elastin and formic-acid

The authors relate the findings in the 1H solid state line shape (at 60 MHz) of human aortic walls (n = 12) in native state and after histologically controlled selective lysis of collagen and elastin. An analysis of the line shape shows a composite free induction decay (FID) consisting of a low amplitude (3-7%) fast decaying component (T2 approximately 20 microseconds) and a slow decaying one (T2 > 1 ms). The fast component is identified as the protons of the collagen macromolecules. The second moment computed from the experimental fast component of the FID is in agreement with published studies examining the motional characteristics of collagen by multinuclear NMR employing spin labeling. A theoretical second moment is computed for the collagen macromolecular backbone from the atomic positions in the superhelix. Comparison with the observed experimental values allows determination of the step angle (29 degrees) of the fast rotational motion of the collagen strands along their long axis.

Topics: Aged; Aged, 80 and over; Aorta; Collagen; Elastin; Electron Spin Resonance Spectroscopy; Female; Formates; Humans; Hydrogen; Macromolecular Substances; Magnetic Resonance Spectroscopy; Male; Middle Aged; Signal Processing, Computer-Assisted; Trypsin

The present study examined procedures of specimen preparation for observing elastin components in the formic acid-digested tissue by scanning electron microscopy (SEM). The rat thoracic aorta fixed in 4% paraformaldehyde was treated with 90% formic acid for 85-96 hr at 45 degrees C and processed in two different ways: 1) the tissues were freeze-dried directly from water and 2) they were treated with tannic acid and osmium followed by critical point drying. The former procedure caused marked deformation of elastin components, while the latter preserved them well in shape and arrangement. Thus, the three-dimensional organization and ultrastructure of the elastin components were precisely demonstrated in this study.

Topics: Animals; Aorta; Elastin; Formates; Microscopy, Electron, Scanning; Rats

1. The apparent surface areas of elastin samples as well as of several other fibrous protein preparations (collagen, keratin, polymeric stroma of aorta) were determined using two different approaches: (a) the Brunauer-Emmett-Teller method with 85Kr and (b) microflow calorimetry with n- and tert.-butanol as adsorbents in a heptane stream. 2. Areas of heat signals obtained by flow calorimetry for the adsorption and desorption of n- and tert.-butanol were substantially equivalent; desorption was more protracted than adsorption, the difference between the speed of desorption and adsorption increased with decreasing chain length of the alcohols (methanol, ethanol, n-propanol and n-butanol). 3. An inverse linear relationship was found between the energy change recorded during the adsorption process and the chain length of the alcohols (methanol, ethanol, n-propanol, n-butanol). 4. Heats of adsorption of tert.-butanol were systematically found to be significantly lower than those of n-butanol with all the protein samples investigated. 5. The apparent surface areas of the protein samples determined with tert.-butanol were on the average of the same order or only slightly higher than those obtained with 85Kr. Results obtained with n-butanol were significantly higher. The difference between surface areas obtained with n- and tert.-butanol depended on the nature of the protein sample, on its method of preparation and to some extent on the residual humidity of the sample. 6. The results could be explained on the basis of the hydrophobic theory of elastin structure (see ref. 4) and confirmed our former conclusions (see ref. 3) concerning the significantly higher surface areas of elastin samples purified by different procedures as compared to collagen or to keratin. They also confirmed the accessibility of the surface of elastic fibers to the molecular probes used in the polymeric stroma of aorta.

Topics: Adsorption; Animals; Binding Sites; Butanols; Calorimetry; Cattle; Elastin; Formates; Heptanes; Humans; Krypton Radioisotopes; Surface Properties; Thermodynamics

Topics: Animals; Aorta; Aorta, Thoracic; Chromatography; Copper; Deficiency Diseases; Diet; Elastin; Formates; Histocytochemistry; Pancreatic Elastase; Proteins; Research; Swine