1
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Zajac JWP, Muralikrishnan P, Tohidian I, Zeng X, Heldt CL, Perry SL, Sarupria S. Flipping out: role of arginine in hydrophobic interactions and biological formulation design. Chem Sci 2025; 16:6780-6792. [PMID: 40110519 PMCID: PMC11915020 DOI: 10.1039/d4sc08672d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2024] [Accepted: 03/09/2025] [Indexed: 03/22/2025] Open
Abstract
Arginine has been a mainstay in biological formulation development for decades. To date, the way arginine modulates protein stability has been widely studied and debated. Here, we employed a hydrophobic polymer to decouple hydrophobic effects from other interactions relevant to protein folding. While existing hypotheses for the effects of arginine can generally be categorized as either direct or indirect, our results indicate that direct and indirect mechanisms of arginine co-exist and oppose each other. At low concentrations, arginine was observed to stabilize hydrophobic polymer folding via a sidechain-dominated direct mechanism, while at high concentrations, arginine stabilized polymer folding via a backbone-dominated indirect mechanism. Upon introducing partially charged polymer sites, arginine destabilized polymer folding. Further, we found arginine-induced destabilization of a model virus similar to direct-mechanism destabilization of the charged polymer and concentration-dependent stabilization of a model protein similar to the indirect mechanism of hydrophobic polymer stabilization. These findings highlight the modular nature of the widely used additive arginine, with relevance in the information-driven design of stable biological formulations.
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Affiliation(s)
- Jonathan W P Zajac
- Department of Chemistry, University of Minnesota Minneapolis MN 55455 USA
- Chemical Theory Center, University of Minnesota Minneapolis MN 55455 USA
| | - Praveen Muralikrishnan
- Department of Chemical Engineering and Materials Science, University of Minnesota Minneapolis MN 55455 USA
- Chemical Theory Center, University of Minnesota Minneapolis MN 55455 USA
| | - Idris Tohidian
- Department of Chemical Engineering, Michigan Technological University Houghton MI 49931 USA
| | - Xianci Zeng
- Department of Chemical Engineering, University of Massachusetts Amherst MA 01003 USA
| | - Caryn L Heldt
- Department of Chemical Engineering, Michigan Technological University Houghton MI 49931 USA
| | - Sarah L Perry
- Department of Chemical Engineering, University of Massachusetts Amherst MA 01003 USA
| | - Sapna Sarupria
- Department of Chemistry, University of Minnesota Minneapolis MN 55455 USA
- Chemical Theory Center, University of Minnesota Minneapolis MN 55455 USA
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2
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Polanowski P, Sikorski A. Monte Carlo Simulations of Polymer Collapse in an Explicit Solvent of Varying Quality. Polymers (Basel) 2025; 17:978. [PMID: 40219366 PMCID: PMC11991173 DOI: 10.3390/polym17070978] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2025] [Revised: 03/27/2025] [Accepted: 03/28/2025] [Indexed: 04/14/2025] Open
Abstract
The behavior of a single homopolymer chain in an explicit solvent in a wide range of poor and good solvents was investigated. For this purpose, a two-dimensional coarse-grained model based on a triangular lattice was used. Simulations were carried out by the Monte Carlo method using the Cooperative Motion Algorithm to study high-density systems. The scaling relations of the parameters describing the phase transitions of the chain were determined. For systems with polymer-solvent attraction, significant changes in chain size and shape were observed. This was associated with the mechanism of chain penetration by solvents and the formation of structures via a mechanism called 'Bridging-Induced Attraction', similar to those discovered for three dimensions.
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Affiliation(s)
- Piotr Polanowski
- Department of Molecular Physics, Technical University of Łódź, 90-924 Łódź, Poland;
| | - Andrzej Sikorski
- Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland
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3
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Dhibar S, Jana B. Optimized Collective Variable for Collapse Transition in Linear Hydrophobic Polymers: Importance of Hydration Water and End-to-End Distance. J Chem Theory Comput 2024; 20:7404-7415. [PMID: 39252562 DOI: 10.1021/acs.jctc.4c00753] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/11/2024]
Abstract
Choosing an appropriate collective variable (CV) for any biomolecular process is a challenging task. Researchers are developing methods to solve this issue using a variety of methodologies, most recently using machine learning (ML) methods. In this work, we investigate the mechanism of collapse transition across various lengths of polymer systems through adaptively sampled multiple short trajectories utilizing the Time Lagged Independent Component Analysis (TICA) framework. From TICA analysis, it is revealed that the radius of gyration (Rg) and end-to-end distance serve as good order parameters (OPs) for these systems describing overall energy landscapes. Markov state model (MSM) and mean first passage time (MFPT) analysis suggest that hydration water (Nw) plays a determining role in dictating the time scale and barrier for the collapsed transition for the C40 system. P-fold analysis on identifying transition state ensembles (TSE) identified by committor analysis also strengthens the role of Nw in such a transition. TICA, MSM, and committor analyses on the collapse transition for C45 reveal similarities with C40 systems in different aspects. Furthermore, we propose a pipeline integrating XGBoost regression along with an interpretable ML model, Shapley Additive exPlanation (SHAP) to precisely elucidate the contribution of each OP locally at the TSE. Through this approach, we observe that the collapse transition is primarily driven by Nw for both polymer systems. A carefully designed protocol for the collapsed transition of C60 systems indirectly reiterates the above result. Overall, our results suggest that while the end-to-end distance should be considered for better resolution of metastable states in the landscape, Nw is the crucial coordinate to be used in enhanced sampling for the exploration of actual collapse transitions for linear hydrophobic polymer systems. The Python code for analyzing the contribution of different OPs in the TSE using an ML-aided protocol is available on GitHub (https://github.com/saikat-ai/linear_polymer_project).
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Affiliation(s)
- Saikat Dhibar
- School of Chemical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India
| | - Biman Jana
- School of Chemical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India
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4
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Garduño-Juárez R, Tovar-Anaya DO, Perez-Aguilar JM, Lozano-Aguirre Beltran LF, Zubillaga RA, Alvarez-Perez MA, Villarreal-Ramirez E. Molecular Dynamic Simulations for Biopolymers with Biomedical Applications. Polymers (Basel) 2024; 16:1864. [PMID: 39000719 PMCID: PMC11244511 DOI: 10.3390/polym16131864] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2024] [Revised: 04/13/2024] [Accepted: 04/13/2024] [Indexed: 07/17/2024] Open
Abstract
Computational modeling (CM) is a versatile scientific methodology used to examine the properties and behavior of complex systems, such as polymeric materials for biomedical bioengineering. CM has emerged as a primary tool for predicting, setting up, and interpreting experimental results. Integrating in silico and in vitro experiments accelerates scientific advancements, yielding quicker results at a reduced cost. While CM is a mature discipline, its use in biomedical engineering for biopolymer materials has only recently gained prominence. In biopolymer biomedical engineering, CM focuses on three key research areas: (A) Computer-aided design (CAD/CAM) utilizes specialized software to design and model biopolymers for various biomedical applications. This technology allows researchers to create precise three-dimensional models of biopolymers, taking into account their chemical, structural, and functional properties. These models can be used to enhance the structure of biopolymers and improve their effectiveness in specific medical applications. (B) Finite element analysis, a computational technique used to analyze and solve problems in engineering and physics. This approach divides the physical domain into small finite elements with simple geometric shapes. This computational technique enables the study and understanding of the mechanical and structural behavior of biopolymers in biomedical environments. (C) Molecular dynamics (MD) simulations involve using advanced computational techniques to study the behavior of biopolymers at the molecular and atomic levels. These simulations are fundamental for better understanding biological processes at the molecular level. Studying the wide-ranging uses of MD simulations in biopolymers involves examining the structural, functional, and evolutionary aspects of biomolecular systems over time. MD simulations solve Newton's equations of motion for all-atom systems, producing spatial trajectories for each atom. This provides valuable insights into properties such as water absorption on biopolymer surfaces and interactions with solid surfaces, which are crucial for assessing biomaterials. This review provides a comprehensive overview of the various applications of MD simulations in biopolymers. Additionally, it highlights the flexibility, robustness, and synergistic relationship between in silico and experimental techniques.
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Affiliation(s)
- Ramón Garduño-Juárez
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Cuernavaca 62210, Mexico
| | - David O Tovar-Anaya
- Laboratorio de Bioingeniería de Tejidos, División de Estudios de Posgrado e Investigación, Coyoacán 04510, Mexico
| | - Jose Manuel Perez-Aguilar
- School of Chemical Sciences, Meritorious Autonomous University of Puebla (BUAP), University City, Puebla 72570, Mexico
| | | | - Rafael A Zubillaga
- Departamento de Química, Universidad Autónoma Metropolitana-Iztapalapa, Mexico City 09340, Mexico
| | - Marco Antonio Alvarez-Perez
- Laboratorio de Bioingeniería de Tejidos, División de Estudios de Posgrado e Investigación, Coyoacán 04510, Mexico
| | - Eduardo Villarreal-Ramirez
- Laboratorio de Bioingeniería de Tejidos, División de Estudios de Posgrado e Investigación, Coyoacán 04510, Mexico
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5
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Herringer NSM, Dasetty S, Gandhi D, Lee J, Ferguson AL. Permutationally Invariant Networks for Enhanced Sampling (PINES): Discovery of Multimolecular and Solvent-Inclusive Collective Variables. J Chem Theory Comput 2024; 20:178-198. [PMID: 38150421 DOI: 10.1021/acs.jctc.3c00923] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2023]
Abstract
The typically rugged nature of molecular free-energy landscapes can frustrate efficient sampling of the thermodynamically relevant phase space due to the presence of high free-energy barriers. Enhanced sampling techniques can improve phase space exploration by accelerating sampling along particular collective variables (CVs). A number of techniques exist for the data-driven discovery of CVs parametrizing the important large-scale motions of the system. A challenge to CV discovery is learning CVs invariant to the symmetries of the molecular system, frequently rigid translation, rigid rotation, and permutational relabeling of identical particles. Of these, permutational invariance has proved a persistent challenge in frustrating the data-driven discovery of multimolecular CVs in systems of self-assembling particles and solvent-inclusive CVs for solvated systems. In this work, we integrate permutation invariant vector (PIV) featurizations with autoencoding neural networks to learn nonlinear CVs invariant to translation, rotation, and permutation and perform interleaved rounds of CV discovery and enhanced sampling to iteratively expand the sampling of configurational phase space and obtain converged CVs and free-energy landscapes. We demonstrate the permutationally invariant network for enhanced sampling (PINES) approach in applications to the self-assembly of a 13-atom argon cluster, association/dissociation of a NaCl ion pair in water, and hydrophobic collapse of a C45H92 n-pentatetracontane polymer chain. We make the approach freely available as a new module within the PLUMED2 enhanced sampling libraries.
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Affiliation(s)
| | - Siva Dasetty
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, United States
| | - Diya Gandhi
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, United States
| | - Junhee Lee
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, United States
| | - Andrew L Ferguson
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, United States
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6
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Polanowski P, Sikorski A. Coil-globule transition in two-dimensional polymer chains in an explicit solvent. SOFT MATTER 2023; 19:7979-7987. [PMID: 37818732 DOI: 10.1039/d3sm00975k] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/13/2023]
Abstract
The structure of two-dimensional polymer chains in a solvent at different temperatures is still far from being fully understood. Computer simulations of high-density macromolecular systems require the use of appropriate algorithms, and therefore the simulations were carried out using the Cooperative Motion Algorithm. The polymer model studied was exactly two-dimensional, coarse-grained and based on a triangular lattice. The theta temperature and temperature of coil-to-globule transition, and critical exponents were determined. The differences between the structure of such a disk and that of a chain in a dense polymer liquid were shown.
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Affiliation(s)
- Piotr Polanowski
- Department of Molecular Physics, Łódź University of Technology, Żeromskiego 116, 90-543 Łódź, Poland
| | - Andrzej Sikorski
- Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland.
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7
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Olczyk P, Sikorski A. Structure of Strongly Adsorbed Polymer Systems: A Computer Simulation Study. MATERIALS (BASEL, SWITZERLAND) 2023; 16:5755. [PMID: 37687448 PMCID: PMC10488969 DOI: 10.3390/ma16175755] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2023] [Revised: 08/02/2023] [Accepted: 08/18/2023] [Indexed: 09/10/2023]
Abstract
The structure of very thin polymer films formed by strongly adsorbed macromolecules was studied by computer simulation. A coarse-grained model of strictly two-dimensional polymer systems was built, and its properties determined by an efficient Monte Carlo simulation algorithm. Properties of the model system were determined by means of Monte Carlo simulations with a sampling algorithm that combines Verdier-Stockmayer, pivot and reputation moves. The effects of temperature, chain length and polymer concentration on the macromolecular structure were investigated. It was shown that at low temperatures, the chain size increases with the concentration, that is, inversely with high temperatures. This behavior should be explained by the influence of inter-chain interactions.
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Affiliation(s)
- Patrycja Olczyk
- Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland
| | - Andrzej Sikorski
- Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland
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8
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Charvati E, Sun H. Potential Energy Surfaces Sampled in Cremer-Pople Coordinates and Represented by Common Force Field Functionals for Small Cyclic Molecules. J Phys Chem A 2023; 127:2646-2663. [PMID: 36893434 DOI: 10.1021/acs.jpca.3c00095] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/11/2023]
Abstract
The complex conformations of the cyclic moieties impact the physical and chemical properties of molecules. In this work, we chose 22 molecules of four-, five-, and six-membered rings and performed a thorough conformational sampling using Cremer-Pople coordinates. With consideration of symmetries, we obtained a total of 1504 conformational structures for four-membered, 5576 for five-membered, and 13509 for six-membered rings. All well-known and many less well-known conformers for each molecule were identified. We represented the potential energy surfaces (PESs) by fitting the data to common analytical force field (FF) functional forms. We found that the general features of PESs can be described by the essential FF functional forms; however, the accuracy of representation can be improved remarkably by including the torsion-bond and torsion-angle coupling terms. The best fit yields R-squared (R2) values close to 1.0 and mean absolute errors in energy less than 0.3 kcal/mol.
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Affiliation(s)
- Evangelia Charvati
- School of Chemistry and Chemical Engineering, Materials Genome Initiative Center, and Key Laboratory of Scientific and Engineering Computing of Ministry of Education, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Huai Sun
- School of Chemistry and Chemical Engineering, Materials Genome Initiative Center, and Key Laboratory of Scientific and Engineering Computing of Ministry of Education, Shanghai Jiao Tong University, Shanghai 200240, China
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9
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Schmid F. Virtual Issue on Polymers: Recent Advances from a Physical Chemistry Perspective. J Phys Chem B 2022; 126:8359-8361. [PMID: 36300292 DOI: 10.1021/acs.jpcb.2c06378] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Affiliation(s)
- Friederike Schmid
- Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudingerweg 9, 55128 Mainz, Germany
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10
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Huang Y, Cheng S. Chain conformations and phase separation in polymer solutions with varying solvent quality. JOURNAL OF POLYMER SCIENCE 2021. [DOI: 10.1002/pol.20210526] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Yisheng Huang
- Department of Physics, Center for Soft Matter and Biological Physics, and Macromolecules Innovation Institute Virginia Polytechnic Institute and State University Blacksburg Virginia USA
| | - Shengfeng Cheng
- Department of Physics, Center for Soft Matter and Biological Physics, and Macromolecules Innovation Institute Virginia Polytechnic Institute and State University Blacksburg Virginia USA
- Department of Mechanical Engineering Virginia Polytechnic Institute and State University Blacksburg Virginia USA
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