Department of Physics, National University of Singapore, Singapore 117542.
Lab Chip. 2013 Jul 21;13(14):2821-6. doi: 10.1039/c3lc50233c.
We report an approach to study the in situ conformational response of single biomolecules such as DNA to a change in environmental solution conditions. These conditions are, for example, the composition of the buffer or the presence of protein. For this purpose, we designed and fabricated a nanofluidic device featuring two arrays of parallel nanochannels in a perpendicular configuration. The cross-sections of the channels are rectangular with a diameter down to 175 nm. These lab-on-a-chip devices were made of polydimethylsiloxane (PDMS) cast on a high quality master stamp, obtained by proton beam writing and UV lithography. Biomolecules can be inserted into the device through the array of channels in one direction, whereas the buffer can be exchanged through the intersecting array of channels in the other direction. A buffer exchange time inside the grid of nanochannels of less than one second was measured by monitoring the conductivity of salt solutions. The exchange time of a protein was typically a few seconds, as determined by imaging the influx of fluorescence labelled protamine. We demonstrate the functionality of the device by investigating the compaction of DNA by protamine and the unpacking of pre-compacted DNA through an increase in the concentration of salt.
我们提出了一种方法，用于研究单分子（例如 DNA）在环境溶液条件变化时的原位构象响应。这些条件例如是缓冲液的组成或蛋白质的存在。为此，我们设计并制造了一种纳米流控装置，其特点是在垂直方向上具有两个平行纳米通道的阵列。通道的横截面为矩形，直径可低至 175nm。这些芯片实验室器件由聚二甲基硅氧烷（PDMS）制成，浇铸在由质子束写入和紫外光刻制成的高质量主印模上。生物分子可以通过一个方向的通道阵列插入到器件中，而缓冲液可以通过另一个方向的相交通道阵列进行交换。通过监测盐溶液的电导率，我们测量了在纳米通道网格内的缓冲液交换时间不到一秒。通过荧光标记鱼精蛋白的流入来成像，我们确定蛋白质的交换时间通常为几秒钟。我们通过研究鱼精蛋白对 DNA 的压缩和解压缩，以及通过增加盐浓度来解开预压缩的 DNA，证明了该器件的功能。
