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In oxygenic plants, photons are captured with high quantum efficiency by two specialized reaction centers (RC) called Photosystem I (PS I) and Photosystem II (PS II). The captured photon triggers rapid charge separation and the photon energy is converted into an electrostatic potential across the nanometer-scale (\sim6~\nm) reaction centers. The exogenous photovoltages from a single PS I RC have been previously measured using the technique of Kelvin force probe microscopy (KFM). However, biomolecular photovoltaic applications require two-terminal devices. This paper presents for the first time, a micro-device for detection and characterization of isolated PS I RCs. The device is based on an AlGaN/GaN high electron mobility transistor (HEMT) structure. AlGaN/GaN HEMTs show high current throughputs and greater sensitivity to surface charges compared to other field-effect devices. PS I complexes immobilized on the floating gate of AlGaN/GaN HEMTs resulted in significant changes in the device characteristics under illumination. An analytical model has been developed to estimate the RCs of a major orientation on the functionalized gate surface of the HEMTs. [ABSTRACT FROM PUBLISHER]

Monokine induced by interferon gamma (MIG) is an important biomarker for early monitoring of transplant rejection. This letter presents a novel technique for detecting human MIG by using immunologically-modified field effect transistors. Detection of MIG with anti-MIG antibody in high concentration phosphate buffer saline solution was achieved for the first time. To provide specific MIG detection capability, anti-MIG IgG molecular affinity interface receptors were formed on a short self-assembled monolayer on a floating gold sensing gate of a biochemically modified AlGaN/GaN high electron mobility transistor device. [ABSTRACT FROM PUBLISHER]