Nonlinear optical microtomography of biological structures

非线性光学显微镜(NLO)是一种非侵入性的成像手段，由于其能够显示生物结构中无标记的非中心对称组织的分子聚集体和界面而迅速流行起来。除了使用信号强度作为对比机制外，还可以使用显微镜中非线性信号的光谱和偏振测量来研究生物样品，以揭示可视化结构的分子组织。将偏振和光谱成像方法与生物分子非线性光学性质的从头计算相结合，提供了一种强大的结构研究工具，为重建突出结构的分子组织提供了可能性。因此，我们建议发展非线性光学显微层析成像方法来研究生物晶体和有序聚集体的分子结构。NLO微层析成像将基于二次谐波产生(SHG)和振动和频率产生(V-SFG)的非线性显微测量。获得的有关分子组织的信息将用于研究胶原和肌球蛋白纤维、淀粉样聚集体以及淀粉颗粒和纤维素纤维。对蛋白质和多糖的非线性光学性质的基本了解将有助于推进几个应用领域：胶原蛋白的结构性质和含量与癌症的发生发展有关，因此胶原蛋白的非线性光学成像将为体内癌症的非侵入性诊断提供方法。肌肉收缩过程中肌球蛋白结构的动态成像将有助于研究纳米运动的收缩机制，并有助于研究心律失常和各种类型的肌病。对淀粉样蛋白结构的研究将有助于了解参与神经退行性疾病进展的聚集体的毒性。淀粉颗粒和纤维素纤维的合成和降解的研究将为在食品、纸浆和造纸工业中使用非线性显微镜进行药品、纸张、生物降解塑料和生物燃料的质量控制提供基础。

Nonlinear optical (NLO) microscopy is a noninvasive imaging modality that is rapidly gaining in popularity due to its ability to visualize label free noncentrosymmetrically organized molecular aggregates and interfaces in biological structures. In addition to employing signal intensity as a contrast mechanism, biological samples can be investigated using spectroscopic and polarization measurements of nonlinear signals in the microscope revealing molecular organization of the visualized structures. Combination of the polarization and spectroscopic imaging methods with ab initio calculations of nonlinear optical properties of biomolecules renders a powerful structural investigation tool that provides possibility to reconstruct molecular organization of the highlighted structures. Therefore, we propose to develop nonlinear optical microtomography method to study molecular structure of biological crystals and ordered aggregates. The NLO microtomography will be based on nonlinear microscopy measurements of second harmonic generation (SHG) and vibrational sum frequency generation (V-SFG). The obtained information about molecular organization will be used to study collagen and myosin fibrils, amyloid aggregates, as well as starch granules and cellulose fibrils. The fundamental understanding about the nonlinear optical properties of proteins and polysaccharides will help to advance several application areas: The collagen structural properties and content are linked to the development of cancer, therefore NLO imaging of collagen will provide with method for noninvasive cancer diagnostics in vivo. Dynamic imaging of myosin structure in muscles during contraction will enable to study contractility mechanisms of the nanomotors and will aid in studying cardiac arrhythmias and various types of myopathies. The study of amyloid structures will help to understand the toxicity of aggregates involved in progression of the neurodegenerative disorders. Investigations of synthesis and degradation of starch granules and cellulose fibers will provide basis for using nonlinear microscopy in food, pulp and paper industry for quality control of pharmaceuticals, paper, biodegradable plastics, and biofuel.