Chemical composition of human bone

The mineral and non-collagenous organic components of normal human femoral cortex were examined following powdering, demineralization with EDTA and digestion with bacterial collagenase. The protein, hexose, sialic acid and uronic acid contents of the matrix were determined. Neonatal bone had lower levels of mineral and calcium and higher levels of organic material and sialic acid than adult bone, suggesting increased glycoprotein content in neonatal bone. The soluble non-collagenous matrix of human femoral cortex was examined by gel filtration on Sephadex G100 and by ion-exchange chromatography on DEAE-cellulose. Four fractions were eluted off Sephadex-G100: a large molecular weight fraction, a shoulder on the descending portion of this, both of which contained sialic acid and two smaller molecular weight fractions. The material eluted off DEAE-cellulose was separated into 6 fractions which were similar to those found for beef and rabbit bone matrix. Human bone matrix appeared more resistant to collagenase digestion than beef bone, soluble collagen eluted later off DEAE-cellulose than beef bone; sialic acid gave 3 peaks: a major and two lesser ones. The sialic acid-containing material in the fifth fraction was probably bound to proteoglycan. Rabbit bone has 2 to 3 sialic acid peaks whereas beef bone has one, indicating species differences in cortical bone matrix.