The Stability of Natural History Specimens In Fluid-preserved Collections

Natural history museum collections are incomparable storehouses of geological, biological, and genetic resources throughout the world. Some of the materials composing the specimens in these collections are vulnerable to deterioration when stored in fluids. Samples were taken from liquid storage media surrounding mammal specimens in the National Museum of Natural History (NMNH), Smithsonian Institution and analyzed for amino acids, lipids, and fatty acids using gas chromatography-mass spectrometry and high- performance ion-exchange chromatography. The results show the presence of the C12, C14, C16, C18, C20, C22, and C24 fatty acids in the fluids. The percent of each fatty acid in the mixture is typical for the lipids found in the sampled specimens. Amino acid profiles indicated that peptides and amino acids also were being leached into the storage fluids. These profiles indicated a general protein loss, but the high glycine and alanine content (about 30%) also indicates some structural protein loss. In addition, heating experiments using the proteins collagen and keratin in different preservative fluids show that 70 % ethanol is a better preservative than 50 % iso-propanol, and that, in general, hair (keratin) is more stable than skin (collagen). These projects form the baseline for an understanding of the deterioration process of proteinaceous materials in storage fluids and provide information from which new preservation policies can be developed. Reconsideration of present methods is especially important because of developments that allow examination of specimens at the molecular level. Fluids that preserve morphology may not adequately preserve sources of chemical information, such as DNA