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Proceedings Paper

Technique for determination of the number of PapA units in an E. coli P pilus
Author(s): Magnus Andersson; Erik Fällman; Bernt Eric Uhlin; Ove Axner
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Paper Abstract

Optical tweezers have previously been used to characterize the force-vs.-elongation dependence of the PapA rod of uropathogenic E. coli P pili. It was found that the PapA rod elongates in several elongation regions. In the two first, the elongation originates from an elastic stretching and a sequential unfolding of the layer-to-layer bonds (and thereby of the helical structure). Region III is characterized by an elongation that originates from an elastic stretching and an opening of the head-to-tail bonds in the linearized PapA rod. The opening of these bonds takes place in a random order, wherefore the response in this region is affected by entropy. Since the entropic softening of a macromolecule depends on the number of units, the shape of this region can be used to assess the number of PapA units. We provide in this work a recipe for how this can be done solely from the form of region III. An advantage with this technique is that it does not require a continuous monitoring of the elongation of a single PapA rod from unstretched conditions, which often is difficult because of simultaneous multi-pili binding; it suffices to detect it in the third region at which binding often is mediated by only one pilus. Another advantage is that it does not require any prior knowledge about (or assessment of) any physical entity of the PapA rod; the number of PapA units can be assessed solely from the shape of the curve in the third elongation region.

Paper Details

Date Published: 21 February 2006
PDF: 12 pages
Proc. SPIE 6088, Imaging, Manipulation, and Analysis of Biomolecules, Cells, and Tissues IV, 608814 (21 February 2006); doi: 10.1117/12.642261
Show Author Affiliations
Magnus Andersson, Umeå Univ. (Sweden)
Erik Fällman, Umeå Univ. (Sweden)
Bernt Eric Uhlin, Umeå Univ. (Sweden)
Ove Axner, Umeå Univ. (Sweden)


Published in SPIE Proceedings Vol. 6088:
Imaging, Manipulation, and Analysis of Biomolecules, Cells, and Tissues IV
Daniel L. Farkas; Dan V. Nicolau; Robert C. Leif, Editor(s)

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