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Dive into the research topics where Sattar Taheri-Araghi is active.

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Featured researches published by Sattar Taheri-Araghi.


Trends in Microbiology | 2015

Cell-size maintenance: universal strategy revealed

Suckjoon Jun; Sattar Taheri-Araghi

How cells maintain a stable size has fascinated scientists since the beginning of modern biology, but has remained largely mysterious. Recently, however, the ability to analyze single bacteria in real time has provided new, important quantitative insights into this long-standing question in cell biology.


Annual review of biophysics | 2015

Single-Cell Physiology.

Sattar Taheri-Araghi; Steven D. Brown; John T. Sauls; Dustin B. McIntosh; Suckjoon Jun

Single-cell techniques have a long history of unveiling fundamental paradigms in biology. Recent improvements in the throughput, resolution, and availability of microfluidics, computational power, and genetically encoded fluorescence have led to a modern renaissance in microbial physiology. This resurgence in research activity has offered new perspectives on physiological processes such as growth, cell cycle, and cell size of model organisms such as Escherichia coli. We expect these single-cell techniques, coupled with the molecular revolution of biologys recent half-century, to continue illuminating unforeseen processes and patterns in microorganisms, the bedrock of biological science. In this article we review major open questions in single-cell physiology, provide a brief introduction to the techniques for scientists of diverse backgrounds, and highlight some pervasive issues and their solutions.


Frontiers in Microbiology | 2015

Self-Consistent Examination of Donachie's Constant Initiation Size at the Single-Cell Level

Sattar Taheri-Araghi

How growth, the cell cycle, and cell size are coordinated is a fundamental question in biology. Recently, we and others have shown that bacterial cells grow by a constant added size per generation, irrespective of the birth size, to maintain size homeostasis. This “adder” principle raises a question as to when during the cell cycle size control is imposed. Inspired by this question, we examined our single-cell data for initiation size by employing a self-consistency approach originally used by Donachie. Specifically, we assumed that individual cells divide after constant C + D minutes have elapsed since initiation, independent of the growth rate. By applying this assumption to the cell length vs. time trajectories from individual cells, we were able to extract theoretical probability distribution functions for initiation size for all growth conditions. We found that the probability of replication initiation shows peaks whenever the cell size is a multiple of a constant unit size, consistent with the Donachies original analysis at the population level. Our self-consistent examination of the single-cell data made experimentally testable predictions, e.g., two consecutive replication cycles can be initiated during a single cell-division cycle.


Langmuir | 2015

How Cell Concentrations Are Implicated in Cell Selectivity of Antimicrobial Peptides.

Azadeh Bagheri; Sattar Taheri-Araghi; Bae-Yeun Ha

Antimicrobial peptides (AMPs) are known to selectively bind to and kill microbes over host cells. Contrary to a conventional view, there is now evidence that AMPs cell selectivity varies with cell densities and is not uniquely determined. Using a coarse-grained model, we study how the cell selectivity of membrane-lytic AMPs, defined as the ratio between their minimum hemolytic (MHC) and minimum inhibitory concentrations (MIC), depends on cell densities or on the way it is measured. A general picture emerging from our study is that the selectivity better captures peptides intrinsic properties at low cell densities. The selectivity, however, decreases and becomes less intrinsic as the cell density increases, as long as it is chosen to be the same for both types of cells. Importantly, our results show that the selectivity can be excessively overestimated if higher host cell concentrations are used; in contrast, it becomes mistakenly small if measured for a mixture of both types of cells, even with similar choices of cell densities (i.e., higher host cell densities). Our approach can be used as a fitting model for relating the intrinsic selectivity to the apparent (cell-density-dependent) one.


Langmuir | 2010

Electrostatic Bending of Lipid Membranes: How Are Lipid and Electrostatic Properties Interrelated?

Sattar Taheri-Araghi; Bae-Yeun Ha

Electrostatic modification of lipid headgroups and its effect on membrane curvature are not only relevant in a variety of contexts such as cell shape transformation and membrane tubulation but also are intriguingly implicated in membrane functions. For instance, the gating (open vs closed) properties of mechanosensitive channels can be influenced by membrane curvature and ion valence. However, a full theoretical description of membrane electrostatics is still lacking; in the past, membrane bending has often been considered under a few assumptions about how bending modifies lipid arrangements and surface charges. Here, we present a unified theoretical approach to spontaneous membrane curvature, C(0), in which lipid properties (e.g., packing shape) and electrostatic effects are self-consistently integrated. For the description of electrostatic interactions, especially between a lipid charge and a divalent counterion, we implement the Poisson-Boltzmann (PB) approach by incorporation of finite ionic sizes, so as to capture both lateral and transverse charge correlations on the membrane surface. Our results show that C(0) is sensitive to the way lipid rearrangements and divalent counterions are modeled. Interestingly, it can change its sign in the presence of divalent counterions, thus stabilizing reverse hexagonal (H(II)) phases. Our results show how electrostatic modification of headgroups influences the preferred structure of lipid aggregates (inverted micelles vs bilayers).


Current Biology | 2015

Cell-size control and homeostasis in bacteria

Sattar Taheri-Araghi; Serena Bradde; John T. Sauls; Norbert S. Hill; Petra Anne Levin; Johan Paulsson; Massimo Vergassola; Suckjoon Jun


Physical Review Letters | 2007

Physical basis for membrane-charge selectivity of cationic antimicrobial peptides.

Sattar Taheri-Araghi; Bae-Yeun Ha


Physical Review E | 2005

Charge renormalization and inversion of a highly charged lipid bilayer: effects of dielectric discontinuities and charge correlations.

Sattar Taheri-Araghi; Bae-Yeun Ha


Biophysical Journal | 2010

Cationic antimicrobial peptides: a physical basis for their selective membrane-disrupting activity

Bae-Yeun Ha; Sattar Taheri-Araghi


Bulletin of the American Physical Society | 2007

Physical basis for membrane-charge selectivity of cationic antimicrobial peptides

Bae-Yeun Ha; Sattar Taheri-Araghi

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Bae-Yeun Ha

University of Waterloo

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Suckjoon Jun

University of California

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John T. Sauls

University of California

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Paul Talledo

California State University

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Mehdi Snoussi

California State University

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Norbert S. Hill

Washington University in St. Louis

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Petra Anne Levin

Washington University in St. Louis

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