Biomedical subjects
Publications and source records attributed to D Bensimon.
Recent technical developments that allow precise force measurements on single molecules, together with numerical simulations of biomolecules under stress, offer new insight into how stress affects molecular interactions, and how large the force developed by a travelling enzyme such as RNA polymerase can be.
Single linear DNA molecules were bound at multiple sites at one extremity to a treated glass cover slip and at the other to a magnetic bead. The DNA was therefore torsionally constrained. A magnetic field was used to rotate the beads and thus to coil and pull the DNA. The stretching force was determined by analysis of the Brownian fluctuations of the bead. Here the elastic behavior of individual lambda DNA molecules over- and underwound by up to 500 turns was studied. A sharp transition was discovered from a low to a high extension state at a force of approximately 0.45 piconewtons for underwound molecules and at a force of approximately 3 piconewtons for overwound ones. These transitions, probably reflecting the formation of alternative structures in stretched coiled DNA molecules, might be relevant for DNA transcription and replication.
Explore the source record for details and available documents.
In a process called "molecular combining," DNA molecules attached at one end to a solid surface were extended and aligned by a receding air-water interface and left to dry on the surface. Molecular combing was observed to extend the length of the bacteriophage lambda DNA molecule to 21.5 +/- 0.5 micrometers (unextended length, 16.2 micrometers). With the combing process, it was possible to (i) extend a chromosomal Escherichia coli DNA fragment (10(6) base pairs) and (ii) detect a minute quantity of DNA (10(3) molecules). These results open the way for a faster physical mapping of the genome and for the detection of small quantities of target DNA from a population of molecules.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
A stochastic model is presented to describe gene regulation during growth conditions (non-steady-state), with an emphasis on the distribution of gene activation times. A non-Poissonian distribution, with a smaller variability than in steady-state, is obtained when gene activation by the regulatory protein(s) occurs before the protein(s) reach their saturation concentration. The model is applied to the regulation of initiation of chromosomal replication in Escherichia coli. The rate of initiation is shown to depend linearly on the concentration of the initiator molecule, DnaA, in good agreement with recently published data. It is suggested that the variability of initiation times could be growth rate dependent, with slow growing cells being more synchronized than fast growing ones.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.