L. Finzi

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Papers by L. Finzi

Direct observation of large chiral domains in chloroplast thylakoid membranes by differential polarization microscopy

Proceedings of the National Academy of Sciences, 1990

Direct observation of large chiral domains in chloroplast thylakoid membranes by differential pol... more

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Thermal Broadening of Gaussian Subbands of the Reaction Centre Complex of Photosystem II

Photosynthesis: from Light to Biosphere, 1995

<title>Manipulation of single-DNA molecules and measurements of their elastic properties under an optical microscope</title>

Optical Methods for Ultrasensitive Detection and Analysis: Techniques and Applications, 1991

ABSTRACT Single molecules of DNA can be visualized in solution by epifluorescence microscopy, man... more ABSTRACT Single molecules of DNA can be visualized in solution by epifluorescence microscopy, manipulated and extended by a variety of mechanical, electrical and chemical means as described previously. This has been used to design experiments under an optical microscope, in which DNA molecules are extended by a known force, to determine the elastic response of the molecules, both in the presence and absence of ethidium bromide. It is found that at lower forces (smaller extensions) the molecules behave as entropic springs with a persistence length of 500 angstroms, and that at the ionic strengths used, the intercalation of ethidium bromide does not alter this persistence length, while it appears to elongate the contour length of the molecule by about 30%.

Design and application of a computer‐controlled confocal scanning differential polarization microscope

Review of Scientific Instruments, 1988

Based on the confocal scanning and differential polarization imaging technique, a computer-contro... more Based on the confocal scanning and differential polarization imaging technique, a computer-controlled confocal scanning differential polarization microscope has been built. This system possesses extensive image processing capability that provides digitized regular and/or differential polarization images. This microscope combines the advantages of the confocal design and the extended electronic sensitivity of polarization modulated instrumentation to achieve the measurement of an anisotropy

Physiological Levels of Salt and Polyamines Favor Writhe and Limit Twist in DNA

Macromolecules, 2012

Quantitative analysis of single molecule experiments show that adding either of two natural polya... more Quantitative analysis of single molecule experiments show that adding either of two natural polyamines, spermine or spermidine, produced more compact plectonemes in DNA in physiological concentrations of monovalent salt. They also promoted plectoneme formation at lower values of torsion in measurements of extension versus twist. Quantifying changes in the plectonemic DNA using some results from simple rod models suggested that exposure to polyamines reduced the radii and increased the densities of plectonemes. Thus, polyamines may limit the twist density by favoring writhe which maintains the B-form. Although polymerases may significantly stretch the double helix, denature DNA, and produce twist instead of writhe, natural polyamines stabilize base-pairing, limit twist to maintain the B-form, and promote supercoiling, which is conducive to replication and transcription and essential for DNA packaging.

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Probing DNA Stiffness with Magnetic Tweezers

Biophysical Journal, 2011

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The Effect of HU Protein on Lac-Repressor-Mediated DNA Looping

Biophysical Journal, 2015

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Multiplexed, Tethered Particle Microscopy for Studies of DNA-Enzyme Dynamics

Methods in enzymology, 2017

DNA is the carrier of genetic information and, as such, is at the center of most essential cellul... more DNA is the carrier of genetic information and, as such, is at the center of most essential cellular processes. To regulate its physiological function, specific proteins and motor enzymes constantly change conformational states with well-controlled dynamics. Twenty-five years ago, Schafer, Gelles, Sheetz, and Landick employed the tethered particle motion (TPM) technique for the first time to study transcription by RNA polymerase at the single-molecule level. TPM has since then remained one of the simplest, most affordable, and yet incisive single-molecule techniques available. It is an in vitro technique which allows investigation of DNA-protein interactions that change the effective length of a DNA tether. In this chapter, we will describe a recent strategy to multiplex TPM which substantially increases the throughput of TPM experiments, as well as a simulation to estimate the time resolution of experiments, such as transcriptional elongation assays, in which lengthy time averaging ...

Calibration of optical tweezers with differential interference contrast signals

Review of Scientific Instruments, 2002

A comparison of different calibration methods for optical tweezers with the differential interfer... more A comparison of different calibration methods for optical tweezers with the differential interference contrast (DIC) technique was performed to establish the uses and the advantages of each method. A detailed experimental and theoretical analysis of each method was performed with emphasis on the anisotropy involved in the DIC technique and the noise components in the detection. Finally, a time of

A Combined Single Molecule FRET/Magnetic Tweezers Instrument to Calibrate Molecular Tension - Based Fluorescence Probes

Biophysical Journal, 2014

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DNA supercoiling: a regulatory signal for the λ repressor

Proceedings of the National Academy of Sciences of the United States of America, Jan 28, 2014

Topoisomerases, polymerases, and the chirality introduced by the binding of histones or nucleoid-... more Topoisomerases, polymerases, and the chirality introduced by the binding of histones or nucleoid-associated proteins affect DNA supercoiling in vivo. However, supercoiling is not just a by-product of DNA metabolism. Supercoiling is an indicator of cell health, it modifies the accessibility of chromatin, and coordinates the transcription of genes. This suggests that regulatory, protein-mediated loops in DNA may sense supercoiling of the genome in which they are embedded. The λ repressor (CI) maintains the quiescent (lysogenic) transcriptome of bacteriophage λ in infected Escherichia coli. CI-mediated looping prevents overexpression of the repressor protein to preserve sensitivity to conditions that trigger virulence (lysis). Experiments were performed to assess how well the CI-mediated DNA loop traps superhelicity and determine whether supercoiling enhances CI-mediated DNA looping. CI oligomers partitioned plasmids into topological domains and prevented the passage of supercoiling be...

format_quoteλ repressor efficiently traps supercoils in a stochastic process, highlighting dynamic supercoil behavior in plasmid systems.format_quote

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Single-molecule kinetic studies on DNA transcription and transcriptional regulation

Biophysical journal, 1995

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Single molecule detection and manipulation: first results at LENS

Influence of stretching and twisting on LacR-Dna complex formation

Lambda genetic switch sensitivity depends on complex looping kinetics driven by nonspecific binding

Chapter Nine-Quantitative Analysis of DNA-Looping Kinetics from Tethered Particle Motion Experiments

Atomic force microscopy study ofDN A deposited onpoly L-ornithine-coated mica