ABSTRACT
Considerable effort has been directed toward developing artificial peptide-based foldamers. However, detailed structural analysis of δ-peptide foldamers consisting of only aliphatic δ-amino acids has not been reported. Herein, we rationally designed and stereoselectively synthesized aliphatic homo-δ-peptides forming a stable helical structure by using a chiral cyclopropane δ-amino acid as a monomer unit. Structural analysis of the homo-δ-peptides using circular dichroism, infrared, and NMR spectroscopy indicated that they form a stable 14-helical structure in solution. Furthermore, we successfully conducted X-ray crystallographic analysis of the homo-δ-peptides, demonstrating a right-handed 14-helical structure. This helical structure of the crystal was consistent with those predicted by theoretical calculations and those obtained based on NMR spectroscopy in solution. This stable helical structure is due to the effective restriction of the backbone conformation by the structural characteristics of cyclopropane. This work reports the first example of aliphatic homo-δ-peptide foldamers having a stable helical structure both in the solution and crystal states.
ABSTRACT
Rosai-Dorfman disease (RDD) is a rare disorder characterized by the proliferation of histiocytes in the sinus of the affected lymph nodes, which leads to massive lymphadenopathy. RDD usually presents as an increased inflammatory response and lymph node swelling. We herein report the case of a hemodialysis patient with a fever, hypercalcemia and increased serum calcitriol level who was histologically diagnosed to have RDD. Immunohistochemistry revealed an increased expression of 1α-hydroxylase by histiocytes in the dilated sinus, indicating the extrarenal overproduction of calcitriol. Treatment with oral prednisolone decreased the serum levels of inflammatory markers and calcitriol, normalized the serum calcium level and mitigated the systemic lymph node enlargement.
