Near-Field Stationary Sample Terahertz Spectroscopic Polarimetry for Biomolecular Structural Dynamics Determination,ACS Photonics

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Near-Field Stationary Sample Terahertz Spectroscopic Polarimetry for Biomolecular Structural Dynamics Determination
ACS Photonics ( IF 6.5 ) Pub Date : 2021-02-03 , DOI: 10.1021/acsphotonics.0c01876
Yanting Deng ₁ , Jeffrey A. McKinney ₁ , Deepu K. George ₁ , Katherine A. Niessen ₁ , Akansha Sharma ₁ , Andrea G. Markelz ₁

Affiliation

THz polarimetry on environmentally sensitive and microscopic samples can provide unique insight into underlying mechanisms of complex phenomena. For example, near-field THz anisotropic absorption successfully isolated protein structural vibrations which are connected to biological function. However, to determine how these vibrations impact function requires high throughput measurements of these complex systems, which is challenged by the need for near field detection, sample environmental control and full polarization variation. Stationary sample anisotropic terahertz spectroscopy (SSATS) and near-field stationary sample anisotropic terahertz microscopy (SSATM) have been proposed using synchronous control of THz and electro optic probe polarizations along an iso-response curve. Here we realize these techniques through robust control and calibration of the THz and NIR polarization states. Both methods rapidly measure the linear dichroism in the far field and near field. Validation measurements using standard birefringent sucrose single crystals found the crystal orientation can be determined by scanning the reference polarization and the synchronous pump–probe polarization settings can be optimized to eliminate artifacts. SSATM is then used to determine spectral reproducibility and dehydration effects for a series of chicken egg white lysozyme samples. Reproducible anisotropic absorbance bands are found at about 30, 44, 55, and 62 cm^–1. These bands initially sharpen with slow dehydration, similar to the increase in resolution achieved in X-ray crystallographic protein structure determination. The SSATM technique confirms the reliability of anisotropic absorption characterization of protein intramolecular vibrations and opens an avenue for rapid determination of how these long-range dynamics affect biological function.

中文翻译：

近场固定样品太赫兹光谱极化测定生物分子结构动力学

对环境敏感和微观样品的太赫兹偏振能提供对复杂现象潜在机理的独特见解。例如，近场太赫兹各向异性吸收成功地分离了与生物功能有关的蛋白质结构振动。但是，要确定这些振动如何影响功能，需要对这些复杂系统进行高通量测量，这受到对近场检测，样品环境控制和完全偏振变化的需求的挑战。利用同步控制太赫兹频率和沿等响应曲线的电光探头极化，已经提出了静止样品各向异性太赫兹光谱（SSATS）和近场固定样品各向异性太赫兹显微镜（SSATM）。在这里，我们通过鲁棒控制和校准THz和NIR偏振态来实现这些技术。两种方法都可以快速测量远场和近场中的线性二向色性。使用标准双折射蔗糖单晶进行的验证测量发现，可以通过扫描参考偏振确定晶体取向，并且可以优化同步泵浦-探针偏振设置以消除伪影。然后将SSATM用于确定一系列鸡蛋白溶菌酶样品的光谱重现性和脱水作用。在约30、44、55和62 cm处发现可再现的各向异性吸收带使用标准双折射蔗糖单晶进行的验证测量发现，可以通过扫描参考偏振确定晶体取向，并且可以优化同步泵浦-探针偏振设置以消除伪影。然后将SSATM用于确定一系列鸡蛋白溶菌酶样品的光谱重现性和脱水作用。在约30、44、55和62 cm处发现可再现的各向异性吸收带使用标准双折射蔗糖单晶进行的验证测量发现，可以通过扫描参考偏振确定晶体取向，并且可以优化同步泵浦-探针偏振设置以消除伪影。然后将SSATM用于确定一系列鸡蛋白溶菌酶样品的光谱重现性和脱水作用。在约30、44、55和62 cm处发现可再现的各向异性吸收带^–1。这些条带最初随着缓慢的脱水而变尖锐，类似于X射线晶体学蛋白质结构测定中获得的分辨率提高。SSATM技术证实了蛋白质分子内振动的各向异性吸收表征的可靠性，并为快速确定这些远程动力学如何影响生物学功能开辟了道路。

更新日期：2021-02-17

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