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Measurement of the mechanical properties of isolated tectorial membrane using atomic force microscopy.

ABSTRACT: The tectorial membrane (TM) is an extracellular matrix situated over the sensory cells of the cochlea. Its strategic location, together with the results of recent TM-specific mutation studies, suggests that it has an important role in the mechanism by which the cochlea transduces mechanical energy into neural excitation. A detailed characterization of TM mechanical properties is fundamental to understanding its role in cochlear mechanics. In this work, the mechanical properties of the TM are characterized in the radial and longitudinal directions using nano- and microindentation experiments conducted by using atomic force spectroscopy. We find that the stiffness in the main body region and in the spiral limbus attachment zone does not change significantly along the length of the cochlea. The main body of the TM is the softest region, whereas the spiral limbus attachment zone is stiffer, with the two areas having averaged Young's modulus values of 37 +/- 3 and 135 +/- 14 kPa, respectively. By contrast, we find that the stiffness of the TM in the region above the outer hair cells (OHCs) increases by one order of magnitude in the longitudinal direction, from 24 +/- 4 kPa in the apical region to 210 +/- 15 kPa at the basilar end of the TM. Scanning electron microscopy analysis shows differences in the collagen fiber arrangements in the OHC zone of the TM that correspond to the observed variations in mechanical properties. The longitudinal increase in TM stiffness is similar to that found for the OHC stereocilia, which supports the existence of mechanical coupling between these two structures.

SUBMITTER: Gueta R

PROVIDER: S-EPMC1595430 | biostudies-literature | 2006 Oct

REPOSITORIES: biostudies-literature

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Measurement of the mechanical properties of isolated tectorial membrane using atomic force microscopy.

Gueta Rachel R Barlam David D Shneck Roni Z RZ Rousso Itay I

Proceedings of the National Academy of Sciences of the United States of America 20060925 40

The tectorial membrane (TM) is an extracellular matrix situated over the sensory cells of the cochlea. Its strategic location, together with the results of recent TM-specific mutation studies, suggests that it has an important role in the mechanism by which the cochlea transduces mechanical energy into neural excitation. A detailed characterization of TM mechanical properties is fundamental to understanding its role in cochlear mechanics. In this work, the mechanical properties of the TM are cha ...[more]

PMID: 17001011

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Project description:Structural Biology (SB) techniques are particularly successful in solving virus structures. Taking advantage of the symmetries, a heavy averaging on the data of a large number of specimens, results in an accurate determination of the structure of the sample. However, these techniques do not provide true single molecule information of viruses in physiological conditions. To answer many fundamental questions about the quickly expanding physical virology it is important to develop techniques with the capability to reach nanometer scale resolution on both structure and physical properties of individual molecules in physiological conditions. Atomic force microscopy (AFM) fulfills these requirements providing images of individual virus particles under physiological conditions, along with the characterization of a variety of properties including local adhesion and elasticity. Using conventional AFM modes is easy to obtain molecular resolved images on flat samples, such as the purple membrane, or large viruses as the Giant Mimivirus. On the contrary, small virus particles (25-50 nm) cannot be easily imaged. In this work we present Frequency Modulation atomic force microscopy (FM-AFM) working in physiological conditions as an accurate and powerful technique to study virus particles. Our interpretation of the so called "dissipation channel" in terms of mechanical properties allows us to provide maps where the local stiffness of the virus particles are resolved with nanometer resolution. FM-AFM can be considered as a non invasive technique since, as we demonstrate in our experiments, we are able to sense forces down to 20 pN. The methodology reported here is of general interest since it can be applied to a large number of biological samples. In particular, the importance of mechanical interactions is a hot topic in different aspects of biotechnology ranging from protein folding to stem cells differentiation where conventional AFM modes are already being used.

Dataset Information

Measurement of the mechanical properties of isolated tectorial membrane using atomic force microscopy.

Publications

Measurement of the mechanical properties of isolated tectorial membrane using atomic force microscopy.

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