scholarly journals Assessment of DNA damage with an adapted independent reaction time approach implemented in Geant4‐DNA for the simulation of diffusion‐controlled reactions between radio‐induced reactive species and a chromatin fiber

2020 ◽  
Author(s):  
Hoang Ngoc Tran ◽  
José Ramos‐Méndez ◽  
Wook‐Geun Shin ◽  
Yann Perrot ◽  
Bruce Faddegon ◽  
...  
2008 ◽  
Vol 23 (12) ◽  
pp. 3303-3308 ◽  
Author(s):  
Chien-Neng Liao ◽  
Ching-Hua Lee

Reactions of molten Sn–xCu (x = 0.05 to 1.0) alloys with Te substrate at 250 °C were investigated. A dosage of 0.1 wt% Cu in Sn is found to be effective in suppressing the vigorous Sn/Te reaction by forming a thin CuTe at the solder/Te interface. The CuTe morphology changes from irregular clusters into a layered structure with increasing Cu content in Sn. With the same reaction time, the CuTe thickness increases proportionally to the square root of Cu content in Sn–Cu alloys, suggesting a diffusion-controlled growth for CuTe.


2019 ◽  
Vol 63 (1) ◽  
pp. 167-176 ◽  
Author(s):  
Macarena Moronta-Gines ◽  
Thomas R.H. van Staveren ◽  
Kerstin S. Wendt

Abstract In the nuclei of eukaryotic cells, the genetic information is organized at several levels. First, the DNA is wound around the histone proteins, to form a structure termed as chromatin fiber. This fiber is then arranged into chromatin loops that can cluster together and form higher order structures. This packaging of chromatin provides on one side compaction but also functional compartmentalization. The cohesin complex is a multifunctional ring-shaped multiprotein complex that organizes the chromatin fiber to establish functional domains important for transcriptional regulation, help with DNA damage repair, and ascertain stable inheritance of the genome during cell division. Our current model for cohesin function suggests that cohesin tethers chromatin strands by topologically entrapping them within its ring. To achieve this, cohesin’s association with chromatin needs to be very precisely regulated in timing and position on the chromatin strand. Here we will review the current insight in when and where cohesin associates with chromatin and which factors regulate this. Further, we will discuss the latest insights into where and how the cohesin ring opens to embrace chromatin and also the current knowledge about the ‘exit gates’ when cohesin is released from chromatin.


2012 ◽  
Vol 32 (10) ◽  
pp. 2461-2467 ◽  
Author(s):  
John R. Mercer ◽  
Kelly Gray ◽  
Nichola Figg ◽  
Sheetal Kumar ◽  
Martin R. Bennett

Author(s):  
Yukako Asano ◽  
Shigenori Togashi ◽  
Yoshishige Endo

We applied microreactors to the three following reactions: a consecutive bromination reaction, the two-step Sandmeyer reaction, and an acetylation reaction including solvent effects. We obtained the reaction rate constants from few experimental data or quantum chemical calculations and optimized the reaction conditions such as the reaction times and temperature. We then experimentally validated them by microreactors. A consecutive bromination reaction, where the objective reaction was followed by the side reaction, was one of the processes. The reaction temperature played an important role in the effects of a microreactor. The yield of the objective product was improved by about 40% using a microreactor. The two-step Sandmeyer reaction was also applied, where the 1st-step reaction was followed by the 2nd-step reaction to produce the objective product. The 1st-step reaction had the diffusion-controlled process, while the 2nd-step reaction had the reaction-controlled one. The yield of the objective product was improved when microreactors were used and the reaction time for the 2nd-step reaction was set appropriately. Moreover, an acetylation reaction including solvent effects on reaction rates was considered and the solvent effects could be predicted from quantum chemical calculations. The calculation suggested that acetic acid with the larger electron-accepting property gave more stability to the species formed in the transition state. The reaction time was shortened using a microreactor, when the reaction process was changed from reaction-controlled to diffusion-controlled by changing the solvent used.


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