I myself have never seen a separate peak that was a single sulfur atom. I've seen, in a moderately-radiation-damaged dataset, little shards of anomalous scattering density in Phaser-generated LLG maps. They were in the interior of the protein, and the closest possible atoms were sulfurs. They were not in positions suggestive of Fourier truncation ripples, so I hypothesized that these sulfurs were ionized and landed at the nearest convenient location, and left it at that.
JPK
