ENDOR studies of γ-irradiated l-cystine dihydrochloride. The hyperfine tensors from CH2 protons in the anion and the cation

Akira Naito, Kazuyuki Akasaka, Hiroyuki Hatano

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Abstract

The ENDOR signals from the CH2 protons of the disulfide anion and of the disulfide cation produced in a single crystal of l-cystine dihydrochloride γ-irradiated at 77 K have been detected and the hyperfine tensors determined. The principal values of the hyperfine tensors for the two nonequivalent protons are found to be (33.1, 27.6, 25.9) MHz and (24.0, 18.9, 17.3) MHz for the anion, (21.3, 17.5, 16.5) MHz and (14.3, 5.5, 4.1) MHz for the cation. UHF INDO calculations have been performed, which predict that the unpaired electron of the anion occupies the antibonding sigma-type orbital of the disulfide bond, whereas that of the cation occupies the antiboding π-type orbitals, both constructed dominantly from the sulfur 3p orbitals. The UHF INDO results combined with the point dipole approximation for the dipolar hyperfine tensors have given assignments of the ENDOR signals to specific protons of the CH2 groups. The isotropic parts of the hyperfine tensors for the CH2 protons are interpreted by hyperconjugation mechanism, i.e., by the relation a = B cos2 φ, where B is determined to be 25.9 and 36.8 G for the anion and the cation, respectively. © 1976.

Original languageEnglish
Pages (from-to)53-62
Number of pages10
JournalJournal of Magnetic Resonance (1969)
Volume24
Issue number1
DOIs
StatePublished - 1976 Jan 1
Externally publishedYes

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Tensors
Protons
Negative ions
Positive ions
Cystines
Sulfur
Electrons

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ENDOR studies of γ-irradiated l-cystine dihydrochloride. The hyperfine tensors from CH2 protons in the anion and the cation. / Naito, Akira; Akasaka, Kazuyuki; Hatano, Hiroyuki.

In: Journal of Magnetic Resonance (1969), Vol. 24, No. 1, 01.01.1976, p. 53-62.

Research output: Contribution to journalArticle

Naito, Akira; Akasaka, Kazuyuki; Hatano, Hiroyuki / ENDOR studies of γ-irradiated l-cystine dihydrochloride. The hyperfine tensors from CH2 protons in the anion and the cation.

In: Journal of Magnetic Resonance (1969), Vol. 24, No. 1, 01.01.1976, p. 53-62.

Research output: Contribution to journalArticle

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AU - Akasaka,Kazuyuki

AU - Hatano,Hiroyuki

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N2 - The ENDOR signals from the CH2 protons of the disulfide anion and of the disulfide cation produced in a single crystal of l-cystine dihydrochloride γ-irradiated at 77 K have been detected and the hyperfine tensors determined. The principal values of the hyperfine tensors for the two nonequivalent protons are found to be (33.1, 27.6, 25.9) MHz and (24.0, 18.9, 17.3) MHz for the anion, (21.3, 17.5, 16.5) MHz and (14.3, 5.5, 4.1) MHz for the cation. UHF INDO calculations have been performed, which predict that the unpaired electron of the anion occupies the antibonding sigma-type orbital of the disulfide bond, whereas that of the cation occupies the antiboding π-type orbitals, both constructed dominantly from the sulfur 3p orbitals. The UHF INDO results combined with the point dipole approximation for the dipolar hyperfine tensors have given assignments of the ENDOR signals to specific protons of the CH2 groups. The isotropic parts of the hyperfine tensors for the CH2 protons are interpreted by hyperconjugation mechanism, i.e., by the relation a = B cos2 φ, where B is determined to be 25.9 and 36.8 G for the anion and the cation, respectively. © 1976.

AB - The ENDOR signals from the CH2 protons of the disulfide anion and of the disulfide cation produced in a single crystal of l-cystine dihydrochloride γ-irradiated at 77 K have been detected and the hyperfine tensors determined. The principal values of the hyperfine tensors for the two nonequivalent protons are found to be (33.1, 27.6, 25.9) MHz and (24.0, 18.9, 17.3) MHz for the anion, (21.3, 17.5, 16.5) MHz and (14.3, 5.5, 4.1) MHz for the cation. UHF INDO calculations have been performed, which predict that the unpaired electron of the anion occupies the antibonding sigma-type orbital of the disulfide bond, whereas that of the cation occupies the antiboding π-type orbitals, both constructed dominantly from the sulfur 3p orbitals. The UHF INDO results combined with the point dipole approximation for the dipolar hyperfine tensors have given assignments of the ENDOR signals to specific protons of the CH2 groups. The isotropic parts of the hyperfine tensors for the CH2 protons are interpreted by hyperconjugation mechanism, i.e., by the relation a = B cos2 φ, where B is determined to be 25.9 and 36.8 G for the anion and the cation, respectively. © 1976.

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