The role of water in determining structure and function of macromolecules and macromolecular assemblies /

The interaction of biological molecules with water is an important determinant of structural properties both in molecular assemblies, and in conformation of individual macromolecules. By observing the effects of manipulating the activity of water (which can be accomplished by limiting its concentration or by adding additional solutes, "osmotic stress"), one can learn something about intrinsic physical properties of biological molecules as well as measure an energetic contribution of closely associated water molecules to overall equilibria in biological reactions. Here two such studies are reported. The first of these examines several species of lysolipid which, while present in relatively low concentrations in biomembranes, have been shown to affect many cellular processes involving membrane-protein or membrane-membrane interactions. Monolayer elastic constants were determined by combining X-ray diffraction and the osmotic stress technique. Spontaneous radii of curvature of lysophosphatidylcholines were determined to be positive and in the range +30A to +70A, while lysophosphatidylethanolamines proved to be essentially flat. Neither lysolipid significantly affected the bending modulus of the monolayer in which it was incorporated. The second study examines the role of water in theprocess of polymerization of actin into filaments. Water activity was manipulated by adding osmolytes and the effect on the equilibrium dissociation constant (measured as the criticalmonomer concentration) was determined. As water activity was decreased, the critical concentration was reduced for Ca-actin but not for Mg-actin, suggesting that 10-12 fewer water molecules are associated with Ca-actin in the polymerized state. Thisunexpectedly small amount of water is discussed in the context of the common structural motif of a nucleotide binding cleft.

Second Welland Canal - Book 3, Survey Map 3 - Vanalstines Creek and Back Water in Thorold

Survey map of the Second Welland Canal created by the Welland Canal Company showing the canal in Thorold Township near Port Robinson. Identified structures associated with the Canal include towing path. The surveyors' measurements and notes can be seen in red and black ink and pencil. Local area landmarks are also identified and include roads (ex. Road to Font Hill), bridges, Back Water, and Vanalstines Creek. Properties and property owners of note are: Lots 203, 204, and 205, John Coulter, and Samuel Hill.

Second Welland Canal - Book 3, Survey Map 4 - Back Water in Thorold

Survey map of the Second Welland Canal created by the Welland Canal Company showing the Back Water from the canal in Thorold Township near Port Robinson. The surveyors' measurements and notes can be seen in red and black ink and pencil. Local area landmarks are also identified and include the Back Water from the canal. Properties and property owners of note are: Lots 205 and 206, and McAlpine.