TABLE 1.

MALDI-TOF-MS analysis of cleavage products of npAβ and pAβ

Shown are the various peptide fragments generated upon cleavage of npAβ and pAβ variants by different proteases and their calculated mass (Da) and observed mass (Da) by MALDI-TOF. 1–40* represents the double-ionized full-length peptide (m/2z instead of normal m/z). The indicated masses of the full-length peptide (1–40) and the double-ionized full-length peptide (1–40*) of both peptide variants are the mean values (n = 10). The difference between the observed mass and the calculated mass is ∼1–5 Da. The proteolytic products with a mass below 1000 kDa and C-terminal fragments of Aβ generated after the proteolytic cleavage were barely detectable even at spectrum recordings at low mass range (between 100 and 1000 kDa). ND, peaks that were not detected by MALDI-TOF-MS.

Peptide fragment	npAβ		pAβ
	Calculated mass	Observed mass	Calculated mass	Observed mass
	Da		Da
1–7	888.4	ND	889.4	ND
1–8	975.4	ND	1055.4	ND
1–12	1423.6	ND	1503.6	1508.3
1–13	1560.7	1560.5	1640.7	1644.3
1–14	1697.7	1697.1	1777.7	1782.5
1–15	1825.8	1826.3	1905.8	1910.7
1–16	1953.9	1957.7	2033.9	2038.2
1–17	2067.0	2069.4	2147.8	ND
1–18	2166.0	2164.6	2246.0	2251.8
1–19	2313.1	2316.3	2393.1	2399.4
1–20	2460.2	2460.2	2540.2	2545.8
1–28	3260.5	3261.2	3340.5	3340.3
1–29	3317.6	3321.8	3397.6	ND
8–40	3456.8	3451.2	3536.8	ND
9–40	3369.8	3367.7	3369.8	ND
15–28	1580.8	1584.7	1580.8	1584.7
15–40	2647.4	2646.8	2647.4	ND
16–40	2519.4	ND	2519.4	ND
18–40	2278.2	ND	2278.2	ND
19–40	2179.1	ND	2179.1	ND
20–40	2032.1	ND	2032.1	ND
30–40	1028.3	ND	1028.3	ND
1–40	4327.2	4328.4	4407.2	4414.6
1–40*	2163.6	2164.5	2203.6	2204.3