Amyloid fibrils were isolated from the tissues of nine patients with amyloidosis in a state of high purity by homogenization of the tissue followed by extraction with distilled water. Physical, chemical, and ultrastructural studies suggest that amyloid fibrils from different individuals resemble each other, but are not identical. In tissue sections as well as by negative staining of isolated fibrils, morphologic variations were observed. Among the isolated fibrils at least three types were noted. The majority resembled those described previously. However, one subject had two types of fibrils which differed in size and appearance. Most of the preparations sedimented as a single component with a sedimentation coefficient of 45-50S or as a larger polymer. However, two of the preparations had sedimentation coefficients of 8-9S, and a third one had a major 95S component and a minor 9S fraction. While the preparations of amyloid were not sufficiently pure for amino acid analyses, peptide maps demonstrated differences among amyloid preparations from different subjects. The amyloid fibrils in their native state proved to be remarkably resistant to digestion by a number of proteolytic enzymes. Several chemical methods were tried to produce smaller subunits. Of these, the most successful one was the use of 0.1 M NaOH which yielded a smaller, soluble fraction with sedimentation coefficients ranging from 1.1 to 2.8S. Accompanying this degradation, there was little loss of peptides or carbohydrates. Based on the results of the chemical analyses, it is estimated that the subunit produced by sodium hydroxide had a molecular weight of approximately 35,000-40,000.

Adolescent↗

PubMed1968

The characterization of soluble amyloid prepared in water.

Amyloid was extracted from the spleen of a patient with primary amyloidosis by homogenizing it at high speed with water after preliminary treatments, first to remove proteins soluble in saline, and then to remove salts. The extracts containing amyloid appeared to be clear at concentrations up to 6 mg/ml of protein. The material gave little sediment on being centrifuged up to 20,000 g for 1 hr, but the protein was sedimented at 100,000 g in 1 hr. The amyloid could be precipitated from the extracts by addition of NaCl to 0.0075 mole/liter or of CaCl(2) to 0.0025 mole/liter. The protein-bound Congo red formed a red precipitate and this property was used to estimate recovery and purity of amyloid during extraction. On electronmicroscopy the isolated amyloid proved to be morphologically pure. It existed either as single filaments measuring 60-80 A in diameter or as large aggregates of these filaments.Freshly isolated amyloid in water sedimented as a single homogeneous peak with an s degrees (20,[unk]) of about 45-50S. On standing, the solution became cloudy and more rapidly sedimenting components appeared. On electrophoresis the material migrated as a homogeneous peak towards the anode. The protein had an amino acid composition different from that of all known serum proteins. It was rich in acidic amino acids and had little cysteine and methionine and no hydroxyproline. The total content of carbohydrate was less than 2%.

Amino Acids↗

PubMed1966