Environmental probe

Finally, the ability to regulate in situ the upconversion properties of an ion, or conversely to use upconversion as an in situ environmental probe, has not been demonstrated, although all of the key ingredients have been individually de-... 

Fluorescence spectroscopy was utilized as the diagnostic to evaluate these phenomena. It will be shown that a single probe molecule, a derivative of dimethylaminonaphthalenesulfonamide, (dansyl, J.) can function both as an environmental probe to evaluate the degree of solvation of polymer chains in the gel phase and also serve as a sensitive indicator for the diffusion of ionic reagents through the crosslinked gel network. 

The use of a spectroscopic technique (specifically, UV-Vis absorption spectrophotometry) to quantify the solvent effect provides doubtless advantages. Thus, the solute is in its electronic ground state, in thermodynamic equilibrium with its environment, so the transition is vertical and the solvation sphere remains unchanged throughout. These advantages make designing a good environmental probe for any of the previous three effects quite easy. 

It has been suggested that water penetrates micelles up to at least the first seven carbons, beyond which there exists a non-polar core. This is a compromise between earlier extreme proposals that water permeates nearly to the centre of the micelle and that water at the surface of the micelle meets a non-aqueous core at an abrupt interface. The motional freedom of a molecule in a micelle depends upon the extent of penetration and, although it is difficult to generalize from experiments involving large environmental probes incorporated into micellar aggregates, it appears that the micelle interior is relatively fluid. ... 

K. Fredriksson, B. Galle, K. Nystrom, S. Svanberg Mobile lidar system for environmental probing. Appl. Opt. 20, 4181 (1981)... 

The above study utilized pyrene as an environmental probe. The steady-state fluorescence spectrum of pyrene possesses five distinct vibronic bands. The third vibronic band at approximately 383 nm is allowed and is insensitive to solvent polarity. The first vibronic, however, is forbidden and yields enhanced values of... 

Chi c, the two transitions in the visible (Qy, QJ are only weakly allowed, while two in the blue or near-UV spectral region By, BJ are intense 3 x 10 ). The Q -band is less forbidden (e ,3, =< 10 ) and progressively red-shifted in chlorin- and bacteriochlorin-type chlorophylls (Figure 117.2). These pigments have, therefore, two regions of intense absorptions in the red to near-IR (Qy) and in the blue to near-UV spectral ranges (Soret or 5-bands). The Q, -band remains weak in the chlorins but is moderately intense in the bacteriochlorins. Because in the latter, the B, - and B -bands are also well separated, all four canonical transitions are clearly discernible in the bacteriochlorophyUs. The significance of this fact was first realized by Scherz et al., who used it, subsequently, as a sensitive environmental probe. °> ... 

In other words, the tautomerism of histidines constitutes a molecular environmental probe. Moreover, model studies for the interior of proteins should not be made using water but wet polar organic liquids as solvents. 

Catalan J, Diaz C, Garcia-Bianco F. Effects of medium on decarboxylation kinetics 3-carboxybenzisoxazoles and their potential use as environmental probes in biochemistry. J Org Chem. 2000 65 3409-3415. 

---