ASPARTIC-ACID RACEMIZATION AND AMINO-ACID-COMPOSITION OF THE ORGANIC ENDOSKELETON OF THE DEEP-WATER COLONIAL ANEMONE GERARDIA - DETERMINATION OF LONGEVITY FROM KINETIC-EXPERIMENTS

An age of 250 (+/-70) yr is estimated for a specimen of the colonial a nemone Gerardia collected alive from 630 m depth off the Bahamas. This age is calculated from (1) the difference in aspartic acid (Asp) race mization measured in the outermost (youngest) and innermost (oldest) l ayers of the trunk of the organic endoskeleton of the specimen and (2) the estimated rate of Asp racemization, as extrapolated from heating experiments. A progressive increase in D/L Asp values was observed fro m the outermost (0.052) to the innermost (0.099) layer of the trunk. A sp racemization rates determined at 60, 80, and 100 degrees C in the l aboratory were used to determine the Arrhenius parameters, from which the rate at present ambient temperature (12.5 degrees C) was calculate d. The activation energy of Asp racemization was estimated to be 29.1 kcal/mol. The estimated age (250 yr) is much younger than that suggest ed by radiocarbon measurements of the specimen (ca. 1800 yr). The amin o acid composition of the endoskeleton of Gerardia is unusual, with hi stidine comprising 30% of the total. The composition resembles protein s of the endoskeleton of antipatharians (black corals). Copyright (C) 1997 Elsevier Science Ltd.