TABLE 1.

Averaged stiffness values determined for viruses, liposomes, and virosomes

Shown is a summary of the averaged stiffness values determined for bromelain-treated, untreated, and pH 5-treated viruses (phase 2), liposomes with or without cholesterol, and virosomes for a particle size of 75–100 nm in diameter. The data for all individual particles analyzed are shown in Fig. 6. The S.D. value was obtained from the difference between each data point and the fitted value.

	WT virus	Bald virus	Liposome	WT virus, low pH	Liposome + cholesterol	Virosome
No. of particles (d = 75–100 nm)	24	25	9	12
No. of FZ curves analyzed	121	185	39	47
Stiffness (nN/nm) (mean ± S.D.)	0.03 ± 0.01	0.05 ± 0.02	0.02 ± 0.01	0.02 ± 0.01
Mean height (nm) (mean ± S.D.)	85 ± 7	85 ± 5	82 ± 7	91 ± 7
No. of particles (all)	43	48	43	31	13	6
Global fit stiffness k ± S.E. (nN/nm) for d = 100 nm	0.023 ± 0.002	0.037 ± 0.002	0.014 ± 0.001	0.017 ± 0.001	0.015 ± 0.002	0.010 ± 0.002