Single-molecule probe method

One of the primary compounds that the cell membrane is composed of is DMPC, because of its surface activity caused by a hydrophobic zwitterion. A hydrodynamic model of the DMPC membrane can evaluate the intrinsic viscosity (r]i) of the surfactant monolayer, eliminating the contribution of the viscosity of dodecane and aqueous phases. The T]i values listed in Table 10.1 are about 2-4 times higher than the apparent i. The maximum t]i value, 0.75 Pa s, is comparable to that of a common viscous liquid such as glycerin (0.945 Pa s). This study demonstrated that a single molecule probing method could successfully measure the hydrodynamic properties of the interface. 

A single molecule probing is an ultimate method for measuring the properties of the nano-environment at the liquid/liquid interface. A number of studies on single molecule detection in solutions [18-20] and at tbe solid/liquid interface [21-23] were reported, but there were no studies on single molecule detection at the liquid/liquid interface. 

The Nile Red was doped in various sol-gels to probe their micro-polarity (Lobnik, 2001). Ormosil prepared with higher fractions oformosil precursors are stable after preparation. These materials hold great promise for gas sensing. The nanoscale properties of organically modified sol-gel-derived silicate thin films, in which Nile Red was doped at nanomolecular concentrations, were studied by single-molecule spectroscopic methods (Bardo,2001). 

Abstract Chemists may find it difficult to admit that their concepts and opportunities have always been strongly influenced by the available methods for characterization and analysis. Physics, has, of course, the lead when it comes to the visualization of single molecules in real space and to the detection of their specific, not ensemble-averaged properties. The challenge for chemistry is to provide molecules as objects of study which really disclose new concepts of structure and function. This chapter presents a chemical approach toward nanosciences which comprises (i) design and synthesis, (ii) immobilization, often using principles of self-assembly, (iii) visualization, e.g. by scanning probe... 

The other molecular probe method is the single-probe method (SP method), which is separately proposed by Avnir and Jaroniec,93 and Pfeifer et al.108-112 In the SP method, a single adsorption isotherm is analyzed using a modified FHH theory. The FHH model was developed independently by Frenkel,113 Halsey,114 and Hill,115 and describes the multilayer adsorption coverage. Since the SP method uses only one probe molecule, this method is more convenient than the MP method. However, there are many theoretical limitations in applying the SP method to determination of the surface fractal dimension. Therefore, it is really necessary to discuss whether the SP method is an adequate tool to investigate the surface fractal dimension or not before applying the SP method to certain system. 

In principle, there are two methods for the AFM probing of amorphous layers, namely (i) an active probing, which probes the surface chemistry, and (ii) a passive probing, which probes the surface physics. The active AFM probing, which is essentially an extension of the AFM-based single molecule studies, relies on the measurement of LF by an AFM tip that is fimctionahsed with molecular recognition-active molecules (e.g., a potentially complementary DNA). 

The techniques involved are single-molecule spectroscopy including optical (fluorescence) methods and single-molecule mechanical manipulation including scanning probe techniques (e.g., force measurements). 

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