Variations in the phosphorus content of estuarine waters of the Chesapeake Bay near Solomons Island, Maryland

Studies by Cowles and Brambel (1938), Newcombe and Lang (1939), and Newcombe, Horne and Shepherd (1939) have provided information on the quantitative methods for estimating inorganic phosphorus and, also, on the vertical and horizontal distribution of this nutrient substance in the waters of the Chesapeake Bay...

Observations on the alkalinity of estuarine waters of the Chesapeake Bay near Solomons Island, Maryland

Kolthoff (1926) without particular reference to sea water has defined buffer capacity (alkalinity, in the case of added strong base) of a solution quantitatively as the number of equivalents of added strong base or strong acid required to change the pH of one liter of solution one unit. Buch, in 1930, redefined this concept with reference to sea water as the number of moles of carbonic acid which must be added to one liter of the water in order to change its pH by one unit

Orientation of the Calcium Channel β Relative to the α12.2 Subunit Is Critical for Its Regulation of Channel Activity

BACKGROUND: The Ca(v)beta subunits of high voltage-activated Ca(2+) channels control the trafficking and biophysical properties of the alpha(1) subunit. The Ca(v)beta-alpha(1) interaction site has been mapped by crystallographic studies. Nevertheless, how this interaction leads to channel regulation has not been determined. One hypothesis is that betas regulate channel gating by modulating movements of IS6. A key requirement for this direct-coupling model is that the linker connecting IS6 to the alpha-interaction domain (AID) be a rigid structure. METHODOLOGY/PRINCIPAL FINDINGS: The present study tests this hypothesis by altering the flexibility and orientation of this region in alpha(1)2.2, then testing for Ca(v)beta regulation using whole cell patch clamp electrophysiology. Flexibility was induced by replacement of the middle six amino acids of the IS6-AID linker with glycine (PG6). This mutation abolished beta2a and beta3 subunits ability to shift the voltage dependence of activation and inactivation, and the ability of beta2a to produce non-inactivating currents. Orientation of Ca(v)beta with respect to alpha(1)2.2 was altered by deletion of 1, 2, or 3 amino acids from the IS6-AID linker (Bdel1, Bdel2, Bdel3, respectively). Again, the ability of Ca(v)beta subunits to regulate these biophysical properties were totally abolished in the Bdel1 and Bdel3 mutants. Functional regulation by Ca(v)beta subunits was rescued in the Bdel2 mutant, indicating that this part of the linker forms beta-sheet. The orientation of beta with respect to alpha was confirmed by the bimolecular fluorescence complementation assay. CONCLUSIONS/SIGNIFICANCE: These results show that the orientation of the Ca(v)beta subunit relative to the alpha(1)2.2 subunit is critical, and suggests additional points of contact between these subunits are required for Ca(v)beta to regulate channel activity