Physics Department, East Carolina University, Greenville, NC 27858-4353, USA.
Chirality. 2012 Sep;24(9):706-17. doi: 10.1002/chir.22006. Epub 2012 May 25.
A single-beam spectrometer equipped with a photoelastic modulator can be configured to measure a number of different parameters useful in characterizing chemical and biochemical materials including natural and magnetic circular dichroism, linear dichroism, natural and magnetic fluorescence-detected circular dichroism, and fluorescence polarization anisotropy as well as total absorption and fluorescence. The derivations of the mathematical expressions used to extract these parameters from ultraviolet, visible, and near-infrared light-induced electronic signals in a dichrometer assume that the dichroic signals are sufficiently small that certain mathematical approximations will not introduce significant errors. This article quantifies errors resulting from these assumptions as a function of the magnitude of the dichroic signals. In the case of linear dichroism, improper modulator programming can result in errors greater than those resulting from the assumption of small signal size, whereas for fluorescence polarization anisotropy, improper modulator phase alone gives incorrect results. Modulator phase can also impact the values of total absorbance recorded simultaneously with linear dichroism and total fluorescence.
一台配备有光弹调制器的单光束分光光度计可以配置为测量多种不同的参数，这些参数对于表征化学和生化材料非常有用，包括自然和磁圆二色性、线二色性、自然和磁荧光探测圆二色性、荧光偏振各向异性以及总吸收和荧光。从分光光度计中紫外、可见和近红外光诱导的电子信号中提取这些参数的数学表达式的推导假设，二色性信号足够小，某些数学近似不会引入显著的误差。本文将量化这些假设所带来的误差，这些误差是作为二色性信号的函数来表示的。在线二色性的情况下，调制器编程不当可能会导致比信号尺寸小的假设所带来的误差更大，而对于荧光偏振各向异性，仅仅是调制器相位不当就会给出错误的结果。调制器相位也会影响与线二色性和总荧光同时记录的总吸光度的值。
