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Review
Physical Sciences
Biophysics

Leon Kaub

,

Christoph Schmitz

,

Carmen Nussbaum-Krammer

Abstract: Introduction: Low-field nuclear magnetic resonance (NMR)-based stimulation is an emerging non-invasive biophysical approach for tissue modulation, penetrating deeper than optical or mechanical techniques. However, the mechanisms linking physical exposure to biological response remain unclear.Areas covered: This review examines the physical principles of low-field NMR-based stimulation, focusing on cyclic adiabatic passage, longitudinal relaxation time (T1), and how field parameters and tissue relaxation properties may shape the distribution of the perturbation. Low-field NMR-based stimulation studies were identified in PubMed and Ovid/Embase from inception to 28 December 2025; other literature through targeted searches and the authors’ domain knowledge. Clinical studies suggest a favorable safety profile and improvements in pain, function and quality of life in several musculoskeletal indications, although between-group superiority was inconsistent. Experimental studies indicate modulation of inflammatory signaling, mitochondrial function, metabolism and redox-sensitive pathways. Four mechanistic questions are emphasized: how relaxation-weighted perturbations reach intracellular signaling; how a spin-level perturbation could trigger biochemical change; what determines specificity; and how weak perturbations are amplified.Expert opinion: Low-field NMR-based stimulation constitutes a physically definable exposure regime, but an NMR-specific biological transduction mechanism has not yet been established. Progress requires rigorously controlled, parameter-resolved experiments capable of supporting or rejecting resonance-specific interpretations.

Article
Physical Sciences
Biophysics

Eleonora Alfinito

,

Matteo Beccaria

Abstract: Protein-based biosensors exploit the extraordinary selectivity of proteins toward specific ligands—other proteins, ions, electromagnetic signals—often surpassing engineered recognition systems. Ligand binding induces structural rearrangements that alter a protein’s electrical and dielectric properties, and in electrical biosensors these changes, particularly in conductance, are what allow the target analyte to be quantified. Yet despite decades of effort, no unified strategy exists for defining and calculating protein permittivity (κ), a quantity central to interpreting such signals. Here we present a computationally inexpensive framework for evaluating protein permittivity, built on a network representation of the protein derived from its three-dimensional topology, in which each amino acid’s permittivity is assigned continuously between a dry, intrinsic value and the bulk solvent value according to its coordination number. Applied to 60 structurally diverse proteins, the model reveals a robust relationship between effective permittivity and a simple topological compactness index. As a proof of concept, we compute the electrical impedance of apo-azurin and of the protein NP_888769.1 under two electrode-contact configurations, finding a measurable, geometry-dependent response that vanishes under a uniform dielectric constant—an experimentally testable signature of internal dielectric structure that invites a re-examination of what protein permittivity experiments actually measure.

Article
Physical Sciences
Biophysics

Vladimir Binhi

,

Igor Usovik

,

Ivan Koshel

Abstract: The radical pair mechanism (RPM) struggles to explain the biological effects of weak magnetic fields due to rapid spin decoherence. To address this, we propose a mechanism based on the quantum behavior of a nanoscopic molecular rotator (approximately 1 nm in size) modeling an amino acid residue in a biosynthesizing enzyme. Using the Liouville–von Neumann equation with chemical kinetics and phenomenological decoherence, we show that MF effects arise from modulation of the rotator’s quantum interference pattern rather than from spin prohibition. Our results demonstrate that effects of several tens of percent occur in very weak magnetic fields (below 0.1 mT), are relatively robust to decoherence, and that while temperature promotes decoherence, it also enables the formation of a magnetic field-sensitive interference pattern. Under realistic parameters, the angular distribution of the rotator’s probability density rotates by several degrees in the geomagnetic field. The rotator mechanism implies that evolution has adapted organisms to use the geomagnetic field for nearly error-free biosynthesis; under hypomagnetic fields, biosynthetic errors increase. Unlike the RPM, this mechanism achieves high sensitivity by operating via magnetic field-induced phase changes rather than magnetic moment energy, thereby circumventing the standard quantum limit. Although tentative and lacking direct experimental evidence, the quantum rotator mechanism provides a biophysically transparent interpretation of hypomagnetic field effects, magnetic storms, and animal magnetic navigation, opening new avenues for research and medical applications.

Article
Physical Sciences
Biophysics

Paolo Renati

,

Pierre Madl

Abstract: In the last decade significant progress has been made in understanding the crucial role of melanin in the energy production in cells and tissues (accounting for up to 90 % of the total in organisms) [1]. This requires rethinking the central role of glucose and ATP which instead are thought to play a primary role in building biomass [2]. The mechanism by which melanin absorbs a wide range of the electromagnetic (em) spectrum (from FIR to far UV and ionizing radiations helping organisms to cope with exposure to X- or γ rays [3]) and dissociates water molecules (releasing oxygen, hydrogen and free energy), has been extensively verified to occur in biological systems [4]. This mechanism has also been reproduced in laboratory and showed valuable applications in water revitalization and purification treatments [5]. In terms of bioenergetics, these findings highlight the importance for mammals (including humans) of sunlight exposure (which provides the full em spectrum) while maintaining adequate hydration to maintain a good homeostasis and optimal health. This process of hydrolysis and oxygen production through melanin and light had been proposed by Arturo Solìs Herrera and thus termed human photosynthesis [1]. However, the proposed dissociation of water molecules (with an initial electron transition at around 7 eV and ionization threshold at 12.62 eV) is not explainable within the still semi-classical vision of quantum mechanics (QM), especially when triggered by photons with much lower energy). In contrast, a description of water and biological matter in terms of Quantum Field Theory (QFT) that takes into account the key role of coherence and the interplay with hydrophilic surfaces provides a clear and physically sound picture [6]. In this paper we would propose a possible semi-quantitative theoretical framework for this fundamental biological process, which appears to underpin most metabolism in heterotrophic organisms, by interpreting water and living matter in terms of Quantum Electro-Dynamics(QED) [7]. This will allow us to make important progress in biochemistry and medicine too.

Article
Physical Sciences
Biophysics

Zaoxia Niu

,

Lijuan Zhang

,

Bolin Sun

,

Chang Wang

,

Gengmei Min

,

Zongwen Chai

,

Yang Shao

Abstract: Glutathione S-transferases (GSTs) plays pivotal roles in plant growth, abiotic stress responses, detoxification of xenobiotics, and maintenance of redox homeostasis. In this study, transcriptomic analysis was employed to identify differentially expressed genes (DEGs) in pea of DX27 under low temperature stress(-4°C) at 3, 6, and 12 h. GO and KEGG enrichment analyses of global transcriptomic data further revealed that DEGs were significantly enriched in oxidation-reduction processes, stress responses, glutathione metabolism, and secondary metabolite biosynthesis—functional categories. A total of 52 PsatGST genes were identified and classified into nine subfamilies based on phylogenetic relationships. Chromosomal localization revealed a non-random distribution across seven chromosomes. Promoter cis-element analysis indicated that PsatGST genes harbor diverse regulatory elements associated with light responsiveness, hormone signaling (auxin, abscisic acid, gibberellin, salicylic acid, and MeJA), and abiotic/biotic stress responses (low-temperature, wounding, and anaerobic induction). PsatGSTU18 and PsatGSTF2 expression analysis showing pronounced up-regulation at 12 h under low temperature stress (-4°C) at 3, 6, and 12 h. These findings provide a foundational framework for understanding the evolutionary history and functional diversification of the PsatGSTs gene family and offer valuable candidate genes for breeding stress-tolerant pea varieties.

Article
Physical Sciences
Biophysics

Subhalaxmi Das

,

Nikos Ch. Karayiannis

,

Supriya Roy

Abstract: Caffeine (1,3,7-trimethylxanthine) is a widely consumed psychoactive drug and neurostimulant, yet its molecular organization and permeation behavior in lipid membranes not fully understood. In the present study, we employ microseconds-long, united-atom Molecular Dynamics simulations to investigate caffeine interactions with a solvated DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) bilayer at its fluid phase. Caffeine molecules initially aggregate in the aqueous phase to form ordered stackings, which successively permeate into the membrane. The stacked assemblies gradually dissolve, reaching a stable dispersed state where caffeine molecules preferentially reside near the headgroup–acyl chain interface and orient parallel to the lipid acyl chains, consistent with previous experimental and simulation studies. Simulations initiated with caffeine in the membrane core converge to the same equilibrium state, indicating a preferred localization at the interface region. Density profiles and caffeine distributions suggest that direct translocation across the membrane is unlikely. Caffeine partitioning transiently reduces slightly bilayer thickness and increases the membrane surface area, while enhancing acyl chain stiffness near the hydrophilic part of the membrane. These observed trends are reproducible over different system sizes and independent simulations. Overall, this study provides atomic-level insights into the caffeine permeation process, including its effect on the lipid bilayer structure.

Article
Physical Sciences
Biophysics

Lingling Chen

,

Chuansheng Shen

,

Jian Gao

Abstract: Spatial self-organized patterns are ubiquitous features of vegetation ecosystems, and cyclic nontransitive competition serves as a crucial intrinsic mechanism for sustaining biodiversity. However, existing studies lack cross-scale comparative analyses of vegetation territorial competition based on multiple models. This study combines lattice models and continuous differential equation models to investigate the territorial occupation dynamics and spatial evolution of vegetation communities driven by cyclic competition. The results demonstrate that cyclic competition acts as a core mechanism maintaining vegetation biodiversity, which enables the self-organization of stable spiral wave patterns in space and supports the long-term dynamic coexistence of multiple species. Discrete and continuous models exhibit highly consistent macroscopic dynamical behaviors, which reveal the intrinsic dynamical characteristics of cyclic competitive systems. By integrating microscopic lattice simulation and macroscopic differential equation analysis, this study verifies that spiral waves represent a highly robust species coexistence mode and clarifies the coupled regulatory effects of species richness and stochasticity on system evolution. The findings further deepen the understanding of the complexity of vegetation ecosystems and provide important theoretical references for subsequent theoretical derivation and field observational research on vegetation community competition and evolution.

Concept Paper
Physical Sciences
Biophysics

Ricard Solé

,

Joel Romero-Hernández

,

Guim Aguadé-Gorgorió

,

Manlio De Domenico

Abstract: Complex diseases challenge one of the oldest assumptions in medicine: that illness can be reduced to a single cause. Instead, increasing evidence suggests that many pathologies emerge from the collective dynamics of components interacting across molecular, cellular, physiological, behavioral, and ecological scales. Thus, we revisit the fundamental question of what a disease is through the lens of complex systems theory. In particular, we argue that diseases are better understood as emergent dynamical states of living systems that arise from the breakdown, reorganization, or destabilization of regulatory networks. Within this framework, mathematical models can describe health and disease as alternative attractors in a multidimensional state space, and disease onset often reflects critical transitions driven by stress, perturbation, or loss of resilience. Therefore, concepts from nonlinear dynamics, network theory, ecology, and statistical physics (such as bifurcations, hysteresis, phase transitions, and multistability) provide a unifying language to describe phenomena as diverse as patient comorbidity, psychiatric disorders, cancer progression, epidemic spreading, or neurodegeneration. We also discuss how multiscale models can bridge molecular mechanisms with organism-level behavior to reveal universal principles of complex diseases. This perspective implies that the future of medicine may depend on understanding not only the components of biological systems, but also the laws governing their collective organization, which could open new avenues for prediction, prevention, and control.

Article
Physical Sciences
Biophysics

Raneem Aldadah

,

Amina Dervic

,

Esma Zajimovic

,

Altijana Hromić-Jahjefendić

,

Muhamed Adilović

,

Vladimir N. Uversky

Abstract: Traumatic brain injury (TBI) triggers complex molecular responses that remain incompletely understood at the structural level, where it's highly connected to neurodegeneration and synaptic dysfunction. Growing evidence implicates intrinsically disordered proteins (IDPs), and proteins with intrinsically disordered regions (IDRs), as key regulators of stress-responsive signaling. In this study, we represent an in silico study of the 24 TBI-relevant proteins, such as MAPT, SERF2, SERBP1, BEX3, TDP43, NFL, C9orf16, C9orf58, APP, NRN1, NEFM, SYNGAP1, SNAP25, DLG4, APOC2, HCLS1, HMGB1, FUS, EPHA4, SEMA4D, S100B, PLEK, CAMK2A, and SNCA, integrating analysis of the predisposition for intrinsic disorder and liquid–liquid phase separation (LLPS) through RIDAO, FuzDrop, and AlphaFold platforms. We demonstrate that more than 90% of residues in SERF2, BEX3, MAPT, SERBP1, HMGB1, SNCA, and FUS are predicted as disordered. The amino acid sequences of NEFM, HCLS1, C9orf16, NEFL, C9orf58, SNAP25, SYNGAP1, S100B, and TDP43 contain between 50% and 90% of disordered residues, and the disorder contents of APP, APOC2, and DLG4 are 47.53%, 45.54% and 33.29%. Only five proteins (SEMA4D, PLEK, CAMK2A, EPHA4, and NRN1) have less than 30% disordered residues. The high prevalence of disorder in TBI-associated proteins correlates with their strong propensity for spontaneous liquid-liquid phase separation (LLPS). In fact, 15 proteins (FUS, SYNGAP1, MAPT, NEFM, SERBP1, HCLS1, SERF2, BEX3, C9orf16, TDP43, HMGB1, APP, NEF, DLG4, and SNCA) are expected to act as droplet drivers, and five more proteins (SEMA4D, C9orf58, SNAP25, CAMK2A, and EPHA4) can serve as droplet clients. The gene ontology analysis emphasized that the 24 TBI-related proteins (TBIome) are functionally associated with synaptic regulation, RNA metabolism, cytoskeletal dynamics, and mitochondrial stress response. We also show that human proteins interacting the members of TBIome are on average a bit more disordered than the human brain proteins in general. This extended TBI interactome is functionally connected to cytoplasmic translation, translation, synaptic vesicle cycle, modulation of chemical synaptic transmission, regulation of neurotransmitter levels, regulation of synaptic plasticity, neurotransmitter secretion, synaptic vesicle exocytosis, protein localization to synapse, and trans-synaptic signaling. Many of these proteins have strong LLPS potential as well. Therefore, high intrinsic disorder propensity and strong LLPS potential represent shared structural and functional features of proteins linked to the TBI-related pathophysiology. Collectively, these findings support a model in which disorder-based mechanisms contribute to post-traumatic molecular reprogramming, which underlie the pathological roles of TBI-related proteins.

Review
Physical Sciences
Biophysics

Boris Y. Zaslavsky

,

Mark Stovsky

,

Vladimir N. Uversky

Abstract: Aqueous two-phase systems (ATPSs) provide a versatile, fully aqueous platform for probing solute–water interactions and protein structure. This review first surveys the diversity and phase behavior of biphasic aqueous systems formed by polymers and salts. We describe how phase diagrams characterize ATPS formation and composition, and how both polymer chemistry and salt identity, more than molecular size alone, govern phase separation by modulating the solvent properties of water. Building on a modified binodal model, we show that phase separation and solute partitioning can be understood in terms of changes in aqueous solvent dipolarity/polarizability, hydrogen-bond donor/acceptor properties, hydrophobicity, and electrostatics, quantified via solvatochromic probes and homologous solute series. These measurements underpin solvent interaction analysis (SIA), in which the partition coefficients of small molecules and proteins across panels of ATPSs are used to generate “structural signatures” that sensitively report on amino acid substitutions, conformational changes, aggregation, ligand binding, osmolyte effects, and post-translational modifications, independent of protein size. We discuss how SIA can be implemented in vial-, plate-, and microfluidic formats and combined with diverse analytical readouts (HPLC, MS, colorimetric and immunoassays), and contrast this structure-focused approach with conventional concentration-only proteomic and biomarker strategies. Particular emphasis is placed on structure-based biomarker discovery, where disease-relevant shifts in proteoform distributions—especially glycosylation changes—are often more informative than bulk protein levels, and where SIA can complement or simplify complex glycomics and top-down proteomics workflows. As a case study, we describe the recently FDA approved isoPSA assay, which applies SIA principles to prostate-specific antigen by measuring cancer-associated structural alterations in circulating PSA via its partition behavior in a proprietary ATPS. IsoPSA generates a single index that discriminates high-grade prostate cancer from benign and low-grade conditions. Prospective, longitudinal, and MRI-integrated clinical studies demonstrate that IsoPSA® improves pre-biopsy risk stratification, reduces unnecessary biopsies, and provides robust negative and positive predictive characteristics within the PSA “gray zone.” Collectively, the data support aqueous solvent interaction analysis as a broadly applicable, mechanistically grounded technology for protein characterization, drug–protein interaction studies, and structure-centric biomarker development, exemplified by the clinical translation of IsoPSA.

Review
Physical Sciences
Biophysics

Matteo Gori

,

Roberto Franzosi

,

Giulio Pettini

,

Marco Pettini

Abstract: We review a theoretical and experimental programme aimed at understanding two intimately related fundamental phenomena in biophysics: (i) the classical analogue of Fröhlich phonon condensation in macromolecules driven out of thermal equilibrium, and (ii) the consequent activation of long-range resonant electrodynamic intermolecular forces. Both phenomena are underpinned by explicit Hamiltonian models. The first is derived by applying the time-dependent variational principle (TDVP) to the quantum Wu--Austin model, producing a fully classical Hamiltonian in action-angle variables whose nonlinear rate equations exhibit a nonequilibrium phase transition, the channelling of supplied energy into the lowest-frequency collective mode. The second is grounded in a classical electrodynamic Hamiltonian for two coupled oscillating dipoles whose normal-mode structure predicts long-range (\( \sim 1/r^3 \)) resonant interactions, absent at thermal equilibrium but activated by out-of-equilibrium collective oscillations. We also discuss a complementary Hamiltonian approach that connects Fröhlich's rate equations directly to Hamilton's equations of motion, clarifying the role of bath-mediated nonlinear coupling and the conditions for strong condensation at room temperature. In addition, the TDVP is applied to a Davydov--Holstein--Fröhlich Hamiltonian describing electron--phonon motion along the backbone of a specific DNA sequence and its cognate restriction enzyme EcoRI: the time-domain Fourier cross-spectrum of the resulting electron currents exhibits a sharp co-resonance peak for the canonical recognition sequence that disappears upon randomisation, providing a sequence-specific electrodynamic signature of DNA--protein recognition. Experimental evidence from THz near-field spectroscopy, fluorescence correlation spectroscopy, and direct observation of protein clustering is reviewed in relation to these theoretical predictions. The results establish a coherent physical picture suggesting that metabolic energy supply can play a role in driving macromolecules into coherently oscillating states that activate selective, distance-reaching electrodynamic forces capable of contributing to the organisation of biochemical reactions in living matter.

Review
Physical Sciences
Biophysics

Xinyu Yang

,

Yuting Sun

,

Hong Jin

,

Jianguo Feng

,

Shangzhong Jin

Abstract: Given that red blood cells (RBCs) are the most abundant cells in blood, their morphology and mechanics strongly affect blood rheology. Furthermore, changes in the physiological functions and health status of an organism can also affect RBC mechanics. Therefore, understanding the mechanical properties of RBCs holds substantial research value in the biomedical field. Optical tweezers (OT) technology has become a crucial method for measuring and analyzing the mechanical properties of RBCs, owing to their unique advantages such as non-contact manipulation and piconewton-level force sensitivity. This review first outlines the basic mechanical properties of RBCs, the mechanical sensing principles of optical tweezers, and their basic manipulation modes. It then focuses on the measurement and application of key mechanical parameters, such as the deformation index and shear modulus. Furthermore, the review also covers the integration of optical tweezers with Raman spectroscopy, fluorescence, and microfluidics. These combined approaches allow for the simultaneous acquisition of mechanical and molecular data, dynamic monitoring of mechanical state changes, and analysis of external stimuli and physiological mechanisms, thereby supporting disease diagnosis, drug efficacy evaluation, as well as artificial blood quality assessment.

Article
Physical Sciences
Biophysics

Bo Hua Sun

Abstract: The pervasive allometric scaling laws in biology, most notably Kleiber’s law (BM3/4), conflict with the predictions of classical Euclidean dimensional analysis (BM2/3). While the West-Brown-Enquist (WBE) model resolved this paradox using hierarchical fractal networks, and Barenblatt’s incomplete similarity formalized the fractional exponents, a rigorous symmetry framework connecting the two has been lacking. In this paper, we reconstruct dimensional analysis from the perspective of Lie group theory, demonstrating that incomplete similarity corresponds to a deformed scaling Lie group parameterized by anomalous dimensions. We show that the internal fractal network breaks the isotropic Euclidean scaling symmetry. Crucially, we formulate natural selection and physical optimization as a constrained optimization problem on the Lie group parameters. Maximizing the throughput exponent subject to the physical bounds of fractal dimensions uniquely selects the anomalous parameters, rigorously yielding the 3/4-power law. Substituting these optima back into the Lie group action reveals an algebraic dimensional promotion: the broken symmetry is restored, but the effective group is isomorphic to a 4D Euclidean scaling group. This provides a rigorous algebraic foundation for the “fourth dimension of life,” establishing allometric scaling as the universal geometric invariant of optimized resource-distribution networks.

Article
Physical Sciences
Biophysics

Anna Krivetskaya

,

Tatiana Savelieva

,

Daniil Kustov

,

Igor Romanishkin

,

Kirill Linkov

,

Sergey Kharnas

,

Kanamat Efendiev

,

Polina Alekseeva

,

Vladimir Makarov

,

Victor Loschenov

+1 authors

Abstract: Gastrointestinal (GI) cancers account for a quarter of all cancer cases worldwide and are responsible for a third of cancer deaths. One of the characteristic features of GI tissue is its multilayered structure, which in addition to multiple scattering, complicates optical-spectral analysis. The risk of lymph node metastasis in GI cancer is primarily related to the depth of tumor invasion. The use of spectroscopic diagnostics and photodynamic therapy for the detection and treatment of GI cancer is a rapidly developing field. The method proposed in this paper for layer-by-layer optical properties assessment, suitable for real-time clinical application to the walls of hollow organs, allows for both determining the depth of tumor invasion into the GI organ wall and calculating the absorbed dose layer-by-layer. This paper proposes a method for recording spectral data in two geometries, diffuse reflectance and transmission, using light delivery from both the external and internal surfaces of the gastrointestinal tract wall. Layer-by-layer assessment of optical properties was performed using a developed algorithm based on the inverse adding-doubling method with initial optical properties values ​​determined using the modified two-stream Kubelka-Munk model with the accuracy equal to 86±13%. The method was approbated in clinical conditions.  Based on the results of the work, the developed method for assessing the optical properties of multilayered biological tissues exhibited sufficient speed and accuracy for in vivo application to personalize laser-induced therapy by correction of the laser dose.

Article
Physical Sciences
Biophysics

Samina Masood

,

Angel Arrieta

,

Derek Smith

Abstract: We study the effects of weak magnetic fields (around 2 mT) on the growth of Staphylococcus aureus (S. aureus) in the presence of a few sweeteners (monosaccharides, disaccharides, sugar alcohols, and consumer-grade sweeteners). Bacterial growth rates were compared in various magnetic fields at room temperature. Bacterial growth was estimated using optical absorbance measurements at various wavelengths, and pH values were manually estimated using pH strips. Absorbance was measured at 492 nm and 630 nm, which are wavelengths comparable to the size of a cell of S. aureus after division. This comparability plays a vital role in the scale of measured absorbance values. The results imply that bacterial growth may be reduced due to acidic byproducts formed by metabolizing sugars or sugar alcohols, as an increasingly acidic solution is less ideal for bacterial growth. Magnetic fields were also found to have a minor effect on pH estimates. These results reveal potential effects on microorganisms in the presence of sugars and sugar alcohols in addition to weak magnetic fields, demonstrating the contribution of various environmental conditions with increasing prevalence in the modern day.

Article
Physical Sciences
Biophysics

Matthew T. Colbourne

,

Lea Gassab

,

Travis J. A. Craddock

Abstract: Microtubules contain ordered aromatic amino-acid networks whose optical excitations have been proposed to support non-trivial energy-transfer dynamics. Here, we examined whether bound tryptamine ligands can perturb the excitonic structure of the tubulin tryptophan network. A virtual screen of 294 tryptamines was performed across seven known binding regions of the tubulin heterodimer using AutoDock Vina. From this screen, top-ranked tryptamine ligands were carried forward for excited-state analysis. Geometry optimization and time-dependent density functional theory (TD-DFT) calculations were used to obtain vertical excitation energies and transition dipole moments for the ligand-bound states in the ultraviolet range. These ligand properties were then incorporated into a tight-binding Hamiltonian describing the tubulin tryptophan excitation network in order to evaluate changes in exciton energies and eigenvector delocalization. The calculations indicate that tryptamine binding can modify the excitonic landscape of tubulin in a ligand-dependent manner, with the magnitude of the perturbation governed by excitation wavelength, transition dipole strength, and spatial orientation relative to the intrinsic tryptophan network. These results support the possibility that aromatic ligands may provide a chemically tunable route to altering the optical response of tubulin and motivate future experimental tests of ligand-dependent modulation of microtubule photophysics.

Article
Physical Sciences
Biophysics

Katarina Žikić

,

Dejan Žikić

Abstract: Pulse wave propagation through blood vessels is affected by many biophysical parameters that change with aging. The aim of this study was to investigate both theoretically and experimentally how the pulse wave velocity changes in the vertical position and to introduce a new parameter in biophysics - pulse wave acceleration - PWA. On a biophysical model of the cardiovascular system, placed in horizontal and vertical position, pressure waveforms were measured along the arterial tree at several sites at different diastolic pressures and pump frequencies. Blood flow waveforms on the carotid and femoral arteries in the supine and standing position were measured on the subjects. The results showed that the pulse pressure wave accelerates in the direction of gravity and decelerates in the opposite direction both in the model and in humans. A new biophysical parameter - PWA - was defined, and the experimental results are in agreement with the mathematical model. Due to the acceleration of the pulse wave, the reflected wave in the standing position arrives earlier in systole and affects the increase in pressure. The novel biophysical parameter provides a more accurate assessment of the age of the cardiovascular system and a more precise diagnosis of increased blood pressure.

Article
Physical Sciences
Biophysics

Vaitheeswaran R.

Abstract: FLASH radiotherapy, characterized by ultra-high dose rates, has been shown to reduce normal tissue toxicity while preserving tumor control, yet its underlying mechanism remains unresolved. Existing models based on radiolytic oxygen depletion (ROD) successfully capture dose-rate dependence but fail to explain key experimental features, including threshold-like onset, saturation of the sparing effect, and sensitivity to temporal delivery structure. Here, we propose a mechanistic framework — Memory-modulated Radiolytic Oxygen Depletion (M-ROD) — that extends classical ROD by incorporating a bounded, history-dependent internal state. The dynamical structure of this state — cooperative activation, bounded feedback, and characteristic decay — is consistent with that of cooperative biological regulatory processes, including gene regulatory networks. In this framework, dose-rate–dependent stress activates a nonlinear biological state that evolves through induction, bounded feedback, and decay, modulating radiosensitivity alongside oxygen effects. We show that the framework reproduces the defining characteristics of FLASH, including sharp threshold-like transitions, plateau behavior, and strong dependence on pulse spacing, duty cycle, and irradiation sequence, while reducing to conventional radiobiology under low dose-rate conditions. The pulse-spacing sensitivity that distinguishes M-ROD from memoryless models requires the state to relax on a characteristic timescale τ_M of approximately 10–100 ms; we show that bioelectric membrane dynamics, treated as a passive RC system using parameter values from standard electrophysiology, naturally produce relaxation in this range without parameter tuning. The model predicts that the magnitude of the FLASH effect is governed by the extent of state activation rather than dose rate alone, providing a mechanistic explanation for variability across experiments. These results support the interpretation of FLASH as an emergent state transition in a dynamical biological system and offer experimentally testable predictions that distinguish it from memoryless models.

Article
Physical Sciences
Biophysics

Maurizio Viviani

,

Nicola Bragazzi

,

Gaositwe Bolani

,

Simonetta Papa

,

Luca Giacomelli

,

Roberto Eggenhöffner

Abstract: Forward osmosis (FO) membranes are commonly evaluated through macroscopic observables such as water flux and reverse solute flux. However, these quantities do not necessarily reveal whether water permeation and solute leakage remain governed by the same dominant transport pathways, particularly in heterogeneous nanostructured membranes where selective nanochannels and defect-mediated pores can contribute differently to solvent and solute transport. Here, we introduce a hierarchical diagnostic framework to assess transport coherence loss in heterogeneous FO membranes. The framework comprises a baseline model (BM), an extended model (EM) including chemistry–geometry coupling through accessibility loss, and a full model (FM) incorporating selective pore-size heterogeneity. The flux ratio R=Js/Jw is used as a regime-based diagnostic descriptor of transport organization, and its normalized form is used to map coherence variations across the state-space defined by structural selectivity and nanochemical state. The results show that chemistry–geometry coupling produces the first clear reorganization of the coherence landscape, whereas pore-size heterogeneity mainly broadens the response while preserving its dominant topology. Simulations based on both Monte Carlo and experimentally derived pore-size distributions show consistent trends. Overall, the BM–EM–FM hierarchy offers an interpretable framework for describing transport coherence loss and the emergence of leakage-prone regimes in heterogeneous FO membranes.

Article
Physical Sciences
Biophysics

C.K. Gamini Piyadasa

Abstract: Ant navigation is widely explained through pheromone-mediated trail formation and reinforcement, which accounts for efficient shortest-path selection in two-dimensional environments. However, certain three-dimensional foraging behaviors—such as navigation toward suspended food sources or the rapid use of newly established material paths—raise questions about whether chemical gradients alone fully explain route detection and selection. This paper examines experimental observations that appear difficult to reconcile with purely diffusion-based pheromone models and proposes an expanded framework incorporating the concept of Intrinsic Energy Spin (IESpin) fields. According to this hypothesis, all entities possess an intrinsic spin (ISpin) that encodes their fundamental intrinsic properties. The ISpin field propagates through space and interacts with other entities in the universe, giving rise to an IESpin field. These fields are proposed to propagate preferentially through continuous matter, potentially allowing organisms to detect spatial pathways and resource signatures via field gradients. The hypothesis generates experimentally testable predictions concerning material-dependent transmission, pheromone-independent navigation, and the possible existence of non-chemical sensory mechanisms in ants.

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