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1.
Phys Rev Lett ; 123(20): 208103, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31809067

RESUMO

Within a living cell, the myriad of proteins that bind DNA introduce heterogeneously spaced kinks into an otherwise semiflexible DNA double helix. To investigate the effects of heterogeneous nucleosome binding on chromatin organization, we extend the wormlike chain model to include statistically spaced, rigid kinks. On timescales where nucleosome positions are fixed, we find that the probability of chromatin loop formation can vary by up to six orders of magnitude between two sets of nucleosome positions drawn from the same distribution. On longer timescales, we show that continuous rerandomization due to nucleosome turnover results in chromatin tracing out an effective WLC with a dramatically smaller Kuhn length than bare DNA. Together, these observations demonstrate that nucleosome spacing acts as the primary source of the structural heterogeneity that dominates local and global chromatin organization.


Assuntos
Cromatina/química , Cromatina/metabolismo , Modelos Biológicos , Cromatina/genética , DNA/química , DNA/genética , DNA/metabolismo , Calefação , Humanos , Modelos Químicos , Modelos Genéticos , Modelos Moleculares , Nucleossomos/química , Nucleossomos/genética , Nucleossomos/metabolismo
2.
J Chem Phys ; 151(23): 230902, 2019 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-31864250

RESUMO

Polymeric materials are ubiquitous in our daily lives, and they play a significant role in many technological applications. The general predictive framework for the behavior of soft polymeric materials can be divided into two vastly different approaches. Highly coarse-grained models capture polymers as flexible random walks, resulting in general predictions of physical behavior but lack chemical specificity. Detailed atomistic models contain molecular detail but are frequently computationally intractable for exhaustive materials discovery. In this perspective, we discuss theoretical models that successfully bridge these disparate approaches. We identify intermediate-scale physical models that are amenable to theoretical analyses while containing sufficient granular detail to capture a range of molecular-level processes. We then provide several problems in materials engineering and biological physics where multiscale physics is essential in their behavior.


Assuntos
DNA/química , Polímeros/química , Humanos , Modelos Moleculares
3.
Nat Chem Biol ; 15(4): 401-409, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30858596

RESUMO

We describe three optical tags, ArrayG, ArrayD and ArrayG/N, for intracellular tracking of single molecules over milliseconds to hours. ArrayG is a fluorogenic tag composed of a green fluorescent protein-nanobody array and monomeric wild-type green fluorescent protein binders that are initially dim but brighten ~26-fold on binding with the array. By balancing the rates of binder production, photobleaching and stochastic binder exchange, we achieve temporally unlimited tracking of single molecules. High-speed tracking of ArrayG-tagged kinesins and integrins for thousands of frames reveals novel dynamical features. Tracking of single histones at 0.5 Hz for >1 hour with the import competent ArrayG/N tag shows that chromosomal loci behave as Rouse polymers with visco-elastic memory and exhibit a non-Gaussian displacement distribution. ArrayD, based on a dihydrofolate reductase nanobody array and dihydrofolate reductase-fluorophore binder, enables dual-color imaging. The arrays combine brightness, fluorogenicity, fluorescence replenishment and extended fluorophore choice, opening new avenues for tracking single molecules in living cells.


Assuntos
Corantes Fluorescentes/química , Microscopia de Fluorescência/métodos , Imagem Individual de Molécula/métodos , Linhagem Celular , Cor , Corantes Fluorescentes/síntese química , Proteínas de Fluorescência Verde , Células HeLa , Humanos , Anticorpos de Domínio Único
4.
Proc Natl Acad Sci U S A ; 115(50): 12739-12744, 2018 12 11.
Artigo em Inglês | MEDLINE | ID: mdl-30478042

RESUMO

We use a chromosome-scale simulation to show that the preferential binding of heterochromatin protein 1 (HP1) to regions high in histone methylation (specifically H3K9me3) results in phase segregation and reproduces features of the observed Hi-C contact map. Specifically, we perform Monte Carlo simulations with one computational bead per nucleosome and an H3K9me3 pattern based on published ChIP-seq signals. We implement a binding model in which HP1 preferentially binds to trimethylated histone tails and then oligomerizes to bridge together nucleosomes. We observe a phase reminiscent of heterochromatin-dense and high in H3K9me3-and another reminiscent of euchromatin-less dense and lacking H3K9me3. This segregation results in a plaid contact probability map that matches the general shape and position of published Hi-C data. Analysis suggests that a roughly 20-kb segment of H3K9me3 enrichment is required to drive segregation into the heterochromatic phase.


Assuntos
Cromatina/genética , Segregação de Cromossomos/genética , Epigênese Genética/genética , Proteínas Cromossômicas não Histona/genética , Eucromatina/genética , Heterocromatina/genética , Histonas/genética , Humanos , Método de Monte Carlo , Nucleossomos/genética , Probabilidade
5.
Phys Rev Lett ; 121(14): 148001, 2018 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-30339454

RESUMO

Biological systems are equipped with a diverse repertoire of proteins that regulate DNA topology with precision that is beyond the reach of conventional polymer chemistry. Here, we harness the unique properties of topoisomerases to synthesize Olympic hydrogels formed by topologically interlinked DNA rings. Using dynamic light scattering microrheology to probe the viscoelasticity of DNA topological networks, we show that topoisomerase II enables the facile preparation of active, adenosine triphosphate-driven Olympic hydrogels that can be switched between liquid and solid states on demand. Our results provide a versatile system for engineering switchable topological materials that may be broadly leveraged to model the impact of topological constraints and active dynamics in the physics of chromosomes and other polymeric materials.


Assuntos
DNA Topoisomerases Tipo II/química , DNA/química , Hidrogéis/síntese química , Proteínas de Ligação a Poli-ADP-Ribose/química , DNA/síntese química , Hidrogéis/química , Conformação Molecular , Plasmídeos/química
6.
Phys Rev E ; 97(6-1): 062410, 2018 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30011517

RESUMO

Despite the innate complexity of the cell, emergent scale-invariant behavior is observed in many biological systems. We investigate one example of this phenomenon: the dynamics of large complexes in the bacterial cytoplasm. The observed dynamics of these complexes is scale invariant in three measures of dynamics: mean-squared displacement (MSD), velocity autocorrelation function, and the step-size distribution. To investigate the physical mechanism for this emergent scale invariance, we explore minimal models in which mobility is modeled as diffusion on a rough free-energy landscape in one dimension. We discover that all three scale-invariant characteristics emerge generically in the strong disorder limit. (Strong disorder is defined by the divergence of the ensemble-averaged hop time between lattice sites.) In particular, we demonstrate how the scale invariance of the relative step-size distribution can be understood from the perspective of extreme-value theory in statistics (EVT). We show that the Gumbel scale parameter is simply related to the MSD scaling parameter. The EVT mechanism of scale invariance is expected to be generic to strongly disordered systems and therefore a powerful tool for the analysis of other systems in biology and beyond.


Assuntos
Modelos Biológicos , Simulação por Computador , Citoplasma/metabolismo , Difusão , Escherichia coli , Proteínas de Fluorescência Verde/metabolismo , Modelos Estatísticos , RNA Mensageiro/metabolismo
7.
Phys Rev Lett ; 120(6): 067802, 2018 Feb 09.
Artigo em Inglês | MEDLINE | ID: mdl-29481283

RESUMO

The order-disorder phase transition and the associated phase diagrams of semiflexible diblock copolymers are investigated using the wormlike chain model, incorporating concentration fluctuations. The free energy up to quartic order in concentration fluctuations is developed with chain-rigidity-dependent coefficients, evaluated using our exact results for the wormlike chain model, and a one-loop renormalization treatment is used to account for fluctuation effects. The chain length N and the monomer aspect ratio α directly control the strength of immiscibility (defined by the Flory-Huggins parameter χ) at the order-disorder transition and the resulting microstructures at different chemical compositions f_{A}. When monomers are infinitely thin (i.e., large aspect ratio α), the finite chain length N lowers the χN at the phase transition. However, fluctuation effects become important when chains have a finite radius, and a decrease in the chain length N elevates the χN at the phase transition. Phase diagrams of diblock copolymers over a wide range of N and α are calculated based on our fluctuation theory. We find that both finite N and α enhance the stability of the lamellar phase above the order-disorder transition. Our results demonstrate that polymer semiflexibility plays a dramatic role in the phase behavior, even for large chain lengths (e.g., N≈100).

8.
Soft Matter ; 13(15): 2760-2772, 2017 Apr 12.
Artigo em Inglês | MEDLINE | ID: mdl-28338151

RESUMO

Copolymers play an important role in a range of soft-materials applications and biological phenomena. Prevalent works on block copolymer phase behavior use flexible chain models and incorporate interactions using a mean-field approximation. However, when phase separation takes place on length scales comparable to a few monomers, the structural rigidity of the monomers becomes important. In addition, concentration fluctuations become significant at short length scales, rendering the mean-field approximation invalid. In this work, we use simulation to address the role of finite monomer rigidity and concentration fluctuations in microphase segregation of random copolymers. Using a field-theoretic Monte-Carlo simulation of semiflexible polymers with random chemical sequences, we generate phase diagrams for random copolymers. We find that the melt morphology of random copolymers strongly depends on chain flexibility and chemical sequence correlation. Chemically anti-correlated copolymers undergo first-order phase transitions to local lamellar structures. With increasing degree of chemical correlation, this first-order phase transition is softened, and melts form microphases with irregular shaped domains. Our simulations in the homogeneous phase exhibit agreement with the density-density correlation from mean-field theory. However, conditions near a phase transition result in deviations between simulation and mean-field theory for the density-density correlation and the critical wavemode. Chain rigidity and sequence randomness lead to frustration in the segregated phase, introducing heterogeneity in the resulting morphologies.

9.
Biophys J ; 112(3): 532-542, 2017 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-28088300

RESUMO

The cellular cytoplasm is a complex, heterogeneous environment (both spatially and temporally) that exhibits viscoelastic behavior. To further develop our quantitative insight into cellular transport, we analyze data sets of mRNA molecules fluorescently labeled with MS2-GFP tracked in real time in live Escherichia coli and Saccharomyces cerevisiae cells. As shown previously, these RNA-protein particles exhibit subdiffusive behavior that is viscoelastic in its origin. Examining the ensemble of particle displacements reveals a Laplace distribution at all observed timescales rather than the Gaussian distribution predicted by the central limit theorem. This ensemble non-Gaussian behavior is caused by a combination of an exponential distribution in the time-averaged diffusivities and non-Gaussian behavior of individual trajectories. We show that the non-Gaussian behavior is a consequence of significant heterogeneity between trajectories and dynamic heterogeneity along single trajectories. Informed by theory and simulation, our work provides an in-depth analysis of the complex diffusive behavior of RNA-protein particles in live cells.


Assuntos
Citoplasma/metabolismo , RNA Bacteriano/metabolismo , RNA Fúngico/metabolismo , Proteínas Recombinantes de Fusão/metabolismo , Difusão , Escherichia coli/citologia , Modelos Biológicos , Movimento , RNA Mensageiro/metabolismo , Saccharomyces cerevisiae/citologia
10.
ACS Cent Sci ; 3(12): 1294-1303, 2017 Dec 27.
Artigo em Inglês | MEDLINE | ID: mdl-29296670

RESUMO

The development of experimental techniques capable of probing the viscoelasticity of soft materials over a broad range of time scales is essential to uncovering the physics that governs their behavior. In this work, we develop a microrheology technique that requires only 12 µL of sample and is capable of resolving dynamic behavior ranging in time scales from 10-6 to 10 s. Our approach, based on dynamic light scattering in the single-scattering limit, enables the study of polymer gels and other soft materials over a vastly larger hierarchy of time scales than macrorheology measurements. Our technique captures the viscoelastic modulus of polymer hydrogels with a broad range of stiffnesses from 10 to 104 Pa. We harness these capabilities to capture hierarchical molecular relaxations in DNA and to study the rheology of precious biological materials that are impractical for macrorheology measurements, including decellularized extracellular matrices and intestinal mucus. The use of a commercially available benchtop setup that is already available to a variety of soft matter researchers renders microrheology measurements accessible to a broader range of users than existing techniques, with the potential to reveal the physics that underlies complex polymer hydrogels and biological materials.

11.
Polymers (Basel) ; 9(3)2017 Mar 11.
Artigo em Inglês | MEDLINE | ID: mdl-30970780

RESUMO

Instability and structural transitions arise in many important problems involving dynamics at molecular length scales. Buckling of an elastic rod under a compressive load offers a useful general picture of such a transition. However, the existing theoretical description of buckling is applicable in the load response of macroscopic structures, only when fluctuations can be neglected, whereas membranes, polymer brushes, filaments, and macromolecular chains undergo considerable Brownian fluctuations. We analyze here the buckling of a fluctuating semiflexible polymer experiencing a compressive load. Previous works rely on approximations to the polymer statistics, resulting in a range of predictions for the buckling transition that disagree on whether fluctuations elevate or depress the critical buckling force. In contrast, our theory exploits exact results for the statistical behavior of the worm-like chain model yielding unambiguous predictions about the buckling conditions and nature of the buckling transition. We find that a fluctuating polymer under compressive load requires a larger force to buckle than an elastic rod in the absence of fluctuations. The nature of the buckling transition exhibits a marked change from being distinctly second order in the absence of fluctuations to being a more gradual, compliant transition in the presence of fluctuations. We analyze the thermodynamic contributions throughout the buckling transition to demonstrate that the chain entropy favors the extended state over the buckled state, providing a thermodynamic justification of the elevated buckling force.

12.
Biophys J ; 111(7): 1339-1349, 2016 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-27705758

RESUMO

Topological constraints, such as those associated with DNA supercoiling, play an integral role in genomic regulation and organization in living systems. However, physical understanding of the principles that underlie DNA organization at biologically relevant length scales remains a formidable challenge. We develop a coarse-grained simulation approach for predicting equilibrium conformations of supercoiled DNA. Our methodology enables the study of supercoiled DNA molecules at greater length scales and supercoiling densities than previously explored by simulation. With this approach, we study the conformational transitions that arise due to supercoiling across the full range of supercoiling densities that are commonly explored by living systems. Simulations of ring DNA molecules with lengths at the scale of topological domains in the Escherichia coli chromosome (∼10 kilobases) reveal large-scale conformational transitions elicited by supercoiling. The conformational transitions result in three supercoiling conformational regimes that are governed by a competition among chiral coils, extended plectonemes, and branched hyper-supercoils. These results capture the nonmonotonic relationship of size versus degree of supercoiling observed in experimental sedimentation studies of supercoiled DNA, and our results provide a physical explanation of the conformational transitions underlying this behavior. The length scales and supercoiling regimes investigated here coincide with those relevant to transcription-coupled remodeling of supercoiled topological domains, and we discuss possible implications of these findings in terms of the interplay between transcription and topology in bacterial chromosome organization.


Assuntos
Simulação por Computador , DNA Bacteriano/química , DNA Super-Helicoidal/química , Modelos Genéticos , Conformação de Ácido Nucleico , Algoritmos , Escherichia coli , Hidrodinâmica , Método de Monte Carlo , Transcrição Genética
13.
ACS Cent Sci ; 2(9): 584-585, 2016 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-27725953
14.
Biophys J ; 110(2): 338-347, 2016 Jan 19.
Artigo em Inglês | MEDLINE | ID: mdl-26789757

RESUMO

The motion of chromosomal DNA is essential to many biological processes, including segregation, transcriptional regulation, recombination, and packaging. Physical understanding of these processes would be dramatically enhanced through predictive, quantitative modeling of chromosome dynamics of multiple loci. Using a polymer dynamics framework, we develop a prediction for the correlation in the velocities of two loci on a single chromosome or otherwise connected by chromatin. These predictions reveal that the signature of correlated motion between two loci can be identified by varying the lag time between locus position measurements. In general, this theory predicts that as the lag time interval increases, the dual-loci dynamic behavior transitions from being completely uncorrelated to behaving as an effective single locus. This transition corresponds to the timescale of the stress communication between loci through the intervening segment. This relatively simple framework makes quantitative predictions based on a single timescale fit parameter that can be directly compared to the in vivo motion of fluorescently labeled chromosome loci. Furthermore, this theoretical framework enables the detection of dynamically coupled chromosome regions from the signature of their correlated motion.


Assuntos
Cromossomos/química , DNA/química , Loci Gênicos , Simulação de Dinâmica Molecular , Cromossomos/genética , Movimento (Física)
15.
ACS Cent Sci ; 2(12): 910-915, 2016 Dec 28.
Artigo em Inglês | MEDLINE | ID: mdl-28058280

RESUMO

While transport in conjugated polymers has many similarities to that in crystalline inorganic materials, several key differences reveal the unique relationship between the morphology of polymer films and the charge mobility. We develop a model that directly incorporates the molecular properties of the polymer film and correctly predicts these unique transport features. At low degree of polymerization, the increase of the mobility with the polymer chain length reveals trapping at chain ends, and saturation of the mobility at high degree of polymerization results from conformational traps within the chains. Similarly, the inverse field dependence of the mobility reveals that transport on single polymer chains is characterized by the ability of the charge to navigate around kinks and loops in the chain. These insights emphasize the connection between the polymer conformations and the transport and thereby offer a route to designing improved device morphologies through molecular design and materials processing.

16.
Biophys J ; 109(3): 618-29, 2015 Aug 04.
Artigo em Inglês | MEDLINE | ID: mdl-26244743

RESUMO

DNA looping plays a key role in many fundamental biological processes, including gene regulation, recombination, and chromosomal organization. The looping of DNA is often mediated by proteins whose structural features and physical interactions can alter the length scale at which the looping occurs. Looping and unlooping processes are controlled by thermodynamic contributions associated with mechanical deformation of the DNA strand and entropy arising from thermal fluctuations of the conformation. To determine how these confounding effects influence DNA looping and unlooping kinetics, we present a theoretical model that incorporates the role of the protein interactions, DNA mechanics, and conformational entropy. We show that for shorter DNA strands the interaction distance affects the transition state, resulting in a complex relationship between the looped and unlooped state lifetimes and the physical properties of the looped DNA. We explore the range of behaviors that arise with varying interaction distance and DNA length. These results demonstrate how DNA deformation and entropy dictate the scaling of the looping and unlooping kinetics versus the J-factor, establishing the connection between kinetic and equilibrium behaviors. Our results show how the twist-and-bend elasticity of the DNA chain modulates the kinetics and how the influence of the interaction distance fades away at intermediate to longer chain lengths, in agreement with previous scaling predictions.


Assuntos
Proteínas de Ligação a DNA/química , DNA/química , Simulação de Dinâmica Molecular , Conformação de Ácido Nucleico , Sequência de Bases , DNA/metabolismo , Proteínas de Ligação a DNA/metabolismo , Elasticidade , Entropia , Dados de Sequência Molecular , Ligação Proteica , Estresse Mecânico
17.
Biophys J ; 108(1): 146-53, 2015 Jan 06.
Artigo em Inglês | MEDLINE | ID: mdl-25564861

RESUMO

The physical mechanism by which Escherichia coli segregates copies of its chromosome for partitioning into daughter cells is unknown, partly due to the difficulty in interpreting the complex dynamic behavior during segregation. Analysis of previous chromosome segregation measurements in E. coli demonstrates that the origin of replication exhibits processive motion with a mean displacement that scales as t(0.32). In this work, we develop a model for segregation of chromosomal DNA as a Rouse polymer in a viscoelastic medium with a force applied to a single monomer. Our model demonstrates that the observed power-law scaling of the mean displacement and the behavior of the velocity autocorrelation function is captured by accounting for the relaxation of the polymer chain and the viscoelastic environment. We show that the ratio of the mean displacement to the variance of the displacement during segregation events is a critical metric that eliminates the compounding effects of polymer and medium dynamics and provides the segregation force. We calculate the force of oriC segregation in E. coli to be ∼0.49 pN.


Assuntos
Segregação de Cromossomos , Cromossomos Bacterianos , DNA Bacteriano , Escherichia coli/genética , Modelos Genéticos , Algoritmos , Conformação de Ácido Nucleico , Polímeros/química , Substâncias Viscoelásticas/química
18.
J Phys Condens Matter ; 27(6): 064109, 2015 Feb 18.
Artigo em Inglês | MEDLINE | ID: mdl-25563699

RESUMO

Gene regulation in eukaryotes requires the segregation of silenced genomic regions into densely packed heterochromatin, leaving the active genes in euchromatin regions more accessible. We introduce a model that connects the presence of epigenetically inherited histone marks, methylation at histone 3 lysine-9, to the physical compaction of chromatin fibers via the binding of heterochromatin protein 1 (HP1). Our model demonstrates some of the key physical features that are necessary to explain experimental observations. In particular, we demonstrate that strong cooperative interactions among the HP1 proteins are necessary to see the phase segregation of heterochromatin and euchromatin regions. We also explore how the cell can use the concentration of HP1 to control condensation and under what circumstances there is a threshold of methylation over which the fibers will compact. Finally, we consider how different potential in vivo fiber structures as well as the flexibility of the histone 3 tail can affect the bridging of HP1. Many of the observations that we make about the HP1 system are guided by general thermodynamics principles and thus could play a role in other DNA organizational processes such as the binding of linker histones.


Assuntos
Epigênese Genética , Heterocromatina/metabolismo , Modelos Moleculares , Proteínas Cromossômicas não Histona/química , Proteínas Cromossômicas não Histona/metabolismo , Metilação de DNA , Heterocromatina/química , Heterocromatina/genética , Conformação de Ácido Nucleico , Conformação Proteica , Termodinâmica
19.
Soft Matter ; 11(3): 439-48, 2015 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-25412023

RESUMO

Clathrin-mediated endocytosis involves the coordinated assembly of clathrin cages around membrane indentations, necessitating fluid-like reorganization followed by solid-like stabilization. This apparent duality in clathrin's in vivo behavior provides some indication that the physical interactions between clathrin triskelia and the membrane effect a local response that triggers fluid-solid transformations within the clathrin lattice. We develop a computational model to study the response of clathrin protein lattices to spherical deformations of the underlying flexible membrane. These deformations are similar to the shapes assumed during intracellular trafficking of nanoparticles. Through Monte Carlo simulations of clathrin-on-membrane systems, we observe that these membrane indentations give rise to a greater than normal defect density within the overlaid clathrin lattice. In many cases, the bulk surrounding lattice remains in a crystalline phase, and the extra defects are localized to the regions of large curvature. This can be explained by the fact that the in-plane elastic stress in the clathrin lattice are reduced by coupling defects to highly curved regions. The presence of defects brought about by indentation can result in the fluidization of a lattice that would otherwise be crystalline, resulting in an indentation-driven, defect-mediated phase transition. Altering subunit elasticity or membrane properties is shown to drive a similar transition, and we present phase diagrams that map out the combined effects of these parameters on clathrin lattice properties.


Assuntos
Membrana Celular/química , Vesículas Revestidas por Clatrina/química , Clatrina/química , Fluidez de Membrana , Modelos Biológicos , Membrana Celular/metabolismo , Clatrina/metabolismo , Vesículas Revestidas por Clatrina/metabolismo , Elasticidade , Endocitose , Método de Monte Carlo , Transição de Fase
20.
Proc Natl Acad Sci U S A ; 111(49): 17396-401, 2014 Dec 09.
Artigo em Inglês | MEDLINE | ID: mdl-25411314

RESUMO

Storage and retrieval of the genetic information in cells is a dynamic process that requires the DNA to undergo dramatic structural rearrangements. DNA looping is a prominent example of such a structural rearrangement that is essential for transcriptional regulation in both prokaryotes and eukaryotes, and the speed of such regulations affects the fitness of individuals. Here, we examine the in vitro looping dynamics of the classic Lac repressor gene-regulatory motif. We show that both loop association and loop dissociation at the DNA-repressor junctions depend on the elastic deformation of the DNA and protein, and that both looping and unlooping rates approximately scale with the looping J factor, which reflects the system's deformation free energy. We explain this observation by transition state theory and model the DNA-protein complex as an effective worm-like chain with twist. We introduce a finite protein-DNA binding interaction length, in competition with the characteristic DNA deformation length scale, as the physical origin of the previously unidentified loop dissociation dynamics observed here, and discuss the robustness of this behavior to perturbations in several polymer parameters.


Assuntos
DNA/química , Biofísica , Elasticidade , Regulação da Expressão Gênica , Cinética , Modelos Moleculares , Conformação de Ácido Nucleico , Polímeros/química , Estrutura Secundária de Proteína , Estrutura Terciária de Proteína , Proteínas/química , Termodinâmica
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