Ferritins

Sample material Serum or plasma (citrate or oxalate), heparin and EDTA are not recommended for plasma separation. The serum and plasma samples can be stored in the refrigerator for one week at +2 C to -h8°C. 

Interferences No relevant interference is exercised by haemolytic (haemoglobin up to 4.75 g/1), lipaemic (triglycerides up to 2220 mg/dl or cholesterol up to 684 mg/dl) and icteric (bilirubin up to 50 mg/dl) samples. However, strongly haemolytic samples should not be applied. 

References Packing leaflet LI 0494-E 1/87, LIM 0662-H 10/89, ST12, ST17, ST44, ST96, ST104. 

3-Morpholinosydnonimine (SIN-1) generates ONOO by releasing O2 and NO essentially in a simultaneous manner. Within 8h of exposure SIN-1 

Ferritin is internalised by A549 cells after 30 min in a concentration-dependent manner (Foster et al. 1998). These data agree with observations for pre- 

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Xanthine oxidase, mol wt ca 275,000, present in milk, Hver, and intestinal mucosa (131), is required in the cataboHsm of nucleotides. The free bases guanine and hypoxanthine from the nucleotides are converted to uric acid and xanthine in the intermediate. Xanthine oxidase cataly2es oxidation of hypoxanthine to xanthine and xanthine to uric acid. In these processes and in the oxidations cataly2ed by aldehyde oxidase, molecular oxygen is reduced to H2O2 (133). Xanthine oxidase is also involved in iron metaboHsm. Release of iron from ferritin requires reduction of Fe " to Fe " and reduced xanthine oxidase participates in this conversion (133). 

Iron Absorption. A very important effect of ascorbic acid is the enhancement of absorption of nonheme iron from foods. Ascorbic acid also enhances the reduction of ferric iron to ferrous iron. This is important both in increasing iron absorption and in its function in many hydroxylation reactions (140,141). In addition, ascorbic acid is involved in iron metaboHsm. It serves to transfer iron to the Hver and to incorporate it into ferritin. 

Two classes of antioxidants are known the low-molecular weight compounds (tocopherols, ascorbate, -carotene, glutathione, uric acid and etc.) and the proteins (albumin, transferrin, caeruloplasmin, ferritin, etc.) including antioxidant enzymes (e.g. superoxide dismutase, catalase, glutathione peroxidase). 

FIGURE 2.15 Influence of the pore size of Sephacryl HR on the separation of proteins of various molecular mass. The protein mixture is composed of ferritin, aldolase, ovalbumin, and chymotrypsinogen A. [Reproduced from Hagel et al. (1989), with permission.]... 

FIGURE 7.17 Separation of a complex mixture on Fractogel EMD BioSEC (S) with a column dimension of 1000 X 50 mm (Superformance glass column). The sample contained ferritin (I), immunoglobulin G (2), transferrin (3), ovalbumin (4), myoglobin (5), aprotinin (6), and vitamin B, (7). Five milliliters of the mixture was injected onto the column at a flow rate of 3 ml/min (eluent 20 mAI sodium phosphate buffer, 0.1 M NaCI, pH 7.2). 

METALLOPROTEINS. Metalloproteins are either metal storage forms, as in the case of ferritin, or enzymes in which the metal atom participates in a catalyti-cally important manner. We encounter many examples throughout this book of the vital metabolic functions served by metalloenzymes. 

Metalloproteins contain metal atoms Ferritin Iron 35... 

Ferritin is a globular iron-storage protein that stores iron as FeJ+. To leave the ferritin, Fe3+ must first be reduced to Fe2+. Ferritin has two types of channels through which the Fe"+ could leave a three-fold channel and a four-fold channel. The three-fold channel is lined with the amino acids aspartate (Asp) and glutamate (Glu) and the four-fold channel is lined with the amino acid leucine (Leu). Through which channel is the Fe + more likely to leave the ferritin protein Explain your answer. 

Atkinson, B.G., Blaker, T,W Tomlinson, J., Dean, R.L. (1990). Ferritin is a translationally regulated heat shock protein of avian reticulocytes. J. Biol. Chem. 265, 14156-14162. 

FIG. 8 Electron micrographs of freeze-etched preparations of whole cells from (a, b) Bacillus sphaericus CCM 2120 exhibiting a square S-layer lattice or from (c, d) Thermoanaerobacter ther-mohydrosulfuricus Llll-69 carrying a hexagonally ordered S-layer lattice, (a, c) Native S-layer lattices (b, d) S-layer lattices after covalent binding of ferritin to carbodiknide-activated carboxylic acid groups of the S-layer protein. Bars, 100 nm. 

FIG. 13 Schematic drawing of writing with molecnles on S-layers. The tip of a scanning force microscope is nsed to drag-and-drop positively charged ferritin molecnles. 

Ferritin, an iron-binding protein, prevents ionized iron (Fe ) from reaching toxic levels within cells. Elemental iron stimulates ferritin synthesis by causing the release of a cytoplasmic protein that binds to a specific region in the 5 nontranslated region of ferritin mRNA. Disruption of this protein-mRNA interaction activates ferritin mRNA and results in its translation. This mechanism provides for rapid control of the synthesis of a protein that sequesters Fe +, a potentially toxic molecule. 

Although iron deficiency is a common problem, about 10% of the population are genetically at risk of iron overload (hemochromatosis), and elemental iron can lead to nonen2ymic generation of free radicals. Absorption of iron is stricdy regulated. Inorganic iron is accumulated in intestinal mucosal cells bound to an intracellular protein, ferritin. Once the ferritin in the cell is saturated with iron, no more can enter. Iron can only leave the mucosal cell if there is transferrin in plasma to bind to. Once transferrin is saturated with iron, any that has accumulated in the mucosal cells will be lost when the cells are shed. As a result of this mucosal barrier, only about 10% of dietary iron is normally absorbed and only 1-5% from many plant foods. 

Various other protein hormones circulate in the blood but are not usually designated as plasma proteins. Similarly, ferritin is also found in plasma in small amounts, but it too is not usually characterized as a plasma protein. 

Once inside an enterocyte, iron can either be stored as ferritin or transferred across the basolateral mem-... 

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