Albumin, serum iodine

Purify the iodinated protein from excess reactants by gel filtration using a desalting resin. The column may be pre-treated by passing a solution of bovine serum albumin (BSA) through it to eliminate nonspecific binding sites that could cause significant protein loss in small-sample applications. 

Hughes, W.L., and Straessle, R. (1950) Preparation and properties of serum and plasma proteins. XXIV. Iodination of human serum albumin./. Am. Chem. Soc. 72, 452-457. 

Figure 3. Autoradiograph of radio-iodinated bovine serum albumin (BSA), adsorbed onto glass and subsequently immersed in phosphate-buffered saline for (from left to right) 0, 1, 2, 4, and 16 h. Reproduced from Michaeli et al. (7) with permission of Academic Press.

It is widely employed as a disinfectant in medicine (Povidone-iodine) because of its mildness, low toxicity, and water solubility. According to the U.S. Pharmacopeia, l ovidone-iodme is a free-flowing, brown powder dial contains from 9-12% available iodine. 11 is soluble in water and lower alcohols. When dissolved in water, the uncomplexed free iodine level is very low however, tine complexed iodine acts as a reservoir and by equilibrium replenishes the free iodine lo the equilibrium level. This prevents free iodine from being deactivated because the free form is continually available at effective biocidal levels from this large reservoir. PVP will interact with other small anions and resembles serum albumin and other proteins in this regard. It can be salted in with anions such as NaSC.N or out with NasSOa much like water-soluble proteins. 

Serum albumin labeled with an iodine radionuclide was firstly used as a substrate for determining protease activity by Absolon This method was later on modified several times and applied for assaying various proteolytic activities in different materials. Mego et al. injected denaturated I-human %rum albumin into the tail vein of rats and measured the rate of intralysosomal proteolysis on isolated lysosomes containing endocytosed substrate. This method was also used for the determining the intralysosomal pH on the basis of differences found in the rate of I-albumin breakdown in intact and lysed lysosomes C-bovine serum albumin, I-casein or I-albumin have been alternatively used as substrate for measuring the activity of trypsin, chymotrypsin and papain - ). 

Bovine plasma albumin and dog serum albumin have been iodinated with di- I-labeled methyl p-hydroxybenzimidate. The authors did not attempt to obtain maximum specific activity, but rather examined the effect of reaction conditions on the rate of amidination and yield of iodinated product. The set of conditions given above is only one of the many tested. It was chosen because it gave the highest incorporation of I. Overall the results showed that the iodination reaction will proceed at pH 7.5-9.5 and... 

A water-insoluble lactoperoxidase, linked to CNBr-activated Sepharose beads, capable of iodinating serum albumin, is commercially available (Worthington Biochemical Corp.), and may be useful where avoidance of contamination of the product by the enzyme is important. 

Grade USP lists iodinated 131I serum albumin, rose bengal sodium 131I injection, sodium iodide 131I capsules and solution, sodium iodohippurate 131I injection. 

An interesting study on the fate of injected placental alkaline phosphatase (N17) has been reported by Posen et al. (P18), who measured heat-stable alkaline phosphatase. Following injection, there was an initial rapid fall in enzyme activity lasting 3-5 hours and then a less rapid disappearance. After 4 hours, two thirds of the initial activity remained, but it took several weeks for complete disappearance. These kinetics resembled those known for serum albumin labeled with iodine-131. 

Phenols and phenol ethers are very good substrates for haloperoxidases. The first aromatic substrate to be used in enzymatic iodination was tyrosine. This substrate was iodinated using chloroperoxidase from Caldariomyces Jumago1441 and thyroid peroxidase1451. Horseradish peroxidase and lactoperoxidase have been used to lable proteins with radioactive isotopes of iodide111 and bromoperoxidase from Penicillus capitatus has been employed to lable human serum albumin with the radioactive isotope of bromine1461. 

Tatum JL, Burke TS, Hirsch JI et al (1983) Pitfall to modified in vivo method of technetium-99m red blood cell labeling - iodinated contrast media. Clin J Nucl Med 8 585-587 Thrall JH, Freitas JE, Swanson D, Rogers WL, Clare JM, Brown ML, Pitt B (1978) Clinical comparison of cardiac blood pool visualization with technetium 99m red blood cells labeled in vivo and with technetium 99m human serum albumin. J Nucl Med 19 796-803 United States Pharmacopeial Convention (2005) Official Monographs USP 28, technetimn Tc 99m pyrophosphate injection. United States Pharmacopeia (USP) 28-national formulary (NF) 23, p 1862... 

S1I -labelled form, iodinaled (,lll) human serum albumin, J,f HSA, Albumotope u,f, Macroscan-131, Risa-I31-H. Normal human serum albumin mildly jodinated with radio-active iodine (1311) which has a half-life of 8 days, and emits beta and gamma rays. Contains not more than one atom of iodine par molecule of albumin (mol wt 60,000). Physical and chemical proparties essentially the same as those of albumin. Stable at 10° for at least 3 weeks. Supplied for injection in aq isotonic sodium chloride soln. 

Metabolism and Transport of Iodine Iodide, supplied by food, is bound to serum proteins, especially to albumin. 

T4), monoiodotyrosine (MIT), and diiodotyrosine (DIT). The orthodox view states that the iodothyronines, namely T3 and T4, account for all the organic iodine in normal human serum (P9, Wll). However, there are claims that the iodotyrosines, MIT and DIT, also occur in significant amounts in the serum (D5), but if this is true, then they are strongly associated with, or bound to, serum albumin and are not subject to the rapid clearance known for free serum iodotyrosines (W4). 

It is obvious that T4 by RIA and T4 by CPBA are unaffected by contaminating iodine. However, it should be stressed that both total T4 and PBI are uniformly affected by abnormalities in the T4-binding serum proteins, namely TBG, TBPA, and albumin as referred to in Section 2.2. In summary, where drugs or any other extrathyroidal factor increases any of the binding proteins (usually TBG) there is a concomitant increase in PBI or total T4 levels in the serum, and a decrease in the T3 resin uptake. Conversely, decreases in TBP are associated with decreases in PBI and in total T4, and increases in T3 resin uptake. 

An improved method for the purification of radiolabelled glycoprotein hormones is based on their competitive elution from immobilized concanavalin A with methyl a-D-glucopyranoside. The method separates free iodine, damaged hormone, and radiolabelled bovine serum albumin. 

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