Immunoglobulins radiolabeling

Nucleic acid probes are commonly labeled by enzymatic incorporation of radiolabeled nucleotides or enzymatic addition of radiolabeled phosphate groups to the nucleic acid chain. Proteins, in particular immunoglobulins, are labeled commonly by direct... 

Haas GG Jr, D Cruz OJ, DeBault LE. Comparison of the indirect immunobead, radiolabeled, and immunofluorescence assays for immunoglobulin G serum antibodies to human sperm. Fertil Steril 1991 55 377-88. 

Unlike most other endoradiotherapeutic agents, radiolabeled mAbs are macromolecules. While there are five classes of human immunoglobulins from which this type of agent could be developed, the vast majority of mAbs utilized for radioimmunotherapy are IgG. These molecules have an approximate molecular weight of 150 kDa and are the predominant immunoglobulin class found in the blood. A schematic structure of an IgG molecule is... 

The predominant mechanism of radiolabelling of antibodies with radioiodine involves electrophilic substitution of the icxline into the activated phenolic ring of tyrosine side-chains as shown in Scheme 1. Provided that low substitution ratios are used it is unlikely that radiolabelling will take place at any other site in the large immunoglobulin molecule but in proteins lacking tyrosine residues... 

In contrast, much more studies have been devoted to the ditfusion of small molecules in the multilayers, because of its importance in applications like permeation membranes or biosensing. Both IR spectroscopy [316] and fluorescence measurements [317] have shown the diffusion of protons in the multilayers, and thus an influence of the pH of the outer solution even far inside the films. The influence of water on the thickness of the multilayers is also well-documented [111,318]. Diffusion of radiolabeled salt ions has also been measured [125,312], Voltamperometry showed that PAH/PAA films had little effect on the diffusion of Fe(CN)g , but that PAH/PSS films could hinder its transport [116], 6-CF [96], acridine orange [81], daunomycin [251], 2 -3 cyclic adenosine monophosphate [252], bisulfite [313], and different diazonium salts [147,313] have been shown to permeate deeply in multilayers built by ESA. Immunoglobulin G (IgG) could permeate or not in a superlattice made of anti-IgG layers and PAH/PSS spacer layers, depending on the thickness of the spacer layer. The diffusion constants of rhodamine and of 2,2,6,6,-tetramethyl-4-piperidinol-l-oxide (TEMPOL) in PAH/PSS multilayers have been quantified [113,114],... 

Studies of allotypy in hare immunoglobulins were also reported by Landucci-Tosi et al. (119) who used insolubilized antiallotype antisera, prepared against IgG of the domestic rabbit, and radiolabeled hare IgG. In addition to the b5 marker observed by Mandy and Rodkey, they detected b4 and b6 on 70-80% of the IgG molecules in a typical preparation b5 was present on 55%. Since the sum exceeds 100%, two or three markers must be present on the same molecule. The markers were found in the IgG of all hares from a variety of geographical sources this work suggests that the markers are isotypic rather than allotypic in hares. The difference in results obtained by the two laboratories may be attributable to differences in the cross-reactivity of the antisera employed. 

Figure 2. A. Intratumor accumulation of various Cr-tagged proteins in solid tumor-bearing mice o, neocarzinostatin (NCS) (12 kDa) , SMANCS (16 kDa, but known to bind to albumin) , ovomucoid (29 kDa) , bovine serum albumin (69kOa) , mouse serum albumin (68 kDa) , mouse immunoglobulin G (160 kDa). Radiolabeled proteins were injected i.v. at time zero. Values are based on radioactivity (cf. Fig. 2). The tumor model in both A and B was solid sarcoma S-180 in mice. (From ref. 26, with permission). B. Relationship of drug distribution and molecular size to plasma concentration, AUC (area under the concentration curve), renal clearance, and intratumor uptake as expressed by percentage of injected dose. Putative polymer drugs are 1-Tyr-HPMA-copolymers of various molecular sizes given i.v. at 1.8 xlO cpm. The tumor model was sarcoma S-180 in mice. (From ref. 28 with permission).

---