Acetyl group known as paracetamol), and acetylsalicylic acid (better known as aspirin). The introduction of an acetyl group into a molecule is called acetylation. In biological organisms, acetyl groups are commonly transferred from acetyl-CoA to other organic molecules. Acetyl-CoA is an intermediate both in the biological synthesis and in the breakdown of many organic molecules. Acetyl-CoA is also created during the second stage of cellular respiration, the Krebs Cycle, by the action of pyruvate dehydrogenase on pyruvic acid. Histones and other proteins are often modified by acetylation. For example, on the DNA level, histone acetylation by acetyltransferases (HATs) causes an expansion of
Birch bark manuscript In Indian sculpture, a Birch bark manuscript is easily identified by the droop. A palm leaf manuscript is stiff. On July 26, 1951, during excavations in Novgorod, a Soviet expedition led by Artemiy Artsikhovsky found the first Russian birch bark writing in a layer dated to c. 1400. Since then, more than 1,000 similar documents were discovered in Staraya Russa, Smolensk, Torzhok, Pskov, Tver, Moscow, Ryazan, and Vologda, although Novgorod remains by far the most prolific source of them. In Ukraine, birch bark documents were found in Zvenyhorod, Volynia. In Belarus, several documents were unearthed in Vitebsk and Mstislavl. The