Mathé Jérôme, Di Meglio Jean-Marc, Tinland Bernard
Matériaux et Polymères aux Interfaces, Laboratoire MPI, Université d'Evry-Val d'Essonne, 91025 Evry Cedex, France.
J Colloid Interface Sci. 2008 Jun 1;322(1):315-20. doi: 10.1016/j.jcis.2008.02.005. Epub 2008 Feb 7.
We report a study on the dynamics of latex polystyrene beads and of DNA molecules confined in two dimensions, using fluorescence video-microscopy. We particularly focus on the character of the confined objects (hard or soft) and on the nature of the confinement: liquid (in a soap film) or solid (between two glass plates). For weak confinements, whatever the nature of confinement, we observe that DNA molecules and latex beads behave very similarly: the tighter the confinement, the slower the diffusion with a good agreement with theory. For strong confinements between solid walls (thickness of confinement smaller than the bulk radius of gyration), DNA coils are not immobilized and still diffuse. We show in this case that the conformation of DNA chains is in good agreement with the predictions of De Gennes and Brochard (radius approximately e (-1/4), with e the confinement gap); on the other hand, we cannot really check the theoretical predictions for the diffusion coefficient. Interestingly, strong confinement of latex beads in a soap film leads to a anomalous slow diffusion, certainly associated with an additional viscous drag generated by the interfaces.
我们报告了一项利用荧光视频显微镜对二维受限的乳胶聚苯乙烯珠和DNA分子动力学的研究。我们特别关注受限物体的特性（硬或软）以及受限的性质：液体（在肥皂膜中）或固体（在两块玻璃板之间）。对于弱受限情况，无论受限性质如何，我们观察到DNA分子和乳胶珠的行为非常相似：受限越紧密，扩散越慢，这与理论吻合良好。对于固体壁之间的强受限情况（受限厚度小于本体回转半径），DNA螺旋并未固定，仍会扩散。我们在此情况下表明，DNA链的构象与德热纳和布罗沙尔的预测相符（半径约为e^(-1/4)，其中e为受限间隙）；另一方面，我们无法真正检验扩散系数的理论预测。有趣的是，乳胶珠在肥皂膜中的强受限会导致异常缓慢的扩散，这肯定与界面产生的额外粘性阻力有关。
