Dual Label Interactions

Most homogenous detection methods make use of distance-dependent interactions between two labels. For example, a fluorescence donor can pass its energy by a ra- 

19-times increased fluorescence upon binding of 11 A 5 -CGGCTATTACGGC-3 5-times increased fluorescence upon binding of 11C 5-CGGCTCTTACGGC-3 Fig. 4.2.7. Homogeneous DNA detection with FIT-probes. 

The fluorescence is quenched by collisional quenching and fluorescence resonance energy-transfer (FRET). When the probe sequence anneals to the target sequence fluorescence 

Murakami, M. Nakaura, Y. Nakatsuji, S. Nagahara, Q. Tran-Cong, K. Makino, Nucleic Acids Res. 1991, 19, 4097-4102. 

Svanvik, A. Stahlberg, U. Sehlstedt, R. Sjoback, M. Kubista, Anal. Biochem. 2000, 287, 179-182. 

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Fig. 4.2.8. Homogeneous DNA detection by employing fluorescence resonance energy transfer between two labels. Dual label interaction between (a) dyes that bind to dsDNA...

These studies demonstrate that treatments that have been reported to modify the heat stability of milk also may change the distribution of tracer milk proteins between the physical phases of milk. Analysis of these interactions may provide useful information about the mechanisms of these effects. In unpublished experiments, we have extended this approach for studying homogenized milk-based systems, also containing a lipid phase, to investigate lipid-protein interactions. Dual-label experiments, for example in milk containing M-/3-L and 3H-methyl-/c-casein, could be applied to the isolation and characterization of protein complexes in milk. Labeled caseins could prove valuable as probes for elucidating micelle structure. 

In many cases there is an interaction between the carrier and the active component of the catalyst so that the character of the active surface will change. For example, the electronic character of the supported catalyst may be influenced by the transfer of electrons across the catalyst-carrier interface. In some cases the carrier itself has a catalytic activity for the primary reaction, an intermediate reaction, or a subsequent reaction, and a dual-function catalyst is thereby obtained. Materials of this type are widely employed in reforming processes. There are other cases where the interaction of the catalyst and support are much more subtle and difficult to label. For example, the crystal size and structure of supported metal catalysts as well as the manner in which the metal is dispersed can be influenced by the nature of the support material. 

The SRK framework is used with the cognitive work analysis approach to conduct the worker competencies phase. Vicente (1999) presented a worker competencies analysis of the Dual Reservoir System Simulation (DURESS) II process control microworld. Here, the worker competencies are expressed in terms of the skill-, rule-, and knowledge-based behaviors required. Most of the demands associated with industrial process control are cognitive rather than perceptual-motor in nature, and only limited tasks require skill-based behavior. Vicente suggested that operators should have basic perceptual skills and should be able to recognize and keep track of the labels for the various components within DURESS II. He also suggested that operators should be able to directly interact with displays rather than have to... 

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