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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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Young modulus measurements:  deformation of the chromosome inside the  pipette under aspiration. Deformation is  measured as a function of the pressure difference (ΔP) between inside the pipette  and the culture medium. From top to bottom: (a) ΔP = 0; (b) ΔP = 44 Pa. Arrows indicate the tip of the chromosome. Bar, 5 μm.
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Figure 7: Young modulus measurements: deformation of the chromosome inside the pipette under aspiration. Deformation is measured as a function of the pressure difference (ΔP) between inside the pipette and the culture medium. From top to bottom: (a) ΔP = 0; (b) ΔP = 44 Pa. Arrows indicate the tip of the chromosome. Bar, 5 μm.

Mentions: We now return to the elasticity regime where the deformations are relatively small (ε < 2). Using aspiration of chromosomes, we measured the deformation as a function of pressure inside the pipette (Fig. 7). Results for 10 metaphase chromosomes are shown in Fig. 8; at metaphase Ymeta = 1,000 ± 200 Pa. As mentioned above, the Poisson ratio of metaphase chromosomes was measured to be 0.20 ± 0.05. Thus, the metaphase chromosome has a Young modulus about two orders of magnitude less than that of the thin filament.


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

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

Young modulus measurements:  deformation of the chromosome inside the  pipette under aspiration. Deformation is  measured as a function of the pressure difference (ΔP) between inside the pipette  and the culture medium. From top to bottom: (a) ΔP = 0; (b) ΔP = 44 Pa. Arrows indicate the tip of the chromosome. Bar, 5 μm.
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Related In: Results  -  Collection

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

Figure 7: Young modulus measurements: deformation of the chromosome inside the pipette under aspiration. Deformation is measured as a function of the pressure difference (ΔP) between inside the pipette and the culture medium. From top to bottom: (a) ΔP = 0; (b) ΔP = 44 Pa. Arrows indicate the tip of the chromosome. Bar, 5 μm.
Mentions: We now return to the elasticity regime where the deformations are relatively small (ε < 2). Using aspiration of chromosomes, we measured the deformation as a function of pressure inside the pipette (Fig. 7). Results for 10 metaphase chromosomes are shown in Fig. 8; at metaphase Ymeta = 1,000 ± 200 Pa. As mentioned above, the Poisson ratio of metaphase chromosomes was measured to be 0.20 ± 0.05. Thus, the metaphase chromosome has a Young modulus about two orders of magnitude less than that of the thin filament.

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
Related in: MedlinePlus