Sensitivity enhancement steady state techniques

Beyond its general use as a means of sensitivity enhancement of spin-V2 nuclei with low magnetogyric ratios, the specific heteronuclear NOE has occasionally been used as a tool in structural studies [77] and is capable of providing a unique source of stractural information in favourable circumstances. Techniques for its observation largely parallel those for homonuclear experiments in the form of ID steady-state difference and 2D transient experiments, so there is nothing fundamentally new to understand here. The main limitation with these approaches is the low sensitivity associated with the observation of the low-y spin, meaning heteronuclear NOEs tend to be far less used than their homonuclear proton counterparts. The most widespread applications have involved the NOE, and more recently the H- Li NOE [78], in which... 

In this chapter, electrochemical properties of ET proteins at electrode interfaces studied by spectroelectrochem-ical techniques are described. In situ spectroelectrochemical techniques at well-defined electrode surfaces are sufficiently selective and sensitive to distinguish not only steady state structures and oxidation states of adsorbed species but also dynamics of reactants, products, and intermediates at electrode surfaces on a monolayer level. The spectroelectrochemical techniques used in studies of ET proteins include IR reflection-absorption, potential-modulated UV-vis reflectance (electroreflectance), surface-enhanced Raman scattering (SERS) and surface plasmon resonance, total internal reflection fluorescence, (TIRE) and absorbance linear dichroism spectroscopies. 

The majority of measurements for electroanalysis with microelectrodes are recorded under steady-state conditions by using either chronoamperometry (CA), linear sweep voltammetry (LSV) or cyclic voltammetry (CV) [1,2, 9,10]. Moreover, to solve problems related to the selectivity between species with similar redox potentials, pulsed techniques such as differential pulse voltammetry (DPV) [1, 7, 43 5] and square-wave voltammetry (SWV) [1, 45-49] have been employed. The use of the latter technique also minimizes the influence of oxygen in aerated natural samples [47]. In order to enhance sensitivity in these measurements, fast-scan voltammetry (FSV) [50] or the accumulation of analytes onto an electrode surface has also been performed, in conjunction with stripping analysis (SA) [51]. 

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