a 4.53 A resolution density map in Fig. 2a and a 3.23 A resolution map in Fig. 2b

A 4-nt G-C mismatched substrate yields a RAD51 mini-filament density map at 4.53 Å resolution. The density shows an unbent dsDNA interacting with two adjoining NTDs of the presynaptic filament, presenting the initial recruitment state of homologous dsDNA (Figure 2a).
Increasing the mismatch to 8-nt yielded another density map at 3.23Å (Figure 2b), where dsDNA displayed pronounced curvature, interacting with four adjoining NTDs (N+1, N+2, N+3, and N+4).
These two structures represent the recruitment of homologous dsDNA via nonspecific interactions of NTDs.

以4个核苷酸（nucleotide, nt）的G-C碱基错配底物为研究对象，我们获得了分辨率为4.53埃（Å）的RAD51微型丝状体密度图。该密度图显示，未弯曲的双链DNA（double-stranded DNA, dsDNA）与突触前丝状体的两个相邻N端结构域（N-terminal domain, NTD）相互作用，呈现出同源双链DNA的初始招募状态（图2a）。
将错配碱基数目提升至8个核苷酸后，我们得到了另一幅分辨率为3.23埃的密度图（图2b），其中双链DNA呈现出显著弯曲，与四个相邻的N端结构域（N+1、N+2、N+3及N+4）相互作用。
上述两种结构分别代表了通过N端结构域的非特异性相互作用实现同源双链DNA招募的过程。