Table 1.

Summary of primary techniques.

Technique	Abbreviation	Description
Mass Spectrometry	MS	Electrospray ionization (ESI) tandem MS is used to determine regions on peptides where metals bind, by analyzing the molecular masses of fragments where the amide backbone of the peptide has been cleaved while preserving protein-metal interactions. The fragmentation pattern indicates the binding region(s), as the fragments containing the residue(s) that interact(s) with the metal show a characteristic mass increase.
Scanning Transmission X-ray Microscopy	STXM	Synchrotron soft X-ray microscopy is used in transmission mode to obtain images at tens of nanometer spatial resolution, acquired sequentially in stacks as a function of energy. These data contain spectral information about the chemistry of each region of interest selected within the image.
X-ray Absorption Near-Edge Spectroscopy	XANES	Synchrotron hard X-ray microscopy is used in fluorescence mode to obtain energy scans from elements of interest, where the structure of the spectrum is sensitive to the local chemical environment of the scattering element.
Transmission Electron Microscopy	TEM	Electron beam imaging is used to investigate the forms of peptide aggregate present in the samples analyzed by MS, STXM, and XANES.