Substituted plants, isotopically

Resonance Raman spectra of [Fe2S2(Cys)4] proteins, illustrated in Fig. 21 for adrenodoxin and a plant ferredoxin, are substantially more complex, as might be expected. With the aid of isotope substitution and model compound data, it has nevertheless been possible to characterize the modes completely and to assign them to vibrations involving primarily the bridging or terminal sulfur atoms (superscripts b and t, respectively. 

Proper internal standards have to be applied for quantitative analyses performed using any kind of instrumental system. Isotopomers of the analyzed compounds substituted with stable isotopes ( H, and/or are especially convenient internal standards as they have chromatographic properties identical with the native compounds, and the ratio of signal intensity of both types of ions may be easily calculated. Finally, analyses should be performed in a fairly high number of repetitions (above six) due to the biological diversity of plant material studied. 

Food adulteration Quality assurance of food products is an important activity in the food industry where the substitution of lower cost alternatives constitutes fraud as well as a public health risk. Stable isotope measurements have been successfully applied to many instances where all-natural fruit juices, honey and maple syrup have been artificially sweetened. This is possible when the added sugar is from a plant species which follows a different photosynthetic pathway from that of the bulk material (C3 versus C4 plants), leading to a d C composition of the food product intermediate to the 124 difference between the two plant types. 

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