使用FVS-6000光谱仪的振动圆二色光谱

智能文字提取功能测试中

一般认为，手性化合物具有不同的生物活性，这取决于每个化合物的绝对构型。因此，手性化合物的分离和研究是至关重要的。手性化合物的官能团已经被研究用于开发用于许多应用的先进分子。手性化合物的研究已经扩展到天然产物、药物和其他功能分子等多个领域，可以指出，在这些研究中，手性化合物的结构分析是一个非常重要的课题。本文报道了FVS-6000对典型手性化合物的标准性能和测量结果，我们认为FVS-6000是手性化合物分析的不可或缺的工具。Application NoteDate： April 12， 2011 260-PO-0224 Measurement of Vibrational Circular Dichroism spectra using the FVS-6000 It is generally understood that chiral compounds have different bioactivities depending upon the absolute configuration of each compound. Some familiar examples include glutamic acid and thalidomide. L-glutamic acid demonstrates the “Umami" taste*1， while D-glutamic acid has a bitter taste， similarly， the R form of thalidomide is a sedative， but the S form has teratogenic activity. Thus， the separation and study of chiral compounds is critical for many reasons. The functionalities of chiral compounds have been studied for the development of advanced molecules for many applications. The study of chiral compounds has spread to several fields such as natural products， pharmaceuticals and other functional molecules， and it can be pointed out that among those studies， the structural analysis of chiral compounds is a very important topic. X-ray Diffraction (XRD)，Nuclear Magnetic Resonance (NMR) and Electronic Circular Dichroism (ECD) using UV/is light are employed as primary methods for the structural analysis of chiral compounds. In this paper， the measurement of chiral compounds by Vibrational Circular Dichroism (VCD) using infrared light will be outlined. VCD is a method to measure the difference of absorbance intensity between left-hand and right-hand circularly polarized light as shown in Figure 1. It is an advantage of VCD that this method can be applied to almost all organic compounds in the same way as infrared (IR) spectroscopy. In addition， by comparing the measurement results with calculated results by ab-initio molecular orbital calculations， the absolute configuration of the sample can be determined . However， since the peak intensity of VCD spectra are 1，000 - 10，000 t imes weaker than that of standard IR spectra， spectroscopic instruments with high sensitivity and stability with very small baseline f luctuations are required. The FVS-6000 VCD system has a high sensitivity detector， suitable optical filter technology and a thermostatted Photo Elastic Modulator (PEM) to accurately measure the weak VCD peaks. The measurement results of typical chiral compounds and hemoglobin as a model protein using the FVS-6000 are reported. *1 Umami taste is the fifth taste sensation in addition to sweet， acid， salty and bitter taste. Figure 2： External view of the FVS-6000 Figure 1： Principles of VCD spectroscopy < Measurement results> Figures 3 through 6 illustrate the measurement results for alpha-pinene； 1，1-Bi-2-naphthol； proline and hemoglobin， respectively. Both IR and VCD spectra can be obtained by the FVS-6000. The identification of the absolute configuration of chiral compounds can be determined from both the IR and the VCD spectra as well as the analysis of the molecular structure. Figure 3 demonstrates the IR and VCD spectra of alpha-pinene which is a typical standard sample to validate a VCD instrument system. IR spectra of the R- and S- form of alpha-pinene are completely overlapped ， while their VCD spectra are symmetric， clearly identifying each alpha-pinene enantiomer.Since the peak shapes of the VCD spectra obtained illustrate typical alpha-pinene spectra， it is confirmed that high quality VCD spectra can be measured by the FVS-6000. Figure 4 outlines measurement results for 1，1-Bi-2-naphthol which is used as a ligand for t ransition-metal catalyzed asymmetric synthesis and is a precursor for chiral l igands such as BINAP. The small peaks due to the anisotropy factor 'g value'(VCD peak/IR peak) around 1600 and 1500 cm1 attributed to the benzene ring are clearly shown. These results demonstrate that the FVS-6000 is a very effective system for evaluation of chiral compounds which have similar structures. Figure 5 illustrates the measurement results of proline which is one of the amino acids. Good， symmetrical VCD spectra were obtained for the D- and L-forms. Since amino acids demonstrate different bioactivities between the D- and L- forms， studies regarding structure and bioactivity are increasingly popular. Liquid samples can be easily measured by VCD instrumentation so the structural analysis of amino acids can be performed similar to physiological conditions. Figure 6 contains the measurement results for hemoglobin. Hemoglobin is known as a spherical model protein which contains rich alpha-helix structures， and in addition， its VCD spectrum shape is very different f rom that of concanavalin A， which contains a rich beta-sheet structure. The addition of VCD spectral results to i nformation obtained from ECD and IR spectra can provide much more accurate secondary structure analysis of proteins in solvents. We also believe that VCD can also be a powerful tool for the analysis of DNA and chiral polymers other than proteins. In this paper， the standard performance and measurement results of typical chiral compounds using the FVS-6000 were reported and we believe the FVS-6000 can be an essential and indispensable tool for analysis of chiral compounds. Figure 3： Spectra of alpha-pinene (neat， 50 pm pathlength BaF2 liquid cell) 一 L-proline Figure 5： Spectra of proline (solvent： D，O， concentration： 0.9 M 25 pm pathlength CaF， liquid cell) (S)-(-)-1，1'-Bi-2-naphthol * Since the noise i n t he range of 1250-1190 cm-1 is excessive due to solvent absorption， t he data in this range are cut from the spectral figures. Figure 4： Spectra of 1，1'-Bi-2-naphthol (solvent： CHCl， concentration： 0.162 M，50 pm pathlength BaF2 liquid cell) hemoglobin Figure 6： Spectra of hemoglobin (solvent： D2O， concentration： 50 mg/mL，25 pm pathlength CaF， liquid cell)