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Transient electric birefringence study of highly dilute agarose solutions
Author(s) -
Dormoy Y.,
Candau S.
Publication year - 1991
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360310110
Subject(s) - agarose , chemistry , birefringence , electric field , dipole , rotational diffusion , exponential function , exponential decay , molecular physics , diffusion , analytical chemistry (journal) , optics , thermodynamics , chromatography , physics , mathematical analysis , mathematics , organic chemistry , quantum mechanics , molecule , nuclear physics
In order to characterize the first step of agarose gelation, highly dilute solutions (2·10 −3 to 0.5 g/L) have been studied by means of the transient electric birefringence technique. The field‐free decay curves of the birefringence are well described by a stretched‐exponential B ( t ) ≈ exp(− t /τ) β ; the value of the exponent β is close to 0.5 whatever the agarose concentration. The suspended particles observed by electron microscopy present a rod‐like shape with a constant diameter (∼50 Å), without any branching; they are polydisperse with a distribution of lengths approximately exponential. The mean length of these fibers, deduced from their mean rotational diffusion coefficient, is proportional to the 0.37 power of the agarose concentration in the solution. Furthermore, these particles possess a strong permanent electrical dipole confirming the side‐to‐side arrangement of helices into bundles; this dipole is roughly proportional to the particle length, indicating a self‐similarity in the unidirectional growth of the agarose fibers, even when approaching the gelling concentration.