[127-I]- or carrier-free [125-I]monoiodoinsulin

[Tetrakis(3-nitrotyrosine)]insulin

“…Although one or perhaps two of the tyrosines in insulin can be modified by iodination (Garratt, 1964;Izzo et al, 1964;Rosa et al, 1967;Sodoyez et al, 1975) or nitration (Morris et al, 1970) without substantial effect on the hormonal activity, extensive iodination leads to inactive products (Izzo et al, 1964;Rosa et al, 1967). This, when coupled with the fact that three of the four tyrosines are conserved in all insulin species for which sequences are known (Dayhoff, 1976), implies a fundamental role for some of the tyrosine phenolic groups in the hormonal response.…”

“…Therefore the substantial hormonal activity of TNTI (over 50% of that of insulin) would argue against a fundamental role for most of the phenolic groups in the hormonal response. However, it is possible that only one or two of the tyrosine residues in insulin are essential in the hormonal response-a possibility which is supported by the hormonal activity of partially iodinated or nitrated insulins (Sodoyez et al, 1975;Morris et al, 1970). If this is so, then the pKa values (7.3) of the TNTI are close enough to physiological conditions so that 50% of one or two of the critical nitrotyrosine residues could be in the nonionized form, especially when absorbed to a lipid membrane, and thus account for the hormonal response.…”

Synthesis and in Vitro Evaluation of18F- and19F-Labeled Insulin: A New Radiotracer for PET-based Molecular Imaging Studies

“…A number of radiolabeled analogues of insulin have been reported as tracers for studying the biochemistry of the hormone and its role in disease progression and for evaluating different insulin delivery strategies. 125 I-Labeled insulin, in which the isotope is bound to the aromatic ring of A14 tyrosine, is perhaps the best-known radiolabeled insulin derivative, but it is used solely for in vitro studies. − There are few reports of the synthesis of radiolabeled insulin analogues for in vivo molecular imaging studies using PET. Potential limitations of the studies that have been reported (which involved labeling insulin with 18 F , and 124 I , ) include products that are of questionable stability, a lack of chemical and biological characterization data, and/or low overall production yields.…”