I read a paper by Ross and Poirier [1, p. S12] which has the following lines (see section Commonalities of amyloid structure) that describe the structure of protein in a fibril:

The most extensively characterized amyloid fibril is that formed from the β-amyloid (Aβ) peptide implicated in AD. Using SOLID-STATE NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY, the in-register, parallel β-sheet organization of fibrils formed by Aβ10–35, a fragment of the full-length 42-residue Aβ peptide, was first described.

I couldn't understand what "in-register, parallel β-sheet" means.


  1. Ross, C. A.; Poirier, M. A. Protein Aggregation and Neurodegenerative Disease. Nat Med 2004, 10 (7), S10–S17. https://doi.org/10/dppb95.
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    $\begingroup$ Searching 'protein structure' gets 250 hits on chemistrySE, and 500 hits on biology SE. Thus you might have luck on either site. I'd give it a bit, and if you don't get a satisfactory answer here, ask it on biologySE (or perhaps ask that the question be moved there). $\endgroup$ – theorist Nov 18 '19 at 6:11
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    $\begingroup$ Have you looked for ref 43 in that paper, as this refers to the particular statement. Otherwise you could try emailing the authors. $\endgroup$ – porphyrin Nov 18 '19 at 9:05

There is a clear explanation and figure showing this in the following reference:

Anton Gorkovskiy, Kent R. Thurber, Robert Tycko, Reed B. Wickner, PNAS 2014, 111 (43) E4615-E4622.

A parallel beta sheet is one where the direction from N- to C-termini on adjacent strands run in a parallel direction (rather than antiparallel). In-register means that each residue in one molecule is aligned with the same residue in the neighboring molecule, producing lines of identical residues along the long axis of the filament.

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  • $\begingroup$ Panel b of figure 1 shows the common position of a given amino acid in each aggregated peptide along the la-axis of the fiber; axes defined in panel a of the same figure. $\endgroup$ – Karsten Theis Nov 18 '19 at 11:30

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