Selectivity Sensing mechanism

The principle of pH electrode sensing mechanisms which are based on glass or polymer membranes is well investigated and understood. Common to all potentiometric ion selective sensors, a pH sensitive membrane is the key component for a sensing mechanism. When the pH sensitive membrane separates the internal standard solution with a constant pH from the test solution, the potential difference E across the membrane is determined by the Nemst equation ... 

RNAi and ribozymes represent two additional approaches to gene silencing/down-regulation with therapeutic potential. RNAi is an innate cellular process that achieves silencing of selected genes via an anti-sense mechanism. It shares many characteristics with the antisense-based approach described above, but also some important differences, e.g. in the exact mechanism by which the antisense effect is achieved. 

Other sensors are mostly grouped towards the triethylamine. In the case of porphyrins 6-8, 13 the coordinated metal is no longer able to drive the selectivity pattern and the presence of the peripheral alkyl chains completely shadows the coordination interactions. This result can explain the failure to observe the coordination interaction in the sensing mechanism of the metal complexes of the closely related alkyl chains functionalized phthalocyanines reported in the past by Gopel and coworkers [22]. 

This effect is complete in the case of porphyrins 6-8,13, which behave in the same way, independent of metal present in the inner core of the macrocycle. In conclusion, the introduction of these alkyl chains from one side gives a higher porosity to the molecular film and, as a consequence, both a speed up of the response and an increase of the sensor response. On the other hand there is a significant decrease of the importance of the selective interactions in the sensing mechanism of the organic material and, as a consequence, a lowering of the selectivity of the sensor. 

The significant emission enhancement of these chemosensors and the high selectivity towards phosphorylated peptides enabled the detection of phosphorylated peptides by naked inspection of the emission change. This is illustrated in the photograph shown in Fig. 5. Such fluorescence intensification of the chemosensors is clearly ascribed to the phosphate-assisted binding of the second Zn cation. A schematic illustration of the sensing mechanism toward the phosphorylated peptide is depicted in Scheme 11. In the absence of a phosphorylated peptide, the second Dpa site of the chemosensor is... 

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