Spectroscopic tags

DoeringW.E., Nie S.M., Spectroscopic tags using dye-embedded nanoparticles and surface-enhanced Raman scattering, Anal. Chem. 2003 75 6171-6176. 

An experiment with an irreversible inhibitor should carry with it a control experiment involving the addition of a substrate if the location of the reaction with inhibitor is at the active site, then the addition of a substrate will slow down the rate of inhibition. For example, the reactivity of papain (5 pM) with a 1.71 pM solution of 4-toluenesulphonylamidomethyl chloromethyl ketone suffers a drop of 1.68-fold when the substrate (methyl hippurate) is changed from 12.7 to 21.1 mM. The inhibitor which reacts covalently with the enzyme should carry either a radioactive or spectroscopic tag which would enable the location of the altered amino acid to be determined in the sequence, and hence in the three-dimensional X-ray crystallographic map of the enzyme. An alternative approach is to design an inhibitor with groups (analogous to those attached to the substrate) which force it to bind at the active site (Scheme 11.18). 

Kim JH, Kim JS, Choi H, Lee SM, Jun BH, Yu KN, KukE, Kim YK, Jeong DH, Cho MH, Lee YS (2006) Nanoparticle probes with surface enhanced Raman spectroscopic tags for cellular cancer targeting. Anal Chem 78 6967-6973... 

W. E. Doering and S.M. Nie, Spectroscopic Tags Using Dye-Embedded Nanoparticles and Surface-Enhanced Raman Scattering, Anal. Chem. 75, 6171 (2003)... 

Many derivatives of fluorescein containing a reactive group at the C-5 position are commercially available [11], Fluorescein isothiocyanate, for example, is widely used as protein tag [12]. These substances have essentially the same spectroscopic properties as the parent compound with the additional capability of binding covalently to proteins. Because of their high emission quantum yields, fluorescein conjugates are extensively used as tracers for microinjection in living cells to gather information on the structure and function of cells, localization of proteins, and cell-to-cell and intracellular diffusion [13-17]. 

Cell and Small Animal Imaging with Surface-Enhanced Raman Spectroscopic (SERS) and Other Nanoparticle Tags... 

Forster s theory [1], has enabled the efficiency of EET to be predicted and analyzed. The significance of Forster s formulation is evinced by the numerous and diverse areas of study that have been impacted by his paper. This predictive theory was turned on its head by Stryer and Haugland [17], who showed that distances in the range of 2-50 nm between molecular tags in a protein could be measured by a spectroscopic ruler known as fluorescence resonance energy transfer (FRET). Similar kinds of experiments have been employed to analyze the structure and dynamics of interfaces in blends of polymers. 

The carbohydrate being eluted from a GPC column can be detected by a number of physical or chemical means (e.g., variation in refractive index or viscosity and colorimetric or fluorometric spectroscopic analysis). For the purpose of these experiments, the cellulose was tagged with a fluorescent label, dichlorotriazinylaminofluorescein (DTAF), which permits easy detection of very small quantities. The chromatographic system was set up to allow for convenient analysis of cellulose with a maximum resolution of the molecular weight distribution and a minimum of change to the sample. 

An important reagent in fluorous chemistry is the fluorous version of the Marshall resin, dubbed FluoMar (4). This separation tag is reported to dissolve readily in dichloromethane, tetrahydrofuran, and ethyl acetate and can, as many other fluorous reagents, be monitored by traditional chromatographic and spectroscopic methods. The usefulness of (4) was demonstrated in a multistep parallel synthesis of a 3 X 3 array of diamides, where the final products were efficiently purified by F-SPE and cleaved from the FluoMar tag. Tentative results indicated that the homogeneous kinetics of the soluble (4) resulted in reactions that proceeded approximately three times faster than polymer-support bound reactions using standard Marshall resin. 

Flumphreys, J.M. and Chappie, C. (2004) Immunodetection and quantification of cytochromes P450 using epitope tagging immunological, spectroscopic, and kinetic analysis of cinnamate 4-hydroxylase.. Immunol. Methods, 292, 97-107. 

Another excellent method of quantitative analysis makes use of tagging with radioactive or stable isotopes [29,30]. Detection is by radiation, mass spectroscopy [31], or nuclear magnetic resonance [32], Unfortunately, experiments involving radioactivity require elaborate precautions and special laboratory rooms to avoid contamination and meet legal requirements, and mass-spectroscopic and NMR equipment is expensive and may not be available. 

Qian X, Peng X-H, Ansari DO, Yin-Goen Q, Chen GZ, Shin DM, Yang L, Young AN, Wang MD, Nie S (2008) In vivo tumor targeting and spectroscopic detection with surface-enhanced Raman nanoparticle tags. Nat Biotechnol 26 83... 

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