Development of Super Sensitive Position Detector and Its Application on the Studies of Plasma Membrane Proteins

利用象限雪崩光电二极管作为光电传感器，研制了一种新型的超灵敏位置探测器。该位置探测器与新研制的反射式偏振光学显微镜对接，以近JR(810 Nm)外腔半导体激光器为光源，可通过优化温度和电压来获得最大的S/N比。以直径为10-100 nm的胶体金粒子为标准样品，获得了-gt；100 S/N的0.5-2V输出信号。在此信号强度范围内，位置测量的带宽为0-17 MHz(-3dB)，通过PZT平台移动标准样品来检测系统的空间分辨率。在375倍的放大倍数下，空间分辨率优于3 nm。此时，空间分辨率是由电源的波动决定的，使用更稳定的电源，应该提高到1 nm以上。可以追踪200 nm-phi区域内的运动。使用该系统，测量了质膜蛋白的横向运动。虽然在33ms的视频率时间窗内无法检测到与细胞骨架结合的膜蛋白，但新研制的位置检测器的时间分辨率超过1ms，可以观察到限制在300-500 nm范围内的快速布朗尼南扩散运动。细胞骨架结合蛋白的这种受限运动暗示了细胞骨架细丝的灵活性。

A new-type super-sensitive position detector was developed using a quadrant avalanche photodiode (4APD) as the photo sensor. This position detector was interfaced to a newly-developed reflective polarisation optical microscope with a near-JR (810 nm) external cavity diode Laser as the light source, In this system, temperature and voltage of 4APD can be optimised to achieve maximum S/N ratio.Using colloidal gold particles with a diameter of 10-100 nm as standard samples, 0.5-2 V output signal with>100 S/N was obtained. At this range of signal intensity, bandwidth of position measurement was 0-17 MHz (-3dB).Spatial resolution of the system was examined by moving the standard sample by a PZT stage. At 375x magnification of the microscope, spatial resolution better than 3 nm was achieved. At this time, the spatial resolution is determined by a fluctuation of the power supply, and using more stable power supply, it should be improved to more than 1 nm. Movement within a 200 nm-phi area can be traced.Using this system, lateral movement of plasma membrane proteins were measured. Although membrane proteins which is bound to the cytoskeleton was undetectable in 33 ms video-rate time window, rapid and Browninan diffusion movement restricted within an area of 300-500 nm was observed by more than 1 ms time resolution of the newly developed position detector. Such restricted movement of cytoskeleton-bound proteins suggests flexibility of the cytoskeletal filaments.