Rockholt D L, Royce C R, Richards E G
Biophys Chem. 1976 Jul;5(1-2):55-75. doi: 10.1016/0301-4622(76)80026-9.
The "Optical Multichannel Analyzer" (OMA) is a commercially available instrument that with the absorption optical system of the ultracentrifuge, provides an entire 500 channel intensity profile of a cell in real time. With its own analog-todigital converter, the OMA integrates a selectable number of 32.8 msec scans to provide a time-averaged image in digital form. This paper describes an interface-controller for operation of the OMA with single- and double-sector cells in multi-cell rotors, simulating double-beam measurement required for absorbance determinations. The desired sector is selected by "gating" the intensifier stage of a "Silicon Intensified Target" vidicon (SIT) used as the light detector. The cell location in the rotor and the position of the gate relative to the cell centerline is obtained from a phase-locked loop circuit which divides each rotation of the rotor into 3600 parts independent of rotor speed. (This circuit employed with photo-multiplier scanners would select the gate position for integration of photomultiplier pulses.) From examination of appropriate signals with an oscilloscope, it was verified that gate positions and widths are located with an accuracy of 0.1degree or better and with a precision of +/- 0.1 mus. The light intensity profile for any desired cell can be examined in "real time", even during acceleration of the rotor. Additional circuits employing a 10 MHz crystal clock 1) control the automatic collection of data for all sectors in multicell rotors at digitally selected time intervals, 2) display the rotor speed, and 3) indicate the elapsed time of the experiment. Constructed but not tested are additional circuits for pulsing a laser into the absorption or Rayleigh optical system. The accuracy of the pulsed SIT has been demonstrated by measurement of absorbances of solutions and also by sedimentation equilibrium experiments with myoglobin. The estimated error is 0.003 for absorbances ranging from 0 to 1. The interface-controller operates extremely well, but problems related to the pulsed SIT (optimum gate position relative to the sector opening shape of high-voltage pulse, slight pincushion distortion) require more work.
“光学多通道分析仪”（OMA）是一种商用仪器，它与超速离心机的吸收光学系统配合使用，可实时提供细胞完整的500通道强度分布图。OMA通过自身的模数转换器，对选定数量的32.8毫秒扫描进行积分，以数字形式提供时间平均图像。本文介绍了一种接口控制器，用于在多池转子中操作OMA与单扇区和双扇区池，模拟吸光度测定所需的双光束测量。通过对用作光探测器的“硅增强靶”视像管（SIT）的增强器级进行“选通”来选择所需扇区。转子中细胞的位置以及门相对于细胞中心线的位置是从一个锁相环电路获得的，该电路将转子的每一次旋转分成3600个部分，与转子速度无关。（该电路与光电倍增管扫描仪配合使用时，将选择门位置以对光电倍增管脉冲进行积分。）通过示波器检查适当的信号，证实门位置和宽度的定位精度为0.1度或更高，精度为±0.1微秒。即使在转子加速期间，也可以“实时”检查任何所需细胞的光强度分布图。采用10MHz晶体时钟的附加电路：1）以数字选择的时间间隔控制多池转子中所有扇区的数据自动采集，2）显示转子速度，3）指示实验的经过时间。已构建但未测试用于将激光脉冲输入吸收或瑞利光学系统的附加电路。通过测量溶液的吸光度以及用肌红蛋白进行沉降平衡实验，已证明了脉冲SIT的准确性。对于吸光度范围为0至1的情况，估计误差为0.003。接口控制器运行得非常好，但与脉冲SIT相关的问题（相对于高压脉冲扇区开口形状的最佳门位置、轻微的枕形失真）需要更多的工作。
