China
Africa
Explore chapters and articles related to this topic
Theoretical Consideration Of Solubility
Published in A. L. Horvath, Halogenated Hydrocarbons, 2020
The methyl group releases electron in any environment, consequently it strengthens a base and weakens an acid. Methyl groups unstabilize a molecule by replacing a hydrogen atom that would otherwise be split out in conjuction with a neighboring atom. The attraction of one molecule for another is greater than its attraction for water molecules. As a result, the crystal lattice energy is increased, and the substance falls out of solution. This however, happens more often among heterocyclic substances.
General Introductory Topics
Published in Vadim Backman, Adam Wax, Hao F. Zhang, A Laboratory Manual in Biophotonics, 2018
Vadim Backman, Adam Wax, Hao F. Zhang
In the process of methylation, methyl groups are added to cytosine residues in gene promoters, thus silencing gene transcription. The best-studied type of histone modification is acetylation, which converts the positively charged amine group on a side chain of a histone into a neutral amide. This inhibits the binding free energy between the DNA and the histone and allows DNA to be more accessible by nuclear transcription factors that initiate transcription. Thus, histone acetylation is associated with more transcriptionally active chromatin.
Glossary of scientific and technical terms in bioengineering and biological engineering
Published in Megh R. Goyal, Scientific and Technical Terms in Bioengineering and Biological Engineering, 2018
Methylation refers to the addition of a methyl group (–CH3) to a molecule, most commonly in the context of DNA where cytosine and, less often, adenine residues can be modified in this way, sometimes resulting in a change in transcription.
Animal models and mechanisms of tobacco smoke-induced chronic obstructive pulmonary disease (COPD)
Published in Journal of Toxicology and Environmental Health, Part B, 2023
Priya Upadhyay, Ching-Wen Wu, Alexa Pham, Amir A. Zeki, Christopher M. Royer, Urmila P. Kodavanti, Minoru Takeuchi, Hasan Bayram, Kent E. Pinkerton
In addition to RNA interference, other epigenetic modifications might be mediated by different mechanisms, including DNA methylation and histone modification, which might also play essential roles in COPD development. DNA methylation is a chemical modification that involves addition of a methyl group to cytosine residues in CpG dinucleotides, resulting in formation of 5-methylcytosine. DNA methylation might occur in promoter regions of genes, leading to gene silencing or reduced gene expression. In COPD, alterations in DNA methylation patterns were noted in genes involved in inflammation, oxidative stress, and tissue remodeling, which are critical processes in COPD pathogenesis (Alfahad et al. 2021). Previously Zeng et al. (2020) suggested that cigarette-induced oxidative stress plays a role in mediating pulmonary apoptosis and hypermethylation of the B-cell lymphoma/leukemia-2 (Bcl-2) promoter, an apoptosis regulator, in COPD through DNA methyltransferase enzyme 1 (DNMT1), a key DNA methyltransferase enzyme. Similarly, aberrant DNA methylation was reported to be a widespread occurrence in small airways of COPD patients and was associated with altered expression of genes and pathways related to COPD, such as NF-E2-related factor 2 oxidative response pathway (Vucic et al. 2014).
Association between global DNA methylation (LINE-1) and occupational particulate matter exposure among informal electronic-waste recyclers in Ghana
Published in International Journal of Environmental Health Research, 2022
Ibrahim Issah, John Arko-Mensah, Laura S. Rozek, Katie Rentschler, Thomas P. Agyekum, Duah Dwumoh, Stuart Batterman, Thomas G. Robins, Julius N. Fobil
DNA methylation, the covalent addition of a methyl group to the 5ʹ carbon of cytosine in a CpG dinucleotide, is the most stable and best-studied epigenetic mark that often responds to environmental stimuli and is critical in regulating gene expression and maintaining chromosomal integrity (Jamebozorgi et al. 2018; Lei et al. 2018). Most studies have focused on the influence of PM on either global methylation or gene-specific methylation (Baccarelli et al. 2009; Madrigano et al. 2011; Kile et al. 2013). The Long interspersed nucleotide elements-1 (LINE-1) are often used as surrogates for global DNA methylation measurement, given their relatively uniform spread across the genome (Yang et al. 2004). They are repetitive elements or transposons, constitute approximately 18% of the human genome, and are usually heavily methylated to suppress retrotransposition (Perera et al. 2020). Because DNA methylation marks are labile and respond to environmental stimuli, LINE-1 methylation is often used as an epigenetic biomarker of effect where low methylation levels correlate with genome instability (Rozek et al. 2014).
The deamination mechanism of the 5,6-dihydro-6-hydro-6-hydroxylcytosine and 5,6-dihydro-5-methyl-6-hydroxylcytosine under typical bisulfite conditions
Published in Molecular Physics, 2019
Lingxia Jin, Gongwei Qin, Caibin Zhao, Xiaohu Yu, Jiufu Lu, Hao Meng
DNA methylation usually involves addition of a methyl group to the C5 site of cytosine (Cyt), yielding 5-methylcytosine (5-MeCyt). 5-MeCyt has been proven to have an impact on a variety of cellular processes that affect development [1,2] and gene expression [3] as well as the development of various diseases [4]. 5-MeCyt is known to regulate gene transcription and thereby affect tumorigenesis [5,6]. The level of epigenetic methylation has to be precisely regulated in eukaryotic genomes, since changes of the methylation pattern lead to severe genetic malfunctions [7]. Therefore, the detection of the occurrence and distribution of 5-MeCyt in the genome is very crucial to serve as an important biomarker for diagnosis as well as disease therapy [8–10]. It is well known that both Cyt and 5-MeCyt are complementary to guanine, but the discrimination of them is much more complex. To date, although many of those chemical and physical methods were used to discriminate between Cyt and 5-MeCyt, the method of bisulfite sequencing is simple and inexpensive [11–15]. It has been regarded as the gold standard for 5-MeCyt detection and therefore widely used to detect 5-MeCyt at single base resolution in a large variety of cell types and disease models. This method is based on the selective bisulfite-mediated deamination of Cyt to uracil in the presence of 5-MeCyt, which remains unchanged as a result of slower deamination [16]. The sites of epigenetic markers can be revealed by comparison of the output of conventional sequencing methods before and after bisulfite treatment, as Cyt will be sequenced as thymine (T), and 5-MeCyt as Cyt [17].