13C and 1H NMR studies of helix‐coil transition of poly(β‐benzyl‐L‐aspartate) and poly(γ‐benzyl‐L‐glutamate): Behavior in nonprotonating solvent mixtures, and origin of solvent‐induced chemical shift

From the results of 13C‐nmr measurement of poly(β‐benzyl‐L‐aspartate) and its model compounds in dimethyl sulphoxide/deuterated chloroform mixtures, it was found that the side chain of poly(β‐benzyl‐L‐aspartate) is solvated by dimethyl sulphoxide in the region more than dimethyl sulphoxide 20% (v/v), where the backbone maintains the α‐helix. The chemical shift differences in the benzyl group carbons of poly(γ‐benzyl‐L‐glutamate) (trifluoroacetic acid/deuterated chloroform) accompanied by the helix‐coil transition, originate from the interaction between the ester group of the side chain and trifluoroacetic acid. The chemical shift difference in the ester carbon is similar. On the other hand, the chemical shift differences of the side‐chain carbons in the alkyl portion (Cβ, Cγ) originate not only from the interaction between the ester group of the side chain and trifluoroacetic acid, but also from some other unknown factors. The chemical shift differences of the side‐chain carbons of poly(β‐benzyl‐L‐aspartate) originate from the interaction between the ester group of the side chain and trifluoroacetic acid.

[1]  Y. Inoue,et al.  A Study of stepwise conformational changes in poly(β‐benzyl‐L‐aspartate) with the helix–coil transition by means of proton and carbon‐13 NMR , 1977, Biopolymers.

[2]  Y. Inoue,et al.  Carbon‐13 and proton nmr studies of helix–coil transition of poly(γ‐benzyl‐L‐glutamate) , 1975 .

[3]  P. Temussi,et al.  N.m.r. studies of the helix-coil transition of polypeptides in non-protonating solvent mixtures , 1973 .

[4]  J. F. Hinton,et al.  NMR studies of the structure of aqueous amide solutions , 1972 .

[5]  F. Bovey.  Nuclear magnetic resonance and optical studies of polypeptide chain conformation , 1968 .

[6]  S. Hanlon.  The protonation of poly-gamma-benzyl-L-glutamate in mixed solvents containing dichloroacetic acid. , 1966, Biochemistry.

[7]  F. Bovey.  NMR observations of polypeptide conformations , 1974 .

[8]  P. Cary,et al.  Nuclear magnetic resonance of synthetic polypeptides , 1973 .

[9]  I. Morishima,et al.  Conformational dependence of the inductive effect in the .sigma.-electron system as studied by carbon-13 nuclear magnetic resonance , 1973 .

[10]  B. Ninham,et al.  Nuclear Magnetic Resonance Investigation of the Helix to Random Coil Transformation in Poly (α-amino acids). II. Poly(γ-benzyl L-glutamate) , 1970 .

[11]  R. Glick,et al.  Proton nuclear magnetic resonance studies of model polypeptides. Aspects of the helix-random coil interconversion. , 1967, Biochemistry.

[12]  S. Hanlon,et al.  PROTONATION OF POLYPEPTIDES IN "HELIX-BREAKING" SOLVENTS: SPECTRAL AND OPTICAL-ROTATORY PROPERTIES IN SOLUTIONS CONTAINING STRONG ORGANIC ACIDS. , 1965, Biochemistry.

[13]  R. Gillespie,et al.  A NUCLEAR MAGNETIC RESONANCE INVESTIGATION OF THE PROTONATION OF AMIDES IN FLUOROSULPHURIC ACID , 1963 .