Liudmila Romanova & Alexander V Snegursky 
Amino Acid Molecules Fragmentation by Low-Energy Electrons 

Amino acids belong to biologically relevant organic substances involved in live organisms. Generally, they include the amine (NH2) and the carboxylic acid (COOH) functional groups. In general, their generic formula looks like H2NCHRCOOH, with R being an organic substituent (a "side-chain"). As seen, their main constituents are carbon, hydrogen, oxygen and nitrogen atoms, however, other elements (say, sulfur) are also found in their side-chains. As of today, a dozens of amino acids are classified quite differently. From the structural viewpoint and according to locations of their functional groups, amino acids are commonly classified as the a-, b-, I and I’- ones. Being involved in forming proteins, amino acids are the second (after water) largest component of live tissues. Together with proteins, they play a significant role in a number of live organism-related processes, e.g. neurotransmitter transport and biosynthesis.