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Dive into the research topics where Arthur La Porta is active.

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Featured researches published by Arthur La Porta.


Proceedings of the National Academy of Sciences of the United States of America | 2002

Single molecule analysis of RNA polymerase elongation reveals uniform kinetic behavior

Karen Adelman; Arthur La Porta; Thomas J. Santangelo; John T. Lis; Jeffrey W. Roberts; Michelle D. Wang

By using single-molecule measurements, we demonstrate that the elongation kinetics of individual Escherichia coli RNA polymerase molecules are remarkably homogeneous. We find no evidence of distinct elongation states among RNA polymerases. Instead, the observed heterogeneity in transcription rates results from statistical variation in the frequency and duration of pausing. When transcribing a gene without strong pause sites, RNA polymerase molecules display transient pauses that are distributed randomly in both time and distance. Transitions between the active elongation mode and the paused state are instantaneous within the resolution of our measurements (<1 s). This elongation behavior is compared with that of a mutant RNA polymerase that pauses more frequently and elongates more slowly than wild type.


Review of Scientific Instruments | 2001

A silicon strip detector system for high resolution particle tracking in turbulence

Greg Voth; Arthur La Porta; Alice M. Crawford; Eberhard Bodenschatz; Curt Ward; J. P. Alexander

We describe a high speed imaging system that is used to track tracer particles in highly turbulent flows. The system uses silicon strip detectors designed for high energy physics experiments and is capable of reading two detectors at a frame rate of 70 kHz. Each detector contains 512 strips and measures a one-dimensional projection of the light striking it. The position measurements from this system have a dynamic range of 6400:1. Extensions to higher frame rates and more detectors are possible. We describe the detectors, readout system, supporting systems, and give an evaluation of the measurement accuracy.


Physical Review E | 2013

Optimal reconstruction of the folding landscape using differential energy surface analysis

Arthur La Porta; Natalia A. Denesyuk; Michel de Messieres

In experiments and in simulations, the free energy of a state of a system can be determined from the probability that the state is occupied. However, it is often necessary to impose a biasing potential on the system so that high energy states are sampled with sufficient frequency. The unbiased energy is typically obtained from the data using the weighted histogram analysis method (WHAM). Here we present differential energy surface analysis (DESA), in which the gradient of the energy surface, dE/dx, is extracted from data taken with a series of harmonic biasing potentials. It is shown that DESA produces a maximum likelihood estimate of the folding landscape gradient. DESA is demonstrated by analyzing data from a simulated system as well as data from a single-molecule unfolding experiment in which the end-to-end distance of a DNA hairpin is measured. It is shown that the energy surface obtained from DESA is indistinguishable from the energy surface obtained when WHAM is applied to the same data. Two criteria are defined which indicate whether the DESA results are self-consistent. It is found that these criteria can detect a situation where the energy is not a single-valued function of the measured reaction coordinate. The criteria were found to be satisfied for the experimental data analyzed, confirming that end-to-end distance is a good reaction coordinate for the experimental system. The combination of DESA and the optical trap assay in which a structure is disrupted under harmonic constraint facilitates an extremely accurate measurement of the folding energy surface.


Physical Review Letters | 2004

Optical Torque Wrench: Angular Trapping, Rotation, and Torque Detection of Quartz Microparticles

Arthur La Porta; Michelle D. Wang


Molecular Cell | 2004

Molecular Mechanism of Transcription Inhibition by Peptide Antibiotic Microcin J25

Karen Adelman; Julia Yuzenkova; Arthur La Porta; Nikolay Zenkin; Jookyung Lee; John T. Lis; Sergei Borukhov; Michelle D. Wang; Konstantin Severinov


Physical Review Letters | 2012

Single-molecule study of G-quadruplex disruption using dynamic force spectroscopy.

Michel de Messieres; Jen-Chien Chang; Barbara Brawn-Cinani; Arthur La Porta


Archive | 2001

Effect of Dilute Polymer Solutions on Dissipation Range Quantities in Bulk Turbulence

Alice M. Crawford; Arthur La Porta; Eberhard Bodenschatz; James C. Alexander


Biophysics | 2013

1P117 Single Nucleosome under Tension and Torsion(28. Bioengineering,Poster)

Jen-Chien Chang; Michel de Messieres; Arthur La Porta


Biophysical Journal | 2012

Single-Molecule Optical Trap Study of Human CCR5 mRNA Structure

Michel de Messieres; Jen-Chien Chang; Ashton T. Belew; Arturas Meskauskas; Jonathan D. Dinman; Arthur La Porta


Archive | 2001

Modification of Turbulence by Polymers

Arthur La Porta; Alice M. Crawford; Gregory A. Voth; Eberhard Bodenschatz; James C. Alexander

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Michel de Messieres

National Institutes of Health

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Karen Adelman

National Institutes of Health

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