Biophysical Journal

Red blood cells (RBCs) are vital for transporting oxygen from the lungs to the body's tissues through the intricate circulatory system. They achieve this by binding and releasing oxygen molecules to the abundant hemoglobin within their cytosol. The volume of RBCs affects the amount of oxygen they can carry, yet whether this volume is optimal for transporting oxygen through the circulatory system remains an open question. This study explores, through high-fidelity numerical simulations, the impact of RBC volume on advectve oxygen transport efficiency through arterioles which form the area of greatest flow resistance in the circulatory system...

No abstract text is available yet for this article.

Voltage-gated potassium channels are critical in modulating cellular excitability, with Slo (slowpoke) channels forming a unique family characterized by their large conductance and dual regulation by electrical signals and intracellular messengers. Despite their structural and evolutionary similarities, Slo1 and Slo3 channels exhibit significant differences in their voltage-gating properties. This study investigates the molecular determinants that differentiate the voltage-gating properties of human Slo1 and mouse Slo3 channels...

The inositol 1,4,5-triphosphate receptor (IP3 R) mediates Ca release in many cell types and is pivotal to a wide range of cellular processes. High resolution cryo-electron microscopy (Cryo-EM) studies have provided new structural details of IP3 R type 1 (IP3 R1), showing that channel function is determined by the movement of various domains within and between each of its four subunits. Channel properties are regulated by ligands, such as Ca and IP3, which bind at specific sites and control the interactions between these domains...

No abstract text is available yet for this article.

OBJECTIVE: Alpha-Synuclein (α-Syn), a presynaptic neuronal protein encoded by the SNCA gene, is involved in the pathogenesis of Parkinson's disease. Point mutations and multiplications of the α-Syn (A30P and A53T) are correlated with early-onset Parkinson's disease characterized by rapid progression and poor prognosis. Currently, the clinical identification of SNCA variants, especially disease-related A30P and A53T mutants, remains challenging and also time-consuming. This study has aimed to develop a novel label-free detection method for distinguishing the SNCA mutants using transmission terahertz (THz) time-domain spectroscopy...

Cell membranes act as semi-permeable barriers, often restricting the entry of large or hydrophilic molecules. Nonetheless, certain amphiphilic molecules, like antimicrobial and cell-penetrating peptides, can cross these barriers. In this study, we demonstrate that specific properties of transmembrane proteins/peptides can enhance membrane permeation of amphiphilic peptides. Using coarse-grained molecular dynamics with free energy calculations, we identify key translocation-enhancing attributes of transmembrane proteins/peptides: a continuous hydrophilic patch, charged residues preferably in the membrane center, and aromatic hydrophobic residues...

Disordered proteins are conformationally flexible proteins that are biologically important and have been implicated in devastating diseases such as Alzheimer's and cancer. Unlike stably-folded structured proteins, disordered proteins sample a range of different conformations that needs to be accounted for. Here, we treat disordered proteins as polymer chains, and compute a dimensionless quantity called instantaneous shape ratio (Rs ), as Rs = Ree 2 /Rg 2 , where Ree is end-to-end distance and Rg is radius of gyration...

As the main gatekeeper of the nucleocytoplasmic transport in eukaryotic cells, the nuclear pore complex (NPC) faces the daunting task of facilitating the bidirectional transport of a high volume of macromolecular cargoes while ensuring the selectivity, speed, and efficiency of this process. The competition between opposing nuclear import and export fluxes passing through the same channel is expected to pose a major challenge to transport efficiency. It has been suggested that phase separation-like radial segregation of import and export fluxes within the assembly of intrinsically disordered proteins that line the NPC pore could be a mechanism for ensuring efficient bidirectional transport...

Controlling mesenchymal stem cells (MSCs) differentiation remains a critical challenge in their therapeutic application. Numerous biophysical and mechanical stimuli influence stem cell fate, however, their relative efficacy and specificity in mechanically directed differentiation remain unclear. Yes-associated protein (YAP) is one key mechanosensitive protein that controls MSC differentiation. Previous studies have related nuclear mechanics with YAP activity, but we still lack an understanding of what nuclear deformation specifically regulates YAP, and its relationship with mechanical stimuli...

The Na+ -activated K+ channel KNa 1.1, encoded by the KCNT1 gene, is an important regulator of neuronal excitability. How intracellular Na+ ions bind and increase channel activity is not well understood. Analysis of KNa 1.1 channel structures indicate that there is a large twisting of the βN-αQ loop in the intracellular RCK2 domain between the inactive and Na+ -activated conformations, with a lysine (K885, human subunit numbering) close enough to potentially form a salt bridge with an aspartate (D839) in βL in the Na+ -activated state...

The micropipette aspiration technique is commonly used in the field of mechanobiology, offering a variety of measurement types. To extract biophysical parameters from the experiments, numerical analysis is required. Although previous works have developed techniques for the partial automation of this analyses, these approaches are relatively time-consuming for the researchers. In this article we describe the development and application of an artificial-intelligence tool for the completely-automatic analysis of micropipette aspiration experiments...

Stochastic models of gene expression are typically formulated using the chemical master equation, which can be solved exactly or approximately using a repertoire of analytical methods. Here, we provide a tutorial review of an alternative approach based on queueing theory that has rarely been used in the literature of gene expression. We discuss the interpretation of six types of infinite server queues from the angle of stochastic single-cell biology and provide analytical expressions for the stationary and non-stationary distributions and/or moments of mRNA/protein numbers, and bounds on the Fano factor...

Many ion channels are known to behave as an allosteric protein, coupling environmental stimuli captured by specialized sensing domains to the opening of a central pore. The classic Monod-Wyman-Changeux (MWC) model, originally proposed to describe binding of gas molecules to hemoglobin, has been widely used as a framework for analyzing ion channel gating. Here we address the issue of how accurate the MWC model predicts activation of the capsaicin receptor TRPV1 by vanilloids. Taking advantage of a concatemeric design that makes it possible to lock TRPV1 in states with zero-to-four bound vanilloid molecules, we showed quantitatively that the overall gating behavior is satisfactorily predicted by the MWC model...

During the last decade, Artificial Intelligence (AI) has increasingly been applied in biophysics and related fields, including cellular engineering and reprogramming, offering novel approaches to understand, manipulate, and control cellular function. The potential of AI lies in its ability to analyze complex datasets and generate predictive models. AI algorithms can process large amounts of data from single-cell genomics and multiomic technologies, allowing researchers to gain mechanistic insights into the control of cell identity and function...

G-quadruplexes (GQs) play key regulatory roles within the human genome and have also been identified to play similar roles in other eukaryotes, bacteria, archaea, and viruses. Human immunodeficiency virus 1 (HIV-1), the etiological agent of acquired immunodeficiency syndrome (AIDS), can form two GQs in its long terminal repeat (LTR) promoter region, each of which act to regulate viral gene expression in opposing manners. The major LTR GQ, called LTR-III, is a distinct hybrid GQ containing a 12-nucleotide duplex loop attached to the quadruplex motif...

Early embryogenesis of the nematode Caenorhabditis elegans progresses in an autonomous fashion within a protective chitin eggshell. Cell division timing and the subsequent, mechanically guided positioning of cells is virtually invariant between individuals, especially before gastrulation. Here, we have challenged this stereotypical developmental program in early stages by mechanically perturbing the embryo, without breaking its eggshell. Compressing embryos to about 2/3 of their unperturbed diameter only resulted in markedly slower cell divisions...

Conformational dynamics of RNA plays crucial for variety of cellular functions including acting as regulators of gene expression to being molecular scaffolds and sensors. The liquid-liquid phase separation of RNAs and the formation of stress granules partly relies on RNA's conformational plasticity and its ability to engage in multivalent interactions. Recent experiments with homopolymeric and low-complexity RNAs have revealed significant differences in phase separations due to differences in base chemistry of RNA units...

Lytic polysaccharides monooxygenases (LPMOs) catalyze a reaction that is crucial for the biological decomposition of various biopolymers and for the industrial conversion of plant biomass. Despite the importance of LPMOs, the exact molecular-level nature of the reaction mechanism is still debated today. Here, we investigated the pH dependent conformation of a second sphere histidine (His) that we call the "stacking histidine", which is conserved in fungal AA9 LPMOs, and is speculated to assist catalysis in several of the LPMO reaction pathways...

The physicochemical characteristics of the various subpopulations of high-density lipoproteins (HDLs) and, in particular, their surface properties determine their ability to scavenge lipids and interact with specific receptors and peptides. Five representative spheroidal HDL subpopulation models were mapped from a previously reported equilibrated coarse-grained (CG) description to an atomistic representation for subsequent molecular dynamics simulation. For each HDL model a range of finer-level analyses were undertaken, including the component-wise characterisation of HDL surfaces, the average size and composition of hydrophobic surface patches, dynamic protein secondary structure monitoring, as well as the proclivity for solvent exposure of the proposed beta-amyloid (Aβ) binding region of apolipoprotein A-I (apoA-I), 'LN'...