Biomedical subjects

B Dubertret

Publications and source records attributed to B Dubertret.

6 recordsLinked to original sources

PubMed2006

Full-field optical sectioning and three-dimensional localization of fluorescent particles using focal plane modulation.

We present a technique for imaging fluorescent particles based on the axial modulation of the objective's focal plane position. This technique provides full-field optical sectioning and can be used to localize the fluorophores in three dimensions. We describe the technique and apply it to image 200 nm diameter fluorescent beads immobilized in a gel. We show that full-field optical sectioning is obtained and that the beads are localized with a precision of 10 nm in the transverse plane and 14 nm in the axial direction.

Journal Article↗

PubMed2001

Dynamics of DNA-protein interaction deduced from in vitro DNA evolution.

We report the first experimental study of the dynamics of in vitro evolution of DNA. Starting from a random pool of DNA sequences, we used cycles of selection (binding to the lac repressor protein), amplification, and mutations to evolve to a unique DNA sequence, the lac operator. Statistical analysis of the DNA sequences obtained during the cycles of evolution shows that the DNA bases are selected at different rates. The rates of selection provide a quantitative measure of the interaction of the DNA bases with the protein during the complex formation. A model reproduces the evolution dynamics of the DNA population but cannot give the fine structure of the DNA-protein interaction.

Bacterial Proteins↗

PubMed2001

Single-mismatch detection using gold-quenched fluorescent oligonucleotides.

Here we describe a hybrid material composed of a single-stranded DNA (ssDNA) molecule, a 1.4 nm diameter gold nanoparticle, and a fluorophore that is highly quenched by the nanoparticle through a distance-dependent process. The fluorescence of this hybrid molecule increases by a factor of as much as several thousand as it binds to a complementary ssDNA. We show that this composite molecule is a different type of molecular beacon with a sensitivity enhanced up to 100-fold. In competitive hybridization assays, the ability to detect single mismatch is eightfold greater with this probe than with other molecular beacons.

Base Pair Mismatch↗

PubMed2000

Geometrical models of the renewal of the epidermis.

We give a review of the different models developed recently that describe the renewal of the epidermis. These models, based on concepts borrowed from statistical mechanics, geometry and topology, shed new light on the understanding of the organization and the dynamics of the system. We discuss in detail a topological model of the dynamics of the inner-most layer of the epidermis: the basal layer.

Biomechanical Phenomena↗

PubMed1997

The renewal of the epidermis: a topological mechanism.

Using a topological approach, we study the dynamics of the basement membrane of the mammalian epidermis when basal cells detach or divide. A theoretical characterization of the steady state of the tissue, in very good agreement with experimental data, includes for the first time the division and the disappearance of cells in a two-dimensional random cellular structure. We predict a strong correlation between the size of the attachment of basal cells to the basement membrane and their biological behavior (division or detachment). This suggests that the main factor determining the fate of basal cells, and thus controlling the renewal of the epidermis, is the cells' surface tension and adhesion.

Animals↗

PubMed1995

The stationary state of epithelia.

A tissue is a geometrical, space-filling, random cellular network; it remains in this steady state while individual cells divide. Cell division is a local, elementary topological transformation which establishes statistical equilibrium of the structure. We describe the physical conditions to maintain stationary the epidermis (of mammals or of the cucumber), in spite of the fact that cells constantly divide and die. Specifically, we study the statistical equilibrium of the basal layer, a corrugated surface filled with cells, constituting a two-dimensional topological froth. Cells divide and detach from the basal layer, and these two topological transformations are responsible for the stationary state of the epidermis. The topological froth is capable of responding rapidly and locally to external constraints, and is a good illustration of the plasticity of random cellular networks. Statistical equilibrium is controlled by entropy, both as a measure of disorder and as information, and is characterized by observable relations between average cell shapes and sizes. The technique can be applied to any random cellular network in dynamical equilibrium. Mitosis as the dominating topological transformation and the fact that the distribution of cell shapes is very narrow are the only inputs specific to biology.

Animals↗