The complexation energy of the one-electron oxidized guanine–cytosine base pair and its parent system with small cations. A DFT-study

A DFT study of hexene hydrogenation catalysed by the RuH(CO)(Cl)(PCy3)2 complex is presented. The investigation explores the feasibility of two different mechanisms: the first exploits a single phosphine complex and the second uses a two phosphines complex. The energy barriers involving a hydrogen transfer have a ten kcal.mol-1 higher than the one obtained through the single-phosphine mechanism. These results confirm the experimental hypothesis claiming that the departure of a phosphine is favourable at the beginning of the reaction which is the substitution of the catalyst model RuHCl(CO)(PMe3)2 by the real catalyst RuHCl(CO)(PCy3)2 shows no significant influence on the energetic barriers of hexene hydrogenation mechanism. The most important step of the mechanism is the kinetically determining step. The heterolytic cleavage of ruthenium-complexed H2 molecule leads to the generation of two Ru-H bonds and the oxidation of the ruthenium from Ru(II) to Ru(IV). The energy profile of this step is not relative to an elementary reaction because a shouldering is observed after the transition state. This results in an unusual gradient norm profile with five extrema. This is a direct consequence of the asynchronous nature of the different processes taking place during this step. In the case of the model complex RuHCl(CO)(IMes)(PMe3) with IMes = ( N , N '-bis( mesityl)imidazol-2-ylidene), an increase of the free enthalpy of activation is observed during the kinetically determining step, which is in agreement with the experimental work.

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Kinetic and mechanistic insight into the formation of amphetamine using the Leuckart–Wallach reaction and interaction of the drug with GpC·CpG base-pair step of DNA: a DFT study

Monatshefte für Chemie - Chemical Monthly ◽

10.1007/s00706-018-2145-7 ◽

2018 ◽

Vol 149 (6) ◽

pp. 1045-1057 ◽

Cited By ~ 1

Author(s):

Hoda Ostovari ◽

Ehsan Zahedi ◽

Iraj Sarvi ◽

Abolfazl Shiroudi

Keyword(s):

Base Pair ◽

Dft Study ◽

Mechanistic Insight ◽

Insight Into

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Tandemly repeated exons encode 81-base repeats in multiple, developmentally regulated Schistosoma mansoni transcripts.

Molecular and Cellular Biology ◽

10.1128/mcb.8.11.4745 ◽

1988 ◽

Vol 8 (11) ◽

pp. 4745-4755 ◽

Cited By ~ 21

Author(s):

R E Davis ◽

A H Davis ◽

S M Carroll ◽

A Rajkovic ◽

F M Rottman

Keyword(s):

Alternative Splicing ◽

Schistosoma Mansoni ◽

Base Pair ◽

Transcription Initiation ◽

Tandem Repeats ◽

Developmentally Regulated ◽

Alternative Transcription ◽

Exon Usage ◽

The One ◽

Base Insertion

The adult Schistosoma mansoni cDNA clone 10-3 encodes an antigen that is recognized by sera from infected humans. We characterized multiple developmentally regulated transcripts homologous to the 10-3 cDNA and portions of the complex genomic loci encoding those transcripts. Transcripts of approximately 950, 870, and 780 nucleotides were expressed in adults, whereas only the 780-nucleotide transcript was observed in the larval stage. These transcripts were highly similar, containing variable numbers of identical direct tandem repeats of 81 bases. Although the sequence of the repeating elements and sequences 3' to them were identical in all the transcripts, sequences 5' of the repeating elements exhibited variations, including a 27-base insertion, alternative start sites for transcription, and alternate 5' exon usage. These transcripts appeared to be derived in part by the developmentally controlled alternative splicing of small exons and the use of alternative transcription initiation sites from the one or two complex loci of at least 40 kilobase pairs. Each 81-base repeat in the transcripts was encoded by three dispersed 27-base-pair exons. These 27-base-pair exons were contained within highly conserved, reiterated 3-kilobase-pair genomic tandem arrays.

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