Polymer Physics Research Articles

Intramolecular structural heterogeneity altered by long-range contacts in an intrinsically disordered protein

Short-range interactions and long-range contacts drive the 3D folding of structured proteins. The proteins' structure has a direct impact on their biological function. However, nearly 40% of the eukaryotes proteome is composed of intrinsically disordered proteins (IDPs) and protein regions that fluctuate between ensembles of numerous conformations. Therefore, to understand their biological function, it is critical to depict how the structural ensemble statistics correlate to the IDPs' amino acid sequence. Here, using small-angle X-ray scattering and time-resolved Förster resonance energy transfer (trFRET), we study the intramolecular structural heterogeneity of the neurofilament low intrinsically disordered tail domain (NFLt). Using theoretical results of polymer physics, we find that the Flory scaling exponent of NFLt subsegments correlates linearly with their net charge, ranging from statistics of ideal to self-avoiding chains. Surprisingly, measuring the same segments in the context of the whole NFLt protein, we find that regardless of the peptide sequence, the segments' structural statistics are more expanded than when measured independently. Our findings show that while polymer physics can, to some level, relate the IDP's sequence to its ensemble conformations, long-range contacts between distant amino acids play a crucial role in determining intramolecular structures. This emphasizes the necessity of advanced polymer theories to fully describe IDPs ensembles with the hope that it will allow us to model their biological function.

Packaging of DNA Integrated with Metal Nanoparticles in Solution.

The transformation of high-molecular DNA from a random swollen coil in a solution to a discrete nanosized particle with the ordered packaging of a rigid and highly charged double-stranded molecule is one of the amazing phenomena of polymer physics. DNA condensation is a well-known phenomenon in biological systems, yet its molecular mechanism is not clear. Understanding the processes occurring in vivo is necessary for the usage of DNA in the fabrication of new biologically significant nanostructures. Entropy plays a very important role in DNA condensation. DNA conjugates with metal nanoparticles are useful in various fields of nanotechnology. In particular, they can serve as a basis for creating multicomponent nanoplatforms for theranostics. DNA must be in a compact state in such constructions. In this paper, we tested the methods of DNA integration with silver, gold and palladium nanoparticles and analyzed the properties of DNA conjugates with metal nanoparticles using the methods of atomic force microscopy, spectroscopy, viscometry and dynamic light scattering. DNA size, stability and rigidity (persistence length), as well as plasmon resonance peaks in the absorption spectra of systems were studied. The methods for DNA condensation with metal nanoparticles were analyzed.

Flexibility Analysis of DNA Nanotubes with Prescribed Circumferences and Their Pearl-Necklace Assemblies with Gold Nanoclusters.

DNA has been demonstrated as a powerful platform for the construction of inorganic nanoparticles (NPs) into complex three-dimensional assemblies. Despite extensive research, the physical fundamental details of DNA nanostructures and their assemblies with NPs remain obscure. Here, we report the identification and quantification of the assembly details of programmable DNA nanotubes with monodisperse circumferences of a 4, 5, 6, 7, 8, or 10 DNA helix and their pearl-necklace-like assemblies with ultrasmall gold nanoparticles, Au25 nanoclusters (AuNCs), liganded by -S(CH2)nNH3+ (n = 3, 6, 11). The flexibilities of DNA nanotubes, analyzed via statistical polymer physics analysis through atomic force microscopy (AFM), demonstrate that ∼2.8 power exponentially increased with the DNA helix number. Moreover, the short-length liganded AuS(CH2)3NH3+ NCs were observed to be able to form pearl-necklace-like DNA-AuNC assemblies stiffened than neat DNA nanotubes, while long-length liganded AuS(CH2)6NH3+ and AuS(CH2)11NH3+ NCs could fragment DNA nanotubular structures, indicating that DNA-AuNC assembling can be precisely manipulated by customizing the hydrophobic domains of the AuNC nanointerfaces. We prove the advantages of polymer science concepts in unraveling useful intrinsic information on physical fundamental details of DNA-AuNC assembling, which facilitates DNA-metal nanocomposite construction.

Exploring Intra- and Inter-Regional Interactions in the IDP α-Synuclein Using smFRET and MD Simulations.

Theoretical concepts from polymer physics are often used to describe intrinsically disordered proteins (IDPs). However, amino acid interactions within and between regions of the protein can lead to deviations from typical polymer scaling behavior and even to short-lived secondary structures. To investigate the key interactions in the dynamic IDP α-synuclein (αS) at the amino acid level, we conducted single-molecule fluorescence resonance energy transfer (smFRET) experiments and coarse-grained molecular dynamics (CG-MD) simulations. We find excellent agreement between experiments and simulations. Our results show that a physiological salt solution is a good solvent for αS and that the protein is highly dynamic throughout its entire chain, with local intra- and inter-regional interactions leading to deviations from global scaling. Specifically, we observe expansion in the C-terminal region, compaction in the NAC region, and a slightly smaller distance between the C- and N-termini than expected. Our simulations indicate that the compaction in the NAC region results from hydrophobic aliphatic contacts, mostly between valine and alanine residues, and cation-π interactions between lysine and tyrosine. In addition, hydrogen bonds also seem to contribute to the compaction of the NAC region. The expansion of the C-terminal region is due to intraregional electrostatic repulsion and increased chain stiffness from several prolines. Overall, our study demonstrates the effectiveness of combining smFRET experiments with CG-MD simulations to investigate the key interactions in highly dynamic IDPs at the amino acid level.

Atomistic modelling and structural characterisation of coated gold nanoparticles for biomedical applications

This study presents the results of atomistic structural characterisation of 3.7-nm-diameter gold nanoparticles (NP) coated with polymer polyethylene glycol-based ligands of different lengths (containing 2–14 monomers) and solvated in water. The system size and composition are selected in connection to several experimental studies of radiosensitisation mechanisms of gold NPs. The coating structure and water distribution near the NP surface are characterised on the atomistic level by means of molecular dynamics simulations. The results of simulations carried out in this study, combined with the results of our recent study (Verkhovtsev et al. in J Phys Chem A 126:2170–2184, 2022) and those from the field of polymer physics, are used to calculate key structural parameters of the coatings of radiosensitising gold NPs. On this basis, connections between the coating structure and distribution of water are established for different NP sizes as well as lengths and surface densities of coating molecules. The quantitative analysis of water distribution in the vicinity of coated metal NPs can be used to evaluate the radiosensitising effectiveness of a particular NP system based on the proximity of water to the NP metal core, which should impact the production of hydroxyl radicals and reactive oxygen species in the vicinity of metal NPs exposed to ionising radiation.Graphical abstract

Toward a 3D physical model of diffusive polymer chains.

Recent studies in polymer physics have created macro-scale analogs to solute microscopic polymer chains like DNA by inducing diffusive motion on a chain of beads. These bead chains have persistence lengths of O(10) links and undergo diffusive motion under random fluctuations like vibration. We present a bead chain model within a new stochastic forcing system: an air fluidizing bed of granular media. A chain of spherical 6 mm resin beads crimped onto silk thread are buffeted randomly by the multiphase flow of grains and low density rising air "bubbles". We "thermalize" bead chains of various lengths at different fluidizing airflow rates, while X-ray imaging captures a projection of the chains' dynamics within the media. With modern 3D printing techniques, we can better represent complex polymers by geometrically varying bead connections and their relative strength, e.g., mimicking the variable stiffness between adjacent nucleotide pairs of DNA. We also develop Discrete Element Method (DEM) simulations to study the 3D motion of the bead chain, where the bead chain is represented by simulated spherical particles connected by linear and angular spring-like bonds. In experiment, we find that the velocity distributions of the beads follow exponential distributions rather than the Gaussian distributions expected from polymers in solution. Through use of the DEM simulation, we find that this difference can likely be attributed to the distributions of the forces imparted onto the chain from the fluidized bed environment. We anticipate expanding this study in the future to explore a wide range of chain composition and confinement geometry, which will provide insights into the physics of large biopolymers.

Maxwell-Dirac Isomorphism Revisited: From Foundations of Quantum Mechanics to Geometrodynamics and Cosmology

Although electrons (fermions)and photons (bosons) produce the same interference patterns in the two-slit experiments, known in optics for photons since the 17th Century, the description of these patterns for electrons and photons thus far was markedly different. Photons are spin one, relativistic and massless particles while electrons are spin half massive particles producing the same interference patterns irrespective to their speed. Experiments with other massive particles demonstrate the same kind of interference patterns. In spite of these differences, in the early 1930s of the 20th Century, the isomorphism between the source-free Maxwell and Dirac equations was established. In this work, we were permitted replace the Born probabilistic interpretation of quantum mechanics with the optical. In 1925, Rainich combined source-free Maxwell equations with Einstein’s equations for gravity. His results were rediscovered in the late 1950s by Misner and Wheeler, who introduced the word "geometrodynamics” as a description of the unified field theory of gravity and electromagnetism. An absence of sources remained a problem in this unified theory until Ranada’s work of the late 1980s. However, his results required the existence of null electromagnetic fields. These were absent in Rainich–Misner–Wheeler’s geometrodynamics. They were added to it in the 1960s by Geroch. Ranada’s solutions of source-free Maxwell’s equations came out as knots and links. In this work, we establish that, due to their topology, these knots/links acquire masses and charges. They live on the Dupin cyclides—the invariants of Lie sphere geometry. Symmetries of Minkowski space-time also belong to this geometry. Using these symmetries, Varlamov recently demonstrated group-theoretically that the experimentally known mass spectrum for all mesons and baryons is obtainable with one formula, containing electron mass as an input. In this work, using some facts from polymer physics and differential geometry, a new proof of the knotty nature of the electron is established. The obtained result perfectly blends with the description of a rotating and charged black hole.

International Polymer Characterization Conference (POLY‐CHAR [Halle|Siegen] 2022)

The International Polymer Characterization Conference POLY-CHAR [Halle│Siegen] 2022 took place as a live digital event from 22nd to 25th May 2022. Organized jointly by the Fraunhofer IMWS in Halle, Germany, and the Institute of Physical Chemistry I of the University of Siegen, Germany, the IUPAC (International Union of Pure and Applied Chemistry)-endorsed conference brought together more than 100 participants from five continents, who shared their research findings ranging from theoretical to experimental and fundamental to applied aspects of polymers. As a a nonprofit, non-governmental organization POLY-CHAR is devoted to creating a friendly interdisciplinary environment to share information, organize student exchange and cooperation, to hold international meetings and to provide a platform for scientist from all over the word. The annual POLY-CHAR conferences are not limited to mere “POLYmer CHARacterization”. Instead, POLY-CHAR offers an open platform for sharing ideas, presenting results, meeting old and making new friends in the scientific community. Topics cover a wide area in synthesis, characterization, modification and application of polymeric materials and composites, probably best summarized under the terms “Advanced Materials' and ‘Functional Materials”. The live digital format chosen for POLY-CHAR [Halle│Siegen] 2022 enabled unrestricted worldwide participation in times of global uncertainty regarding travel restrictions due to the COVID-19 pandemic. On the first day of the conference the POLY-CHAR Short Course was held. The topics of the lectures presented on the subsequent days by 5 plenary speakers, 24 invited speakers, 66 oral speakers, 9 poster presenters from 28 countries included (i) polymer synthesis, (ii) polymer characterization, (iii) polymer physics, theory and simulations, (iv) circular economy of polymers and sustainable applications, (v) polymers for biomedical applications, biopolymers, biomedical materials and biotechnology, (vi) biopolymers in nutrition and health, (vii) elastomers, amorphous materials, nanomaterials and smart materials, (viii) mechanics of polymers, and (ix) adhesives, coatings, and advanced hybrid materials. In addition to several POLY-CHAR and IUPAC prizes for outstanding oral presentations and posters of young scientists, the following prestigious prizes were awarded to well renowned scientists to honor their academic achievements: The Richard Robert Ernst Award went to Prof. Dr. Jianyong Jin (The University of Auckland, New Zealand), the Jean-Marie Lehn Award went to Prof. Dr. Zheng Li (Peking University, China) and the Pierre-Gilles de Gennes Award was awarded to José Luis Gómez Ribelles (Universitat Polìtècnica de València, Spain). This conference volume represents a focused selection of contributions from different areas of polymer and materials science. The next conference in the series, POLY-CHAR [Auckland] 2023, will be held in presence in Auckland, New Zealand, from January 22nd to 26th, 2023. This meeting will be co-hosted by Prof. Jianyong Jin and Prof. Duncan McGillvray. Sven Henning, Fraunhofer IMWS, Germany Ralf Lach, Institut für Polymerwerkstoffe e.V. (IPW), Germany Holger Schönherr, University of Siegen, Germany

Polymer materials for solving actual problems of membrane gas

Membrane gas separation using polymeric membranes is one of rapidly developing energy-conserving technologies. This review describes the scope of membrane gas separation problems and demonstrates the relevance of membrane methods for their solution. The basic concepts and regularities of diffusion gas transfer and principles and characteristics of membrane gas separation are considered. The main physicochemical approaches to the selection of membrane materials considering both the properties of the gas–polymer system and the structure and physical properties of polymers are discussed. The considered issues are combined within a common approach to substantiate the choice of both existing commercial polymers and advanced polymeric materials to address important gas separation problems such as separation of air components; carbon dioxide, hydrogen and helium recovery from natural and industrial gas mixtures; and separation of a nitrogen and methane mixture. The avenues of development of the membrane materials science to solve each of the mentioned problems of membrane gas separation are demonstrated. The review is intended for specialists in the synthesis and physics of polymers for planning the research and assessing the applicability of polymeric materials for various practical gas separation problems and for specialists in the membrane materials science and membrane technology. <br> The bibliography includes 165 references.

Cold‐Resistant Rubbers Based on Flexible Polymer Chains

Comprehensive SummaryAs one of the three types of polymeric materials, rubber has played an irreplaceable role in various fields such as industrial production, aerospace, military, and national defense. Improving the cold resistance of rubbers and extending their service temperature range have always been one of the main focuses in rubber research. However, there have been few detailed public reports or literatures on the progress or summary of cold‐resistant rubbers, creating an invisible barrier for new researchers wishing to enter this field of research. Therefore, starting from the basis of polymer physics, this review introduces the research difficulties in this field and systematically summarizes the research progress in constructing cold‐resistant rubbers based on three different types of flexible polymer chains in recent years. In addition, several important properties of cold‐resistant rubbers including mechanical performance, oil resistance, and self‐healing ability are also discussed along with the summary of recent progresses. Finally, the future challenges and prospects of cold‐resistant rubbers are discussed. It is hoped that this review will attract more attentions from polymer or material scientists, thus activating the fundamental research in the field of cold‐resistant rubber and promoting its practical application.

Lamellae Grating Assembly in Ring-Banded Spherulites

Despite excruciating attempts by polymer physicists in last several decades, lamellar assembly in ring-banded spherulites (RBSs) is still an unsolved and highly debated puzzle. In an unprecedented manner, the banded rings, based on a model polymer, are mapped with advanced synchrotron microbeam X-ray diffraction. According to the diffraction map and microscopy-dissection morphology, the periodically banded structure is composed of lamellae self-assembled as structural gratings. The comparison of a real-time micrograph with this mapping shows the sequential arrangement and orientation of lamellae in gratings. Lamellar assembly in RBS is fully explained with experimental evidence. This methodology can be applied to a wide variety of polymers to analyze spherulites displaying periodic self-assembled patterns.

The Kirkwood-Riseman Model of Polymer Solution Dynamics Is Qualitatively Correct.

The Rouse model is the foundational basis of much of modern polymer physics. The period alternative, the Kirkwood-Riseman model, is rarely mentioned in modern monographs. The models are qualitatively different. The models do not agree as to how many internal modes a polymer molecule has. In the Kirkwood-Riseman model, polymers in a shear field perform whole-body rotation; in the Rouse model, polymers respond to shear with an affine deformation. We use Brownian dynamics to show that the Kirkwood-Riseman model for chain motion is qualitatively correct. Contrary to the Rouse model, in shear flow, polymer coils rotate. Rouse modes are cross-correlated. The amplitudes and relaxation rates of Rouse modes depend on the shear rate. Several alternatives to Rouse modes as collective coordinates are discussed.

Effect of solvation and concentration on F8BT chain solution behavior and film condensed structure

Chain behavior of semi-rigid conjugated polymer in solution, correlation with condensed structure of the films and dynamic evolution in the process from solution to film are hot questions that have received close attention but have not yet solved. In this study, the scaling law obtained by laser light scattering and rheology was combined with fluorescence emission spectroscopy, transmission electron microscopy (TEM) and atomic force microscopy (AFM). The chain behavior of the semi-rigid conjugated polymer poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT, the number-average molecular weights (Mn) was 19.8 kg/mol) in solution and the condensed structure of the film were studied, the intrinsic physical relationship between the chain behavior in solution and condensed structure of the film and its dynamic evolution from solution to film were revealed. According to the concentration-dependent scaling relationship by rheology, some important parameters and chain motion characteristics in solution were revealed, such as toluene solvent was just θ solvent of F8BT, and the critical contact concentration between F8BT dilute solution and semidilute unentangled solution was found to be at 7.9 mg/mL, it firstly revealed the precursor solution concentration for film-forming (usually 10–20 mg/mL) was basically in the semidilute unentangled concentration range. The above results enrich the understanding of chain behavior in solution and the formation mechanisms of thin films condensed structure to semi-rigid conjugated polymers. The research is significant to manipulate the chain behavior in solution to construct condensed structures of the film to establish the structure-function relationship between solution state and photoelectronic device performance based on polymer physics.

Time–Concentration Superposition for Linear Viscoelasticity of Polymer Solutions

The concentration dependence of linear viscoelastic properties of polymer solutions is a well-studied topic in polymer physics. Dynamic scaling theories allow qualitative predictions of polymer solution rheology, but quantitative predictions are still limited to model polymers. Meanwhile, the scaling properties of non-model polymer solutions must be determined experimentally. In present paper, the time-concentration superposition (TCS) of experimental data is shown to be a robust procedure for studying the concentration scaling properties of binary and ternary polymer solutions. TCS can not only identify whether power law scaling may exist or not, and over which concentration range, but also unambiguously estimate the concentration scaling exponents of linear viscoelastic properties for a range of non-model polymer solutions.

POLY‐CHAR 2020

POLY-CHAR 2020 [Venice] is an International Polymer Characterization Conference, under the auspices of the Scientific Committee of POLY-CHAR and International Union of Pure and Applied Chemistry (IUPAC). This event was originally scheduled in May 2020 and it was held, for the first time in virtual format, from 12th to 14th April 2021. This conference was hosted by University of Padova, Italy. A total of 8 plenary speakers, 27 invited speakers, 57 oral speakers, 8 poster presenters and 100 participants from 27 countries attended POLY-CHAR 2020 [Venice]. Due to the travel restriction worldwide, it was not possible to be physically together next to the posters, exchange ideas in front of a coffee or experience lecturing in a real conference hall. However, despite difficulties related to different time zones, attendance was surprisingly high and active, with many questions asked and with a remarkable interaction between participants. The conference spanned a wide spectrum of themes, among which polymers and the environment, food, forensics, adhesives, coatings, preservation of cultural heritage, 3D printing, nanomaterials and smart materials, mechanics of polymers and nanoindentation, in addition to the more traditional themes of polymer chemistry, physics and characterization. As a tradition in POLY-CHAR, young researchers and students were rewarded for their excellent work. In particular, the POLY-CHAR prizes for the Best Oral Presentations were awarded to Veronika Gajdosova, Anna Liguori and Zhiqiang Zeng. Two IUPAC Awards for Best Student Posters were presented to Zrinka Buhin Šturlić and to Yu Jeong Bae and the POLY-CHAR Prize for the Best Student Poster went to Laura Dehondt. This special issue of Macromolecular Symposia is the last act of an exciting conference, a token of appreciation for the efforts of the attendees. In it, the reader will find a glimpse of the interdisciplinarity of this event and the contributions of several authors coming from different parts of the world, sharing their research findings from theoretical to applicative aspects of polymers, for the advancement of knowledge. On our part, as guest editors of this journal and as chairs of the organizing committee, we wish to thank all the researchers who made this event a success and to invite all the readers to participate to the upcoming editions and submit their papers to the corresponding special issue of Macromolecular Symposia. Finally, we would like to dedicate this issue to the memory of Melissa Chan, Dusan Berek and R.P. Singh, who passed away in 2022. They were more than colleagues, but rather members of the POLY-CHAR family, and they will be deeply missed. Valerio Causin, Università di Padova, Italy Carla Marega, Università di Padova, Italy

Unexpected Slow Relaxation Dynamics in Pure Ring Polymers Arise from Intermolecular Interactions.

Ring polymers have fascinated scientists for decades, but experimental progress has been challenging due to the presence of linear chain contaminants that fundamentally alter dynamics. In this work, we report the unexpected slow stress relaxation behavior of concentrated ring polymers that arises due to ring-ring interactions and ring packing structure. Topologically pure, high molecular weight ring polymers are prepared without linear chain contaminants using cyclic poly(phthalaldehyde) (cPPA), a metastable polymer chemistry that rapidly depolymerizes from free ends at ambient temperatures. Linear viscoelastic measurements of highly concentrated cPPA show slow, non-power-law stress relaxation dynamics despite the lack of linear chain contaminants. Experiments are complemented by molecular dynamics (MD) simulations of unprecedentedly high molecular weight rings, which clearly show non-power-law stress relaxation in good agreement with experiments. MD simulations reveal substantial ring-ring interpenetrations upon increasing ring molecular weight or local backbone stiffness, despite the global collapsed nature of single ring conformation. A recently proposed microscopic theory for unconcatenated rings provides a qualitative physical mechanism associated with the emergence of strong inter-ring caging which slows down center-of-mass diffusion and long wavelength intramolecular relaxation modes originating from ring-ring interpenetrations, governed by the onset variable N/ND, where the crossover degree of polymerization ND is qualitatively predicted by theory. Our work overcomes challenges in achieving ring polymer purity and by characterizing dynamics for high molecular weight ring polymers. Overall, these results provide a new understanding of ring polymer physics.

The Bacterial Nucleoid: From Electron Microscopy to Polymer Physics-A Personal Recollection.

In the 1960s, electron microscopy did not provide a clear answer regarding the compact or dispersed organization of the bacterial nucleoid. This was due to the necessary preparation steps of fixation and dehydration (for embedding) and freezing (for freeze-fracturing). Nevertheless, it was possible to measure the lengths of nucleoids in thin sections of slow-growing Escherichia coli cells, showing their gradual increase along with cell elongation. Later, through application of the so-called agar filtration method for electron microscopy, we were able to perform accurate measurements of cell size and shape. The introduction of confocal and fluorescence light microscopy enabled measurements of size and position of the bacterial nucleoid in living cells, inducing the concepts of "nucleoid occlusion" for localizing cell division and of "transertion" for the final step of nucleoid segregation. The question of why the DNA does not spread throughout the cytoplasm was approached by applying polymer-physical concepts of interactions between DNA and proteins. This gave a mechanistic insight in the depletion of proteins from the nucleoid, in accordance with its low refractive index observed by phase-contrast microscopy. Although in most bacterial species, the widely conserved proteins of the ParABS-system play a role in directing the segregation of newly replicated DNA strands, the basis for the separation and opposing movement of the chromosome arms was proposed to lie in preventing intermingling of nascent daughter strands already in the early replication bubble. E. coli, lacking the ParABS system, may be suitable for investigating this basic mechanism of DNA strand separation and segregation.

A polyelectrolyte handle for single‐molecule force spectroscopy

AbstractSingle‐molecule force spectroscopy is a powerful tool for the quantitative investigation of the biophysics, polymer physics and mechanochemistry of individual polymer strands. One limitation of this technique is that the attachment between the tip of the atomic force microscope and the covalent or noncovalent analyte in a given pull is typically not strong enough to sustain the force at which the event of interest occurs, which makes the experiments time‐consuming and inhibits throughput. Here we report a polyelectrolyte handle for single‐molecule force spectroscopy that offers a combination of high (several hundred pN) attachment forces, good (~4%) success in obtaining a high‐force (>200 pN) attachment, a non‐fouling detachment process that allows for repetition, and specific attachment locations along the polymer analyte.

Foundations of Polymer Thermoelectronics.

Building the foundations of polymer thermoelectronics became possible only after the correction of thermodynamic errors in traditional, semiconductor electronics. It was these errors that determined the saturation of its operating parameters of semiconductor electronic devices, in particular, the saturation of the maximum clock frequency of processors. But even if in semiconductors, although these thermodynamic errors manifested themselves not only in the instrumental, but also in the technological aspect, they did not prohibit semiconductor electronics themselves. Whereas, without eliminating thermodynamic errors, the technology of polymers itself made it possible to create only a limited range of materials with low electrical conductivity – materials with low leakage currents, and not polymers with different types of conductivity required for electronics and with given potential barriers for current carriers. In this work, it is shown that there are no fundamental prohibitions either on the creation of polymers with high conductivity, or on the creation of thermionic devices based on them. It’s just that ALL polymer physics is “stuck” on the use of flat electron orbitals, which Pauling introduced for “two-dimensional” graphite and for which he received the Nobel Prize. But, Pauling himself, as an honest scientist, having discovered his mistake, tried to correct it by introducing “curved” orbitals for graphite itself. Now, after the restoration of the Planck-Einstein Quantization, it is shown how to get the correct orbitals instead of the mystical Schrödinger wave functions [1, 2, 3]. Stanislav Ordin, «Gaps and Errors of the Schrödinger Equation»», Journal of Materials and Polymer Science (J mate poly sci), 2022; 2(3): p. 1-6. Stanislav Vladimirovich Ordin, Book: “FOUNDATIONS OF Planck-Einstein Quantization (Thematic collection of recent studies reviewed in scientific journals).” LAP LAMBERT Academic Publishing, 2021, ISBN 978-620-4-21066-7, 110 pp. Stanislav Ordin, “Foundations of Quantization Principles”. Jenny Stanford Publishing Pte Ltd, 2023, 235 рр.

Unveiling the Machinery behind Chromosome Folding by Polymer Physics Modeling.

Understanding the mechanisms underlying the complex 3D architecture of mammalian genomes poses, at a more fundamental level, the problem of how two or multiple genomic sites can establish physical contacts in the nucleus of the cells. Beyond stochastic and fleeting encounters related to the polymeric nature of chromatin, experiments have revealed specific, privileged patterns of interactions that suggest the existence of basic organizing principles of folding. In this review, we focus on two major and recently proposed physical processes of chromatin organization: loop-extrusion and polymer phase-separation, both supported by increasing experimental evidence. We discuss their implementation into polymer physics models, which we test against available single-cell super-resolution imaging data, showing that both mechanisms can cooperate to shape chromatin structure at the single-molecule level. Next, by exploiting the comprehension of the underlying molecular mechanisms, we illustrate how such polymer models can be used as powerful tools to make predictions in silico that can complement experiments in understanding genome folding. To this aim, we focus on recent key applications, such as the prediction of chromatin structure rearrangements upon disease-associated mutations and the identification of the putative chromatin organizing factors that orchestrate the specificity of DNA regulatory contacts genome-wide.