Joanna Trylska - Academia.edu (original) (raw)

Papers by Joanna Trylska

Journal of Molecular Modeling, 2012

International Journal of Quantum Chemistry, 2001

Biopolymers, 2008

This work is a review of the Poisson-Boltzmann (PB) continuum electrostatics theory and its modif... more This work is a review of the Poisson-Boltzmann (PB) continuum electrostatics theory and its modifications, with a focus on salt effects and counterion binding. The PB model is one of the mesoscopic theories that describes the electrostatic potential and equilibrium distribution of mobile ions around molecules in solution. It serves as a tool to characterize electrostatic properties of molecules, counterion association, electrostatic contributions to solvation, and molecular binding free energies. We focus on general formulations which can be applied to large molecules of arbitrary shape in all-atomic representation, including highly charged biomolecules such as nucleic acids. These molecules present a challenge for theoretical description, because the conventional PB model may become insufficient in those cases. We discuss the conventional PB equation, the corresponding functionals of the electrostatic free energy, including a connection to DFT, simple empirical extensions to this model accounting for finite size of ions, the modified PB theory including ionic correlations and fluctuations, the cell model, and supplementary methods allowing to incorporate site-bound ions in the PB calculations.

Biophysical Journal, 2002

The mechanism of the first steps of the reaction catalyzed by HIV-1 protease was studied through ... more The mechanism of the first steps of the reaction catalyzed by HIV-1 protease was studied through molecular dynamics simulations. The potential energy surface in the active site was generated using the approximate valence bond method. The approximate valence bond (AVB) method was parameterized based on density functional calculations. The surrounding protein and explicit water environment was modeled with conventional, classical force field. The calculations were performed based on HIV-1 protease complexed with the MVT-101 inhibitor that was modified to a model substrate. The protonation state of the catalytic aspartates was determined theoretically. Possible reaction mechanisms involving the lytic water molecule are accounted for in this study. The modeled steps include the dissociation of the lytic water molecule and proton transfer onto Asp-125, the nucleophilic attack followed by a proton transfer onto peptide nitrogen. The simulations show that in the active site most preferable energetically are structures consisting of ionized or polarized molecular fragments that are not accounted for in conventional molecular dynamics. The mobility of the lytic water molecule, the dynamics of the hydrogen bond network, and the conformation of the aspartates in the active center were analyzed.

ACS Chemical Biology, 2013

The majority of antibiotics used in the clinic target bacterial protein synthesis. However, the w... more The majority of antibiotics used in the clinic target bacterial protein synthesis. However, the widespread emergence of bacterial resistance to existing drugs creates a need to discover or develop new therapeutic agents. Ribosomal RNA (rRNA) has been a target for numerous antibiotics that bind to functional rRNA regions such as the peptidyl transferase center, polypeptide exit tunnel, and tRNA binding sites. Even though the atomic resolution structures of many ribosome-antibiotic complexes have been solved, improving the ribosome-acting drugs is difficult because the large rRNA has a complicated 3D architecture and is surrounded by numerous proteins. Computational approaches, such as structure-based design, often fail when applied to rRNA binders because electrostatics dominate the interactions and the effect of ions and bridging waters is difficult to account for in the scoring functions. Improving the classical anti-ribosomal agents has not proven particularly successful and has not kept pace with acquired resistance. So one needs to look for other ways to combat the ribosomes, finding either new rRNA targets or totally different compounds. There have been some efforts to design translation inhibitors that act on the basis of the sequence-specific hybridization properties of nucleic acid bases. Indeed oligonucleotides hybridizing with functional regions of rRNA have been shown to inhibit translation. Also, some peptides have been shown to be reasonable inhibitors. In this review we describe these nonconventional approaches to screening for ribosome inhibition and function of particular rRNA regions. We discuss inhibitors against rRNA that may be designed according to nucleotide sequence and higher order structure.

Challenges and Advances in Computational Chemistry and Physics, 2007

In order to model (bio)molecular systems and to simulate their dynamics one requires the potentia... more In order to model (bio)molecular systems and to simulate their dynamics one requires the potential energy functions at the microscopic, classical and/or quantum levels, as well as fast generators of the free-energy functions at the mezoscopic level. A brief overview of the methods which allow computations of the potential energy functions and the free energies is presented. The ongoing research

PLoS ONE, 2014

The conformational properties of the aminoacyl-tRNA binding site (A-site), and its surroundings i... more The conformational properties of the aminoacyl-tRNA binding site (A-site), and its surroundings in the Escherichia coli 30S ribosomal subunit, are of great relevance in designing antibacterial agents. The 30S subunit A-site is near ribosomal protein S12, which neighbors helices h27 and H69; this latter helix, of the 50S subunit, is a functionally important component of an intersubunit bridge. Experimental work has shown that specific point mutations in S12 (K42A, R53A) yield hyper-accurate ribosomes, which in turn confers resistance to the antibiotic 'paromomycin' (even when this aminoglycoside is bound to the A-site). Suspecting that these effects can be elucidated in terms of the local atomic interactions and detailed dynamics of this region of the bacterial ribosome, we have used molecular dynamics simulations to explore the motion of a fragment of the E. coli ribosome, including the A-site. We found that the ribosomal regions surrounding the A-site modify the conformational space of the flexible A-site adenines 1492/93. Specifically, we found that A-site mobility is affected by stacking interactions between adenines A1493 and A1913, and by contacts between A1492 and a flexible side-chain (K43) from the S12 protein. In addition, our simulations reveal possible indirect pathways by which the R53A and K42A mutations in S12 are coupled to the dynamical properties of the A-site. Our work extends what is known about the atomistic dynamics of the A-site, and suggests possible links between the biological effects of hyper-accurate mutations in the S12 protein and conformational properties of the ribosome; the implications for S12 dynamics help elucidate how the miscoding effects of paromomycin may be evaded in antibiotic-resistant mutants of the bacterial ribosome.

BMC Biophysics, 2011

Biochemical reactions in living systems occur in complex, heterogeneous media with total concentr... more Biochemical reactions in living systems occur in complex, heterogeneous media with total concentrations of macromolecules in the range of 50 - 400 mgml. Molecular species occupy a significant fraction of the immersing medium, up to 40% of volume. Such complex and volume-occupied environments are generally termed 'crowded' and/or 'confined'. In crowded conditions non-specific interactions between macromolecules may hinder diffusion - a major process determining metabolism, transport, and signaling. Also, the crowded media can alter, both qualitatively and quantitatively, the reactions in vivo in comparison with their in vitro counterparts. This review focuses on recent developments in particle-based Brownian dynamics algorithms, their applications to model diffusive transport in crowded systems, and their abilities to reproduce and predict the behavior of macromolecules under in vivo conditions.

Lecture Notes in Computer Science, 2011

stract. Determining force field parameters for molecular dynamics ulations of reduced models of b... more stract. Determining force field parameters for molecular dynamics ulations of reduced models of biomolecules is a long, troublesome, exhaustive process that is often performed manually. To improve parametrization procedure we apply a continuous-space Genetic Alithm (GA). GA is implemented to optimize parameters of a coarseined potential energy function of ribonucleic acid (RNA) molecules.

The Journal of Physical Chemistry B, 2009

Many aminoglycoside antibiotics target bacterial ribosomes and alter their proper functioning as ... more Many aminoglycoside antibiotics target bacterial ribosomes and alter their proper functioning as translational machinery leading to bacterial death. To better understand their several inhibitory mechanisms we applied Brownian dynamics and investigated the kinetics and association of paromomycin, an aminoglycoside representative, with the entire 30S ribosomal subunit. We determined that aminoglycoside specific binding at the ribosomal aminoacyl-tRNA site (A-site) begins with antibiotic diffusion toward any point on the 30S subunit and is followed by exploration of the 30S surface. Surprisingly, there is no direct electrostatic steering of the antibiotic to the A-site. Furthermore, we discovered two possible entrances to the A-site around which the mobility of paromomycin is high. The antibiotic also visits binding sites for other drugs targeting the 30S subunit. We found that paromomycin interacts with different sites located along the helix 44 of 16S rRNA, which might explain the recent experimental findings that paromomycin's other inhibitory role arises from overstabilizing the ribosomal 70S complex. In addition, our simulations revealed an alternate binding cleft in the 30S subunit that may be important for paromomycin's inhibitory effect on translocation. The diffusion limited rate of association was estimated of the order of 10(9) (M.s)(-1) with no dependence on the ionic strength of the solution; the physical origins of this result are explained.

The Journal of Physical Chemistry B, 2009

We describe a method for determining diffusion-controlled rate constants for protein-protein asso... more We describe a method for determining diffusion-controlled rate constants for protein-protein association that explicitly includes the solution pH. The method combines the transient-complex theory for computing electrostatically enhanced association rates with an approach based on a rigorous thermodynamic cycle and partition functions for energy levels characterizing protonation states of associating proteins and their complexes. To test our method we determine the pH-dependent kinetics of association of the HyHEL-5 antibody with its antigen hen egg white lysozyme. It was shown experimentally that their association rate constant depends on pH, increasing linearly in the pH range 6-8 and saturating or even exhibiting a flat maximum in the pH range 8-10. The presented methodology leads to a qualitative agreement with the experimental data. Our approach allows one to study diffusion controlled protein-protein association under different pH conditions by taking into account the ensembles of protonation states rather than just the most probable protonation state of each protein.

Journal of the American Chemical Society, 2005

To explore the relationship between the assembly of the 30S ribosomal subunit and interactions am... more To explore the relationship between the assembly of the 30S ribosomal subunit and interactions among the constituent components, 16S RNA and proteins, relative binding free energies of the T. thermophilus 30S proteins to the 16S RNA were studied based on an implicit solvent model of electrostatic, nonpolar, and entropic contributions. The late binding proteins in our assembly map were found not to bind to the naked 16S RNA. The 5' domain early kinetic class proteins, on average, carry the highest positive charge, get buried the most upon binding to 16S RNA, and show the most favorable binding. Some proteins (S10/S14, S6/S18, S13/S19) have more stabilizing interactions while binding as dimers. Our computed assembly map resembles that of E. coli; however, the central domain path is more similar to that of A. aeolicus, a hyperthermophilic bacteria.

Journal of the American Chemical Society, 2006

High macromolecular concentrations, or crowded conditions, have been shown to affect a wide varie... more High macromolecular concentrations, or crowded conditions, have been shown to affect a wide variety of molecular processes, including diffusion, association and dissociation, and protein folding and stability. Here, we model the effect of macromolecular crowding on the internal dynamics of a protein, HIV-1 protease, using Brownian dynamics simulations. HIV-1 protease possesses a pair of flaps which are postulated to open in the early stages of its catalytic mechanism. Compared to low concentrations, close packed concentrations of repulsive crowding agents are found to significantly reduce the fraction of time that the protease is open. Macromolecular crowding is likely to have a major effect on in vivo enzyme activity, and may play an important regulatory role in the viral life cycle.

Journal of Structural Biology, 2007

We present a one-bead coarse-grained model that enables dynamical simulations of proteins on the ... more We present a one-bead coarse-grained model that enables dynamical simulations of proteins on the time scale of tens of microseconds. The parameterization of the force field includes accurate conformational terms that allow for fast and reliable exploration of the configurational space. The model is applied to the dynamics of flap opening in HIV-1 protease. The experimental structure of the recently crystallized semi-open conformation of HIV-1 protease is well reproduced in the simulation, which supports the accuracy of our model. Thanks to very long simulations and extensive sampling of opening and closing events, we also investigate the thermodynamics and kinetics of the opening process. We have shown that the effect of the solvent slows down the dynamics to the experimentally observed time scales. The model is found to be reliable for application to substrate docking simulations, which are currently in progress.

Journal of Computational Chemistry, 2008

A coarse-grained simulation model for the nucleosome is developed, using a methodology modified f... more A coarse-grained simulation model for the nucleosome is developed, using a methodology modified from previous work on the ribosome. Protein residues and DNA nucleotides are represented as beads, interacting through harmonic (for neighboring) or Morse (for nonbonded) potentials. Force-field parameters were estimated by Boltzmann inversion of the corresponding radial distribution functions obtained from a 5-ns all-atom molecular dynamics (MD) simulation, and were refined to produce agreement with the all-atom MD simulation. This self-consistent multiscale approach yields a coarse-grained model that is capable of reproducing equilibrium structural properties calculated from a 50-ns all-atom MD simulation. This coarse-grained model speeds up nucleosome simulations by a factor of 10 3 and is expected to be useful in examining biologically relevant dynamical nucleosome phenomena on the microsecond timescale and beyond.

Journal of Molecular Modeling, 2012

International Journal of Quantum Chemistry, 2001

Biopolymers, 2008

This work is a review of the Poisson-Boltzmann (PB) continuum electrostatics theory and its modif... more This work is a review of the Poisson-Boltzmann (PB) continuum electrostatics theory and its modifications, with a focus on salt effects and counterion binding. The PB model is one of the mesoscopic theories that describes the electrostatic potential and equilibrium distribution of mobile ions around molecules in solution. It serves as a tool to characterize electrostatic properties of molecules, counterion association, electrostatic contributions to solvation, and molecular binding free energies. We focus on general formulations which can be applied to large molecules of arbitrary shape in all-atomic representation, including highly charged biomolecules such as nucleic acids. These molecules present a challenge for theoretical description, because the conventional PB model may become insufficient in those cases. We discuss the conventional PB equation, the corresponding functionals of the electrostatic free energy, including a connection to DFT, simple empirical extensions to this model accounting for finite size of ions, the modified PB theory including ionic correlations and fluctuations, the cell model, and supplementary methods allowing to incorporate site-bound ions in the PB calculations.

Biophysical Journal, 2002

The mechanism of the first steps of the reaction catalyzed by HIV-1 protease was studied through ... more The mechanism of the first steps of the reaction catalyzed by HIV-1 protease was studied through molecular dynamics simulations. The potential energy surface in the active site was generated using the approximate valence bond method. The approximate valence bond (AVB) method was parameterized based on density functional calculations. The surrounding protein and explicit water environment was modeled with conventional, classical force field. The calculations were performed based on HIV-1 protease complexed with the MVT-101 inhibitor that was modified to a model substrate. The protonation state of the catalytic aspartates was determined theoretically. Possible reaction mechanisms involving the lytic water molecule are accounted for in this study. The modeled steps include the dissociation of the lytic water molecule and proton transfer onto Asp-125, the nucleophilic attack followed by a proton transfer onto peptide nitrogen. The simulations show that in the active site most preferable energetically are structures consisting of ionized or polarized molecular fragments that are not accounted for in conventional molecular dynamics. The mobility of the lytic water molecule, the dynamics of the hydrogen bond network, and the conformation of the aspartates in the active center were analyzed.

ACS Chemical Biology, 2013

The majority of antibiotics used in the clinic target bacterial protein synthesis. However, the w... more The majority of antibiotics used in the clinic target bacterial protein synthesis. However, the widespread emergence of bacterial resistance to existing drugs creates a need to discover or develop new therapeutic agents. Ribosomal RNA (rRNA) has been a target for numerous antibiotics that bind to functional rRNA regions such as the peptidyl transferase center, polypeptide exit tunnel, and tRNA binding sites. Even though the atomic resolution structures of many ribosome-antibiotic complexes have been solved, improving the ribosome-acting drugs is difficult because the large rRNA has a complicated 3D architecture and is surrounded by numerous proteins. Computational approaches, such as structure-based design, often fail when applied to rRNA binders because electrostatics dominate the interactions and the effect of ions and bridging waters is difficult to account for in the scoring functions. Improving the classical anti-ribosomal agents has not proven particularly successful and has not kept pace with acquired resistance. So one needs to look for other ways to combat the ribosomes, finding either new rRNA targets or totally different compounds. There have been some efforts to design translation inhibitors that act on the basis of the sequence-specific hybridization properties of nucleic acid bases. Indeed oligonucleotides hybridizing with functional regions of rRNA have been shown to inhibit translation. Also, some peptides have been shown to be reasonable inhibitors. In this review we describe these nonconventional approaches to screening for ribosome inhibition and function of particular rRNA regions. We discuss inhibitors against rRNA that may be designed according to nucleotide sequence and higher order structure.

Challenges and Advances in Computational Chemistry and Physics, 2007

In order to model (bio)molecular systems and to simulate their dynamics one requires the potentia... more In order to model (bio)molecular systems and to simulate their dynamics one requires the potential energy functions at the microscopic, classical and/or quantum levels, as well as fast generators of the free-energy functions at the mezoscopic level. A brief overview of the methods which allow computations of the potential energy functions and the free energies is presented. The ongoing research

PLoS ONE, 2014

The conformational properties of the aminoacyl-tRNA binding site (A-site), and its surroundings i... more The conformational properties of the aminoacyl-tRNA binding site (A-site), and its surroundings in the Escherichia coli 30S ribosomal subunit, are of great relevance in designing antibacterial agents. The 30S subunit A-site is near ribosomal protein S12, which neighbors helices h27 and H69; this latter helix, of the 50S subunit, is a functionally important component of an intersubunit bridge. Experimental work has shown that specific point mutations in S12 (K42A, R53A) yield hyper-accurate ribosomes, which in turn confers resistance to the antibiotic 'paromomycin' (even when this aminoglycoside is bound to the A-site). Suspecting that these effects can be elucidated in terms of the local atomic interactions and detailed dynamics of this region of the bacterial ribosome, we have used molecular dynamics simulations to explore the motion of a fragment of the E. coli ribosome, including the A-site. We found that the ribosomal regions surrounding the A-site modify the conformational space of the flexible A-site adenines 1492/93. Specifically, we found that A-site mobility is affected by stacking interactions between adenines A1493 and A1913, and by contacts between A1492 and a flexible side-chain (K43) from the S12 protein. In addition, our simulations reveal possible indirect pathways by which the R53A and K42A mutations in S12 are coupled to the dynamical properties of the A-site. Our work extends what is known about the atomistic dynamics of the A-site, and suggests possible links between the biological effects of hyper-accurate mutations in the S12 protein and conformational properties of the ribosome; the implications for S12 dynamics help elucidate how the miscoding effects of paromomycin may be evaded in antibiotic-resistant mutants of the bacterial ribosome.

BMC Biophysics, 2011

Biochemical reactions in living systems occur in complex, heterogeneous media with total concentr... more Biochemical reactions in living systems occur in complex, heterogeneous media with total concentrations of macromolecules in the range of 50 - 400 mgml. Molecular species occupy a significant fraction of the immersing medium, up to 40% of volume. Such complex and volume-occupied environments are generally termed 'crowded' and/or 'confined'. In crowded conditions non-specific interactions between macromolecules may hinder diffusion - a major process determining metabolism, transport, and signaling. Also, the crowded media can alter, both qualitatively and quantitatively, the reactions in vivo in comparison with their in vitro counterparts. This review focuses on recent developments in particle-based Brownian dynamics algorithms, their applications to model diffusive transport in crowded systems, and their abilities to reproduce and predict the behavior of macromolecules under in vivo conditions.

Lecture Notes in Computer Science, 2011

stract. Determining force field parameters for molecular dynamics ulations of reduced models of b... more stract. Determining force field parameters for molecular dynamics ulations of reduced models of biomolecules is a long, troublesome, exhaustive process that is often performed manually. To improve parametrization procedure we apply a continuous-space Genetic Alithm (GA). GA is implemented to optimize parameters of a coarseined potential energy function of ribonucleic acid (RNA) molecules.

The Journal of Physical Chemistry B, 2009

Many aminoglycoside antibiotics target bacterial ribosomes and alter their proper functioning as ... more Many aminoglycoside antibiotics target bacterial ribosomes and alter their proper functioning as translational machinery leading to bacterial death. To better understand their several inhibitory mechanisms we applied Brownian dynamics and investigated the kinetics and association of paromomycin, an aminoglycoside representative, with the entire 30S ribosomal subunit. We determined that aminoglycoside specific binding at the ribosomal aminoacyl-tRNA site (A-site) begins with antibiotic diffusion toward any point on the 30S subunit and is followed by exploration of the 30S surface. Surprisingly, there is no direct electrostatic steering of the antibiotic to the A-site. Furthermore, we discovered two possible entrances to the A-site around which the mobility of paromomycin is high. The antibiotic also visits binding sites for other drugs targeting the 30S subunit. We found that paromomycin interacts with different sites located along the helix 44 of 16S rRNA, which might explain the recent experimental findings that paromomycin's other inhibitory role arises from overstabilizing the ribosomal 70S complex. In addition, our simulations revealed an alternate binding cleft in the 30S subunit that may be important for paromomycin's inhibitory effect on translocation. The diffusion limited rate of association was estimated of the order of 10(9) (M.s)(-1) with no dependence on the ionic strength of the solution; the physical origins of this result are explained.

The Journal of Physical Chemistry B, 2009

We describe a method for determining diffusion-controlled rate constants for protein-protein asso... more We describe a method for determining diffusion-controlled rate constants for protein-protein association that explicitly includes the solution pH. The method combines the transient-complex theory for computing electrostatically enhanced association rates with an approach based on a rigorous thermodynamic cycle and partition functions for energy levels characterizing protonation states of associating proteins and their complexes. To test our method we determine the pH-dependent kinetics of association of the HyHEL-5 antibody with its antigen hen egg white lysozyme. It was shown experimentally that their association rate constant depends on pH, increasing linearly in the pH range 6-8 and saturating or even exhibiting a flat maximum in the pH range 8-10. The presented methodology leads to a qualitative agreement with the experimental data. Our approach allows one to study diffusion controlled protein-protein association under different pH conditions by taking into account the ensembles of protonation states rather than just the most probable protonation state of each protein.

Journal of the American Chemical Society, 2005

To explore the relationship between the assembly of the 30S ribosomal subunit and interactions am... more To explore the relationship between the assembly of the 30S ribosomal subunit and interactions among the constituent components, 16S RNA and proteins, relative binding free energies of the T. thermophilus 30S proteins to the 16S RNA were studied based on an implicit solvent model of electrostatic, nonpolar, and entropic contributions. The late binding proteins in our assembly map were found not to bind to the naked 16S RNA. The 5' domain early kinetic class proteins, on average, carry the highest positive charge, get buried the most upon binding to 16S RNA, and show the most favorable binding. Some proteins (S10/S14, S6/S18, S13/S19) have more stabilizing interactions while binding as dimers. Our computed assembly map resembles that of E. coli; however, the central domain path is more similar to that of A. aeolicus, a hyperthermophilic bacteria.

Journal of the American Chemical Society, 2006

High macromolecular concentrations, or crowded conditions, have been shown to affect a wide varie... more High macromolecular concentrations, or crowded conditions, have been shown to affect a wide variety of molecular processes, including diffusion, association and dissociation, and protein folding and stability. Here, we model the effect of macromolecular crowding on the internal dynamics of a protein, HIV-1 protease, using Brownian dynamics simulations. HIV-1 protease possesses a pair of flaps which are postulated to open in the early stages of its catalytic mechanism. Compared to low concentrations, close packed concentrations of repulsive crowding agents are found to significantly reduce the fraction of time that the protease is open. Macromolecular crowding is likely to have a major effect on in vivo enzyme activity, and may play an important regulatory role in the viral life cycle.

Journal of Structural Biology, 2007

We present a one-bead coarse-grained model that enables dynamical simulations of proteins on the ... more We present a one-bead coarse-grained model that enables dynamical simulations of proteins on the time scale of tens of microseconds. The parameterization of the force field includes accurate conformational terms that allow for fast and reliable exploration of the configurational space. The model is applied to the dynamics of flap opening in HIV-1 protease. The experimental structure of the recently crystallized semi-open conformation of HIV-1 protease is well reproduced in the simulation, which supports the accuracy of our model. Thanks to very long simulations and extensive sampling of opening and closing events, we also investigate the thermodynamics and kinetics of the opening process. We have shown that the effect of the solvent slows down the dynamics to the experimentally observed time scales. The model is found to be reliable for application to substrate docking simulations, which are currently in progress.

Journal of Computational Chemistry, 2008

A coarse-grained simulation model for the nucleosome is developed, using a methodology modified f... more A coarse-grained simulation model for the nucleosome is developed, using a methodology modified from previous work on the ribosome. Protein residues and DNA nucleotides are represented as beads, interacting through harmonic (for neighboring) or Morse (for nonbonded) potentials. Force-field parameters were estimated by Boltzmann inversion of the corresponding radial distribution functions obtained from a 5-ns all-atom molecular dynamics (MD) simulation, and were refined to produce agreement with the all-atom MD simulation. This self-consistent multiscale approach yields a coarse-grained model that is capable of reproducing equilibrium structural properties calculated from a 50-ns all-atom MD simulation. This coarse-grained model speeds up nucleosome simulations by a factor of 10 3 and is expected to be useful in examining biologically relevant dynamical nucleosome phenomena on the microsecond timescale and beyond.