[State of the protein fraction of human bone tissue following space flight]

Amino acid composition and bone mineralization were studied qualitatively and quantitatively on autopsy of the three crewmembers after their 28-day space flight aboard the orbital station Salyut-1. Sixteen amino acids were detected in the bone protein fraction: cystine and cysteine, lysine, histidine, arginine, aspartic acid, serine, glycine, glutamic acid, threonine, alanine, proline, valine, phenylalanine, leucine and isoleucine, oxyproline. Postflight no abnormalities in the amino acid compositions or the bone organic content were found. The role of protein matrices of calcified tissues in mechanisms of bone resistance and adaptation to space flight effects is discussed.