Macromolecular Self-Assembly of Diketopiperazine Tetrapeptides
摘要:
Basic solutions of tetrapeptides derived from L-aspartic acid diketopiperazines are shown to form microcapsules when acidified to pH 2.4. An initial structure-activity study clearly demonstrates that a very delicate balance exists between the tetrapeptides' structure and their ability to self-assemble. Scanning electron micrographs confirm that microcapsules and not solid microspheres are formed.
两个手性OFM单取代的环(升-Glu-升-Glu)和环(d -Glu- d -Glu)显示一个健壮凝胶化在多种有机溶剂和水的能力。与单个对映异构体相反,它们的外消旋体可以形成可快速恢复的触变水凝胶,而触变恢复时间明显缩短。d-和l-对映异构体在细胞单元中的随机排列可诱发这种意想不到的触变行为,导致在最终的3D纤维网络中形成“伪外消旋体”,非晶态自组装体。
Five- and Six-Membered Ring Opening of Pyroglutamic Diketopiperazine
作者:Dennis A. Parrish、Lon J. Mathias
DOI:10.1021/jo0160928
日期:2002.3.1
A variety of ring-opening reactions of pyroglutamic diketopiperazine at both the five-membered and six-memberedrings is described. Mild, basic conditions facilitate nucleophilic attack by amines at the diketopiperazine carbonyls giving pyroglutamides in excellent yield. Reaction with nucleophiles under acidic conditions give bis-glutamate derivatives of 2,5-diketopiperazine (DKP). These reactions
Copper(II) complexes with cyclo(L-aspartyl-L-aspartyl) and cyclo(L-glutamyl-L-glutamyl) derivatives and their antioxidant properties
作者:Raffaele P. Bonomo、Enrico Conte、Giuseppe Impellizzeri、Giuseppe Pappalardo、Roberto Purrello、Enrico Rizzarelli
DOI:10.1039/dt9960003093
日期:——
Two new functionalized cyclodipeptides have been synthesized with the aim of obtaining a good model of superoxide dismutase. Better to mimic the active site of this metalloenzyme, these two compounds have been designed to allow a great co-ordination flexibility. Copper(II) complexes with cyclo(-L-aspartyl-L-aspartyl-) or cyclo(-L-glutamyl-L-glutamyl-)bis(histamine)(L) have been thermodynamically and spectroscopically characterized and their antioxidant activity tested against enzymatically generated O2–. Taking into account the speciation of the system, it has been determined that the more active species against O2– is the [CuL2]2+ complex. Electron spin resonance measurements suggest for this species the presence of four imidazole nitrogen atoms in a slightly tetrahedrally distorted co-ordination plane. The [CuLH–2] complex species also possesses four-nitrogen co-ordination involving two deprotonated peptide nitrogen atoms. The complex [CuL2]2+ showed the highest antioxidant activity and reasons for this behaviour are proposed on the basis of spectroscopic and voltammetric data.
Template-assisted photodimerization of N-unprotected uracil derivatives: selective formation of the cis–syn photodimer
作者:N. M. Weckenmann、C. Maichle-Mössmer、B. J. Nachtsheim
DOI:10.1039/c7cc05353c
日期:——
was investigated. Dual salt bridge formation between the imidazole side chains and the carboxylic acids resulted in preorganization of the uracil monomers and preferential formation of the cis-syn photodimer.
First Interchain Peptide Interaction Detected by ESR in Fully Synthetic, Template-Assisted, Two-Helix Bundles
作者:Alessandra Polese、D. Joe Anderson、Glenn Millhauser、Fernando Formaggio、Marco Crisma、Fernando Marchiori、Claudio Toniolo
DOI:10.1021/ja992079h
日期:1999.12.1
We have designed and synthesized by solution methods two simple two-helix bundles based on a conformationally constrained cyclo-dipeptide template to the side chains of which two short, 2,2,6,6tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic acid spin-monolabeled. 3(10)-helical peptides are covalently tethered. The preferred conformation of the appended chains has been assessed by FTIR absorption. The conclusions are corroborated by an X-ray diffraction analysis of one of the terminally blocked pentapeptide tails. For the first time, a solvent-dependent, inter-helix interaction has been monitored by conventional ESR spectroscopy on fully synthetic peptide systems. Half-field ESR measurements of these side-chain-substituted templates provided an experimental average distance between the two labels that is in good accord with that determined in a molecular modeling study.