Fluorescent molecular sensors

Arimori S, Bell ML, Oh CS et al (2001) Molecular fluorescence sensors for saccharides. Chem Commun 18 1836—1837... 

Let us now consider the case of polyatomic analytes. The analyte can be multifunctional, i.e., it can contain distinct groups of different natures and electrical charges—in this case, the receptor must provide distinct binding sites of appropriate characteristics. A representative case is that of amino acid in their zwitterionic forms NH3 -CH(R)-COO . The first example of a molecular fluorescent sensor amino acid was presented by de Silva J... 

Bis-boronate 7 forms a 1 1 complex with glucose selectively relative to other saccharides, and its enhanced fluorescence can be used as a glucose-selective molecular fluorescence sensor at physiological glucose concentrations." ... 

T. D. James, K. R. A. S. Sandanayake and S. Shinkai, A glucose-specific molecular fluorescence sensor, Angem Chem.,1994,106(21), 2287-2289. T. D. James, K. R. A. S. Sandanayake, R. Iguchi and S. Shinkai, Novel Saccharide-Photoinduced Electron-Transfer Sensors Based on the Interaction of Boronic Acid and Amine,/ Am. Chem. Soc., 1995, 117(35), 8982-8987. 

Haidekker MA, Akers W, Lichlyter D, Brady TP, Theodorakis EA (2005) Sensing of flow and shear stress using fluorescent molecular rotors. Sensor Lett 3 42 18... 

Milich KN, Akers W, Haidekker MA (2005) A ratiometric fluorophotometer for fluorescence-based viscosity measurement with molecular rotors. Sensor Lett 3 237-243... 

The cucurbit [n]uril family (CB[n]) of molecular containers possess remarkable binding affinities and selectivities (Ka values up to 1012M-1, Krei values up to 106) which renders them useful as a component of molecular machines, sensors, and biomimetic systems (123-125). Recently, Wagner and coworkers have reported (126) that CB[10] - with its spacious 870A3 cavity - is capable of acting as a host for free base and metalated tetra (Af-methylpyridinium)porphyrins 19a-d (Fig. 17). Despite the large ellipsoidal deformation of CB[10] upon complexation, the complexed porphyrins retain their fundamental UV/VIS, fluorescence, and electrochemical properties. The CB[ 10] porphyrin... 

Liu B, Bazan GC (2006) Optimization of the molecular orbital energies of conjugated polymers for optical amplification of fluorescent sensors. J Am Chem Soc 128 1188-1196... 

The design of fluorescent sensors is of major importance because of the high demand in analytical chemistry, clinical biochemistry, medicine, the environment, etc. Numerous chemical and biochemical analytes can be detected by fluorescence methods cations (H+, Li+, Na+, K+, Ca2+, Mg2+, Zn2+, Pb2+, Al3+, Cd2+, etc.), anions (halide ions, citrates, carboxylates, phosphates, ATP, etc.), neutral molecules (sugars, e.g. glucose, etc.) and gases (O2, CO2, NO, etc.). There is already a wide choice of fluorescent molecular sensors for particular applications and many of them are commercially available. However, there is still a need for sensors with improved selectivity and minimum perturbation of the microenvironment to be probed. Moreover, there is the potential for progress in the development of fluorescent sensors for biochemical analytes (amino acids, coenzymes, carbohydrates, nucleosides, nucleotides, etc.). 

K. Hamasaki, H. Ikeda, A. Nakamura, A. Ueno, F. Toda, I. Suzuki, andT. Osa, Fluorescence sensors of molecular recognition. Modified cyclodextrins capable of exhibiting guest-responsive twisted intramolecular charge transfer fluorescence, /. Am. Chem. Soc. 775,5035-5040(1993). 

The sorbent materials used to construct this type of sensor are widely varied (ion exchangers, adsorbent solids, polymers) and are employed as particles (larger than 30 pm in order to avoid overpressure in the flow system) or films. Most of these sensors are optical and rely on absorption, reflectance or molecular fluorescence measurements. In order to ensure that the sensing microzone is fully compatible with the detector, the sorbent material used must be as transparent as possible (photometry) or give rise to no appreciable light scatter (fluorimetry) so that the baseline (resulting from passage of the carrier) may be as low as possible. 

Photoinduced electron transfer (PET) has been widely used as the preferred tool in fluorescent sensor design for atomic and molecular species [52-57], PET sensors generally consist of a fluorophore and a receptor linked by a short spacer. The changes in the oxidation/reduction potential of the receptor upon guest binding can alter the PET process creating changes in fluorescence. 

The last group of fluorescent sensors is based on neither photoinduced proton transfer nor photoinduced electron transfer. The best-known example of this kind of molecular device is fluorescein (Figure 16.2e). The evolution of the fluorescence spectrum versus pH should be similar to that of the absorption spectrum. In other words, when increasing the pH, the absorption and emission bands of the acidic form should decrease with a concomitant increase in the absorption and emission bands of the basic form [1],... 

Figure 16.8 Molecular structure of TSQ and Zinquin fluorescent sensors...

Figure 16.9 Molecular structures of Zn2+ fluorescent sensors based on the bis (2-pyridylmethyl)amine (DPA) chelator...

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