Search Results (3)

The allosteric activation of antithrombin (AT) involves a conformational shift from a native, repressed (R) to a heparin-bound, activated (AH) state. Using computational structural analysis, we identified an evolutionarily conserved allosteric communication network (ACN) comprising the residues H120, Y131, and Y166, which undergo key structural displacements during this transition. Site-directed mutagenesis of these residues markedly enhanced AT native reactivity toward FXa and reduced thermal stability, indicating their role in stabilizing the R state. These findings support a three-step “slingshot” model in which the ACN functions as a molecular lock that restrains stored conformational energy, preventing premature activation. Heparin binding disengages this lock, triggering a cascade of structural changes that propagate from the heparin-binding site (HBS) to the reactive center loop (RCL). Additional mutational analyses of residues bridging the β-sheet A (βsA) and the RCL/exosite domains revealed a delicate energetic balance involving the S380 insertion and E381–R197 salt bridge, which collectively tune the activation threshold. Molecular dynamics simulations of ACN mutants further revealed increased flexibility at both HBS and RCL domains, consistent with concerted allosteric coupling. Together, these results provide new mechanistic insights into the structural basis of AT activation and suggest avenues for engineering heparin-independent AT variants. Full article

This work presents the design, fabrication, and rigorous validation of a flexible, wireless, capacitive pressure sensor for the full-range continuous monitoring of ventricular pressure. The proposed system consists of an implantable set and an external readout device; both modules were designed to form an RCL resonant circuit for passive, wireless pressure sensing and signal retrieving. Using surface micromachining and flexible electronics techniques, a two-variable capacitor array and a dual-layer planar coil were integrated into a flexible ergonomic substrate, avoiding hybrid-like connections in the implantable set. The proposed arrangement (capacitor array and dual-layer coil) allows us to optimize the operation pressure range and sensing distance. The use of polyimide as both the flexible substrate and the passivation material is a key feature, ensuring a biocompatible, implantable set that is mechanically flexible and can be folded to a compact size to achieve minimally invasive implantation. An external readout device has also been developed using a discrete printed circuit board (PCB) approach to support pressure measurements. The pressure responsivity of the sensor was validated to the laboratory level using a controlled pressure chamber. The results obtained show that the capacitance value of the sensor changed from 5.68 pF to 33.26 pF as the pressure varied from 0 to 300 mmHg. Correspondingly, the resonance frequency of the implantable set shifted from 12.75 MHz to 5.27 MHz. The sensitivity of the capacitive sensor was approximately 0.58 pF/mmHg and the typical response time was 220 ms. The wireless system performance was evaluated in both air and synthetic biological tissue using a Maxwell–Wien bridge circuit. The results showed a sensing distance longer than 3.5 cm, even under moderate misalignment conditions (up to 1.5 cm). The output voltage was successfully measured, ranging from 502.54 mV to 538.29 mV, throughout the full pressure range, with a measurement error of ±2.2 mV. Full article

An ultra-low-cost RCL meter, aimed at IoT applications, was developed, and was used to measure electrical components based on standard techniques without the need of additional electronics beyond the AVR^® micro-controller hardware itself and high-level routines. The models and pseudo-routines required to measure admittance parameters are described, and a benchmark between the ATmega328P and ATmega32U4 AVR^® micro-controllers was performed to validate the resistance and capacitance measurements. Both ATmega328P and ATmega32U4 micro-controllers could measure isolated resistances from 0.5 Ω to 80 MΩ and capacitances from 100 fF to 4.7 mF. Inductance measurements are estimated at between 0.2 mH to 1.5 H. The accuracy and range of the measurements of series and parallel RC networks are demonstrated. The relative accuracy (a_r) and relative precision (p_r) of the measurements were quantified. For the resistance measurements, typically a_r, p_r < 10% in the interval 100 Ω–100 MΩ. For the capacitance, measured in one of the modes (fast mode), a_r < 20% and p_r < 5% in the range 100 fF–10 nF, while for the other mode (transient mode), typically a_r < 20% in the range 10 nF–10 mF and p_r < 5% for 100 pF–10 mF. a_r falls below 5% in some sub-ranges. The combination of the two capacitance modes allows for measurements in the range 100 fF–10 mF (11 orders of magnitude) with a_r < 20%. Possible applications include the sensing of impedimetric sensor arrays targeted for wearable and in-body bioelectronics, smart agriculture, and smart cities, while complying with small form factor and low cost. Full article