Insulin iodination

Stable double emulsions, based on various block copolymers of polyethylene oxides and polypropylene oxides known as Pluronies, have been used. In a recent example. Cole and Whateley (84) have used complexes of Pluronic F127 PAA (polyaerylie aeid) in the internal aqueous phase. In the oil phase, Span 80 and Pluronie LlOl (5 wt %) were used. The outer interfaee was stabilized by xanthan gum (0.25 wt %) and Tween 80 (1 wt %). Theophylline and I-insulin (iodinated insulin) were ineorporated in the internal aqueous phase of the stabilized multiple emulsion, and the release rates were studied. The release rates were found to be related to the droplet sizes of the emulsion whieh were dependent on the partiele size of the pluronie F127 PAA eomplex in the internal aqueous phase and the type of the lipophilie surfaetant in the oil phase. The authors have used the eomplex between the poloxamer surfactant and PAA that occurred at pH 2 and at low molar ratio as a barrier for the release of active matter from the inner to the outer phase. 

Pig. 1-Time course ( ) of the reaction "between insulin iodinated at 6.4 ID and sodium sulphite at pH 7 and 37°C. The time course (A) of native insulin is also reported. The concentration of insulin and Na2S03 were 0.176 and 31 mM respectively. The titrations were carried out at pH 2, with mM HOPhHg (from Rosa et al., Biochem. J., 103. 407, 1967). 

Pig.6-Biological activilgr (a) and -S-S- reacted/mole ( ) versus iodination degree. Titration results are expressed in taking as 100 the difference between the -S-S- titration value measured on native insulin and that measured on insulin iodinated at 5 ID. 

S-S- Bonds Reactivity and Biological Activity of Insulins Iodinated or Methylated at Different Extents... 

Insulin derivatives lb 401 lodate anions la 188,190 lb 307 Iodine staining lb 278 Iodine-azide reaction lb 85,301-304 Iodide anions la 190 lb 76,77,128,129 Iodide vapor la 46,64,78 lodination la 66... 

FIGURE 6.23 The synthesis of insulin, starting with a cystine-containing peptide. [Kamber et al., 1977]. Moc = methoxycarbonyl, Bpoc = biphenylisopropoxycarbonyl, Trt = trityl, Acm = acetamidomethyl. (a) HOBt-assisted carbodiimide-mediated coupling (b) removal of Trt by HC1 in CF3CH2OH-CH2Cl2 (9 1) at pH 3.5 (c) removal of Bpoc by CF3CH2OH-CH2 Cl2 (9 1) at 60°C (d) removal of Acm and oxidation by iodine. 

Cleavage of the Trt group of one chain 54 with a weak acid to give 55 and its subsequent thiolysis of the. S -SPy derivative of the second chain 57 directs the formation of the first interchain disulfide bond in 58. The second interchain disulfide bridge is formed between the two Acm-protected cysteine residues of the [bis(Acm), bis(tBu), mono-disulfide]-hetero-dimer 58 by treatment with iodine. Finally, treatment of 59 with chlorosilane/sulfoxide produces the third disulfide bond between the two tBu-protected cysteine residues yielding human insulin (42). 

It also inhibits ADH action on distal tubules (diabetes insipidus like state), also has insulin like action on glucose metabolism and decreases thyroxine synthesis by interfering with iodination of thyroxine. 

Isocratic RPC was also successful in separating the position isomers of mono-iodinated insulin. The 125-iodination by the lactoperoxidase method was carried out in phosphate buffer containing 6 M urea and led to the iodination of tyrosyl units, i.e., to substitution in the positions A14, A19, B16, or B26. The retention of the mono-iodinated insulin chains increased in the order A19 < B26 < B16 < A14 on a C 18 column (150 x 4.0 mm dP = 3 pm). The eluent contained 1 % triethylammonium tri-fluoroacetate in water (pH 3) and acetonitrile78). 

Deficiency syndromes of Zn, Cu, Cr, Se and Mo have occurred in patients on total parenteral nutrition (TPN). There is still much research to be done in assessing the nutritional status of many elements and understanding their metabolism, so that normal dietary intake may be supplemented for health benefits. Table 2 is a summary of the amounts required, the functions and the nutritional (usually dietary) imbalances in humans, where known, of the essential trace elements.31-33 (Note that this summary does not attempt to include imbalances related to environmental toxicology and occupational hazards.) Several trace elements have important functions in the immune system. Some are associated with nucleic acid. Others have structural roles, such as Si in cartilage, F and Zn in bone. They may be parts of vitamins, such as Co in vitamin B12, or hormones, such as iodine in thyroid hormones, Zn and Cr have a role in the synthesis and action of insulin.31-33... 

Drugs that show extensive tissue binding are said to have an apparent volume of distribution many times the total body size. For example, digoxin (see Chapter 35), which binds to plasma protein to the extent of 23%, has an apparent volume of distribution of 8 1/kg. The volume of distribution of drugs that do not bind to plasma or tissue proteins varies between the extracellular fluid volume (16 liters) and the total body water (42 liters). Insulin, sodium, and iodine are confined to the extracellular water, whereas caffeine and ethanol are distributed in the total body water. 

Substances also may be attached covalently to proteins for transporting the substances to targets in the body. Examples of this approach have been transporting radioactive iodine or toxic substances attached to antibodies in attempts to kill cancer cells and attaching radioactive metals to proteins and bleomycin for similar purposes (122). A recent novel approach has been that of Wu and Means (123) who have attached insulin to artificially formed liposomes by a reductive alkylation modification. The insulin-liposome aggregate reacts with insulin receptors. 

The dissociation of the single lysine amino group of iodinated insulin has been studied by Gruen et al. (1959a). (The inclination separated the titration region of phenolic residues from the titration region of the amine group.) No abnormalities were observed. 

Insulin Tracer iodination with chloramine T 0.025-0.10 Chromatography on diethylamino-ethyl cellulose column salt gradient, Tris-NaCl-urea P. Freychet, J. Roth, and D. M. Neville, Jr., Biochem. Biophys. Res. Commun., 43 400 (1971)... 

Samols E, Williams HS. Trace-labelling of insulin with iodine. 

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