The behavior of animals, as individuals and in groups, represents some of the most fascinating phenomena in the living world. Yet, its complexity challenges our ability to understand, model, and mimic. What rules govern the complex dynamics of an animal as it seeks out food, attracts a mate, or challenges a predator? Topics in this realm vary from quantification and modeling of individuals in controlled laboratory settings, to systems of flocking birds and schooling fish performing natural collective behavior, to the intricate interplay between small groups of individuals during activities such as courtship and aggression. In the past decades, significant progress has been made in quantifying what animals do and modeling their dynamics. This session builds on this momentum and will bring together physicists thinking about behavior and social interactions across biological systems. The primary goals of our session are to identify key questions and organizing principles in the nascent field of the Physics of Behavior and to encourage new collaborations and directions over the coming years. We will draw from a diverse range of efforts to address these challenges, including experimental work as well as theoretical, computational, and robotic models.

lushi@njit.edu, sangwoos@buffalo.edu, Achandrasekaran@ucsd.edu, sg207@rice.edu, mzaferani@princeton.edu

Biological active matter presents us with the opportunity to explore novel physical principles in living systems that are constantly driven out of equilibrium by energy-consuming processes. It further allows us to create advanced materials that exhibit intelligent and responsive behavior. Additionally, studying active matter provides insights into various biological phenomena, such as the behaviors of cells, migratory animals, and even subcellular motor proteins, as they can be considered active materials. Recent discoveries have highlighted several key aspects of biological active matter, such as functionalization, spatiotemporal regulation/control, role of confinement, hydrodynamic instabilities, phase separation, and other dissipative behaviors. This focus session will bring together experimentalists and theorists who are studying the physics behind a wide range of biological and bio-inspired active matter systems, including cytoskeletal/chromatin networks, microswimmers, biological tissues, and composites of living and non-living materials. This focus session will highlight recent advancements in the microscopic origins of activity and the resulting emergent properties.

Biomolecular condensates in living cells are non-membrane-bound compartments enriched with specific proteins and nucleic acids. These condensates are increasingly understood to form through phase transitions and play key roles in many cellular processes, often correlating with diseased states when misregulated. Initially perceived as akin to equilibrium two-phase fluids, recent evidence points to condensates as highly multicomponent, multiphasic assemblies that are often driven out of equilibrium inside the cell. Investigating the physical principles and mechanisms underlying condensate formation and function is therefore an area of major interest. Open questions include: (i) How do interactions between biological macromolecules, often specified by their sequences and/or conformations, encode emergent biophysical properties such as the number and composition of coexisting phases, their resultant material and physical properties, and the nature of the interfaces? (ii) How do aging, maturation, and interactions with cellular surfaces such as membranes and chromatin modulate these biophysical properties and consequently impact condensates’ biological functions? and (iii) How do biochemical and mechanical processes in cells, which are often out of equilibrium, dynamically regulate condensates to perform diverse biological tasks? Understanding general principles requires quantitative measurements on diverse experimental systems, spanning model polyelectrolyte-complex coacervates, in vitro reconstitutions, and in vivo condensates with full complexity across multiple organisms. To guide measurements and their interpretation, in turn, we require advances in theoretical and computational frameworks that explore the statistical physics of soft and multiphase matter in the context of living systems. This focus session aims to foster interdisciplinary communication and collaboration in this exciting area by bringing together experimental, computational, and theoretical experts from polymer science, soft matter physics, engineering, and biology.

kbowal@seas.harvard.edu, kanso@usc.edu, bseleb3@gatech.edu, Benjamin.Larson@ucsf.edu

In many biological collectives, emergent properties arise from the coordinated behavior of individuals, allowing the group as a whole to achieve more than the sum of its parts. This session explores the underlying physical principles that drive collective behaviors in biological systems. Examples include coordination of ciliary appendages to generate fluid flow or cell motility, swarms of bacteria spreading on surfaces, animal or plant cells moving in coordination to close a wound, synchronization of firefly signals, flocks of birds flying in the sky, and schools of fish avoiding predators.
The research presented will be intentionally broad, including collective behaviors from different scales (cells to animals) and will include experimental, computational, and theoretical approaches. Subtopics of special interest are spontaneous or environmentally-triggered collective transitions, mechanics and coordination in tissues, information transfer within animal groups, and mechanically coupled locomotion.

Transcription is a key cellular process, that is intricately controlled by chemical processes, transcription factors and epigenetic modifiers. Multiple studies published over the past few years have focused on a mechanical mode of transcription control, one involving DNA supercoiling, DNA looping, and phase separation. While shedding further light on transcription regulation, such studies also have the potential to discover new physics. This focus session will bring together scientists working on diverse approaches, experimental and theoretical, to understand the principles underlying the interplay of DNA mechanics and gene expression, and hopefully foster discussions towards identifying pressing questions in the field.

This session brings together scientists using theoretical and experimental approaches to understand ecological dynamics across the full spectrum of spatial and temporal scales ranging from minimal communities to large-scale ecological structures. Topics of interest include the ecological and evolutionary rules that govern the assembly, turnover, function, dynamics, and stability of ecosystems, with a primary focus on the structure of interactions between organisms and their coupling with the environment.

Methods from physics are useful for obtaining a quantitative understanding of the evolutionary dynamics of living systems. The research showcased in this Focus Session is purposefully broad, unified by the shared theme of applying a physics lens to evolutionary questions. The topics have ranged from molecular processes of genetic changes to macroscopic patterns of phenotypic variation, emphasizing both experimental and theoretical approaches. We encourage submissions from the full breadth of evolutionary dynamics.

Genome Organization and Subnuclear Phenomena

The eukaryotic genome, tightly packed in the cell nucleus, exhibits a remarkable multiscale organizational hierarchy from DNA and nucleosomes to higher order chromatin assemblies and chromosome territories. At each length scale, unique dynamic and structural features relate to nuclear functions such as DNA damage repair, replication, and gene transcription. The biological physics community is applying methods from polymer physics, statistical mechanics, condensed matter physics, computational physics, and data science to establish general principles and to uncover biophysical rules governing nuclear organization and function. This session will focus on the latest developments in this rapidly advancing field, bringing together experimental, theoretical, and computational scientists in the fields of protein-protein and protein-nucleic acid interactions, genome folding and dynamics, and chromatin structure-function relationships. A breadth of topics will be highlighted including, but not limited to: single molecule interactions, molecular crowding and phase separation in nuclear organization and function, interactions between chromatin and other nuclear components (e.g., nascent and non-coding RNAs, nuclear bodies, lamina and the nuclear envelope), response of the genome to mechanical stress, interplay between epigenetics and genome structure, and structural maintenance of chromosomes through biological motor activities.

modsps@rit.edu, neillin@g.ucla.edu, allen.ehrlicher@mcgill.ca, kenghui@gate.sinica.edu.tw, gerdemci@uwo.ca, tara.finegan@missouri.edu

The mechanical properties of cells and the extracellular matrix impact a wide variety of biological functions such as cell shape, motility, gene expression, cell fate selection, and tissue functions. The goal of this focus session 'Mechanics of Cells and Tissues’ is to bring together researchers from various disciplines working on cell and tissue mechanics and mechanobiology to share their recent experimental and theoretical findings. By doing so, this session will provide a broad understanding of the role that mechanics plays in regulating the function of living cells and tissues, across the molecular to the multicellular scales. The session will feature recent advances in experimental and computational methods that help probe these questions. We welcome submissions from researchers working on a broad range of topics under the cell and tissue mechanics umbrella. Examples include, but are not limited to, passive and active behaviors, mechanical phases of individual cells and cellular collectives, developmental biophysics, mechanical heterogeneity in cells and tissues, viscoelasticity, plasticity and fracture of cells and tissues, tissue shape changes and folding, tissue organization and dynamics beyond 2D such as on curved surface or in 3D, as well as the interplay of mechanics with genetic and biochemical factors.

Neural systems are a fascinating source of challenging problems for physicists, attracting a wide range of approaches to understand the emergence of complex behaviors. From an empirical perspective, modern techniques continuously facilitate progression of new concepts and development of new animal models for analyzing, modeling, and interpreting highly complex data, collected in increasingly naturalistic settings. In parallel, physics approaches stimulate the design of new experiments by generating normative theories of brain computation (e.g., machine learning, artificial neural networks, dynamical systems, molecular and cellular modeling). Finally, neural function is coupled to mass transport (e.g., blood, cerebrospinal fluid, interstitial molecules, neurotransmitters) to maintain homeostasis. This Focus Session welcomes this diversity of approaches and systems, with the goal of enhancing communication and synergy within a highly interdisciplinary community. We hope the session will spur discussion and exchange of ideas on how neural systems function.

Physics of Proteins: Structure & Dynamics, Evolution & Folding, IDP & Assembly, Design & Prediction

This session provides a platform to present and discuss new insights into the physics of proteins based on experimental, theoretical, and computational approaches. Topics will include structure & dynamics of proteins; intrinsically disordered proteins and protein folding & assembly; evolution and function of molecular interactions in proteins; and the rapidly developing area of design & prediction of proteins.

Cytoskeletal filaments, motor proteins, and other passive binding proteins provide cells with an adaptable machinery that can readily generate large-scale structure and mechanical force. It is crucial to understand the physics of these active polymer networks that generate motion in the subcellular world. This focus session will address the physics of their collective behavior, regulation of assembly and disassembly, mechanics and organization, as well as approaches revealing new physics in self-organizing systems. A variety of experimental (in cellular or in vitro systems), theoretical, and computational approaches are welcome.

ejerison@uchicago.edu, shubham.tripathi@yale.edu, ccallan@princeton.edu, cs5096@princeton.edu, k.salaita@emory.edu, slownam@purdue.edu

The immune system is responsible for fighting off diverse pathogens while minimizing damage to the host. This is achieved via coordinated processes across length and time scales: from molecular recognition and cell signaling to tissue and organism level processes. Experimental advances in immune profiling have provided unprecedented insights into immune dynamics; however, general principles of how coordinated behavior emerges in such a distributed, multi-scale system are just now coming into focus. This focus session will bring together scientists using experimental, theoretical, and computational approaches to understand the principles underlying immune system dynamics across scales. The session aims to foster discussion towards identifying the most promising approaches going forward.

The cell cytoplasm is a complex, crowded, and active solution of macromolecules that can behave as a liquid, a gel, or a glass, depending on the context. There has been a recent explosion of reports implicating physical properties of the cytoplasm, such as its viscosity, in a diverse range of critical biological processes - including differentiation, cell viability, cellular aging, and senescence. Our goal with this session is to expose a broad physics audience to this emerging field, and inspire the development of modern methodologies to measure, model, and perturb biophysical properties of the cytoplasm across diverse biological contexts.

The field of quantum biology investigates the impact of quantum mechanics on biological processes, a topic of scientific interest since the early days of quantum mechanics. Recent research has shown that despite the noisy and complex environment of biological systems, quantum effects like charge carrier tunneling, including long-range electron and hydrogen tunneling, are evident and play critical roles in redox reactions and enzyme catalysis. These effects contribute to fundamental biological functions such as respiration, photosynthesis, and enzyme regulation. Additionally, quantum coherence effects observed at room temperature are particularly remarkable. The scope of quantum biology extends from fundamental biomolecular reactions to phenomena like the primary processes in vision, photosynthesis, and avian navigation. This session will extend experimental and theoretical models to explore these complex interactions using quantum mechanics in biological or biophysical systems. The ongoing increase in research activity in this field aims to unravel the pervasive yet subtle quantum effects that underpin critical biophysical processes and mechanisms.

The National Academy of Sciences Decadal Report highlighted the need for excellent biological physics education, even as the field was evolving and new phenomena and explanations were still being discovered. The desire for biological physics curricular material in the community is becoming increasingly apparent, even if teaching the subject encounters difficulties in explaining phenomena across time and length scales. The Living Physics Portal distributes curricular material for introductory physics courses with a biological bent, and a survey from APS DBIO showed a huge interest in the APS community in creating a repository of biological physics curricular material. Accordingly, the goal of the Focus Session is to contribute to establishing a robust conceptual framework for the scholarship of undergraduate and graduate biological physics education. This includes: • Establishing core competencies and learning goals in biological physics instruction. • Developing, field testing, and adapting instructional material and pedagogies that scaffold learning biological physics. • Design modular curricular material that incorporates standard and emerging biological physics content. • Design standalone biological physics curricular material that physics instructors (not necessarily biological physicists) can incorporate into their standard courses (both intro level and upper level courses). • Exposing students to the signature joy of scientific discovery and problem-solving in biological physics. • How AI and computation in general can fit into helping or hurting the construction of a biological physics course or module. These goals are especially difficult to achieve in light of the fact that every institution’s students have their own needs and expectations, that every administration is different, and that every teacher has their own favorite topics to cover– but we aim to address the lack of a one-size-fits-all solution head-on in this Focus Session. From ChatGPT itself: “Join us in shaping the future of biological physics education, where innovation and JEDI drive transformative learning experiences.”

Bacteria have evolved tough and multifunctional compound cell walls consisting of lipid bilayer(s) and covalently crosslinked peptidoglycan networks, typically separated by a polyelectrolyte layer. The cell walls are active materials, grow continuously, and withstand extreme turgor pressures of up to 30 atmospheres. The division of labor between the multiple layers remains poorly understood. An understanding of the mechanical properties of these extremal biomaterials is relevant for fundamental science, biotechnology and medicine since the cell wall synthesis machinery is a prime antibiotic target. This session will provide a platform to discuss new experimental approachse and results as well as progress in mechanical modeling.

Nearly all cell and tissue functions possess a mechanical dimension that encompasses the physics of the underlying processes, and manifests in the living matter's structural dynamics and adaptive interactions with its environments. The cell nucleus is the largest and stiffest organelle that is increasingly recognized as one of the critical sensors of mechanical and structural properties of cell environments. As a sensor the nucleus can directly link the genetic signaling with the mechanical stimuli of cell surrounding, defining, and regulating cell motility properties, differentiation, tissue homeostasis, immune response, neural plasticity, embryogenesis, carcinogenesis, wound healing, among other essential cellular functions. Research in this topic has been promoted by interdisciplinary approaches combining advances in optical light imaging, biophysical approaches, engineering of biomaterials, and computational methods.

This APS DBIO Focus Session will cover the following subtopics:

1. Intra- and extra-nucleus structure and mechanical relationship.

2. Interrelation between chromatin organization, mechanics, and single-cell genetic regulation.

3. Nucleus as a sensor of cell deformation, confinement, and migration.

4. Nuclear mechano-pathology in cancer and immunity