Red blood cell rouleaux formation in dextran solution: dependence on polymer conformation

Abstract

The velocity of rouleaux formation (RF), as previously shown, increases with increasing dextran concentration up to a critical concentration (Ca), beyond which the addition of dextran reduces the RF velocity (RFV). de Gennes' model for polymer solutions suggests that dextrans exist in two conformations: a coil structure at low concentrations, which changes to a network beyond a critical concentration (C*). In the present study we examined the relation between Ca and C* for dextrans of different molecular weight, and found that they coincide. This suggests that the change in dextran behavior, from increasing to decreasing RFV, occurs when their conformation changes from coil to network. In addition, it has been reported that in dilute dextran solutions the intercellular distance (D) between RBC in rouleaux increases with the molecular weight of the dextran. We found that D correlates with Rf, the end-to-end distance of the polymer molecule, and for all dextrans D < or = 1.5 Rf. In accord with de Gennes' Model for polymers between surfaces, this corresponds to intercellular interaction with two overlapping surface-associated polymer layers, which may extend "tails" to interact with the opposing cells.

A pulsed photoacoustic technique for studying red blood cell sedimentation

“…When washed RBCs were used, also bovine serum albumin (Sigma Chemicals CO., St. Louis, MO, USA) with a concentration of 1.0 g/dl (1 % albumin concentration was taken from Ref. 41) was used. The experiments were repeated on two separate days with two different sets of samples (denoted as sample (1-8)_1 and sample (1-8)_2).…”

Directly observed reversible shape changes and hemoglobin stratification during centrifugation of human and Amphiuma red blood cells

“…acid (DIDS), which is known to inhibit anion transport by Band 3, inhibits rouleau formation, presumably by adding net charge or repulsive force to the interface (26). In contrast, rouleau formation with dextrans is known to be biphasic, independent of the size of the dextran used (27,28), with the interesting result that the dextran polymers change their structure (i.e., coil to network) as a function of concentration and the peak of the biphasic response correlates with the transition in the dextran's molecular structure (28). Evidently, there is no specificity in agents that induce rouleau formation, so long as minimum requirements are met (e.g., ref.…”

A new method for the preperative and analytical electrophoresis of cells

“…Such events are very complex and cell surface specific [43,49,53], but our RBC sedimentation studies identified dextran 15000-20000 MW as the most suitable to form a "density cushion" for the RBC. These lower MW dextrans are osmotically active, whereas higher MW dextrans cause cell aggregation and RBC rouleaux formation, and coat the cell surfaces [37,39,44]. Other macromolecular solutions tested included ficolls or PEGs of MW ranging from 1000 to 400000, but these also coated the cell surface and modified cell permeability and electrophoretic mobility, as judged by haemoglobin leakage which compromised and even reversed the direction of cell electrophoresis [23,43,[54][55][56].…”