Heterogeneous distribution of components in the biological membrane is critical in the process of cell polarization. However, little is known about the mechanisms that can generate and maintain the heterogeneous distribution of the membrane components. Here, we report that the propagating wave patterns of the bacterial Min proteins can impose steric pressure on the membrane, resulting in transport and directional accumulation of the component in the membrane. Therefore, the membrane component waves represent transport of the component in the membrane that is caused by the steric pressure gradient induced by the differential levels of binding and dissociation of the Min proteins in the propagating waves on the membrane surface. The diffusivity, majorly influenced by the membrane anchor of the component, and the repulsed ability, majorly influenced by the steric property of the membrane component, determine the differential spatial distribution of the membrane component. Thus, transportation of the membrane component by the Min proteins follows a simple physical principle, which resembles a linear peristaltic pumping process, to selectively segregate and maintain heterogeneous distribution of materials in the membrane.

Developing reliable memory devices with stable information storage capability in water is important for environmental and healthcare applications. However, it is challenging because water easily causes current leakage and information loss in conventional memory devices. This article reports a transistor-based graphene memory for which writing/erasing is through controlling the nanometer-thin water layer between graphene and its silica support. Using an interfacial water layer with a tunable thickness to switch the graphene electron-trapping extent allows the device to function in water, which is completely different from any current memory mechanisms. Stable high- and low-conductance (ON and OFF) states can be achieved by applying positive and negative gate voltages to control the water layer thickness as the writing/erasing processes, which is supported by our atomic force microscopy and Raman spectroscopy experimental results and theoretical predictions. The high stability in water and reversible switching property based on the nanometer-thin insulating water layer could facilitate the realization of ultra-compact 2D nonvolatile memories for various underwater applications.

Helicases are biomolecular motors that unwind nucleic acids, and their regulation is essential for proper maintenance of genomic integrity. E. coli Rep helicase, whose primary role is to help restart stalled replication, serves as a model for Superfamily I helicases. Rep-like helicases contain a flexible subdomain (2B) that regulates their activity; however, the mechanism of control is not well understood. While a monomer of Rep cannot unwind duplex DNA, complete removal of 2B activates the motor for unwinding, though not as processively as locking 2B into one conformation. Here we investigate the behavior of a 2B-deletion variant (RepD2B) in relation to wild-type Rep. Using a single-molecule optical tweezers assay, we show that DNA unwinding by RepD2B monomer is more processive than by wtRep oligomer. Additionally, we find that RepD2B can switch between strands and form a single-stranded DNA loop, both of which limit unwinding. By exploring the effect of force and DNA geometry on helicase activity, we further show that the behaviors mentioned above are highly influenced by duplex stability. In light of our results, we propose a new model for regulation of unwinding by Rep-like helicases. DNA from neutrophil cells is released into the blood stream to forms neutrophil extracellular traps (NETs), as an immune response response to trap circulating pathogens. The mechanosensitive blood-coagulation adhesive protein, von Willebrand Factor (VWF), has been recently identified to interact with DNA of NETs and suggested to play a key stabilization role of such traps during inflammation. Nevertheless, the molecular nature, structural stability, and biological implications of this interaction remained to be elucidated. Here, we addressed this question by performing Brownian Dynamics and Molecular Dynamics simulations. Our simulations revealed an interesting mode of binding in which a specific region in VWF, namely a helix 4 (H4) in its A1 domain, acts as the specific binding site for DNA. In turn, DNA offers multiple unspecific binding sites for the A1 domain. Three arginines of the H4 were identified as key residues anchoring VWF to DNA. Furthermore, simulations varying the ionic strength and extensive in silico mutational studies pointed to electrostatic attraction as the main driving force governing the VWF-DNA interaction. Our data predicts a naturally-occurring mutation of one of the arginines to significantly destabilize the VWF-DNA interaction, a prediction that is currently under experimental validation. Moreover, our data attribute the partial diminish in binding of platelets to VWF, not to competition of DNA and platelets for the same binding site at A1, but rather, to partial unspecific steric preclusion of the platelet binding site upon binding of DNA to VWF. All together, our study provides the molecular basis for the stabilization of DNA-based NETs by VWF, with potential implications during inflammation. . RNA-DNA hybrids are functionally essential structures involved in numerous protein-dependent processes suc...

Heterogeneous distribution of components in the biological membrane is critical in the process of cell polarization. However, little is known about the mechanisms that can generate and maintain the heterogeneous distribution of the membrane components. Here we report that the propagating wave patterns of the bacterial Min proteins can impose corresponding steric pressure on the membrane to establish a directional accumulation of the membrane components, resulting in segregation of the components in the membrane. The diffusivity, influenced by the membrane anchor of the component, and the repulsed ability, influenced by the steric property of the soluble region of the component and molecular crowding, determine the differential spatial distribution of the component in the membrane. Thus, transportation of the membrane components by the Min proteins follows a simple physical principle, which resembles a linear peristaltic pumping process, to selectively segregate and maintain heterogeneous distribution of materials in the membrane.

We have previously demonstrated the potential of gelatin films as a memory device, offering a novel approach for writing, reading, and erasing through the manipulation of gelatin structure and bound water content. Here, we discovered that incorporating a bacteriorhodopsin (BR)–lipid membrane into the gelatin devices can further increase the electron conductivity of the polypeptide-bound water network and the ON/OFF ratio of the device by two folds. Our photocurrent measurements show that the BR incorporated in the membrane sandwiched in a gelatin device can generate a net proton flow from the counter side to the deposited side of the membrane. This leads to the establishment of non-electroneutrality on the gelatin films adjacent to the BR-incorporated membrane. Our Raman spectroscopy results show that BR proton pumping in the ON state gelatin device increases the bound water presence and promotes polypeptide unwinding compared to devices without BR. These findings suggest that the non-electroneutrality induced by BR proton pumping can increase the extent of polypeptide unwinding within the gelatin matrix, consequently trapping more bound water within the gelatin-bound water network. The resulting rise in hydrogen bonds could expand electron transfer routes, thereby enhancing the electron conductivity of the memory device in the ON state.