Risk which is common to an entire class of assets or liabilities. The value of investments may decline over a given time period simply because of economic changes or other events that impact large portions of the market.
Properties of the alpha-helix. 1  The structure repeats itself every 5.4 Angstroms along the helix axis, ie we say that the alpha-helix has a pitch of 5.4 Angstroms. Alpha-helices have 3.6 amino acid residues per turn, ie a helix 36 amino acids long would form 10 turns.
Various types of secondary structure have been discovered, but by far the most common are the orderly repeating forms known as the a helix and the b sheet. An a helix, as the name implies, is a helical arrangement of a single polypeptide chain, like a coiled spring.