NMR and ESR study of the conformations and dynamical properties of poly(L-lysine) in aqueous solutions

Perly, Bruno; Chevalier, Yves; Chachaty, C.

doi:10.1021/ma50005a015

Cited by 9 publications

(9 citation statements)

References 18 publications

(28 reference statements)

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“…While the small measure resonant line broadening at high pD indicates some degree of motional restriction upon formation of periodic secondary structure, the magnitude of broadening effects for this small peptide (DP = 16) does not imply substantial aggregation of peptide monomers. Chemical shift values for the random coil (pD 8.6) structure closely match those reported for a similar sample (pD 7, T = 77 °C) of a larger poly( l -lysine) with an average degree of polymerization of 140 units . Very little change in 1 H chemical shift is observed for the high pD samples in Figure B and C. Several factors might account for this.…”

Section: Resultssupporting

confidence: 81%

Investigation of Hydrophobic Interactions in Colloidal and Biological Systems by Molecular Dynamics Simulations and NMR Spectroscopy

Alaimo

Kumosinski

1997

Langmuir

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Interactions of hydrophobic molecular domains determine many of the functional properties of food proteins and colloidal food aggregates, such as emulsification, gelation, and foaming ability. A molecular basis for macromolecular interactions and conformational stability is established through investigation of simple model systems. Molecular modeling and dynamics simulations have been used to study the role of hydrophobic interaction forces in driving the formation of model amphiphile aggregate systems. An approximation to hydrophobic attraction between hydrocarbon tails was required to achieve stable, dynamic aggregate models for Aerosol-OT (AOT)/water/oil microemulsions, micelles of AOT in water, and a stacked AOT/para-chlorophenol gel in either CCl4 or benzene. One- and two-dimensional NMR spectroscopic methods have been used to characterize the pH and temperature dependent conformational changes in the model polypeptide poly(l-lysine). Changes in proton chemical shifts and line widths indicate that the backbone mobility of poly(l-lysine) is not greatly diminished by the coil−helix transition. ROESY and transverse-ROESY couplings, as well as T 1 and T 2 relaxation measurements, suggest that lysyl side chain mobility remains largely unrestricted upon formation of periodic secondary structure. Molecular dynamics simulations of poly(l-lysine) conformers substantiate the importance of hydrophobic side chain domains in stabilizing secondary structural features in aqueous solution.

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Section: Resultssupporting

confidence: 81%

Investigation of Hydrophobic Interactions in Colloidal and Biological Systems by Molecular Dynamics Simulations and NMR Spectroscopy

Alaimo

Kumosinski

1997

Langmuir

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“…At pH 9−11, a transformation to an α-helix is observed by 13 C NMR . Heating the basic solution leads again to the formation of β-pleated sheets, as revealed by ESR and NMR, optical rotatory dispersion measurements, and Raman spectroscopy . IR measurements showed that the secondary structure is also influenced by the chain length. , According to Scheraga, the β-pleated sheet structure is favored by hydrophobic interactions between the side chains by which the entropy of the surrounding water is increased …”

Section: Introductionmentioning

confidence: 98%

Acid−Base Interactions and Secondary Structures of Poly-l-Lysine Probed by ¹⁵N and ¹³C Solid State NMR and Ab initio Model Calculations

et al. 2008

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The interactions of the 15N-labeled amino groups of dry solid poly-L-lysine (PLL) with various halogen and oxygen acids HX and the relation to the secondary structure have been studied using solid-state 15N and 13C CPMAS NMR spectroscopy (CP = cross polarization and MAS = magic angle spinning). For comparison, 15N NMR spectra of an aqueous solution of PLL were measured as a function of pH. In order to understand the effects of protonation and hydration on the 15N chemical shifts of the amino groups, DFT and chemical shielding calculations were performed on isolated methylamine-acid complexes and on periodic halide clusters of the type (CH3NH3(+)X(-))n. The combined experimental and computational results reveal low-field shifts of the amino nitrogens upon interaction with the oxygen acids HX = HF, H2SO4, CH3COOH, (CH3)2POOH, H3PO4, HNO3, and internal carbamic acid formed by reaction of the amino groups with gaseous CO2. Evidence is obtained that only hydrogen-bonded species of the type (Lys-NH2***H-X)n are formed in the absence of water. 15N chemical shifts are maximum when H is located in the hydrogen bond center and then decrease again upon full protonation, as found for aqueous solution at low pH. By contrast, halogen acids interact in a different way. They form internal salts of the type (Lys-NH3(+)X(-))n via the interaction of many acid-base pairs. This salt formation is possible only in the beta-sheet conformation. By contrast, the formation of hydrogen-bonded complexes can occur both in beta-sheet domains as well as in alpha-helical domains. The 15N chemical shifts of the protonated ammonium groups increase when the size of the interacting halogen anions is increased from chloride to iodide and when the number of the interacting anions is increased. Thus, the observed high-field 15N shift of ammonium groups upon hydration is the consequence of replacing interacting halogen atoms by oxygen atoms.

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“…At pH 9-11 a transformation to a-helices is observed by 13 C NMR. 3 Heating the basic solution leads again to the formation of b-pleated sheets as revealed by ESR and NMR, 4 optical rotatory dispersion measurements 5 and Raman spectroscopy. 6 IR measurements showed that the secondary structure is also influenced by the chain length 7,8 According to Scheraga, the b-pleated sheet structure is favored by hydrophobic interactions between the side chains by which the entropy of the surrounding water is increased.…”

Section: Introductionmentioning

confidence: 99%

Effects of hydration on the acid–base interactions and secondary structures of poly-l-lysine probed by 15N and 13C solid state NMR

Dos

Schimming

Chan-Huot

et al. 2010

Phys. Chem. Chem. Phys.

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Using high resolution solid state (15)N and (13)C NMR spectroscopy we have studied the effects of successive hydration on the (15)N labeled side chain amino groups of solid poly-L-lysine (PLL) in the presence of acids. Generally, hydration leads to the formation of local "ionic fluid" phases composed by flexible side chain ammonium groups, acid anions and small amounts of water. The associated local dynamics reduces the widths of the inhomogeneously broadened (15)N amino signals found for the dry states. The hydration of free base PLL--which consists of mixtures of alpha-helices and beta-pleated sheets--is monitored by a small low-field shift of the amino group signal arising from hydrogen bonding with water, reaching eventually the value of PLL in water at pH 13. No difference for the two conformations is observed. PLL x HF adopts a similar secondary structure with isolated NHF hydrogen bonds; hydration leads only to small low-field shifts which are nevertheless compatible with the formation of ammonium groups in aqueous solution. PLL doped with small amounts of HCl contains ammonium groups which are internally solvated by neighboring free amino groups. Both nitrogen environments are characterized by different chemical shifts. Hydration with less than one water molecule per amino group leads already to a chemical shift averaging arising from fast proton motions along NHN-hydrogen bonds and fast side chain and anion motions.By contrast, the hydration of fully doped PLL x HBr and PLL x HCl is more complex. These systems exist only in beta-pleated sheet conformations forming alkyl ammonium salt structures. Separate (15)N signal components are observed for (i) the dry states, for (ii) wet beta-pleated sheets and for (iii) wet alpha-helices which are successively formed upon hydration. Exchange between these environments is slow, but water motions lead to averaged amino group signals within each of the two wet environments. These results indicate that the different environments form domains. As the replacement of NHBr or of NHCl hydrogen bonds by NHO hydrogen bonds leads to high-field shifts the observation of separated signals is the result of different water content in the three domains. In agreement with previous X-ray powder diffraction studies we observe a dominance of the alpha-helical regions at above 3 water molecules per amino group in the case of PLL x HBr and at about 5 water molecules in the case of PLL x HCl, an effect arising from the limited space between beta-pleated sheets and the larger volume of bromide as compared to chloride.

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NMR and ESR study of the conformations and dynamical properties of poly(L-lysine) in aqueous solutions

Cited by 9 publications

References 18 publications

Investigation of Hydrophobic Interactions in Colloidal and Biological Systems by Molecular Dynamics Simulations and NMR Spectroscopy

Investigation of Hydrophobic Interactions in Colloidal and Biological Systems by Molecular Dynamics Simulations and NMR Spectroscopy

Acid−Base Interactions and Secondary Structures of Poly-l-Lysine Probed by ¹⁵N and ¹³C Solid State NMR and Ab initio Model Calculations

Effects of hydration on the acid–base interactions and secondary structures of poly-l-lysine probed by 15N and 13C solid state NMR

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NMR and ESR study of the conformations and dynamical properties of poly(L-lysine) in aqueous solutions

Cited by 9 publications

References 18 publications

Investigation of Hydrophobic Interactions in Colloidal and Biological Systems by Molecular Dynamics Simulations and NMR Spectroscopy

Investigation of Hydrophobic Interactions in Colloidal and Biological Systems by Molecular Dynamics Simulations and NMR Spectroscopy

Acid−Base Interactions and Secondary Structures of Poly-l-Lysine Probed by 15N and 13C Solid State NMR and Ab initio Model Calculations

Effects of hydration on the acid–base interactions and secondary structures of poly-l-lysine probed by 15N and 13C solid state NMR

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Acid−Base Interactions and Secondary Structures of Poly-l-Lysine Probed by ¹⁵N and ¹³C Solid State NMR and Ab initio Model Calculations