In Alzheimers disease, aggregation of the beta-amyloid peptide (A beta) results in the formation of oligomers and fibrils that are associated with neurodegeneration. Aggregation of A beta occurs through interactions between different regions of the peptide. This paper and the accompanying paper constitute a two-part investigation of two key regions of A beta: the central region and the C-terminal region. These two regions promote aggregation and adopt beta-sheet structure in the fibrils, and may also do so in the oligomers. In this paper, we study the assembly of macrocyclic beta-sheet peptides that contain residues 17-23 (LVFFAED) from the central region and residues 30-36 (AIIGLMV) from the C-terminal region. These peptides assemble to form tetramers. Each tetramer consists of two hydrogen-bonded dimers that pack through hydrophobic interactions in a sandwich-like fashion. Incorporation of a single N-15 isotopic label into each peptide provides a spectroscopic probe with which to elucidate the beta-sheet assembly and interaction: H-1,N-15 HSQC studies facilitate the identification of the monomers and tetramers; N-15-edited NOESY studies corroborate the pairing of the dimers within the tetramers. In the following paper, J. Am. Chem. Soc. 2016, DOI: 10.1021/jacs.6b06001, we will extend these studies to elucidate the coassembly of the peptides to form heterotetramers.