Isomerization and Racemization of Menthols

Racemization and isomerization of type I collagen C-telopeptides in human bone and soft tissues: assessment of tissue turnover.

Urinary excretion of the type I collagen C-telopeptide (CTx) has been shown to be a sensitive index of the rate of bone resorption. The human type I collagen sequence A(1209)HDGGR(1214) of CTx can undergo racemization of the aspartic acid residue Asp(1211) and isomerization of the bond between this residue and Gly(1212). These spontaneous non-enzymic chemical reactions takes place in vivo in bo...

Deamidation, isomerization, and racemization at asparaginyl and aspartyl residues in peptides. Succinimide-linked reactions that contribute to protein degradation.

Aspartyl and asparaginyl deamidation, isomerization, and racemization reactions have been studied in synthetic peptides to model these spontaneous processes that alter protein structure and function. We show here that the peptide L-Val-L-Tyr-L-Pro-L-Asn-Gly-L-Ala undergoes a rapid deamidation reaction with a half-life of only 1.4 days at 37 degrees C, pH 7.4, to give an aspartyl succinimide pro...

Racemization and epimerization.

In recent reports (I ) the term racemization is used inappropriately. It is stated in both reports that Lisoleucine racemizes to D-alloisoleucine. This reaction is epimerization, not racemization. Racemization of L-iSOleucine results in the formation of DLisoleucine. As stated in Eliel (2): "'racemization is the process of producing a racemic modification starting with one of the pure enantiome...

Amino Acid Racemization

Racemization of Meteoritic Amino Acids

Meteorites may have contributed amino acids to the prebiotic Earth, affecting the global ratio of right-handed to left-handed (D/ L) molecules. We calculate D/ L ratios for seven biological, α-hydrogen, protein amino acids over a variety of plausible parent body thermal histories, based on meteorite evidence and asteroid modeling. We show that amino acids in meteorites do not necessarily underg...