Immobilization of DNA for Single Molecule Detection

双螺旋DNA是由腺嘌呤-胸腺嘧啶和胞嘧啶-鸟嘌呤组成的基于特定氢键的互补碱基对组成的超分子结构，携带着遗传信息。由于p电子在碱基对基态的堆积作用，DNA可以作为p电子介质进行光致电子转移。在利用近场光学和光诱导电子转移相结合的新的光学技术检测DNA的单分子方面，多核酸通过空气-水界面上特定的分子间相互作用被固定为二维分子组件或单分子。DNA的主链上带有磷酸基团，与带反电的两亲分子组装在一起，并以多离子复合单分子膜的形式固定在空气-水界面上。我们研究了脱氧核糖核酸对吖啶两亲分子和CAT…双组分单分子膜荧光寿命的影响更多的离子双链两亲分子。当PolyG PolyC溶解于水的亚相时，其荧光发生强烈猝灭。由于荧光寿命不像荧光强度那样短，可能是由于鸟嘌呤碱的电子转移引起的，因此发生了吖啶类荧光的静态猝灭。用电化学方法测量了ITO电极的光致电子转移。通过与多核酸形成络合物，两亲性吖啶染料的阳极光敏化电流增强。PolyG PolyC的鸟嘌呤碱基被吖啶部分的激发态氧化，对光电流的产生是最有效的。用简单铸造法在云母衬底上制备了介观条纹状DNA。将混合/不混合海藻酸水溶液的脱氧核糖核酸水溶液滴在肉质解理的云母表面，加热至约80ﾟC烘干。在铸膜层中观察到平行于溶剂后退方向的介观线条。当在DNA水溶液中加入海藻酸时，可以得到排列规则的条带。这些线条的高度都在10 nm以下。较少

Double-helical DNA is a supramolecular architecture composed of complementary base-pairings of adenine-thymine and cytosine-guanine based on specific hydrogen bonding, and carries genetic information. Due to the stacking interaction of p-electrons at the ground states of the base-pairs, DNA can act as a p-electron medium for the photoinduced electron transfer. Toward the single molecule detection of DNA by using a novel optical technique based on the combination of near field optics and photoinduced electron transfer, polynucleic acids have been immobilized as two-dimensional molecular assemblies or single molecule by means of the specific intermolecular interaction at the air-water interface. DNA, having phosphate groups in its backbone, was assembled with counter charged amphiphiles and fixed as a polyion complex monolayer at the air-water interface. We have investigated the effect of DNA on the fluorescence lifetime of a binary component monolayer of an acridine amphiphile and a cat … More ionic double chain amphiphile. Strong fluorescence quenching was found when polyG polyC was dissolved in a water subphase. Static quenching of acridine fluorescence, probably due to the electron transfer from guanine base, is occurred because the fluorescence life-time is not so reduced as fluorescence intensity. The photoinduced electron transfer to an ITO electrode was measured by an electrochemical method. Anodic photosensitized current of the amphiphilic acridine dye is enhanced by the complex formation with polynucleic acids. PolyG polyC, whose guanine base is assumed to be *idized by the excited state of the acridine moiety, is most effective for photocurrent generation. By using the simple casting method we have prepared mesoscopic stripe pattern of DNA on a mica substrate. An aqueous DNA solution mixed with/without an aqueous alginic acid solution was dropped onto a fleshly cleaved mica surface and dried by heating up to ca. 80ﾟC.The mesoscopic lines parallel to the receding direction of the solvent were observed in the cast film. When alginic acid were added in the aqueous DNA solution, more regularly aligned stripe patterns were obtained. Height of those lines was below 10 nm. Less