Calix[8]arene‐mediated self‐assembly of tetrapeptide H‐Leu‐Leu‐Ile‐Leu‐OMe

Abstract

Conformational analysis of peptide 1, H-Leu-Leu-Ile-Leu-OMe on complexing with macro cycle calix[8]arene has been carried out using (1)H-NMR and FTIR spectroscopic techniques. Stoichiometry of the complex formed in the 1:8 ratio was evidenced by a Job plot. NMR studies of the above peptide show a marked downfield shift and an increase in (3)J values for NH resonances on complexing with calix[8]arene. The characteristic NOE connectivity between N(i+1)H and C(ialpha)H confirm beta-sheet conformation in the complexed state. Both (1)H-NMR and FTIR results indicate that the alpha-amino group of Leu I is proximal to the macrocycle and is involved in hydrogen bond formation with phenolic hydrogen atom of the calix[8]arene. This suggests that calix[8]arene provides a suitable platform for peptide 1 to self-assemble in a parallel beta-sheet conformation. The nature of calix[8]arene interaction with peptide 1 has been studied using dynamic NMR studies, which concludes that a bifurcated hydrogen bonding interaction exists in the molecular interfaces of the assembly.

Cooperative Effect of a Classical and a Weak Hydrogen Bond for the Metal‐Induced Construction of a Self‐Assembled β‐Turn Mimic

“…It is known that the resonances of hydrogen‐bonded protons are shifted downfield relative to protons that are not involved in hydrogen bonds, thereby indicating that they are deshielded due to their participation in the hydrogen bonding 37. A study on proton NMR spectroscopic shifts of these complexes indicated that CH⋅⋅⋅N and amide hydrogen bonds also occur in solution in non‐coordinating solvents (CDCl 3 and C 6 D 6 ).…”

“…It is known that the resonances of hydrogen-bonded protons are shifted downfield relative to protons that are not involved in hydrogen bonds, thereby indicating that they are deshielded due to their participation in the hydrogen bonding. [37] A study on proton NMR spectroscopic shifts of these complexes indicated that C À H···N and amide hydrogen bonds also occur in solution in non-coordinating solvents (CDCl 3 and C 6 D 6 ). Table 1 shows the C À H and the aminopyridine N À H proton shifts, and the shift differences (Dd = 0.3-1.9 and 0.2-2.2 ppm) are largely attributable to aryl CÀH···N and NÀH···O=C hydrogen bonds in CDCl 3 , respectively.…”

Aggregate of Alkoxy-Bridged Re(I)-Rectangles as a Probe for Photoluminescence Quenching

“…Ru(II)-based metallosurfactants, forming inverted aggregates, also have been reported . Furthermore, several calixarenes bearing long aliphatic chains form vesicles or micelles that can bind guest aromatic molecules …”

Synthesis of Novel Dinaphthosulfide,Aza, Oxa, Thia Lariats ContainingUrea and Thiourea Groups in the Side Chain and Their Nanostructures

“…Modified crown ethers and aza crowns are compounds bearing various kinds and number of oxa, aza and thia heteroatom in their structures 8 . The second strategy for the modification of crown ethers and their derivatives is the synthesis of crown compounds with different structures, such as cryptands, calixarenes, lariats and biscrowns [9][10][11][12] .…”