Table 1. Summary of main results of RecA nucleation, polymerization, and stability.

Experimental Conditions a	RecA nucleation, polymerization, and stability
24°C, pH 7.4; DNA with blunt ends (48,502 bp λ-DNA; 595 bp one-end-sealed DNA)	1. Nucleation requires force-induced DNA strand-peeling transition; 2. Polymerization requires high force (> 40 pN); 3. Pre-formed RecA filament is unstable at forces of several pN;
24°C, pH 7.4; DNA with 5’ ssDNA tail (595 bp DNA with 12 nt 5’ ssDNA tail)	1. Spontaneous nucleation and polymerization without assistance of DNA strand-peeling; 2. Pre-formed RecA filament is stable at forces of several pN;
24°C, pH 7.4; 876 bp DNA with two GC rich handles, 600 bp GC rich end-closed DNA	Nucleation and polymerization do not occur during DNA B-to-S transition;
37°C, pH 7.4; DNA with blunt ends (48,502 bp λ-DNA; 595 bp one-end-sealed DNA)	1. Nucleation requires force-induced DNA strand-peeling transition; 2. Progressive polymerization occurs at forces of several pN; 3. Pre-formed RecA filament is stable at forces of several pN;
37°C, pH 7.4; DNA with 5’ ssDNA tail (595 bp DNA with 12 nt 5’ ssDNA tail)	1. Spontaneous nucleation and polymerization without assistance of DNA strand-peeling; 2. Pre-formed RecA filament is stable at forces of several pN;
24°C, pH 6.2; DNA with blunt ends (48,502 bp λ-DNA; 595 bp one-end-sealed DNA)	1. Spontaneous nucleation and polymerization occur at forces of several pN; 2. Pre-formed RecA filament is stable at forces of several pN;

^aAll experiments include 1 µM RecA, 10 mM MgCl₂, 50–150 mM, 1 mM ATP and 1X ATP regeneration system.