Synthesis and conformation of an analog of the helix-loop-helix domain of the Id1 protein containing the O-acyl iso-prolyl-seryl switch motif

Synthetic peptides reproducing the helix-loop-helix (HLH) domains of the Id proteins fold into highly stable helix bundles upon self-association. Recently, we have shown that the replacement of the dipeptide Val-Ser at the loop-helix-2 junction with the corresponding O-acyl iso-dipeptide leads to a completely unfolded state that only refolds after intramolecular O --> N acyl migration. Herein, we report on an Id HLH analog based on the substitution of the Pro-Ser motif at the helix-1-loop junction with the corresponding O-acyl iso-dipeptide. This analog has been successfully synthesized by solid-phase Fmoc chemistry upon suppression of DKP formation. No secondary structure could be detected for the O-acyl iso-peptide before its conversion into the native form by O --> N acyl shift. These results show that the loop-helix junctions are determinant for the folded/unfolded state of the Id HLH domain. Further, despite the high risk of DKP formation, peptides containing O-acyl iso-Pro-Ser/Thr units are synthetically accessible by Fmoc chemistry.

O-acyl isopeptide method: efficient synthesis of isopeptide segment and application to racemization-free segment condensation

We report the establishment of the O-acyl isopeptide method-based racemization-free segment condensation reaction toward future chemical protein synthesis. Peptide segments containing C-terminal O-acyl Ser/Thr residues were successfully synthesized by use of a lower nucleophilic base cocktail for Fmoc removal, and then coupled to an amino group of a peptide-resin without side reactions or epimerization. We also succeeded in performing the segment condensation in a sequential manner and in solution phase conditions as well.

Isopeptide method: development of S-acyl isopeptide method for the synthesis of difficult sequence-containing peptides

A novel strategy for a more efficient synthesis of difficult sequence-containing peptides, the S-acyl isopeptide method, was developed and successfully applied. A model pentapeptide Ac-Val-Val-Cys-Val-Val-NH2 was synthesized via its water-soluble S-acyl isopeptide using an S-acyl isodipeptide unit, Boc-Cys(Fmoc-Val)-OH. An S-acyl isopeptide possessing excellent water solubility could be readily and quantitatively converted to the native peptide via an S--N intramolecular acyl migration reaction at pH 7.4. Thus, the S-acyl isopeptide method provides a useful tool in peptide chemistry.

Thoracoscopic removal of middle mediastinal schwannoma originating from recurrent nerve

Schwannomas of the left recurrent nerve are rare and there is no agreement on how to manage them without causing recurrent nerve dysfunction. We present a 63-year-old male with unspecific clinical symptoms in whom a middle mediastinal mass with a diameter of 5 cm was found incidentally. At thoracoscopic surgery,we found that the encapsulated tumor originated from left recurrent nerve and we performed tumor enucleation without sacrificing the recurrent nerve. The patient did experience postoperative hoarseness and vocal cord paralysis even though we preserved the recurrent nerve. To our knowledge, thoracoscopic removal of a left recurrent nerve schwannoma has not been reported in the literature before.

'O-Acyl isopeptide method' for peptide synthesis: Solvent effects in the synthesis of Abeta1-42 isopeptide using 'O-acyl isodipeptide unit'

'O-Acyl isopeptide method' is an efficient synthetic method for peptides. We designed 'O-acyl isodipeptide units', Boc-Ser/Thr(Fmoc-Xaa)-OH, as important building blocks to enable routine use of the O-acyl isopeptide method. In the synthesis of an Abeta1-42 isopeptide using O-acyl isodipeptide unit Boc-Ser(Fmoc-Gly)-OH, a side reaction, resulting in the deletion of Ser(26) in the O-acyl isopeptide structure, was noticed during coupling of the unit. We observed that the side reaction occurred during the activation step and was solvent-dependent. In DMF or NMP, an intramolecular side reaction, originating from the activated species of the unit, occurred during the activation step. In non-polar solvents such as CHCl(3) or CH(2)Cl(2), the side reaction was less likely to occur. Using CH(2)Cl(2) as solvent in coupling the unit, the target Abeta1-42 isopeptide was synthesized with almost no major side reaction.

[Collapse of the contra-lateral lung after computed tomography-guided marking]

We are performing preoperative percutaneous computed tomography (CT)-guided placement of hook-wires to localize small lesions on the day before thoracoscopic surgery. We report a case of collapse of the contra-lateral lung after CT-guided marking. A 69-year-old man was referred to our department for surgical intervention of multiple small lung tumors in the right upper lobe. At the age of 66, he underwent esophagectomy for esophageal cancer. CT-guided marking was undergone for both tumors on the day before surgery. After marking, collapse of the contra-lateral (left) lung was occurred. Left chest tube was placed in order to maintain adequate ventilation during the operation. Operative findings revealed that sealing test after resections of the lung could not be performed because the fistel to the left chest cavity at the inferior mediastinum after esophagectomy was detected.

Development of O-acyl isopeptide method

During over a decade of study on aspartic protease inhibitors and water-soluble prodrugs, in 2003, we discovered that the presence of an O-acyl instead of N-acyl residue within the peptide backbone significantly changed the secondary structure of the native peptide. In addition, the target peptide was subsequently generated by an O-N intramolecular acyl migration reaction. These findings led to the development of a novel method, called "O-acyl isopeptide method," for the synthesis of peptides containing difficult sequence. Further application of the method to Alzheimer's Abeta1-42 revealed that the O-acyl isopeptide of Abeta1-42 could be effectively synthesized and stored without spontaneous self-assembly. Intact monomer Abeta1-42 could then be obtained from the isopeptide under physiological experimental conditions. We named the O-acyl isopeptide as "Click Peptide," because of its "quick and easy one-way conversion" to the parent Abeta1- 42. Application of the click peptide has provided a new basis for the investigation of the biological functions of Abeta1-42 by inducible activation of its self-assembly. The O-acyl isopeptide method has further evolved as a general method for peptides synthesis with our recent developments of "O-acyl isodipeptide units" and "racemization-free segment condensation methodology." Isodipeptide units have enabled routine use of the O-acyl isopeptide method by avoiding the often difficult esterification reaction on resin. "Racemizationfree segment condensation methodology" has been achieved by employing N-segments possessing a C-terminal urethaneprotected O-acyl Ser/Thr residues. The synthesis of long peptides/proteins by racemization-free segment condensation has thus become possible at Ser/Thr residues instead of Cterminal Gly/Pro residues. As the O-acyl isopeptide method becomes more widely utilized, we have composed this review to facilitate its application for the production of peptides and proteins.

“O-Acyl isopeptide method” for peptide synthesis: synthesis of forty kinds of “O-acyl isodipeptide unit” Boc-Ser/Thr(Fmoc-Xaa)-OH

The O-acyl isopeptide method has recently received attention as an efficient synthetic method for peptides. Herein, forty kinds of "O-acyl isodipeptide unit" Boc-Ser/Thr(Fmoc-Xaa)-OH (1-40) were effectively synthesized in two-steps without epimerization. The O-acyl isodipeptide units are important building blocks to enable the routine use of the O-acyl isopeptide method.

‘Click peptide’: a novel ‘O-acyl isopeptide method’ for peptide synthesis and chemical biology-oriented synthesis of amyloid β peptide analogues

After over a decade of studies on aspartic protease inhibitors and water-soluble prodrugs, we have been developing a novel method, since 2003, called 'O-acyl isopeptide method', for the synthesis of peptides containing difficult sequences. With our recent discoveries of 'O-acyl isodipeptide unit' and the 'racemization-free segment condensation method', this method has further evolved as a general synthetic method for peptides. Moreover, 'Click Peptide', which could be a powerful tool for identifying the pathological functions of amyloid beta peptides in Alzheimer's disease, represents a valuable use of the isopeptide method in Chemical Biology-oriented research.