Key role of higher order symmetry and electrostatic ligand field design in the magnetic relaxation of low-coordinate Er(iii) complexes

2017 ◽  
Vol 46 (35) ◽  
pp. 11913-11924 ◽  
Author(s):  
Saurabh Kumar Singh ◽  
Bhawana Pandey ◽  
Gunasekaran Velmurugan ◽  
Gopalan Rajaraman
Keyword(s):  
Theoretical Analysis ◽  
Magnetic Relaxation ◽  
Higher Order ◽  
Ligand Field ◽  
Barrier Heights

Our theoretical analysis highlights that both symmetry and a suitable ligand field is required to obtain large barrier heights in SIMs. Key role of Lanthanide–halogen covalency in enhancing Ueff is discussed.

Unprecedented magnetic relaxation via the fourth excited state in low-coordinate lanthanide single-ion magnets: a theoretical perspective

2014 ◽  
Vol 50 (98) ◽  
pp. 15513-15516 ◽  
Author(s):  
Saurabh Kumar Singh ◽  
Tulika Gupta ◽  
Maheswaran Shanmugam ◽  
Gopalan Rajaraman
Keyword(s):  
Excited State ◽  
Ab Initio ◽  
Coordination Number ◽  
Magnetic Relaxation ◽  
Theoretical Perspective ◽  
Magnetization Dynamics ◽  
Barrier Heights

How to enhance the barrier heights in lanthanide based SIMs? Using ab initio calculations, we have explored the role of symmetry and the coordination number on the magnetization dynamics of four three-coordinate Ln(iii) SIMs.

The role of S and Mo doping on the dissociation of water molecule on FeOCl surface: Experimental and theoretical analysis

2021 ◽  
pp. 131353
Author(s):  
Xiao Liu ◽  
Wenyi Zhang ◽  
Mingguo Peng ◽  
Guangqun Zhai ◽  
Linchao Hu ◽  
...  
Keyword(s):  
Theoretical Analysis ◽  
Water Molecule ◽  
Mo Doping

scholarly journals Theoretical Study on the Photo-Oxidation and Photoreduction of an Azetidine Derivative as a Model of DNA Repair

Molecules ◽  
2021 ◽  
Vol 26 (10) ◽  
pp. 2911
Author(s):  
Miriam Navarrete-Miguel ◽  
Antonio Francés-Monerris ◽  
Miguel A. Miranda ◽  
Virginie Lhiaubet-Vallet ◽  
Daniel Roca-Sanjuán
Keyword(s):  
Electron Transfer ◽  
Energy Barrier ◽  
Ring Opening ◽  
Dna Lesions ◽  
Barrier Heights ◽  
Dna Lesion ◽  
Electron Reduction ◽  
The Stability ◽  
Electron Transfer Processes

Photocycloreversion plays a central role in the study of the repair of DNA lesions, reverting them into the original pyrimidine nucleobases. Particularly, among the proposed mechanisms for the repair of DNA (6-4) photoproducts by photolyases, it has been suggested that it takes place through an intermediate characterized by a four-membered heterocyclic oxetane or azetidine ring, whose opening requires the reduction of the fused nucleobases. The specific role of this electron transfer step and its impact on the ring opening energetics remain to be understood. These processes are studied herein by means of quantum-chemical calculations on the two azetidine stereoisomers obtained from photocycloaddition between 6-azauracil and cyclohexene. First, we analyze the efficiency of the electron-transfer processes by computing the redox properties of the azetidine isomers as well as those of a series of aromatic photosensitizers acting as photoreductants and photo-oxidants. We find certain stereodifferentiation favoring oxidation of the cis-isomer, in agreement with previous experimental data. Second, we determine the reaction profiles of the ring-opening mechanism of the cationic, neutral, and anionic systems and assess their feasibility based on their energy barrier heights and the stability of the reactants and products. Results show that oxidation largely decreases the ring-opening energy barrier for both stereoisomers, even though the process is forecast as too slow to be competitive. Conversely, one-electron reduction dramatically facilitates the ring opening of the azetidine heterocycle. Considering the overall quantum-chemistry findings, N,N-dimethylaniline is proposed as an efficient photosensitizer to trigger the photoinduced cycloreversion of the DNA lesion model.

Magnetic relaxation of solvent protons by copper(2+)- and dioxovanadium(2+)-substituted transferrin: theoretical analysis and biochemical implications

Biochemistry ◽  
1985 ◽  
Vol 24 (22) ◽  
pp. 6287-6290 ◽  
Author(s):  
Ivano Bertini ◽  
Fabrizio Briganti ◽  
Seymour H. Koenig ◽  
Claudio Luchinat
Keyword(s):  
Theoretical Analysis ◽  
Magnetic Relaxation

Evaluation-driven design of a robust coreference resolution system

2003 ◽  
Vol 9 (3) ◽  
pp. 281-306 ◽  
Author(s):  
ANDREI POPESCU-BELIS
Keyword(s):  
Working Memory ◽  
Theoretical Analysis ◽  
Coreference Resolution ◽  
Knowledge Sources ◽  
Narrative Texts ◽  
Data Annotation ◽  
Evaluation Measures ◽  
Optimal Behavior ◽  
Resolution System

In this paper, we describe a system for coreference resolution and emphasize the role of evaluation for its design. The goal of the system is to group referring expressions (identified beforehand in narrative texts) into sets of coreferring expressions that correspond to discourse entities. Several knowledge sources are distinguished, such as referential compatibility between a referring expression and a discourse entity, activation factors for discourse entities, size of working memory, or meta-rules for the creation of discourse entities. For each of them, the theoretical analysis of its relevance is compared to scores obtained through evaluation. After looping through all knowledge sources, an optimal behavior is chosen, then evaluated on test data. The paper also discusses evaluation measures as well as data annotation, and compares the present approach to others in the field.

Theoretical analysis of RNA polymerase fidelity: a steady-state copolymerization approach

2021 ◽  
Author(s):  
Wenbo Fu ◽  
Qiushi Li ◽  
Yongshun Song ◽  
Yaogen Shu ◽  
Zhongcan Ouyang ◽  
...  
Keyword(s):  
Steady State ◽  
Dna Replication ◽  
Theoretical Analysis ◽  
Rna Polymerase ◽  
Higher Order ◽  
Simplified Models ◽  
Rna Transcription ◽  
Dna Transcription ◽  
Polymerase Fidelity ◽  
Neighbor Effects

Abstract The fidelity of DNA transcription catalyzed by RNA polymerase (RNAP) has long been an important issue in biology. Experiments have revealed that RNAP can incorporate matched nucleotides selectively and proofread the incorporated mismatched nucleotides. However, systematic theoretical researches on RNAP fidelity are still lacking. In the last decade, several theories on RNA transcription have been proposed, but they only handled highly simplified models without considering the high-order neighbor effects and the oligonucleotides cleavage both of which are critical for the overall fidelity. In this paper, we regard RNA transcription as a binary copolymerization process and calculate the transcription fidelity by the steady-state copolymerization theory recently proposed by us for DNA replication. With this theory, the more realistic models considering higher-order neighbor effects, oligonucleotides cleavage, multi-step incorporation and multi-step cleavage can be rigorously handled.

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