing. In addition to shared RNA architectural features, structural similarity between group II intron encoded proteins (IEPs) and the integral spliceosomal protein Prp8 further support a shared catalytic core. These mechanistic and structural similarities support the long-held assertion that group II introns and the eukaryotic spliceosome have a common evolutionary origin. In this review, we discuss how recent structural insights into group II introns and the spliceosome facilitate the chemistry of splicing, highlight similarities between the two systems, and discuss their likely evolutionary connections. This article is part of a Special Issue entitled: RNA structure and splicing regulation edited by Francisco Baralle, Ravindra Singh and Stefan Stamm.


Assuntos
Eucariotos/citologia , RNA Catalítico/química , Spliceossomos/química , Animais , Microscopia Crioeletrônica , Cristalografia , Eucariotos/genética , Evolução Molecular , Humanos , Íntrons , Modelos Moleculares , Conformação de Ácido Nucleico , Processamento de RNA , RNA Catalítico/genética , Spliceossomos/genética
9.
Acta Crystallogr D Struct Biol ; 75(Pt 6): 523-527, 2019 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-31205014

RESUMO

Michael George Rossmann, who made monumental contributions to science, passed away peacefully in West Lafayette, Indiana on 14 May 2019 at the age of 88, following a courageous five-year battle with cancer. Michael was born in Frankfurt, Germany on 30 July 1930. As a young boy, he emigrated to England with his mother just as World War II ignited. Michael was a highly innovative and energetic person, well known for his intensity, persistence and focus in pursuing his research goals. Michael was a towering figure in crystallography as a highly distinguished faculty member at Purdue University for 55 years. Michael made many seminal contributions to crystallography in a career that spanned the entirety of structural biology, beginning in the 1950s at Cambridge where the first protein structures were determined in the laboratories of Max Perutz (hemoglobin, 1960) and John Kendrew (myoglobin, 1958). Michael's work was central in establishing and defining the field of structural biology, which amazingly has described the structures of a vast array of complex biological molecules and assemblies in atomic detail. Knowledge of three-dimensional biological structure has important biomedical significance including understanding the basis of health and disease at the molecular level, and facilitating the discovery of many drugs.


Assuntos
Cristalografia/história , Substâncias Macromoleculares/história , Vírus/ultraestrutura , Distinções e Prêmios , História do Século XX , Humanos , Substâncias Macromoleculares/ultraestrutura
10.
Biochimie ; 164: 95-98, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-30940603

RESUMO

Crystallographic studies of RNA/protein complexes are primordial for the understanding of recognition determinants and catalytic mechanisms in the case of enzymes. However, due to the flexibility and propensity to conformational heterogeneity of RNAs, as well as the mostly electrostatic interactions of RNA/protein complexes, they are difficult to crystallize. We present here a method to trap the two interacting partners in a covalent complex, based on a modified reactive RNA allowing the use of the full range of common crystallogenesis tools. We demonstrate the practicability of our approach with the production of a covalent complex of the Thermus thermophilus m1A58 tRNA modification enzyme, and a modified stem loop mimicking the natural substrate of the enzyme.


Assuntos
RNA de Transferência/química , tRNA Metiltransferases/química , Proteínas de Bactérias/química , Cristalografia , Modelos Moleculares , Ligação Proteica , RNA Bacteriano/química , Especificidade por Substrato , Thermus thermophilus/enzimologia , Thermus thermophilus/genética
12.
Life Sci Alliance ; 2(2)2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30872413

RESUMO

The Rab GTPase family is a major regulator of membrane traffic in eukaryotic cells. The Rab11 subfamily plays important roles in specific trafficking events such as exocytosis, endosomal recycling, and cytokinesis. SH3BP5 and SH3BP5-like (SH3BP5L) proteins have recently been found to serve as guanine nucleotide exchange factors (GEF) for Rab11. Here, we report the crystal structures of the SH3BP5 GEF domain alone and its complex with Rab11a. SH3BP5 exhibits a V-shaped structure comprising two coiled coils. The coiled coil composed of α1, and α4 is solely responsible for the Rab11a binding and GEF activity. SH3BP5 pulls out and deforms switch I of Rab11a so as to facilitate the GDP release from Rab11a. SH3BP5 interacts with the N-terminal region, switch I, interswitch, and switch II of Rab11a. SH3BP5 and SH3BP5L localize to Rab11-positive recycling endosomes and show GEF activity for all of the Rab11 family but not for Rab14. Fluorescence-based GEF assays combined with site-directed mutagenesis reveal the essential interactions between SH3BP5 and Rab11 family proteins for the GEF reaction on recycling endosomes.


Assuntos
Proteínas Adaptadoras de Transdução de Sinal/química , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Fatores de Troca do Nucleotídeo Guanina/metabolismo , Nucleotídeos de Guanina/metabolismo , Proteínas rab de Ligação ao GTP/química , Proteínas rab de Ligação ao GTP/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/genética , Sequência de Aminoácidos , Cristalização , Cristalografia , Endossomos/metabolismo , Células HeLa , Humanos , Ligações de Hidrogênio , Proteínas Mutantes , Ligação Proteica , Conformação Proteica em alfa-Hélice , Domínios Proteicos , Transporte Proteico , Transfecção
13.
Physiol Plant ; 166(1): 44-59, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30847925

RESUMO

The optimized geometries of the CaMn4 OX (X = 5, 6) cluster in the oxygen evolving complex (OEC) of photosystem II (PSII) by large-scale quantum mechanics (QM) and molecular mechanics (MM) calculations are compared with recent serial femtosecond crystallography (SFX) results for the Si (i = 0-3) states. The valence states of four Mn ions by the QM/MM calculations are also examined in relation to the experimental results by the X-ray emission spectroscopy (XES) for the Si intermediates. Geometrical and valence structures of right-opened Mn-hydroxide, Mn-oxo and Mn-peroxide intermediates in the S3 state are investigated in detail in relation to recent SFX and XES experiments for the S3 state. Interplay between theory and experiment indicates that the Mn-oxo intermediate is a new possible candidate for the S3 state. Implications of the computational results are discussed in relation to possible mechanisms of the oxygenoxygen bond formation for water oxidation in OEC of PSII.


Assuntos
Oxigênio/metabolismo , Complexo de Proteína do Fotossistema II/metabolismo , Cristalografia , Manganês , Oxirredução , Espectrometria por Raios X
14.
Drug Discov Today ; 24(5): 1081-1086, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30878562

RESUMO

We present a novel crystallographic screening methodology (MiniFrags) that employs high-concentration aqueous soaks with a chemically diverse and ultra-low-molecular-weight library (heavy atom count 5-7) to identify ligand-binding hot and warm spots on proteins. We propose that MiniFrag screening represents a highly effective method for guiding optimisation of fragment-derived lead compounds or chemical tools and that the high screening hit rates reflect enhanced sampling of chemical space.


Assuntos
Desenho de Drogas , Cristalografia , Ligantes , Peso Molecular , Bibliotecas de Moléculas Pequenas
15.
Nat Commun ; 10(1): 638, 2019 02 07.
Artigo em Inglês | MEDLINE | ID: mdl-30733446

RESUMO

Neurokinin 1 receptor (NK1R) has key regulating functions in the central and peripheral nervous systems, and NK1R antagonists such as aprepitant have been approved for treating chemotherapy-induced nausea and vomiting. However, the lack of data on NK1R structure and biochemistry has limited further drug development targeting this receptor. Here, we combine NMR spectroscopy and X-ray crystallography to provide dynamic and static characterisation of the binding mode of aprepitant in complexes with human NK1R variants. 19F-NMR showed a slow off-rate in the binding site, where aprepitant occupies multiple substates that exchange with frequencies in the millisecond range. The environment of the bound ligand is affected by the amino acid in position 2.50, which plays a key role in ligand binding and receptor signaling in class A GPCRs. Crystal structures now reveal how receptor signaling relates to the conformation of the conserved NP7.50xxY motif in transmembrane helix VII.


Assuntos
Aprepitanto/metabolismo , Cristalografia/métodos , Espectroscopia de Ressonância Magnética/métodos , Receptores da Neurocinina-1/metabolismo , Aprepitanto/química , Humanos , Ligação Proteica , Receptores da Neurocinina-1/química
16.
Physiol Plant ; 166(1): 60-72, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30793319

RESUMO

In nature, an oxo-bridged Mn4 CaO5 cluster embedded in photosystem II (PSII), a membrane-bound multi-subunit pigment protein complex, catalyzes the water oxidation reaction that is driven by light-induced charge separations in the reaction center of PSII. The Mn4 CaO5 cluster accumulates four oxidizing equivalents to enable the four-electron four-proton catalysis of two water molecules to one dioxygen molecule and cycles through five intermediate S-states, S0  - S4 in the Kok cycle. One important question related to the catalytic mechanism of the oxygen-evolving complex (OEC) that remains is, whether structural isomers are present in some of the intermediate S-states and if such equilibria are essential for the mechanism of the O-O bond formation. Here we compare results from electron paramagnetic resonance (EPR) and X-ray absorption spectroscopy (XAS) obtained at cryogenic temperatures for the S2 state of PSII with structural data collected of the S1 , S2 and S3 states by serial crystallography at neutral pH (∼6.5) using an X-ray free electron laser at room temperature. While the cryogenic data show the presence of at least two structural forms of the S2 state, the room temperature crystallography data can be well-described by just one S2 structure. We discuss the deviating results and outline experimental strategies for clarifying this mechanistically important question.


Assuntos
Complexo de Proteína do Fotossistema II/metabolismo , Cristalografia , Espectroscopia de Ressonância de Spin Eletrônica , Temperatura Ambiente , Espectroscopia por Absorção de Raios X
17.
Phys Chem Chem Phys ; 21(12): 6319-6326, 2019 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-30720026

RESUMO

We combine experimental and computational determination of 43Ca solid-state NMR parameters (chemical shift tensors, quadrupolar coupling tensors, and Euler angles) to constrain the structure of the local calcium-ligand coordination environment. A new 43Ca NMR crystallographic approach which includes an extensive survey of the Cambridge Structural Database and a new symmetry benchmark is developed to enhance the selectivity of structural screening. The application of this method to quadrupolar NMR crystallographic investigations is demonstrated by unearthing the calcium local structure of the active pharmaceutical ingredient atorvastatin calcium trihydrate, the active ingredient in Lipitor®, in the absence of diffraction data. This method has been tested by applying it to calcium acetate monohydrate which has a known structure.


Assuntos
Atorvastatina/química , Cálcio/química , Espectroscopia de Ressonância Magnética , Algoritmos , Cristalografia , Difração de Pó
18.
Science ; 363(6429): 884-887, 2019 02 22.
Artigo em Inglês | MEDLINE | ID: mdl-30792304

RESUMO

We report DNA- and RNA-like systems built from eight nucleotide "letters" (hence the name "hachimoji") that form four orthogonal pairs. These synthetic systems meet the structural requirements needed to support Darwinian evolution, including a polyelectrolyte backbone, predictable thermodynamic stability, and stereoregular building blocks that fit a Schrödinger aperiodic crystal. Measured thermodynamic parameters predict the stability of hachimoji duplexes, allowing hachimoji DNA to increase the information density of natural terran DNA. Three crystal structures show that the synthetic building blocks do not perturb the aperiodic crystal seen in the DNA double helix. Hachimoji DNA was then transcribed to give hachimoji RNA in the form of a functioning fluorescent hachimoji aptamer. These results expand the scope of molecular structures that might support life, including life throughout the cosmos.


Assuntos
Pareamento de Bases , DNA/química , DNA/genética , Nucleotídeos/química , RNA/química , RNA/genética , Cristalografia , Fluorescência , Conformação de Ácido Nucleico , Polieletrólitos/química , Biologia Sintética , Termodinâmica
19.
Mikrochim Acta ; 186(2): 76, 2019 01 09.
Artigo em Inglês | MEDLINE | ID: mdl-30627789

RESUMO

A novel nanocomposite consisting of an amorphous seed and a molecularly imprinted covalent organic framework shell was prepared via a heterogeneous nucleation and growth method. By using ibuprofen as the dummy template, a molecularly imprinted covalent organic framework (MICOF) with a large surface area was prepared from 1,3,5-triformylbenzene and 4,4'-diaminobiphenyl. It was placed on the surface of monodisperse amorphous seeds. Owing to strong π-interaction, the MICOF@SiO2 nanocomposite displays fast binding kinetics, large adsorption capacities and selectivity for nonsteroidal anti-inflammatory drugs (NSAIDs). Following desorption from the MICOF@SiO2 with methanol containing 1% ammonium hydroxide, the NSAIDs ketoprofen, ibuprofen, diclofenac, indomethacin, flurbiprofen and naproxen were quantified by HPLC with UV detection. Under optimized conditions, the method exhibits good linearity within the range of 0.002-1.0 µg mL-1, low limits of detection (0.38-2.92 µg L-1), and acceptable repeatability. The recoveries of NSAIDs at three spiking levels range from 77 to 112%, and the RSDs are <9.4%. The method was successfully applied to the analysis of NSAIDs in spiked environmental water samples. Graphical abstract A molecular imprinted covalent organic framework nanocomposite (MICOF@SiO2) was prepared by heterogeneous nucleation and growth method. It was explored as a sorbent for the solid phase extraction of nonsteroidal anti-inflammatory drugs before determination by HPLC with UV detection.


Assuntos
Anti-Inflamatórios não Esteroides/análise , Nanocompostos/química , Extração em Fase Sólida/métodos , Adsorção , Cromatografia Líquida de Alta Pressão/métodos , Cromatografia Líquida de Alta Pressão/normas , Cristalografia , Estruturas Metalorgânicas , Impressão Molecular , Poluentes Químicos da Água/análise
20.
Molecules ; 24(2)2019 Jan 16.
Artigo em Inglês | MEDLINE | ID: mdl-30654590

RESUMO

[TiCp2S5] (phase A), [TiCp2Se5] (phase F), and five solid solutions of mixed titanocene selenide sulfides [TiCp2SexS5-x] (Cp = C5H5-) with the initial Se:S ranging from 1:4 to 4:1 (phases B⁻E) were prepared by reduction of elemental sulfur or selenium or their mixtures by lithium triethylhydridoborate in thf followed by the treatment with titanocene dichloride [TiCp2Cl2]. Their 77Se and 13C NMR spectra were recorded from the CS2 solution. The definite assignment of the 77Se NMR spectra was based on the PBE0/def2-TZVPP calculations of the 77Se chemical shifts and is supported by 13C NMR spectra of the samples. The following complexes in varying ratios were identified in the CS2 solutions of the phases B⁻E: [TiCp2Se5] (51), [TiCp2Se4S] (41), [TiCp2Se3S2] (31), [TiCp2SSe3S] (36), [TiCp2SSe2S2] (25), [TiCp2SSeS3] (12), and [TiCp2S5] (01). The disorder scheme in the chalcogen atom positions of the phases B⁻E observed upon crystal structure determinations is consistent with the spectral assignment. The enthalpies of formation calculated for all twenty [TiCp2SexS5-x] (x = 0⁻5) at DLPNO-CCSD(T)/CBS level including corrections for core-valence correlation and scalar relativistic, as well as spin-orbit coupling contributions indicated that within a given chemical composition, the isomers of most favourable enthalpy of formation were those, which were observed by 77Se and 13C NMR spectroscopy.


Assuntos
Compostos Organometálicos/síntese química , Selênio/química , Sulfetos/síntese química , Dissulfeto de Carbono/química , Espectroscopia de Ressonância Magnética Nuclear de Carbono-13 , Cristalografia , Estrutura Molecular , Compostos Organometálicos/química , Teoria Quântica , Sulfetos/química
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