The Molecular Architecture of the Extracellular Hemoglobin of Ophelia bicornis: Analysis of Individual Molecules

Abstract

The dimensions and shape of extracellular hemoglobin molecules of the marine worm, Ophelia bicornis, were determined by electron microscopy using negative staining and embedding in aurothioglucose. The typical averaged double-layered hexagon has a diameter of 26.5 nm and a height of 18 nm. The three-dimensional reconstruction of the negatively stained samples, using random conical tilting, showed about 60% of the original height of the molecule due to flattening and incomplete embedding in stain. In contrast to this, the specimen embedded in aurothioglucose showed no flattening. The three-dimensional reconstructions agree with the structure found in a previous study on 2-D crystalline arrays. In particular, the main subunit shows more than three mass centers