Interactions and fluctuations deduced from proton field-cycling relaxation spectroscopy of polypeptides, DNA, muscles, and algae

17O Quadrupole Dips in Ammonium Persulphate

“…By magnetising the X H spins in high field and then cycling to low field, 'quadrupole dips' [4] are observed corresponding to the enhanced relaxation of the *H spins at frequencies corresponding to quadru pole transitions. Such dips have also been observed for 14N [1], 35C1 [2], and other abundant nuclei [3], In this paper, we report for the first time the observation of quadrupole dips for a quadrupolar nucleus in low abundance, namely 170 in natural abundance (0.037%). The effect of 170 in natural abundance on has already been shown in a number of com pounds [5][6][7][8].…”

“…Magnetic field cycling spectroscopy provides a con venient m ethod for obtaining quadrupolar param e ters in solids containing an abundant spin 7 = 1/2 nu cleus such as *H as well as a quadrupolar spin (7 ^1 ) present in reasonable abundance [1][2][3]. The m ethod consists in observing the *H n.m.r.…”

Nuclear magnetic relaxation dispersion study of the dynamics in solid homopolypeptides

“…The slight increase in the relaxation rate with increasing temperature is consistent with spin-phonon-like relaxation mechanism represented in Eq. (2). Note that the series of quadrupole peaks, which arise from the coupling of protons bonded directly to amide nitrogens in immobilized polypeptide systems, is observed in this frequency range.…”

“…[1][2][3][4][5][6][7][8] The physical origins of this power law have been related to a spin-phonon-like or spin-fracton relaxation mechanism. [9][10][11][12] The essential idea behind the relaxation mechanism is that the structural fluctuations in the protein propagate along the primary polypeptide chain which causes transient fluctuations in the proton-dipole-dipole couplings, hence, relaxation.…”

Quadrupole-enhanced proton spin relaxation for a slow reorienting spin pair: (I)–(S). A stochastic Liouville approach

“…The quadrupole coupling constant χ = 3.596 MHz is chosen to match the quadrupole frequency of the QD's of a H − 14 N pair [2,35,36].…”