Abstract:
:Compared to contact-mode atomic force microscopy (CMAFM), tapping-mode atomic force microscopy (TMAFM) has the advantage of allowing imaging surfaces of macromolecules, even when they are only weakly attached to the support. In this study, TMAFM is applied to two different regular protein layers whose structures are known to great detail, the purple membrane from Halobacterium salinarum and the hexagonally packed intermediate (HPI) layer from Deinococcus radiodurans, to assess the faithfulness of high-resolution TMAFM images. Topographs exhibited a lateral resolution between 1.1 and 1. 5 nm and a vertical resolution of approximately 0.1 nm. For all protein surfaces, TMAFM and CMAFM topographs were in excellent agreement. TMAFM was capable of imaging the fragile polypeptide loop connecting the transmembrane alpha-helices E and F of bacteriorhodopsin in its native extended conformation. The standard deviation (SD) of averages calculated from TMAFM topographs exhibited an enhanced minimum (between 0.1 and 0.9 nm) that can be assigned to the higher noise of the raw data. However, the SD difference, indicating the flexibility of protein subunits, exhibited an excellent agreement between the two imaging modes. This demonstrates that the recently invented imaging-mode TMAFM has the ability to faithfully record high-resolution images and has sufficient sensitivity to contour individual peptide loops without detectable deformations.
journal_name
Biophys Jjournal_title
Biophysical journalauthors
Möller C,Allen M,Elings V,Engel A,Müller DJdoi
10.1016/S0006-3495(99)76966-3subject
Has Abstractpub_date
1999-08-01 00:00:00pages
1150-8issue
2eissn
0006-3495issn
1542-0086pii
S0006-3495(99)76966-3journal_volume
77pub_type
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