Natural circular dichroism of amino acid films observed in soft X-ray and VUV region using polarizing undulator

Abstract

We observed the natural circular dichroism NCD of amino acid films in the soft X-ray region for the first time [1]. Based on the success, a new generation of detection system is now under preparation. Vacuum ultraviolet NCD of amino acid films was measured successfully using a polarizing undulator [2] installed at the TERAS electron storage ring at AIST, Tsukuba, Japan. A result of NCD measurement for alanine films is described in detail.

Development of vacuum‐ultraviolet circular dichroism measurement system using a polarizing undulator

“…(23), the real CD spectrum should be obtained in principle. However, as mentioned in detail in a previous report, 26 we have even observed the apparent CD spectra of DLLeu films. Such apparent CD spectra originate from the derivative of the absorption spectra.…”

“…37 In addition, for alanine films, a CD peak was observed at around 180 nm and ascribed to the same resonance. 26 Therefore, the CD and LD peaks at around 182 nm of Leu films probably correspond to the same resonance. Some difference in the CD peak wavelength with that of absorption indicates that the absorption peak at f180 nm consists of some resonances that can exhibit CD and others that cannot.…”

“…It was proved that subtracting the derivative of each absorption spectrum from the apparent CD spectrum gives the real CD spectrum. 26 Following this method, we obtained the real CD spectra of our samples. The component originating from the derivative of the absorption spectra was found to be about 20% in the apparent CD spectra.…”

“…Recently, for application to chiral molecules and to extend the VUV-CD measurable region to wavelengths shorter than 140 nm, we have developed an AC modulation spectroscopic technique for VUV-CD and LD measurement 24,25 using the Onuki undulator and have succeeded in measuring CD spectra of isotropic alanine films 26,25 and LD spectra as specular reflectance from a KBr(100) cleaved surface in the wavelength range down to 120 nm. 24 For solid state measurements, LD spectra, as well as CD spectra, are important as probes of molecular orientation and for confirming the findings of CD spectra.…”

Compact optical cell system for vacuum ultraviolet absorption and circular dichroism spectroscopy and its application to aqueous solution sample

“…To compensate for a little non-chiral baseline, the VUV-CD spectrum of R-ACS was subtracted from that of S-ACS. 21 Details of VUV-CD measurements at the TERAS BL-5 and the calibration method have been reported elsewhere. [10][11][12][13] The calibrated CD spectrophotometer (J720WI, JASCO) was also used to obtain the standard CD spectra of ACS aqueous solutions.…”