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Psi loops
Psi-loops consist of two antiparallel strands linked by a '+2' connection
(Richardson, 1981) i.e. with one strand in between, hydrogen
bonded to both of them (Tang et al., 1978)
In contrast to the beta-alpha-beta units these occur very rarely in
proteins (Hutchinson & Thornton, 1990). Just the start and end residues of each of the two strands
involved are included at the moment.
References
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Hutchinson EG and Thornton JM (1990). HERA - A program to
draw schematic diagrams of protein secondary structure. Proteins
Struct. Funct. Genet., 8, 203-212.
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Richardson JS (1981) The anatomy and taxonomy of protein
structure. Adv. Protein Chem. 34, 167-339.
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Tang J, James MNG, Hsu IN, Jenkins JA and Blundell TL
(1978). Structural evidence for gene duplication in the evolution
of the acid proteases. Nature, 271, 618-621.
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22nd May, 1996
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