Human pulmonary surfactant, which is critical for normal lung function, contains several proteins, SPA, SPB, SPC, and SPC. SPB has been determined to be the most critical of the four in allowing surfactant to lower surface tension of the alveoli. It is thought that SPB facilitates lipid trafficking at the air-water interface of the alveoli, which allows for respiration, i.e. expansion and contraction, to occur normally. Both termini of SPB have been shown to maintain some of the function of the wild type peptide. In my research, I use the first 25 residues of SPB, called SPB-N(1-25), or SPB-N. Membrane proteins are especially difficult to express and purify, so part of my research is involved in optimizing protocols related to the expression and purification of SPB-N, to obtain pure samples in high yield. After, in an extension of our desire to fully characterize this peptide, we will use a biophysical technique called power saturation EPR to explore SPB-N's membrane dynamics, and the depth at which it partitions in the membrane. EPR is a technique which requires an unpaired electron, because of its special quantum property of an unpaired spin. Because of this need, I will use a technique called Site Directed Spin Labeling to put a nitroxide spin label, which contains an unpaired electron, on each of the 25 amino acids in SPB-N. This will allow full characterization of the peptide in a lipid environment using power saturation EPR. This is all done to understand SPB in its native environment better, in an effort to design better structural and functional analogues of the peptide to treat patients afflicted with Respiratory Distress Syndrome, which is characterized by a lack of normal pulmonary surfactant function.