Ferrous Promotion of Cross-Linking in Erythrocyte Membranes as it Pertains to Soft-Tissue Preservation

Abstract

Fossils provide important morphological and occasionally molecular evidence about ancient organisms (Schweitzer et al., 1997). Fossilization entails the mineral replacement of endogenous organic structures during which morphological and especially molecular components such as proteins are affected by physical, chemical, and environmental factors (Schweitzer et al., 1997 & 2006; Flannery et al., 1999;Rollo et al., 2002). This multivariate process determines the state of preservation fossil remains are found, which is highly variable (Schweitzer et al., 1997; Allison, 1988). The expectations for the preservation of endogenous biomolecules are extremely low: 100,000 years is the predicted survival limit until complete protein hydrolysis (Bada et al., 1999). However, excellently preserved tissue and cellular components from a 65+ million year old Tyrannosaurus rex was recovered, and conclusively identified collagen amino acid sequences from the de-mineralized tissue (Asara et al., 2007). These unique findings has forced a re-evaluation of the preservation limitations of the fossilization process (Schweitzer et al., 2007). One mechanism proposed by Schweitzer et al. (2007) attempts to explain the preservation of soft tissue microstructures such as red blood cells and molecular constituents through free radical production initiated by oxidation of iron from hemoglobin breakdown. Free radicals are highly reactive and unstable molecules with an unpaired electron which can cause cross-linking of cell constituents such as proteins and lipids (Halliwell and Gutteridge, 1984; Magder, 2006). In order to elucidate this mechanism and its ability to improve cell preservation, I propose that raising the concentrations of Fe (II) may cause increased cross-linking in cell membranes. Research design entails testing for increases in cross-linking through electrophoretic techniques of modern hemoglobin-free (ghost) erythrocytes after exposure to increasing concentrations of free iron. Increases in cross-linking of cell membrane would position iron as a participant in cell preservation. A decrease to no changes in cross-linking would imply that iron alone may not be part of the mechanism. Further studies should be conducted using free hemoglobin in addition to synergistic effects of hemoglobin and iron.