Editing Beta sheet (section)

==In pathology==
Some proteins that are disordered or helical as monomers, such as amyloid β (see [[amyloid plaque]]) can form β-sheet-rich oligomeric structures associated with pathological states. The amyloid β protein's oligomeric form is implicated as a cause of [[Alzheimer's disease|Alzheimer's]]. Its structure has yet to be determined in full, but recent data suggest that it may resemble an unusual two-strand β-helix.<ref name="pmid15944695">{{cite journal | vauthors = Nelson R, Sawaya MR, Balbirnie M, Madsen AØ, Riekel C, Grothe R, Eisenberg D | title = Structure of the cross-beta pine of amyloid-like fibrils | journal = Nature | volume = 435 | issue = 7043 | pages = 773–8 | date = June 2005 | pmid = 15944695 | pmc = 1479801 | doi = 10.1038/nature03680 | bibcode = 2005Natur.435..773N }}</ref>

The side chains from the amino acid residues found in a β-sheet structure may also be arranged such that many of the adjacent sidechains on one side of the sheet are hydrophobic, while many of those adjacent to each other on the alternate side of the sheet are polar or charged (hydrophilic),<ref name="pmid7682699">{{cite journal | vauthors = Zhang S, Holmes T, Lockshin C, Rich A | title = Spontaneous assembly of a self-complementary oligopeptide to form a stable macroscopic membrane | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 90 | issue = 8 | pages = 3334–8 | date = April 1993 | pmid = 7682699 | pmc = 46294 | doi = 10.1073/pnas.90.8.3334 | bibcode = 1993PNAS...90.3334Z | doi-access = free }}</ref> which can be useful if the sheet is to form a boundary between polar/watery and nonpolar/greasy environments.