Protein-free 1-18 INDEX

Soszynski, M., and Bartosz, G., Decrease in accessible thiols as an index of oxidative damage to membrane proteins. Free Radicals Biol. Med. 23, 463-469 (1997). 

Label-free quantification is a very attractive method, because there are no extra costs involved. Instead, there are much higher demands on the reproducibility of technical parameters, such as sample loading, chromatography, and mass accuracy, and more experimental replicates are needed. In the following sections, different approaches to label-free quantification will be discussed the extracted ion chromatogram (XIC), spectral counting (SC), the protein abundance index (PAI), and the LCMS method. 

Ferritin is another protein that is important in the metabolism of iron. Under normal conditions, it stores iron that can be called upon for use as conditions require. In conditions of excess iron (eg, hemochromatosis), body stores of iron are greatly increased and much more ferritin is present in the tissues, such as the liver and spleen. Ferritin contains approximately 23% iron, and apoferritin (the protein moiety free of iron) has a molecular mass of approximately 440 kDa. Ferritin is composed of 24 subunits of 18.5 kDa, which surround in a micellar form some 3000-4500 ferric atoms. Normally, there is a little ferritin in human plasma. However, in patients with excess iron, the amount of ferritin in plasma is markedly elevated. The amount of ferritin in plasma can be conveniently measured by a sensitive and specific radioimmunoassay and serves as an index of body iron stores. 

There are small changes in serum albumin concentration with age, with concomitant small effects on protein binding of some highly bound drugs such as naproxen, salicylate, and warfarin. For such drugs the free concentration rather than the total plasma concentration is a better predictor of drug dose requirements, particularly for drugs with low therapeutic index (difference between the therapeutic... 

In principle, it would be logical to combine plots of the buffer index curves of each of the buffer components of milk and thus obtain a plot which could be compared with that actually found for milk. It is not difficult, of course, to conclude that the principal buffer components are phosphate, citrate, bicarbonate, and proteins, but quantitative assignment of the buffer capacity to these components proves to be rather difficult. This problem arises primarily from the presence of calcium and magnesium in the system. These alkaline earths are present as free ions as soluble, undissociated complexes with phosphates, citrate, and casein and as colloidal phosphates associated with casein. Thus precise definition of the ionic equilibria in milk becomes rather complicated. It is difficult to obtain ratios for the various physical states of some of the components, even in simple systems. Some concentrations must be calculated from the dissociation constants, whose... 

It may also be necessary to determine the free fatty acid content of oily materials as an index of rancidity, since this will affect palatability. Analyses of amino acids can only be conducted in specialized laboratories and are conducted less frequently. Instead most feed mixers (including commercial feed manufacturers) use procedures such as prediction equations based on the protein content of the sample to predict the content of important amino acids. Tests for minerals are more routine and are offered by most laboratories. Tests for vitamins are offered by certain laboratories but are not very frequent since commercial feed manufacturers often disregard any vitamin contribution from the dietary ingredients and add all the necessary vitamins in the form of a supplement. 

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