Intramolecular dipolar nuclear

Under continuous uv irradiation, the observed steady-state polarization (whether by cw or by FT spectrometers) may be substantially modified by various nuclear relaxation processes. For example, Closs and Czeropski (35,36) have demonstrated that CIDNP can be transferred from a group of polarized nuclei to another group not originally polarized. Both the dipolar and the scalar relaxation mechanisms (of the nuclear Overhauser effects) can be operative. The extremely interesting case of intramolecular dipolar nuclear cross relaxation reported by Closs and Czeropski (35) involves the thermal reaction of... 

Inter-/intramolecular distances 0.1-1 nm Nuclear Overhauser effect (1-NMR), dipolar splittings (s-NMR)... 

The natural line-width of the proton resonances is determined by the nuclear spin relaxation times. Nuclear relaxation in solutions of diamagnetic molecules comes mainly from intramolecular proton-proton dipolar coupling modulated by the rotational tumbling of the molecules, and will be discussed in more detail in section VII. Suffice it here to say that the line-width increases in general with increasing size of the molecule. For a small organic molecule a line-width at half height of the resonances of less than one cps would be expected, whereas the resonances... 

NMR spectroscopy is a well-suited technique to study the membrane interactions of antimicrobial peptides by taking advantage of the orientational dependence of nuclear spin interactions. This paper discusses several solid-state NMR experiments to extend information on the peptide structure and dynamics as well as on the effect of antimicrobial peptides on model membranes. More specifically, studies of peptide dynamics by and N CP/MAS and static experiments were reported. A set of orientational restraint potentials for solid-state NMR observables in-eluding N chemical shift and N- H dipolar coupling was developed. The N-H X (X = N,0,S) intramolecular hydrogen bond in the series of 2(2 -heteroaryl)pyrroles and their trifluoroacetyl derivatives was examined by the H, N spectroscopy and density functional theory (DFT)... 

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