Mechanical Forces in the Biological World

Fygenson, Deborah Kuchnir; Bourdieu, Laurent; Faucheux, Luc P.; Libchaber, Albert

doi:10.1007/978-94-009-1722-4_6

Cited by 2 publications

(2 citation statements)

References 36 publications

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“…Microtubules. Another method of deforming lipid bilayers is the polymerization of cytoskeletal proteins, such as tubulin, inside the vesicle. , Figure shows a DIC micrograph of a 2:1 DMPC/DOPS vesicle in which the polymerization of tubulin into a microtubule has stretched the membrane. We observed that when we excited the UV-absorbing fluorophore 6-(9-anthroyloxy)stearic acid, used to label the fluid regions of the vesicle, the microtubules depolymerized faster than our ability to measure them.…”

Section: Resultsmentioning

confidence: 99%

Controlling and Measuring the Interdependence of Local Properties in Biomembranes

et al. 2003

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Local composition, structure, morphology, and phase are interrelated in lipid bilayer membranes. This work describes proofs-of-concept for methods that may be used and combined to modulate, to measure, and to probe the local structure of model membranes through control of membrane curvature in liposomes. These studies are performed using combinations of simultaneous two-color widefield fluorescence imaging, three-dimensional rendering of vesicle domains, and manipulation of the vesicle morphology via micropipet aspiration and the polymerization of cytoskeletal elements inside the membrane. Additionally, we report an electroformation method for preparing unilamellar lipid vesicles that allows hydration of membranes in physiological buffer conditions and formation of multicomponent/multiphase vesicles.

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Section: Resultsmentioning

confidence: 99%

Controlling and Measuring the Interdependence of Local Properties in Biomembranes

et al. 2003

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“…Previous studies have demonstrated that incorporating actin and tubulin into liposomes and inducing these proteins to polymerize results in a morphological change in the liposome; a protrusion of the membrane is observed at one or both ends of the protein polymer (12)(13)(14)(15). The asymmetry occurs frequently, when the MT wraps around within the encapsulating liposome (16).…”

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confidence: 99%

A physical model of axonal damage due to oxidative stress

Counterman

D'Onofrio²,

Andrews³

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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Oxidative damage is implicated in the pathogenesis of neurodegenerative disorders, including Alzheimer's, Parkinson's, and Huntington's diseases, and in normal aging. Here, we model oxidative stress in neurons using photogenerated radicals in a simplified membrane-encapsulated microtubule system. Using fluorescence and differential interference contrast microscopies, we monitor photochemically induced microtubule breakdown on the supported region of membrane in encapsulating synthetic liposomes as a function of lipid composition and environment. Degradation of vesicle-encapsulated microtubules is caused by attack from free radicals formed upon UV excitation of the lipid-soluble fluorescent probe, 6-(9-anthroyloxy)stearic acid. Probe concentration was typically limited to a regime in which microtubule degradation was slow, and microtubule degradation was monitored by changes in the observed protrusion of the membrane surface. The kinetics of microtubule degradation are influenced by lipid saturation level, fluorescent probe concentration, and the presence of free-radical scavengers. This system is sufficient to reproduce some degenerative morphologies found in vivo.O xidative modifications to proteins in neurons have been implicated in a number of degenerative disorders and have become a controversial topic in elucidating the progression of Parkinson's, Huntington's, and Alzheimer's diseases (1-7). Microtubules (MTs) are key cytoskeletal proteins in nerve cell axons. These protein polymers are responsible for many disparate functions of cells, including structural support and imparting polarity, and they are involved in motility and transport of intracellular cargo (8). Fundamental studies of MTs in vivo are complicated by the presence of the full complement of biomolecules that are required for cell survival. Thus, a substantial effort has been devoted to characterizing MT dynamics in vitro, and these studies have led to increased understanding of issues such as dynamic instability (9) and the involvement of molecular motors in producing motility (10). To mimic the confinement of a bilayer, MT assemblies (asters) have previously been examined in rigid, microfabricated wells (11). The drawback of such studies is that interactions between MTs and components of the elastic lipid membrane are neglected. It is important to be able to isolate and to quantify specific factors that impact the structural integrity of the cytoskeleton, while maintaining a simplified cell-like environment.Toward this aim, we have developed a minimal physical system with which to investigate the effects of oxidative stress on the cytoskeleton. Previous studies have demonstrated that incorporating actin and tubulin into liposomes and inducing these proteins to polymerize results in a morphological change in the liposome; a protrusion of the membrane is observed at one or both ends of the protein polymer (12-15). The asymmetry occurs frequently, when the MT wraps around within the encapsulating liposome (16). Here, we employ the membrane as a...

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Mechanical Forces in the Biological World

Cited by 2 publications

References 36 publications

Controlling and Measuring the Interdependence of Local Properties in Biomembranes

Controlling and Measuring the Interdependence of Local Properties in Biomembranes

A physical model of axonal damage due to oxidative stress

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