0000000000281764
AUTHOR
Tomasz Ptak
Experimental and theoretical NMR studies of interaction between phenylalanine derivative and egg yolk lecithin
The interaction of phenylalanine diamide (Ac-Phe-NHMe) with egg yolk lecithin (EYL) in chloroform was studied by 1H and 13C NMR. Six complexes EYL–Ac-Phe-NHMe, stabilized by N–H···O or/and C–H···O hydrogen bonds, were optimized at M06-2X/6-31G(d,p) level. The assignment of EYL and Ac-Phe-NHMe NMR signals was supported using GIAO (gauge including atomic orbital) NMR calculations at VSXC and B3LYP level of theory combined with STO-3Gmag basis set. Results of our study indicate that the interaction of peptides with lecithin occurs mainly in the polar ‘head’ of the lecithin. Additionally, the most probable lecithin site of H-bond interaction with Ac-Phe-NHMe is the negatively charged oxygen in …
Interactions of N-heteroalkylaminomethylenebisphosphonic acids with Cd(II) ions: Electrochemical and spectroscopic investigations
The aminomethylenebisphosphonates are known to be excellent chelators for many metal ions. In this work, the coordination properties of three different aminomethylenebisphosphonates with N-substituted heteroalkyl moieties (L1, L2 and L3) and their N-pyridyl derivative (L4) toward cadmium(II) ions are described. Due to their coordination abilities over a broad range of pH, the compounds of this group are good candidates for heavy metal detoxification. To determine the stability constants and the coordination mode of formed aminomethylenebisphosphonate-cadmium(II) complexes, four analytical methods were employed: potentiometry, pulse polarography (DPP), nuclear magnetic resonance spectroscopy…
Electrochemical and spectroscopic investigations of selected N -heteroalkylaminomethylenebisphosphonic acids with Pb(II) ions
Abstract The coordination properties of aminomethylenebisphosphonic acids towards various metal ions have been exploited during the last decade. These compounds are good chelators for biologically important metal ions, such as Cu(II), Fe(II), Zn(II), Ca(II), and Mg(II), as well as a toxic ion (i.e., Cd(II)). In this study, the interactions of five aminomethylenebisphosphonates with N-substituted heteroalkyl moieties (L1, L2 and L3) and their N-pyridyl (L4) and N-benzylpiperazine (L5) derivatives with Pb(II) ions were investigated. A wide range of analytical methods were employed, including potentiometry, pulse polarography (DPP), nuclear magnetic resonance (NMR) spectroscopy and electrospra…
The impact of model peptides on structural and dynamic properties of egg yolk lecithin liposomes - experimental and DFT studies.
Electron spin resonance (ESR), 1H-NMR, voltage and resistance experiments were performed to explore structural and dynamic changes of Egg Yolk Lecithin (EYL) bilayer upon addition of model peptides. Two of them are phenylalanine (Phe) derivatives, Ac-Phe-NHMe (1) and Ac-Phe-NMe2 (2), and the third one, Ac-(Z)-ΔPhe-NMe2 (3), is a derivative of (Z)-α,β-dehydrophenylalanine. The ESR results revealed that all compounds reduced the fluidity of liposome's membrane, and the highest activity was observed for compound 2 with N-methylated C-terminal amide bond (Ac-Phe-NMe2). This compound, being the most hydrophobic, penetrates easily through biological membranes. This was also observed in voltage an…
Experimental and theoretical NMR and IR studies of the side-chain orientation effects on the backbone conformation of dehydrophenylalanine residue
Conformation of N-acetyl-(E)-dehydrophenylalanine N', N'-dimethylamide (Ac-(E)-ΔPhe-NMe(2)) in solution, a member of (E)-α, β-dehydroamino acids, was studied by NMR and infrared spectroscopy and the results were compared with those obtained for (Z) isomer. To support the spectroscopic interpretation, the Φ, Ψ potential energy surfaces were calculated at the MP2/6-31 + G(d,p) level of theory in chloroform solution modeled by the self-consistent reaction field-polarizable continuum model method. All minima were fully optimized by the MP2 method and their relative stabilities were analyzed in terms of π-conjugation, internal H-bonds and dipole interactions between carbonyl groups. The obtained…