TABLE 1.

Analysis of traces for I27₅, I27₅SAH₁, and I27₅SAH₂ obtained by single molecule force spectroscopy

The experimental results are shown as mean ± S.D. We measured the I27 F_u and P2P, and calculated l_c and p from a WLC fit to the first I27 unfolding peak for protein constructs. A pulling speed of 1000 nm/s was used in all experiments. F_u is the maximum force prior to an I27 unfolding event. P2P is defined as the distance from one unfolding peak to the same force value on the following unfolding event; if the following peak is lower than the preceding one then the distance was measured at the height of the second peak. The predicted l_c was calculated from the number of amino acids in the linker and SAH domains, assuming the SAH domains unfold prior to the I27 domains (see “Experimental Procedures”).

Construct	No. traces	Fu	P2P	lc	p	Predicted lc
		pN	nm	nm	nm	nm
I275	37	174 ± 29	24.2 ± 1.5	47 ± 16	0.50 ± 0.25	34
I275SAH1	51	171 ± 27	24.3 ± 1.2	77 ± 23	0.55 ± 0.22	73
I275SAH2	31	165 ± 25	24.6 ± 1.5	120 ± 22	0.57 ± 0.28	111