Single molecules
Single molecules
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单分子
DOI：
10.1073/pnas.191365898
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发表时间：
2001
影响因子：
11.1
通讯作者：
J. M. Fernandez
中科院分区：
文献类型：
--
作者：
Th. Basché;S. Nie;J. M. Fernandez
首先是一个实验挑战，用单分子进行实验的能力与实验技术和仪器的进步密切相关。扫描探针技术，如扫描隧道显微镜或原子力显微镜（AFM），使用靠近样品（10−9 m）的尖端来测量隧道电流或微弱的机械力，从而可以生成单个原子或分子的真实空间“图像”。在另一种方法中，可以将大分子夹在AFM针尖和基底之间，以确定拉伸单个聚合物链所需的力。类似的实验也可以通过使用光镊来实现，在光镊中，一个大分子被附着在一个微小的珠子和一个基底上。作用在珠上的光的力可用于克服由大分子（2）产生的力而使其平移。在光学领域，单分子（或更一般的单荧光团）在某些凝聚相环境中的荧光发射可以通过先进的光学显微镜成像，如扫描共聚焦显微镜或近场扫描光学显微镜（3）。在低温下，单个荧光团也可以通过频率选择技术分离，该技术利用掺杂剂分子的尖锐光学跃迁频率由于环境的不完美而不同的事实（4）。这些光学技术允许在单分子水平上进行详细的光谱调查，利用光谱，时间分辨和偏振信息。
At first an experimental challenge, the ability to conduct experiments with single molecules has been strongly connected with progress in experimental techniques and instrumentation. Scanning probe techniques, such as the scanning tunneling microscope or the atomic force microscope (AFM), use sharp tips in close proximity (10−9 m) to a sample to measure tunneling currents or weak mechanical forces that, in turn, allow generation of a real-space “image” of a single atom or molecule (1). In another approach, macromolecules can be clamped between an AFM tip and a substrate to determine the forces needed to stretch a single polymer chain. Similar experiments are feasible by use of optical tweezers, where a macromolecule is attached to a tiny bead and a substrate. The light force acting on the bead can be used to translate it against a force generated by the macromolecule (2). In the optical domain, the fluorescence emission of single molecules (or more general single fluorophores) in some condensed-phase environments can be imaged by advanced optical microscopies, such as scanning confocal microscopy or near-field scanning optical microscopy (3). At low temperatures, single fluorophores can also be isolated by a frequency selective technique that uses the fact that the sharp optical transition frequencies of dopant molecules are different because of imperfections of the environment (4). These optical techniques allow for detailed spectroscopic investigations at the single-molecule level, taking advantage of spectral, time-resolved, and polarization information.