Biological labelling experiments

Fig. 9.1. The first biological labeling experiment with colloidal semiconductor nanocrystal quantum dots, reproduced from the 1998 paper by Ahvisatos and Weiss [1]. A larger size of dot, red emitting, has been used to label the actin fibers of the fibroblast cells, while a smaller, green-emitting set of dots is used to label the histone proteins in the nuclei. Today colloidal quantum dots are widely used in biological imaging, demonstrating the important role of nanoparticles in this field...

The following protocol is a general guide for labeling biological macromolecules with Lissamine rhodamine B sulfonyl chloride. Optimization of the fluorophore incorporation level (F/P ratio) may have to be done for specific labeling experiments. 

The biological importance of transamination was confirmed using 15N-labeling experiments (Tannenbaum and Shemin, 1950). 15N-leucine incubated with pig heart muscle gave highly labelled 15N-glutamate, evidence that leucine could be transaminated. Isotope experiments were then extended to the whole range of amino acids. 

By the early 1960s it was clear that simple experiments on P uptake were inadequate to distinguish different species of RNA in mixed populations of cells at different stages of the cell cycle. The future for labeling experiments with 32P in cell biology was to lie mainly with synchronized cells and for studies on nucleic acids, with molecular biological techniques. 

H. Pereira, P. C. Lemos, M. J. T. Carrondo, J. P. S. Crespo, M. A. M. Peis and H. Santos (1996). Model for carbon metabolism in biological phosphorus removal processes based on in vivo 13C labelling experiment. Water Res., 30, 2128-2138. 

This device is highly processive (as shown by labeling experiments this means that during the motional process the walker does not detach from its track or, as defined in molecular biology, it is able to bind to a filament and take successive steps [48]), and operates directionally, repeatedly, and progressively. 

In the course of mechanistic investigations covering these enzymatic reductions, labeling experiments were carried out with biologically produced, selectively deuterated NADPH-mole-cules 4-(/ )-[4- H]NADPH and 4-(5)-[4-2H] NADPH [11], The formation of hydroxy derivatives of opposite stereochemistry is caused by the ketoreductase domains KRl and KR2 from the protein DEBS 1 of the erythromycin poly-ketide-synthase. However, both domains have a preference for the 4-pro-(5)-hydride of the NADPH molecule. Probably the binding of the cofactor in KR domains takes place in an identical manner, whereas the individual y9-keto-acylthioester building blocks in the domains KR 1 and KR 2 of DEBS 1 capture a different orientation relative to the cofactor [11]. 

C-atom on a global scale. However, the actual cycling and turn-over rates of carbon in biological systems within various micro-environments have to be considered short-circuited and much more rapid, as numerous radiocarbon labeling experiments show. Life processes also stimulate and regulate multiple subcycles of carbonate dissolution and reprecipitation (see Chapters 2.2 and 2.4). On the other hand, some carbon deposited in stable continental interiors (cratons) remains protected from dissolution (or oxidation) and recycling from the time of deposition billions (10 ) of years ago up to the present. 

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