Neoglycopeptide synthesis by suzuki-miyaura couplings between glycosyl aryl boronic acids and iodopeptides.

Suzuki-Miyaura coupling reaction was applied in the syntheses of neoglycopeptides. This work utilizes new type of glycosyl aryl boronic acid and readily accessible iodo amino acids/iodopeptides. Both carbohydrate and peptide moieties are unprotected and the final product could be isolated directly. The neoglyco amino acid and neoglycopeptide products feature an O-glycosyl biaryl linker between the carbohydrate and peptide moieties.

Arylation of Phe and Tyr side chains of unprotected peptides by a Suzuki-Miyaura reaction in water.

An efficient arylation in water of tyrosine and phenylalanine side chains from unprotected iodopeptides is accomplished by using Suzuki-Miyaura cross-coupling processes. The method is compatible with the hydrophilic and thermolabile nature of biologically active peptides. Also of interest, the arylated tyrosine peptides can be accessed in one-pot mode starting from native peptides.

Studies on experimental iodine allergy: 3. Low molecular weight elicitogenic antigens of iodine allergy.

We hypothesize that iodine allergy is an immune response to iodinated self proteins produced in vivo from various iodine-containing chemicals. Since an antigenic determinant of experimental iodine allergy is diiodotyrosine (DIT), we designed low molecular weight DIT derivatives having provocative antigenicity without sensitizing immunogenicity. Tetraiododityrosine and hexaiodotrityrosine provoked dose-dependent skin reactions in guinea pigs previously immunized with iodine. No guinea pigs immunized with hexaiodotrityrosine showed anaphylactic reaction by i.v. challenge with hexaiodotrityrosine and none of their antisera showed positive passive cutaneous anaphylaxis (PCA) reaction in guinea pigs, indicating the non-immunogenic nature of the compound. Erythrosine, one of the color additives having a structure common with DIT, was assessed for its immunological property. Enzyme-linked immunosorbent assay (ELISA) inhibition studies on erythrosine revealed that the inhibitory activity of erythrosine was stronger than that of DIT. Furthermore, erythrosine provoked a PCA reaction in animals sensitized with anti-iodine antisera. In conclusion, hexaiodotrityrosine is thought to be useful for skin testing of iodine allergy without any fear of sensitization to the allergen. Erythrosine was shown to provoke an experimental iodine allergy and, also, the relationships between the new concept of iodine allergy and features of clinical findings of adverse effects by iodocontrast media are discussed.

Low-molecular-weight iodoproteins in the congenital goiters of cog/cog mice.

Previously we described sedimentation and immunologic abnormalities of thyroglobulin (Tg) in a strain of mice with inherited congenital goiter and hypothyroidism (cog/cog). The goals of the present study were to determine the extent to which thyroid gland stimulation by TSH accounts for the abnormal properties of cog/cog Tg and to characterize further the abnormally small iodoproteins found in cog/cog mice. Cog/cog and control +/cog and BALB/c mice were fed with either normal or thyroid-hormone-containing diets and were injected with Na125I. Sucrose density gradient centrifugation of labeled thyroid extracts from cog/cog mice on normal diet showed that 82% of the iodine was in iodoproteins smaller than Tg, with sedimentation rates of 3-8S. No 12S and 19S peaks, characteristic of normal Tg, were present, but distinct and stable 12S and 19S peaks emerged after recentrifugation of the 12S and 19S areas. In contrast, in cog/cog mice treated with T4, a smaller (55%) amount of 3-8S iodoproteins and distinct 12S and 19S peaks were present. In both groups of mice, the labeled 3-8S iodoproteins were composed of three fractions: 15% precipitated by antirat Tg serum, 38% precipitated by antimouse albumin serum, and 47% not precipitated by either serum. The 3-8S iodoproteins contained labeled MIT and DIT and no T4. On sodium dodecyl sulfate polyacrylamide gel electrophoresis the 3-8S iodoprotein fraction that reacted with anti-Tg serum contained a distinct electrophoretic band at 49K. The 3-8S nonreactive iodoproteins resolved into several bands of lower molecular weight. We conclude that the 3-8S iodoproteins in cog/cog mice are heterogeneous and that TSH stimulation contributes to the production of these low-molecular-weight iodoproteins.

Buffalo thyroglobulin.

1. Buffalo thyroglobulin is the major iodoprotein of buffalo thyroid with a sedimentation coefficient of 19 S and an apparent molecular mass of 685 kDa. 2. The protein is rich in iodine (1-2%) and thyroxine bound iodine (75%), unlike thyroglobulins of other mammalian species. 3. As a glycoprotein, it has the same sugar residues as noted for other thyroglobulins, and the total carbohydrate content varies from 8.41 to 9.61%. 4. Amino acid composition of buffalo thyroglobulin is similar to other species. However, the protein has 2% more proline than other mammalian thyroglobulins. 5. Glutamic acid is the sole N-terminal amino acid of buffalo thyroglobulin, in contrast to aspartic acid or asparagine for several other species. 6. The quaternary structure of the protein appears to be comprised of eight non-identical subunits.