Efficient Fmoc/solid-phase peptide synthesis of O-phosphotyrosyl-containing peptides and their use as phosphatase substrates

A general synthetic method for the efficient preparation of Tyr(P) -containing peptides is described by the use of Fmoc-Tyr(PO₃¹Bu₂) -OH in Fmoc/solid-phase synthesis followed by simultaneous cleavage of the peptide from the resin and peptide deprotection by acidolytic treatment. The applicability of this approach is demonstrated by the synthesis of H-Ser-Ser-Ser-Tyr(P) -Tyr(P) -OH.TFA and the synthesis of the phosphorylated forms of the two physiological peptides, angiotensin II and neurotensin 8–13. In addition, the three phosphorylated peptides were used as substrates in the study of the local specificity determinants of T-cell protein tyrosine phosphatase. In a competition assay using ³²P-radiolabeled [Tyr(P)]⁴-angiotensin II, both un-labeled synthetic [Tyr(P)]⁴-angiotensin II and Ser-Ser-Ser-Tyr(P) -Tyr(P) reduced the release of ³²P and indicated that they efficiently competed as substrates for the phosphatase. Conversely, [Tyr(P)]⁴-neurotensin 8–13 was ineffective as a competitive substrate and indicated that this particular Tyr(P) -containing peptide sequence was not recognized by the enzyme. The marked difference in the recognition of Asp-Arg-Val-Tyr(P) -Ile-His-Pro-Phe and Arg-Arg-Pro-Tyr(P) -Ile-Leu is consistent with the presence of an acidic residue in the -3 position relative to the Tyr(P) residue.     

Dermoscopic Features of Difficult Melanoma

BACKGROUND: The dermoscopic diagnosis of cutaneous melanoma (CM) may be difficult because some CM lack specific dermoscopic features for melanoma diagnosis. OBJECTIVE: To evaluate whether a diagnosis of CM could be achieved using the classic dermoscopic melanoma-specific criteria, we conducted a retrospective multicenter study of 508 CM samples. METHODS: All the dermoscopic images were analyzed to identify the dermoscopic criteria found in dermoscopically difficult melanomas (DDM) and to examine the possible relation of dermoscopic diagnosis with respect to the difficulty of the dermoscopic diagnosis and the melanoma thickness. RESULTS: A significant percentage of melanomas, 89 of 508 (17.5%), were DDM. The criteria leading to a significant increased risk of DDM were presence of streaks [odds ratio (OR), 2.26; 95% confidence interval (CI), 1.15-4.47), absence or presence of regular pigmentation (OR, 3.41; 95% CI, 1.70-6.85), absence of a blue-whitish veil (OR, 4.04; 95% CI, 2.33-6.99), absence of regression structures (OR, 4.31; 95% CI, 2.42-7.66), and the presence of hypopigmentation (OR, 2.61; 95% CI, 1.49-4.58). CONCLUSION: A significant number of melanomas defy even dermoscopic diagnosis. Only a meticulous comparative and interactive process based on an assessment of all the individual's other nevi ("ugly ducking" sign) and a knowledge about recent changes can lead to the recognition of DDM.