Age-dependent modification of lipid composition and lipid structural order parameter of rat peritoneal macrophage membranes

Abstract Few questions in condensed matter science have proven as difficult to unravel as the interplay between structure and dynamics in supercooled liquids. To explore this link, much research has been devoted to pinpointing local structures and order parameters that correlate strongly with dynamics. Here we use an unsupervised machine learning algorithm to identify structural heterogeneities in three archetypical glass formers—without using any dynamical information. In each system, the unsupervised machine learning approach autonomously designs a purely structural order parameter within a single snapshot. Comparing the structural order parameter with the dynamics, we find strong correlations with the dynamical heterogeneities. Moreover, the structural characteristics linked to slow particles disappear further away from the glass transition. Our results demonstrate the power of machine learning techniques to detect structural patterns even in disordered systems, and provide a new way forward for unraveling the structural origins of the slow dynamics of glassy materials.

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Developmental changes in glucose transport, lipid composition, and fluidity of jejunal BBM

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1997.273.3.r1086 ◽

1997 ◽

Vol 273 (3) ◽

pp. R1086-R1093 ◽

Cited By ~ 6

Author(s):

C. M. Vazquez ◽

N. Rovira ◽

V. Ruiz-Gutierrez ◽

J. M. Planas

Keyword(s):

Glucose Uptake ◽

Glucose Transport ◽

Lipid Composition ◽

Brush Border Membrane ◽

Glucose Transporter ◽

Specific Binding ◽

Molar Ratio ◽

Site Density ◽

Age Related ◽

Age Dependent

Na(+)-dependent D-glucose uptake was studied in jejunal brush-border membrane (BBM) vesicles of chickens at 2 days and 1, 2, 5-6, and 12-14 wk of age. Both initial rates and accumulation ratios of the Na(+)-dependent D-glucose transport were significantly higher during the 1st wk than at other ages. To explain the age-related changes observed in the transport of D-glucose, the phlorizin-specific binding, Na+ permeability, lipid composition, and fluidity were studied. Transporter site density was quantified using 50 mumol/l phlorizin and found to be higher during the 1st wk. During the 2nd wk it decreased and then remained constant. Permeability of Na+, studied using 22Na+, showed that fluxes were similar during the first 6 wk, and a significant decrease was observed in the oldest group. Furthermore, membrane fluidity results showed a significant age-dependent decrease that correlated well with both the increased molar ratio of cholesterol to phospholipid and the decreased ratio of lipid to protein found during development. In conclusion, changes in the density of Na(+)-dependent D-glucose transporter as well as in lipid content and fluidity might be involved in the changes observed in D-glucose uptake during the posthatching development.

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