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Chapter 3.4 of the book “Introduction to Molecular Motion in Polymers" is presented which discusses molecular motion in polymers. It explores internal rotation in small and larger molecules by referring to the rotational isomeric potential, total conformational energy, Boltzmann distribution, rotation of the terminal methyl groups, potential energy in conformational changes, and intramolecular forces.

This article presents an encyclopedia entry about Catechol O-methyltransferase (COMT) and its inhibitors. COMT refers to an enzyme that chemically changes the transfer of the methyl group of S-adenosyl-L-methionine to one of the phenolic group of the catechol substrate. A comparison between soluble COMT and membrane-bound COMT is discussed.

The article presents an encyclopedia entry for "methylxanthines," a naturally occurring drug. High doses of methylxanthines, which include theophylline, theobromine and caffeine, inhibit phosphodiesterases, while lower doses of methylxanthines act as antagonists on adenosine receptors. Methylxanthines may be responsible for the tachycardia and relaxation of smooth muscles.

A definition of the term "5-methyl-cytosine" is presented. It refers to a cytosine, which is modified through the addition of a methyl group through the process of methylation. In the case of vertebrate genomes, 5-methyl-cytosines are mostly found in the 5' position of cytosine residues within CpG dinucleotides.

A definition of the term "DNA methylation," which refers to an epigenetic modification of DNA involving the addition of a methyl group to the position of a cystosine residue, is presented.