Collagen nitrogen content

Stable isotope analyses of the organic fraction of bone and of food samples was carried out on a Micromass Prism Mass Spectrometer in the Stable Isotope Laboratory, Department of Physics, University of Calgary, under the direction of H.R. Krouse. Collagen samples were combusted in a Carlo Erba gas analyser which provides information on the carbon and nitrogen content of the samples andintroduces Nior CO gases into the mass spectrometer for analysis of nitrogen or carbon stable isotopes, respectively. 

V, described elsewhere (4), represents our only example of an excavated ivory with a nitrogen content greater than 1%. The presence of free carbon seems to have protected partially the collagen from the action of groundwater and bacteria. This observation is supported by the gen-... 

The composition of normal human arterial tissues is altered with age in many aspects. Table B6.7 lists the observed changes in human aorta, pulmonary and femoral arteries [20]. There is a tendency that both the dry matter and nitrogen content of arterial tissues decreases with age. However, the relative quantity of collagen [22] and elastin [23, 24] in the arterial wall remains almost unchanged with age. Below the age of 39, the wall of human thoracic aorta has 32.1 5.5% elastin, between the age 40-69, the wall contains 34.4 9.3%, and from 70-89, the elastin content is 36.5 10.1 [24]. 

Quantitation. Various standard protein analytical methods can be nsed for quantitation of collagen. These include determination of the total nitrogen content by Kjeldahl analysis, followed by estimation of the collagen concentration... 

Table 9.4. C N molar ratios (calculated and measured), total C and N content and stable carbon and nitrogen isotope data from bacteria, their growth medium (nutrient broth), and from collagen (infected and non-infected marten bone). The bacteria for inoculation were raised on nutrient broth (nb), with/without additives.

The collagen content is determined by multiplication of the L-hydroxyproline result by a factor of 8 (corresponding to the hydroxyproline content of collagen being equal to 12.5%, where the nitrogen-to-protein factor is 6.25). 

The carbon isotope ratios of marine and freshwater organisms are more variable, depending on local ecological circumstances, and often overlap with those of terrestrial plants and their consumers. These foods typically have much higher nitrogen isotope values, however, and their high protein content will contribute much more carbon to bone collagen than will plants foods which are only 10-20% protein. 

The collagen content of the thoracic aorta was expressed in mg/100 mg of dry, lipid-free aortic tissue. This was done by using the factor of 7.46 to convert the values of hydroxyproline into those of collagen. Elastin is expressed as mg of hydroxyproline liberated by hydroxylysis of this protein by 100 mg of dry, lipid-free aorta. The amount of nitrogen in the collagen extract was determined by the procedure of Houck and Jacob (1958). Histological sections of the aorta and coronary arteries were made and strained by the Oil-Red-0 method (1968). 

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