An essential method for identifying the transport active state (non-shorted with stable reproducible I-V response characteristics) of these protein junctions is impedance response signal analysis. In a functional protein junction with a sandwiched configuration, the electrical behavior can be modeled as a parallel resistor-capacitor (R-C) circuit. At high frequencies, the ac signal fully passes through the capacitive component, producing an ac phase difference of 90°. In contrast, a fully shorted junction exhibits an approximately 0° phase shift, while partially shorted junctions display a high-frequency phase shift between 0° and 90°. This distinct phase response (as a part of the Bode plot) enables identifying the non-shorted protein junctions (Figure ) (Figure ). Impedance-qualified MpD junctions were used for electron transport studies. Approximately 60% of the multi-layered protein junctions were not shorted, with over 40% demonstrating stable performance under the experimental voltage range that could be swept reproducibly in electron transport measurements, making them suitable for further transport measurements. DC measurements provided characteristic junction current values, with current histograms revealing larger variations in junction performance for the thinner HSA than for the thicker bR junctions (Figure ). The variations are sufficiently small so that the junctions with the two types of proteins can be clearly distinguished (Figure ). These protein junction currents are several orders of magnitude lower than those observed in shorted junctions. The obtained average junction current density indicates that the somewhat thicker bR junctions transport electrons more efficiently than the slightly thinner HSA junctions, consistent with previous work, using different contacts and junction configurations.