1 research outputs found
Nanofluidity of Fatty Acid Hydrocarbon Chains As Monitored by Benchtop Time-Domain Nuclear Magnetic Resonance
The functional properties of lipid-rich
assemblies such as serum
lipoproteins, cell membranes, and intracellular lipid droplets are
modulated by the fluidity of the hydrocarbon chain environment. Existing
methods for monitoring hydrocarbon chain fluidity include fluorescence,
electron spin resonance, and nuclear magnetic resonance (NMR) spectroscopy;
each possesses advantages and limitations. Here we introduce a new
approach based on benchtop time-domain <sup>1</sup>H NMR relaxometry
(TD-NMR). Unlike conventional NMR spectroscopy, TD-NMR does not rely
on the chemical shift resolution made possible by homogeneous, high-field
magnets and Fourier transforms. Rather, it focuses on a multiexponential
analysis of the time decay signal. In this study, we investigated
a series of single-phase fatty acid oils, which allowed us to correlate <sup>1</sup>H spin–spin relaxation time constants (<i>T</i><sub>2</sub>) with experimental measures of sample fluidity, as obtained
using a viscometer. Remarkably, benchtop TD-NMR at 40 MHz was able
to resolve two to four <i>T</i><sub>2</sub> components in
biologically relevant fatty acids, assigned to nanometer-scale domains
in different segments of the hydrocarbon chain. The <i>T</i><sub>2</sub> values for each domain were exquisitely sensitive to
hydrocarbon chain structure; the largest values were observed for
pure fatty acids or mixtures with the highest <i>cis</i>-double bond content. Moreover, the <i>T</i><sub>2</sub> values for each domain exhibited positive linear correlations with
fluidity. The TD-NMR <i>T</i><sub>2</sub> and fluidity measurements
appear to be monitoring the same underlying phenomenon: variations
in hydrocarbon chain packing. The results from this study validate
the use of benchtop TD-NMR <i>T</i><sub>2</sub> as a nanofluidity
meter and demonstrate its potential for probing nanofluidity in other
systems of biological interest