ABSTRACT
Centrifugation is a primary means for characterizing the size of proteins, ribonucleic acid, polymers, and subcellular components, as well as for separating particles of different sizes. Ion-exchange chromatography is commonly used when a sample is relatively pure, consisting of several soluble components, all of which may be of interest. Competition for binding sites constantly occurs when a variety of amino acids are potential ligands for a binding site on a transfer RNA. Compartments such as mitochondria are large and enclose many different molecular machines. Other intracellular compartments are smaller, such as the membrane-enclosed transport vesicles that shuttle proteins and hydrophobic molecules inside the cell. Protein components of the ribosomal fragments of thermos thermophilus are shown in a ribbon display, RNA in ball and stick. Oligosaccharides are commonly found attached to proteins following protein synthesis or to lipids in membranes. Micelles are normally formed by single-tailed lipids and consist of a single layer of the polar-nonpolar molecule.
