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15 N and 13 C NMR study of the effects of hydrogen bonding and protonation in linear schiff bases: Models for structural studies of rhodopsin and bacteriorhodopsin
Author(s) -
Muccio D. D.,
Copan W. G.,
Abrahamson W. W.,
Mateescu G. D.
Publication year - 1984
Publication title -
organic magnetic resonance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0030-4921
DOI - 10.1002/mrc.1270220214
Subject(s) - protonation , chemistry , bacteriorhodopsin , schiff base , hydrogen bond , chemical shift , tautomer , pyridine , carbon 13 nmr , computational chemistry , photochemistry , crystallography , stereochemistry , molecule , medicinal chemistry , organic chemistry , ion , biochemistry , membrane
The effects of protonation and hydrogen bonding in linear Schiff bases obtained from n ‐butylamine with butyraldehyde, crotonaldehyde, sorbaldehyde and all‐ trans ‐retinal were studied by means of 15 N and 13 C NMR. The protonation‐induced chemical shifts (Δδ) are an order of magnitude larger for 15 N than for 13 C. For 15 N, this effect was found to increase with the extent of conjugation, culminating in the retinylideneimine (Δδ = −146 ppm), which constitutes a model for the study of the structure of the Schiff base linkage in visual pigments and related systems. Theoretical calculations of protonation‐induced Δδ values based on MINDO/ 3 are in agreement with experimental results.