The Polyelectrolyte Properties of Elastin

Abstract

The charge structure and ionic interactions of elastin prepared from the pig thoracic aorta by acid, alkali, or CNBr extraction have been investigated by potentiometric titration and radiotracer techniques. The number of charged groups was consistent with the amino acid composition, comparable to elastin from other sources and insensitive to the method of preparation. The enthalpies of ionization of the basic groups were comparable for those previously found for proteins but those of the acidic groups were higher. Ionic interactions were predominantly electrostatic although a strong affinity for chloride ions was noted. Changes in ionic interactions as the elastin was stretched had a similar effect to an increase in the apparent fixed charge density of the tissue. Mechanical strain altered the protonation of the elastin and the pK of the carboxyl groups. Conversely, the conformation of the elastin network varied with ionic strength and pH, being particularly sensitive to the degree of ionization of the more basic groups and with the ionic strength and anion composition of the medium. We speculate that strain induced changes in the conformation of elastin altering its reactivity towards lipids, ions or matrix macromolecules or changes in its mechanical properties resulting from changes in its ionic environment may be of physiological or pathological importance.

The molecular structure and physical properties of elastin fibers as revealed by Raman microspectroscopy

“…Raman spectrum for fully hydrated nuchal elastin fibers after water has been exchanged for D 2 O. There is a strong double peak at 2475 and 2400 cm 21 .…”

“…1 Its remarkable physical properties have been under investigation for many years, [2][3][4] but a number of issues remain unresolved. The molecular structure of elastin is well established and many of its unique properties are considered to be due to the presence of extensive hydrophobic domains.…”

Physicochemical properties of arterial elastin and its associated glycoproteins

“…nary elastin than aortic is consistent with our previous measurements on alkali extracted material. 18 Calcium uptake was higher in the microfibril-containing preparations, as might be expected because of the more negative electrostatic charge.…”

“…These procedures have been described in greater detail elsewhere. 18 The tracers employed were as follows:…”

Microcalorimetric investigations of the interactions of small ions with arterial elastin

“…15 Preweighed rings of elastin were incubated for 4 h with a 0.015 or 0.15M solution in deionized water or 1 : 1 water : methanol solution of CaC12, NaC1, NaI, or Na2S04 in which one ion was radio-active (22Na, 45Ca, 35Cl, 1351, or 35S04, Amersham International). The rings were assayed for radioactivity together with aliquots of the incubating medium.…”