The effects of conformational constraints on aspartic acid racemization
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The effects of conformational constraints on aspartic acid racemization. / van Duin, Adri C. T.; Collins, Matthew J.
In: Organic Geochemistry, Vol. 29, No. 5-7, 1998, p. 1227-1232.Research output: Contribution to journal › Conference article › Research › peer-review
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TY - GEN
T1 - The effects of conformational constraints on aspartic acid racemization
AU - van Duin, Adri C. T.
AU - Collins, Matthew J.
PY - 1998
Y1 - 1998
N2 - In short polypeptides, L-aspartic acid (Asp) and L-asparagine (Asn) can undergo isomerization/deamidation reactions via a succinimide (Asu) intermediate resulting in the formation of D-aspartic acid. Some experimental evidence suggests that this reaction, which has been widely used in age determinations, is severely repressed in structured regions of proteins, like for example the triple-helix of collagen, indicating that conformational constraints imposed on the local peptide geometry by the peptide superstructure may inhibit the formation of Asn-containing sequences relative to Asp- or Asn-containing sequences. To examine this, molecular mechanics and molecular dynamics calculations have been performed on constrained and unconstrained Gly-Pro-Asn-Gly-Pro and Gly-Pro-Asu-Gly-Pro pentapeptides. In the constrained calculations, the influence of the protein helix is simulated by fixing the distance between the backbone-nitrogens in the first and last residue at 11.80 Å, a distance similar to that between comparable atoms in the collagen triple-helix. The results from these simulations show that the constraint significantly destabilizes the Asn-containing pentapeptide relative to the Asn-containing sequence; the molecular dynamics simulations, in which the influence of water was specifically taken into account, predict that the constraint raises the energy difference between these two pentapeptides by 8.8 ± 3.8 kcal/mol. This shows that a protein helical structure may severely repress Asp racemization and Asn deamidation. The conservation of such structures should therefore be taken into consideration when using D/L Asp ratios for age determination.
AB - In short polypeptides, L-aspartic acid (Asp) and L-asparagine (Asn) can undergo isomerization/deamidation reactions via a succinimide (Asu) intermediate resulting in the formation of D-aspartic acid. Some experimental evidence suggests that this reaction, which has been widely used in age determinations, is severely repressed in structured regions of proteins, like for example the triple-helix of collagen, indicating that conformational constraints imposed on the local peptide geometry by the peptide superstructure may inhibit the formation of Asn-containing sequences relative to Asp- or Asn-containing sequences. To examine this, molecular mechanics and molecular dynamics calculations have been performed on constrained and unconstrained Gly-Pro-Asn-Gly-Pro and Gly-Pro-Asu-Gly-Pro pentapeptides. In the constrained calculations, the influence of the protein helix is simulated by fixing the distance between the backbone-nitrogens in the first and last residue at 11.80 Å, a distance similar to that between comparable atoms in the collagen triple-helix. The results from these simulations show that the constraint significantly destabilizes the Asn-containing pentapeptide relative to the Asn-containing sequence; the molecular dynamics simulations, in which the influence of water was specifically taken into account, predict that the constraint raises the energy difference between these two pentapeptides by 8.8 ± 3.8 kcal/mol. This shows that a protein helical structure may severely repress Asp racemization and Asn deamidation. The conservation of such structures should therefore be taken into consideration when using D/L Asp ratios for age determination.
KW - Age determination
KW - Collagen
KW - D/L Asp ratio
KW - Molecular dynamics
KW - Molecular mechanics
U2 - 10.1016/S0146-6380(98)00098-9
DO - 10.1016/S0146-6380(98)00098-9
M3 - Conference article
AN - SCOPUS:0032215135
VL - 29
SP - 1227
EP - 1232
JO - Organic Geochemistry
JF - Organic Geochemistry
SN - 0146-6380
IS - 5-7
T2 - 18th International Meeting on Organic Geochemistry
Y2 - 22 September 1997 through 26 September 1997
ER -
ID: 232092735