This thesis describes the structural examination of three proteins employing transmission electron microscopy and molecular modelling. The first protein examined was myelin basic protein (MBP). Based on available physical data, it was possible to define a unique atomic conformation. The second protein studied was upstream binding factor (UBF). Recombinant rat UBF was imaged using transmission electron microscopy and single particle image analysis. A molecular model of the DNA binding domain of UBF was also produced. The image averages displayed characteristic nodes that fit well with the nodes predicted by the molecular model. The last protein studied was surfactant protein A (SP-A), whose function is strongly dependent on the presence of calcium. Direct measurements of SP-A dimensions in the presence of varying concentrations of cations such as calcium. It was demonstrated that the SP-A complexes existed in two conformations: compact and rarefacted, and changed from one to the other at a transition concentration close to physiological.