刘华杰老师曾发现一些植物分类学书籍上植物的手绘图手性出现过错误，本来右旋的画成左旋，或是左旋画成右旋。
最近发现在核小体手性上也有类似的手性问题出现，例如这篇文章Nature Reviews Genetics 11, 476-486 | doi:10.1038/nrg2795，插图中的DNA都画成了右旋在组蛋白上。
再看看下面的图，doi:10.1038/nrg2522
Approximately 147 bp of DNA coils 1.65 times around the histone octamer in a left-handed toroid2.
2. Luger, K., Mader, A. W., Richmond, R. K., Sargent, D. F. & Richmond, T. J. Crystal structure of the nucleosome core particle at 2.8 Å resolution. Nature 389, 251–260 (1997).
看出区别了吗？
自己动手，拿根绳子，按右旋方向扭转，直到绳子自己缩到两根缠在一起，看看这两根是不是左旋啦！
话说DNA有右旋的也有左旋的（Z-DNA），核小体是否也有右旋的呢？
Right-Handed Nucleosome: Myth or Reality? doi:10.1016/j.cell.2009.12.014
In their recent paper in Cell, Furuyama and Henikoff, 2009 (doi:10.1016/j.cell.2009.04.049) report that nucleosomes in centromeres may be right-handed, that is, they wrap DNA in a right-handed manner and induce positive supercoils. This raises intriguing new questions, such as how centromeric histone variants may be assembled into right-handed particles, and why chromatin would retain negative supercoiling in chromosome arms but positive supercoiling in centromeres. We wish to comment on these new findings in the context of topological insights that we have gained from recent in vitro experiments with centromeric nucleosomes and single chromatin fibers submitted to torsional constraints and from 3D modeling of chromatin dynamics. We will also discuss alternative compositions of centromeric nucleosome particles and suggest potential mechanisms by which local positive supercoiling may be established.
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