AFM: one limitation affecting peak number of SP-D dodecamers, could be what I found on a website. “Due to the nature of AFM probes, they cannot normally measure steep walls or overhangs“. This quote is from a website that is mostly in chinese so I didnt bother to read or translate. BUT it is clearly what I have seen as I search for peak number in SP-D molecules (whether trimers, hexamers dodecamers, or higher order multimers).

Case in point is how many times the “tiny peak” which I have noted dozens and dozens of times as a small in height, narrow peak right near the base of the N term peak. It seems to be missed a lot of the time, there are other times when it is very obvious. A couple reasons for its intermittent appearance in AFM could actually be because of the very steep wall on the downslope of the N term peak before the glycosylation peak.

In terms of “overhang” this might also apply to the blending and disappearance of the neck area which is sometimes covered in the CRD peaks which flop around visibly lying over the neck domain.