91影视

The 伪 helix is a right-handed regular repeating structure. It has an average length of ~12 residues, with a length of ~18 脜 and more than three helical turns. Here, each turn has 3.6 residues and a pitch of 5.4 脜.

This polypeptide helix exhibit favorable hydrogen bonding within the polypeptide chain and 蠒 (= -57潞) and 唯 (= -47潞) values.

The hydrogen bonds in the backbone are arranged in such a way that the peptide C=O of the n-th residue points towards the inside of the helix and forms a hydrogen bond with the N-H of the (n+4)-th residue. Thus the inner part of the helix is tightly packed, and the atoms are in van der Waals radius.

The side chains extend towards the outside of the helix to avoid steric hindrance.

The parallel 尾 sheet is formed from more than one 尾 pleated sheet running in the same direction.

In this structure,蠒 = 唯 = 卤 180潞.

Non-parallel hydrogen bonds take place between neighboring polypeptide chains.

The number of atoms in hydrogen-bonded rings is 12.

Right-handed or left-handed crossover connections are observed between the polypeptide strands.

This structure is comparatively less stable due to the distorted and weak hydrogen bonds between the polypeptide chains.

The antiparallel 尾 sheet is formed from more than one 尾 pleated sheet running in the opposite direction.

Like the parallel 尾 sheet, this structure also exhibits 蠒 = 唯 = 卤 180潞.

Parallel hydrogen bonds take place between neighboring polypeptide chains.

The number of atoms in hydrogen-bonded rings is 14 and 10, alternatively.

A hairpin connection is observed between the polypeptide strands.

These sheets are more stable than the parallel 尾 sheets due to well oriented, strong, and stable hydrogen bonds between the polypeptide chains in the antiparallel sheets.