Mazzola L T, Frank C W, Fodor S P, Mosher C, Lartius R, Henderson E
Department of Chemistry, Stanford University, Stanford, California 94305, USA.
Biophys J. 1999 Jun;76(6):2922-33. doi: 10.1016/S0006-3495(99)77447-3.
Atomic force microscopy (AFM) can be used to probe the mechanics of molecular recognition between surfaces. In the application known as "chemical force" microscopy (CFM), a chemically modified AFM tip probes a surface through chemical recognition. When modified with a biological ligand or receptor, the AFM tip can discriminate between its biological binding partner and other molecules on a heterogeneous substrate. The strength of the interaction between the modified tip and the substrate is governed by the molecular affinity. We have used CFM to probe the interactions between short segments of single-strand DNA (oligonucleotides). First, a latex microparticle was modified with the sequence 3'-CAGTTCTACGATGGCAAGTC and epoxied to a standard AFM cantilever. This DNA-modified probe was then used to scan substrates containing the complementary sequence 5'-GTCAAGATGCTACCGTTCAG. These substrates consisted of micron-scale, patterned arrays of one or more distinct oligonucleotides. A strong friction interaction was measured between the modified tip and both elements of surface-bound DNA. Complementary oligonucleotides exhibited a stronger friction than the noncomplementary sequences within the patterned array. The friction force correlated with the measured strength of adhesion (rupture force) for the tip- and array-bound oligonucleotides. This result is consistent with the formation of a greater number of hydrogen bonds for the complementary sequence, suggesting that the friction arises from a sequence-specific interaction (hybridization) of the tip and surface DNA.
原子力显微镜（AFM）可用于探测表面之间分子识别的力学机制。在被称为“化学力”显微镜（CFM）的应用中，经过化学修饰的AFM探针通过化学识别来探测表面。当用生物配体或受体进行修饰时，AFM探针能够在异质底物上区分其生物结合伴侣和其他分子。修饰后的探针与底物之间相互作用的强度由分子亲和力决定。我们已使用CFM来探测单链DNA（寡核苷酸）短片段之间的相互作用。首先，用序列3'-CAGTTCTACGATGGCAAGTC修饰乳胶微粒，并将其环氧连接到标准AFM悬臂上。然后使用这种DNA修饰的探针扫描含有互补序列5'-GTCAAGATGCTACCGTTCAG的底物。这些底物由一个或多个不同寡核苷酸的微米级图案化阵列组成。在修饰后的探针与表面结合的DNA的两个元件之间都测量到了强烈的摩擦相互作用。互补寡核苷酸在图案化阵列中表现出比非互补序列更强的摩擦力。摩擦力与探针和阵列结合的寡核苷酸的测量粘附强度（断裂力）相关。这一结果与互补序列形成更多氢键相一致，表明摩擦力源于探针与表面DNA的序列特异性相互作用（杂交）。
