Ligamentum nuchae elastin from

CONCENTRATIONS OF CROSSLINKS AND LYSINE RESIDUES IN ELASTIN ISOLATED FROM THE LIGAMENTUM NUCHAE OF CATTLE OF INCREASING AGEa... 

The most ready source of elastin of high purity is the ligamentum nuchae of the larger ruminants, and from this source a protein of constant composition can be isolated by a variety of methods depending on the solubilization and removal of other less inert tissue components. Because of the ease with which it may be isolated the elastin of bovine ligamentum nuchae has come to be regarded as the type standard, but it is by no means certain that elastins from other mammals or other tissues in the same mammal are of identical constitution. 

Probably because of the ease with which they can be prepared, purified fiber preparations from bovine ligamentum nuchae have formed the starting point of most chemical investigations of elastin. These preparations how-... 

Fig. 2. Electron micrograph showing the fibrillar structure of an elastic fiber from bovine ligamentum nuchae. (Gotte and Serafini-Fracassini, 1962.) The elastin fibers were treated with dilute sodium hydroxide at 98°C for 1 hr, washed with hot water, and disintegrated ultrasonically at 40 kc. The magnification is 63,000X and the individual fibrils are 10 2 The specimen was shadowed with chromium at 20 degrees.

Paper chromatography was used hy Bowes and Kenten (1949) to examine the amino acid composition of elastin preparations from ligamentum nuchae and skin. The results indicated either that the elastic fibers of skin differ from those of ligamentum nvchac in amino acid composition or that they are less resistant to hot water. This interesting suggestion does not appear to have been pursued. 

Fig. 3. Time-course of solubilization of elastin from three bovine tissues (Golte et al., 1962). The elastin samples (prepared by autoclaving) were suspended in 0.5 N NaOH and maintained at 25°C with gentle rocking. The amino acid composition of the samples is given in Table I. Key O = elastin from bovine ear cartilage A elastin from bovine aorta X = elastin from bovine ligamentum nuchae.

Partridge et al. (W ib) observed that when elastin from ligamentum nuchae of cattle was repeatedly extracted with 0.2. 5 M oxalic acid at 100°C the fibers completely dissolved after about 5 hr total extraction. On dialysis in cellophane only about. 5 % of the total nitrogen of the reaction mixture diffused through the membrane. The bulk of the product was a protein which was soluble in distilled water or buffer solutions at temperatures below 2f>°C, but on raising the temperature of the solution in dilute buffer at pH 4-6 a coacervate phase consisting of liquid droplets separated. The soluble material was thus similar in properties to the hemi-elastin of Horbaczewski (1882). 

La Bella (1961) studied the soluble products released from elastin by pancreatic elastase. Elastin was prepared from beef ligamentum nuchae by repeated extraction with hot 0.1 N NaOH in order to remove extraneous material as completely as possible. The purified product was then treated... 

Such a process was attempted by treating the elastin from ligamentum nuchae first with several successive additions of pancreatic elastase and then further degrading the product with papain imtil all but a few per cent of the product was dialyzable through cellophane. The diffusate was then treated, in series, with a range of ion-exchange resins with varying internal pore diameter. The resins were of the suKonated polystyrene type, in bead form, and had nominal divinylbenzene (DVB) contents of 2 %, %,... 

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