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Elasticity and structure of eukaryote chromosomes studied by micromanipulation and micropipette aspiration.

Houchmandzadeh B, Marko JF, Chatenay D, Libchaber A - J. Cell Biol. (1997)

Bottom Line: Larger deformations of 10 to 100 times irreversibly and progressively transform the chromosomes into a "thin filament," parts of which display a helical organization.Chromosomes break for elongations of the order of 100 times, at which time the applied force is around 100 nanonewtons.Knowing the Young modulus allows us to estimate that the force exerted by the spindle on a newt chromosome at anaphase is roughly one nanonewton.

View Article: PubMed Central - PubMed

Affiliation: Centre National de la Recherche Scientifique (CNRS), Laboratoire de Spectrométrie Physique, Saint-Martin-d'Hères, France. bahram@coucou.ujf-grenoble.fr

ABSTRACT
The structure of mitotic chromosomes in cultured newt lung cells was investigated by a quantitative study of their deformability, using micropipettes. Metaphase chromosomes are highly extensible objects that return to their native shape after being stretched up to 10 times their normal length. Larger deformations of 10 to 100 times irreversibly and progressively transform the chromosomes into a "thin filament," parts of which display a helical organization. Chromosomes break for elongations of the order of 100 times, at which time the applied force is around 100 nanonewtons. We have also observed that as mitosis proceeds from nuclear envelope breakdown to metaphase, the native chromosomes progressively become more flexible. (The elastic Young modulus drops from 5,000 +/- 1,000 to 1,000 +/- 200 Pa.) These observations and measurements are in agreement with a helix-hierarchy model of chromosome structure. Knowing the Young modulus allows us to estimate that the force exerted by the spindle on a newt chromosome at anaphase is roughly one nanonewton.

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Breakage of the thin filament after 75 times extension. Note the irregular undulating shape that appeared. (a) t = 0.0 s; (b) t =  0.2 s; (c) t = 0.5 s; and (d) t = 0.8 s. Because of the fast breakage and relaxation dynamics, it is hard to keep the filament in focus. Bar, 10 μm.
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Figure 5: Breakage of the thin filament after 75 times extension. Note the irregular undulating shape that appeared. (a) t = 0.0 s; (b) t = 0.2 s; (c) t = 0.5 s; and (d) t = 0.8 s. Because of the fast breakage and relaxation dynamics, it is hard to keep the filament in focus. Bar, 10 μm.

Mentions: Finally, for ε ≈ 100, the filament breaks. (The precise value of ε at breaking depends on rate of elongation, ranging from 60 to 100; Fig. 5.) The deflection of the micropipette at the breaking point indicates a force between 90 to 150 nanonewtons. It is not easy to deduce the Young modulus of the thin filament from the force measurement. The thickness d of the thin filament when highly stretched is at the resolution limit of the microscope, and its measurement is critical for the Young modulus [Ythin ≈ F/(εd2)]. Our best estimate is Ythin = 1–5 × 105 Pa.


Elasticity and structure of eukaryote chromosomes studied by micromanipulation and micropipette aspiration.

Houchmandzadeh B, Marko JF, Chatenay D, Libchaber A - J. Cell Biol. (1997)

Breakage of the thin filament after 75 times extension. Note the irregular undulating shape that appeared. (a) t = 0.0 s; (b) t =  0.2 s; (c) t = 0.5 s; and (d) t = 0.8 s. Because of the fast breakage and relaxation dynamics, it is hard to keep the filament in focus. Bar, 10 μm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2139812&req=5

Figure 5: Breakage of the thin filament after 75 times extension. Note the irregular undulating shape that appeared. (a) t = 0.0 s; (b) t = 0.2 s; (c) t = 0.5 s; and (d) t = 0.8 s. Because of the fast breakage and relaxation dynamics, it is hard to keep the filament in focus. Bar, 10 μm.
Mentions: Finally, for ε ≈ 100, the filament breaks. (The precise value of ε at breaking depends on rate of elongation, ranging from 60 to 100; Fig. 5.) The deflection of the micropipette at the breaking point indicates a force between 90 to 150 nanonewtons. It is not easy to deduce the Young modulus of the thin filament from the force measurement. The thickness d of the thin filament when highly stretched is at the resolution limit of the microscope, and its measurement is critical for the Young modulus [Ythin ≈ F/(εd2)]. Our best estimate is Ythin = 1–5 × 105 Pa.

Bottom Line: Larger deformations of 10 to 100 times irreversibly and progressively transform the chromosomes into a "thin filament," parts of which display a helical organization.Chromosomes break for elongations of the order of 100 times, at which time the applied force is around 100 nanonewtons.Knowing the Young modulus allows us to estimate that the force exerted by the spindle on a newt chromosome at anaphase is roughly one nanonewton.

View Article: PubMed Central - PubMed

Affiliation: Centre National de la Recherche Scientifique (CNRS), Laboratoire de Spectrométrie Physique, Saint-Martin-d'Hères, France. bahram@coucou.ujf-grenoble.fr

ABSTRACT
The structure of mitotic chromosomes in cultured newt lung cells was investigated by a quantitative study of their deformability, using micropipettes. Metaphase chromosomes are highly extensible objects that return to their native shape after being stretched up to 10 times their normal length. Larger deformations of 10 to 100 times irreversibly and progressively transform the chromosomes into a "thin filament," parts of which display a helical organization. Chromosomes break for elongations of the order of 100 times, at which time the applied force is around 100 nanonewtons. We have also observed that as mitosis proceeds from nuclear envelope breakdown to metaphase, the native chromosomes progressively become more flexible. (The elastic Young modulus drops from 5,000 +/- 1,000 to 1,000 +/- 200 Pa.) These observations and measurements are in agreement with a helix-hierarchy model of chromosome structure. Knowing the Young modulus allows us to estimate that the force exerted by the spindle on a newt chromosome at anaphase is roughly one nanonewton.

Show MeSH