Macromolecular Dynamics in Red Blood Cells Investigated Using Neutron Spectroscopy

TL;DR

This study uses neutron spectroscopy to analyze hemoglobin dynamics in red blood cells, revealing diffusion behaviors and water interactions consistent with hydrodynamic theory, and comparing cellular and powder protein dynamics.

Contribution

It provides the first in vivo neutron scattering measurements of hemoglobin dynamics in red blood cells, highlighting water's role and comparing cellular and powder protein behaviors.

Findings

Global and internal Hb dynamics measured in ps to ns range.

Diffusion coefficients match hydrodynamic theory predictions.

Higher water content in cells enhances internal protein fluctuations.

Abstract

We present neutron scattering measurements on the dynamics of hemoglobin (Hb) in human red blood cells in vivo. Global and internal Hb dynamics were measured in the ps to ns time- and {\AA} length-scale using quasielastic neutron backscattering spectroscopy. We observed the cross-over from global Hb short-time to long-time self-diffusion. Both short- and long-time diffusion coefficients agree quantitatively with predicted values from hydrodynamic theory of non-charged hard-sphere suspensions when a bound water fraction of around 0.23g H2O/ g Hb is taken into account. The higher amount of water in the cells facilitates internal protein fluctuations in the ps time-scale when compared to fully hydrated Hb powder. Slower internal dynamics of Hb in red blood cells in the ns time-range were found to be rather similar to results obtained with fully hydrated protein powders, solutions and E. coli cells.