In amyloid diseases an insoluble amyloid fibril forms via a soluble oligomeric intermediate. It is this intermediate that mediates toxicity and it has been suggested, somewhat controversially, that it has the α-sheet structure. Nests and α-strands are similar peptide motifs in that alternate residues lie in the α_R and γ_L regions of the Ramachandran plot for nests, or α_R and α_L regions for α-strands. In nests a concavity is formed by the main chain NH atoms whereas in α-strands the main chain is almost straight. Using “Ramachandran propensity plots” to focus on the α_L/γ_L region, it is shown that glycine favours γ_L (82% of amino acids are glycine), but disfavours α_L (3% are glycine). Most charged and polar amino acids favour α_L with asparagine having by far the highest propensity. Thus, glycine favours nests but, contrary to common expectation, should not favour α-sheet. By contrast most charged or polar amino acids should favour α-sheet by their propensity for the α_L conformation, which is more discriminating amongst amino acids than the α_R conformation. Thus, these results suggest the composition of sequences that favour α-sheet formation and point towards effective prediction of α-sheet from sequence.

在淀粉样蛋白疾病中，不溶性淀粉样蛋白原纤维通过可溶性寡聚中间体形成。正是这种中间体介导了毒性，有人提出，有点争议的是，它具有α-折叠结构。巢和 α 链是相似的肽基序，因为交替的残基位于拉马钱德兰图的 α _R和 γ _L区域中的巢，或 α _R和 α _L区域的 α 链。在嵌套中，主链 NH 原子形成凹面，而在 α 链中，主链几乎是直的。使用“Ramachandran 倾向图”关注 α _L /γ _L区域，表明甘氨酸有利于 γ _L（82% 的氨基酸是甘氨酸），但不喜欢 α _L（3% 是甘氨酸）。大多数带电和极性氨基酸偏爱α _L，而天冬酰胺具有迄今为止最高的倾向。因此，甘氨酸有利于巢，但与普遍预期相反，不应该有利于 α-折叠。相比之下，大多数带电或极性氨基酸应该倾向于 α-折叠，因为它们倾向于 αL_{构象，这比αR}构象更能区分氨基酸。因此，这些结果表明有利于α-折叠形成的序列组成，并指向从序列中有效预测α-折叠。