Single-particle and ensemble diffusivities--test of ergodicity.
Single-particle and ensemble diffusivities--test of ergodicity.
复制标题
单粒子和系综扩散率--遍历性检验
DOI：
10.1002/anie.201105388
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发表时间：
2012
影响因子：
--
通讯作者：
Bräuchle
中科院分区：
文献类型：
--
作者：
Naumov;Michaelis;Valiullin;Kärger;Bräuchle
扩散是物质基本成分的无规则的、无所不在的运动。一般来说，它是生命的先决条件，也是自然界和技术中无数过程的关键。经过一个半世纪的扩散测量与大合奏的扩散粒子[1]，选择单粒子跟踪（SPT）与单分子灵敏度[2]最近为我们提供了一个全新的观点扩散。考虑到这一点，物质动力学的一个中心问题现在可以通过直接的实验证据来解决-遍历定理的证明表明，如果在许多随后的时间间隔上取，在时间间隔t期间扩散粒子的平方位移r2（t）的平均值（“时间平均”），同意许多不同粒子的平均值（“系综平均”）。到目前为止，相互矛盾的测量条件阻碍了对同一系统应用总体和单粒子技术：通过用SPT拟合分子随时间的位置来构造扩散单分子的轨迹。因此，分子的荧光信号必须彼此清楚地分离，这需要非常低的浓度。此外，测量受到信噪比的限制，该信噪比受到染料分子的亮度以及积分时间的影响。因此，SPT中可检测的扩散率存在上限。完全相反的条件，即高浓度（用于产生足够强的信号强度）和高扩散率（用于产生可观察到的位移），必须满足应用程序的脉冲场梯度（PFG）技术的NMR，代表最强大的合奏技术的扩散研究。
Diffusion is the irregular, omnipresent motion of the elementary constituents of matter. It is prerequisite for life quite in general and key to innumerable processes in nature and technology. After one and a half centuries of diffusion measurements with large ensembles of diffusing particles [1], the option of single-particle tracking (SPT) with single molecule sensitivity [2] has recently provided us with a totally new view of diffusion. With this in mind, a central problem of matter dynamics can now be addressed by direct experimental evidence–the proof of the ergodic theorem indicating that the average value of the squared displacement r2 (t) of a diffusing particle during a time interval t, if taken over many subsequent time intervals (“time average”), agrees with the average taken over many different particles (“ensemble average”) during one and the same time interval t.So far, the mutually contradicting measuring conditions have prohibited the application of ensemble and single-particle techniques to one and the same system: The trajectory of a diffusing single molecule is constructed by fitting the position of the molecule over time with SPT. Therefore the fluorescence signals of the molecules have to be clearly separated from each other, which requires very low concentrations. Additionally the measurements are limited by the signal-to-noise ratio, which is influenced by the brightness of the dye molecules as well as the integration time. Consequently there is an upper limit for the detectable diffusivity in SPT. Exactly the opposite conditions, namely high concentrations (for generating sufficiently strong signal intensities) and high diffusivities (for giving rise to observable displacements) must be fulfilled for the application of the pulsed field gradient (PFG) technique of NMR, representing the most powerful ensemble technique for diffusion studies.
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DOI：
10.1073/pnas.93.7.2926
发表时间：
1996-04-02
影响因子：
11.1
作者：
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通讯作者：
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DOI：
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发表时间：
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期刊：
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DOI：
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发表时间：
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期刊：
影响因子：
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作者：
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影响因子：
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作者：
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