Structural modeling of human cardiac sodium channel pore domain

<p>The pore domain of human voltage-dependent cardiac sodium channel Na_v1.5 (hNa_v1.5) is the crucial binding targets for anti-arrhythmics drugs and some local anesthetic drugs but its three-dimensional structure is still lacking. This has affected the detailed studies of the binding features and mechanism of these drugs. In this paper, we present a structural model for open-state pore domain of hNa_v1.5 built using single template ROSETTA-membrane homology modeling with the crystal structure of Na_vMs. The assembled structural models are evaluated by rosettaMP energy and locations of binding sites. The modeled structures of the pore domain of hNa_v1.5 in open state will be helpful to explore molecular mechanism of a state-dependent drug binding and help designing new drugs.</p

Near-Infrared Light-Activated Photochemical Internalization of Reduction-Responsive Polyprodrug Vesicles for Synergistic Photodynamic Therapy and Chemotherapy

The use of intracellular reductive microenvironment to control the release of therapeutic payloads has emerged as a popular approach to design and fabricate intelligent nanocarriers. However, these reduction-responsive nanocarriers are generally trapped within endolysosomes after internalization and are subjected to unwanted disintegration, remarkably compromising the therapeutic performance. Herein, amphiphilic polyprodrugs of poly­(<i>N</i>,<i>N</i>-dimethylacrylamide-<i>co</i>-EoS)-<i>b</i>-PCPTM were synthesized via sequential reversible addition–fragmentation chain transfer (RAFT) polymerization, where EoS and CPTM are Eosin Y- and camptothecin (CPT)-based monomers, respectively. An oil-in-water (O/W) emulsion method was applied to self-assemble the amphiphilic polyprodrugs into hybrid vesicles in the presence of hydrophobic oleic acid (OA)-stabilized upconversion nanoparticles (UCNPs, NaYF₄:Yb/Er), rendering it possible to activate the EoS photosensitizer under a near-infrared (NIR) laser irradiation with the generation of singlet oxygen (¹O₂) through the energy transfer between UCNPs and EoS moieties. Notably, the <i>in situ</i> generated singlet oxygen (¹O₂) can not only exert its photodynamic therapy (PDT) effect but also disrupt the membranes of endolysosomes and thus facilitate the endosomal escape of internalized nanocarriers (i.e., photochemical internalization (PCI)). Cell experiments revealed that the hybrid vesicles could be facilely taken up by endocytosis. Although the internalized hybrid vesicles were initially trapped within endolysosomes, a remarkable endosomal escape into the cytoplasm was observed under 980 nm laser irradiation as a result of the PCI effect of ¹O₂. The escaped hybrid vesicles subsequently underwent GSH-triggered CPT release in the cytosol, thereby activating the chemotherapy process. The integration of PDT module into the design of reduction-responsive nanocarriers provides a feasible approach to enhance the therapeutic performance

Photo- and Reduction-Responsive Polymersomes for Programmed Release of Small and Macromolecular Payloads

We report on the preparation of photo- and reduction-responsive diblock copolymers through reversible addition–fragmentation chain transfer (RAFT) polymerization of a coumarin-based disulfide-containing monomer (i.e., CSSMA) using a poly­(ethylene oxide) (PEO)-based macroRAFT agent. The resulting amphiphilic PEO-<i>b</i>-PCSSMA copolymers self-assembled into polymersomes with hydrophilic PEO shielding coronas and hydrophobic bilayer membranes. Upon irradiating the polymersomes with visible light (e.g., 430 nm), the coumarin moieties within the bilayer membranes were cleaved with the generation of primary amine groups, which spontaneously underwent inter/intrachain amidation reactions with the ester moieties, thereby tracelessly cross-linking and permeating the bilayer membranes. Notably, this process only gave rise to the release of small molecule payloads (e.g., doxorubicin hydrochloride, DOX) while large molecule encapsulants (e.g., Texas red-labeled dextran, TR-dextran) were retained within the cross-linked polymersomes due to the preservation of the integrity of the vesicular nanostructures. However, cross-linked polymersomes undergo further structural disintegration upon incubation with glutathione (GSH) due to the scission of disulfide linkages, resulting in the release of macromolecular payloads. Thus, dual-stimuli responsive polymersomes with tracelessly cross-linkable characteristics enable sequential release of payloads with spatiotemporal precision, which could be of promising applications in synergistic loading and programmed release of therapeutics

Rationally Engineering Phototherapy Modules of Eosin-Conjugated Responsive Polymeric Nanocarriers via Intracellular Endocytic pH Gradients

Spatiotemporal switching of respective phototherapy modes at the cellular level with minimum side effects and high therapeutic efficacy is a major challenge for cancer phototherapy. Herein we demonstrate how to address this issue by employing photosensitizer-conjugated pH-responsive block copolymers in combination with intracellular endocytic pH gradients. At neutral pH corresponding to extracellular and cytosol milieu, the copolymers self-assemble into micelles with prominently quenched fluorescence emission and low ¹O₂ generation capability, favoring a highly efficient photothermal module. Under mildly acidic pH associated with endolysosomes, protonation-triggered micelle-to-unimer transition results in recovered emission and enhanced photodynamic ¹O₂ efficiency, which synergistically actuates release of encapsulated drugs, endosomal escape, and photochemical internalization processes

Construction of Polyelectrolyte-Responsive Microgels, and Polyelectrolyte Concentration and Chain Length-Dependent Adsorption Kinetics

We report on the construction of a polyelectrolyte-responsive system evolved from sterically stabilized protonated poly­(2-vinylpyridine) (P2VPH⁺) microgels. Negatively charged sodium dodecylbenzenesulfonate (SDBS) surfactants could be readily internalized into the cationic microgels by means of electrostatic interactions, resulting in microgel collapse and concomitant formation of surfactant micellar domains (P2VPH⁺/SDBS)-contained electrostatic complexes. These internal hydrophobic domains conferred the opportunity of fluorescent dyes to be loaded. The obtained fluorescent microgel complexes could be further disintegrated in the presence of anionic polyelectrolyte, poly­(sodium 4-styrenesulfonate) (PNaStS). The stronger electrostatic attraction between multivalent P2VPH⁺ microgels and PNaStS polyelectrolyte than single-charged surfactant led to triggered release of the encapsulated pyrene dyes from the hydrophobic interiors into microgel dispersion. The process was confirmed by laser light scattering (LLS) and fluorescence measurements. Furthermore, the entire dynamic process of PNaStS adsorption into P2VPH⁺ microgel interior was further studied by stopped-flow equipment as a function of polyelectrolyte concentration and degree of polymerization. The whole adsorption process could be well fitted with a double-exponential function, suggesting a fast (τ₁) and a slow (τ₂) relaxation time, respectively. The fast process (τ₁) was correlated well with the approaching of PNaStS with P2VPH⁺ microgel to form a nonequilibrium complex within the microgel shell, while the slow process (τ₂) was consistent with the formation of equilibrium complexes in the microgel deeper inside. This simple yet feasible design augurs well for the promising applications in controlled release fields

Preorientation of protein and RNA just before contacting

<div><p>Protein and RNA molecules interact and form complexes in many biological processes. However, it is still unclear how they can find the correct docking direction before forming complex. In this paper, we study preorientation of RNA and protein separated at a distance of 5–7 Å just before they form contacts and interact with each other only through pure electrostatic interaction when neglecting the influence of other molecules and complicated environment. Since geometric complementary has no meaning at such a distance, this is not a docking problem and so the conventional docking methods, like FTDock, are inapplicable. However, like the usual docking problem, we need to sample all the positions and orientations of RNA surrounding the protein to find the lowest energy orientations between RNA and protein. Therefore, we propose a long-range electrostatic docking-like method using Fast Fourier Transform-based sampling, LEDock, to study this problem. Our results show that the electrostatically induced orientations between RNA and protein at a distance of 5–7 Å are very different from the random ones and are much closer to those in their native complexes. Meanwhile, electrostatic funnels are found around the RNA-binding sites of the proteins in 62 out of 78 bound protein–RNA complexes. We also tried to use LEDock to find RNA-binding residues and it seems to perform slightly better than BindN Server for 23 unbound protein–RNA complexes.</p> </div

Efficient Synthesis of Single Gold Nanoparticle Hybrid Amphiphilic Triblock Copolymers and Their Controlled Self-Assembly

We report on a robust approach to the size-selective and template-free synthesis of asymmetrically functionalized ultrasmall (<4 nm) gold nanoparticles (AuNPs) stably anchored with a single amphiphilic triblock copolymer chain per NP. Directed NP self-assembly in aqueous solution can be facilely accomplished to afford organic/inorganic hybrid micelles, vesicles, rods, and large compound micelles by taking advantage of the rich microphase separation behavior of the as-synthesized AuNP hybrid amphiphilic triblock copolymers, PEO–AuNP–PS, which act as the polymer–metal–polymer analogue of conventional amphiphilic triblock copolymers. Factors affecting the size-selective fabrication and self-assembly characteristics and the time-dependent morphological evolution of NP assemblies were thoroughly explored

Multi-stage uncertainties manifested in stakeholder decision-making processes during implementation.

<p>Multi-stage uncertainties manifested in stakeholder decision-making processes during implementation.</p

Cell-Penetrating Hyperbranched Polyprodrug Amphiphiles for Synergistic Reductive Milieu-Triggered Drug Release and Enhanced Magnetic Resonance Signals

The rational design of theranostic nanoparticles exhibiting synergistic turn-on of therapeutic potency and enhanced diagnostic imaging in response to tumor milieu is critical for efficient personalized cancer chemotherapy. We herein fabricate self-reporting theranostic drug nanocarriers based on hyperbranched polyprodrug amphiphiles (<b>hPAs</b>) consisting of hyperbranched cores conjugated with reduction-activatable camptothecin prodrugs and magnetic resonance (MR) imaging contrast agent (Gd complex), and hydrophilic coronas functionalized with guanidine residues. Upon cellular internalization, reductive milieu-actuated release of anticancer drug in the active form, activation of therapeutic efficacy (>70-fold enhancement in cytotoxicity), and turn-on of MR imaging (∼9.6-fold increase in <i>T</i>₁ relaxivity) were simultaneously achieved in the simulated cytosol milieu. In addition, guanidine-decorated <b>hPAs</b> exhibited extended blood circulation with a half-life up to ∼9.8 h and excellent tumor cell penetration potency. The hyperbranched chain topology thus provides a novel theranostic polyprodrug platform for synergistic imaging/chemotherapy and enhanced tumor uptake

Schizophrenic Core–Shell Microgels: Thermoregulated Core and Shell Swelling/Collapse by Combining UCST and LCST Phase Transitions

A variety of slightly cross-linked poly­(2-vinylpyridine)–poly­(<i>N</i>-isopropylacrylamide) (P2VP–PNIPAM) core–shell microgels with pH- and temperature-responsive characteristic were prepared via seeded emulsion polymerization. Negatively charged sodium 2,6-naphthalenedisulfonate (2,6-NDS) could be internalized into the inner core, followed by formation of (P2VPH⁺/SO₃^2–) supramolecular complex through the electrostatic attractive interaction in acid condition. The thermoresponsive characteristic feature of the (P2VPH⁺/SO₃^2–)–PNIPAM core–shell microgels was investigated by laser light scattering and UV–vis measurement, revealing an integration of upper critical solution temperature (UCST) and lower critical solution temperature (LCST) behaviors in the temperature range of 20–55 °C. The UCST performance arised from the compromised electrostatic attractive interaction between P2VPH⁺ and 2,6-NDS at elevated temperatures, while the subsequent LCST transition is correlated to the thermo-induced collapse of PNIPAM shells. The controlled release of 2,6-NDS was monitored by static fluorescence spectra as a function of temperature change. Moreover, stopped-flow equipped with a temperature-jump accessory was then employed to assess the dynamic process, suggesting a millisecond characteristic relaxation time of the 2,6-NDS diffusion process. Interestingly, the characteristic relaxation time is independent of the shell cross-link density, whereas it was significantly affected by shell thickness. We believe that these dual thermoresponsive core–shell microgels with thermotunable volume phase transition may augur promising applications in the fields of polymer science and materials, particularly for temperature-triggered release