Development of high performance photoelastic modulator and its application to measurements of solid-state circular dichroism

（1）光弹调制器（PEM）驱动器的改进利用锁相环技术对PEM驱动器进行了优化，使其具有最高的驱动效率，并使其具有较宽的驱动频率范围。（2）薄PEM头的研制为了减小PEM头光学元件中的残余双折射，制作了新型薄PEM头，该残余双折射导致固态CD测量中的伪影信号。从Schnattery型PEM诞生之日起，传统PEM头的厚度为6.4 mm。新型PEM头的厚度为2、3和4 mm。与传统的PEM头相比，新型PEM头的电等效电路中的R值相当低。(3)In DNA在固体表面吸附的圆二度的原位测量通过对DNA在水溶液中在聚乙烯亚胺（PEI）表面的吸附过程的原位圆二度的观察，包括时间分辨测量，来阐明DNA在液/固界面上的构象。吸附过程的特征在于两个阶段，其特征在于CD。在第一阶段，时间（t）<700 s，观察到DNA的时间分辨CD光谱的轻微变化，而在第二阶段，t> 700 s，其中没有进一步的吸附发生，观察到诱导CD以及DNA的CD的变化。（4）聚ε-赖氨酸（PL）的固态圆二色谱（solid-state-CD）研究CD测量通过使用无伪影技术对通过将具有不同pH值的水溶液浇铸到玻璃板上获得的PL膜进行。

(1)Improvement of photoelastic modulator (PEM) driverPEM driver, which is optimized to have highest driving efficiency by means of phase-locked loop technique, was improved to have a wide range of driving frequency.(2)Development of thin PEM headsNovel thin PEM heads were made to minimize residual birefringence in the optical element of PEM head which results in artifact signals in solid-state CD measurements. The thickness of the conventional PEM head had been 6.4 mm from the birth of Schnattery type PEM. The thicknesses of novel PEM heads are 2, 3, and 4 mm. The values of R in the electrical equivalent circuit of PEM head are quite low compared with conventional ones.(3)In situ measurement of CD of DNA adsorbing onto a solid surfaceThe adsorption process of DNA dissolved in aqueous solutions onto the surface of polyethyleneimine (PEI) has been examined by the observation of in situ CD, including time-resolved measurements, to elucidate the conformation of DNA at the liquid/solid interface. The adsorption process can be characterized by two stages that are characterized in terms of CD. In the first stage, time (t) <700s, a slight change in the time-resolved CD spectra of DNA is observed, whereas in the second stage, t>700s, where no further adsorption occurs, a change in the induced CD as well as in the CD of DNA is observed.(4)Structural investigation of Poly(ε-lysine) (PL)by solid state-CD measurements.The conformation of microbial PL was estimated by means of solid-state CD measurements. The CD measurements were done by using artifact-free technique for the PL films obtained by casting the aqueous solution with various pH onto a glass plate.