Pulse-labeling technique

Finally, both constant infusion and pulse label techniques using isotopic labels to estimate whole body protein turnover share the common premise that there is a homogeneous metabolic nitrogen pool of which the plasma constitutes an integral part. That this is in fact an oversimplification, has been shown from animal studies [438]. Despite these, and other objections, work will continue in the search for a reliable method for the estimation of protein synthesis, catabolism and turnover in man. To the clinician such a method would provide information about nitrogen loss from the body resulting from malnutrition, postoperative trauma, burns or severe infection and perhaps more importantly an indication of the success or otherwise of the specific therapeutic regime implemented. 

A kinetic pulse-labelling technique for the detection of transitory intermediates on the aflatoxin biosynthetic pathway has been described. It has been applied to both sterigmatocystin (85) formation in Aspergillus versicolor amd aflatoxin formation in A. parasiticus. The results are largely in accord with the accepted sequence of intermediates. However, one... 

The input of carbon into soil via rhizodeposition and the decay of roots has been quantified in several studies using either pulse or continuous CO -labeling techniques (4,7,13-15), and estimates of carbon rhizodeposition vary considerably. 

Plants grown for longer periods in solid supports such as sand or soil repre-.sent the next level of complexity and, although other techniques are available, carbon flow is most frequently estimated using C labeling experiments. In the laboratory, COt can be supplied to shoots either as a short pulse or continuously, and the carbon flow can be monitored. In the field, due to technical limitations, only COi pulse labeling procedures are possible. A final approach, termed crop studies, involves the measurement of components of crop growth from which... 

Effectiveness of a crude oil demulsifier is correlated with the lowering of shear viscosity and dynamic tension gradient of the oil-water interface. Using the pulsed drop technique, the interfacial dilational modulii with different demulsifiers have been measured. The interfacial tension relaxation occurs faster with an effective demulsifier. Electron spin resonance with labeled demulsifiers indicate that the demulsifiers form reverse micelle like clusters in bulk oil. The slow unclustering of the demulsifier at the interface appears to be the rate determining step in the tension relaxation process. 

Ashikawa, I., J.-J. Yin, W. K. Subczynski, T. Kouyama, J. S. Hyde, and A. Kusumi. 1994. Molecular organization and dynamics in bacteriorhodopsin-rich reconstituted membranes Discrimination of lipid environments by the oxygen transport parameter using a pulse ESR spin-labeling technique. Biochemistry 33 4947 1952. 

A useful adjunct is the well-known pulse-chase technique, in which exposure to a radiolabeled compound for a specified period of time (pulse) is followed by the administration of the same compound that is not labeled (chase). 

Advances in pulsed lasers, microscopy and computer imaging, and the development of labelling techniques in which the donor and acceptor fluorophores become part of the biomolecules themselves have enabled the visualisation of dynamic protein interactions within living cells. 

An alternative pulse sequence that provides the same multiplicities as INEPT but with intensity ratios that follow the binomial theorem is DEPT (distortionless enhancement by polarization transfer).The pulse sequence, depicted in Fig. 12.3a, can be used, like refocused INEPT, for sensitivity enhancement but is usually employed as an editing technique. The three evolution periods T are chosen to approximate 1/2/, but the length of the pulse labeled 0 can be varied. As we show in the following, CH has maximum intensity at 0 = 90° CH2 has zero... 

Isotope pulse-labelling experiments have been the main technique by which carbon can be traced through the plant mycorrhizal soil system in order to quantify its allocation to AMF. By providing plants with... 

In a broad sense, pulse radiolysis can be also regarded as a labeling technique. It causes, by its oxidative or reductive attack, certain changes (i.e. OH-adducts of aromatic and heterocyclic rings or radical intermediates of cystine) which label definite places in protein molecule. This technique is useful for studying the role of functional groups of enzymes... 

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