Microenvironment effects

Generally, the knowledge of microenvironment effects greatly simplifies label choice. This is an advantage of organic dyes as the spectroscopic properties of many... 

R. Hayashi, S. Tazuke, and C. W. Frank, Twisted intramolecular charge-transfer phenomenon as a fluorescence probe of microenvironment. Effect of polymer concentration on local viscosity and microscopic polarity around a polymer chain of poly(methyl methacrylate), Macromolecules 20, 983 (1987). 

Krinichnyi, V.I., Grinberg, O.Ya., Bogatirenko, V.R., Likhtenshtein, G.I., and Lebedev, Ya.S. (1985) Study of microenvironment effect on magnetic resonance parameters of spin-labeled human serum albumin in 2-mm range, Biofizika, 30, 216-203. 

The true seccmd-order rate constant A , for the oximate anion (fi = 12) amounts to ca 1000 M" sec. The parent rate constant fca,obs at pH 8 is about one-half of diat of a-oximate group, closeness of the positively charged atom to the active group, and electrmtatic interaction. 

As with most heterogeneous catalysts, it is often difficult to characterize immobilized enzymes at a molecular level. Most immobilized preparations are often complex mixtures with a distribution of chemically modified protein species. The gross catalytic properties observed are a composite of those of a range of differentially modified individual proteins, often irregularly distributed within the sample. Mass transfer limitations and microenvironment effects further complicate characterization. 

Ionic, hydrophobic, or other interactions between the enzyme and the matrix (microenvironment effects) may also result in changed and values. These essentially reversible effects are mostly caused by variations in the dissociation equilibria of charged groups in the active center. 

The microenvironment effect due to Donnan equilibria is shown by the now classic results (Figure 5) for pH-actlvlty profiles of chymotrypsln on polycatlonlc, and polyanionic supports vs. that of the soluble enzyme. 

Microfabrication technology can build and assemble the components of organ-on-a-chip platforms easily, facilitating the design of in vitro systems to investigate in vivo microenvironment effects. 

Zhu, L., Tong, X., Li, M., Wang, E. Luminescence enhancement of Tb ion in assemblies of amphiphilic linear-dendritic block copolymers Antenna and microenvironment effects. /. Phys. Chem. B., 105,2461-2464 (2001). 

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