sodium-bromate and sodium-thiocyanate

In this investigation, salt effects on monomeric solubility and distribution are separated from self-association for caffeine. For self-associating compounds, the Setschenow equation is inadequate because it does not separate salt effects into their different contributions. Solubilities of caffeine, theophylline, and theobromine were determined in water and salt solutions at 25 degrees C. Caffeine, theophylline, and theobromine solubilities decreased with added Na(2)SO(4) or NaCl (i.e., salting-out) and increased with added NaClO(4) or NaSCN (i.e., salting-in). Caffeine distribution coefficients (D(W/O)) also decreased with added Na(2)SO(4) or NaCl and increased with added NaClO(4) or NaSCN. To separate salt-caffeine effects from salt effects on caffeine self-interaction, salting parameters (k(s)) were calculated from D(W/O) at infinite dilution instead of solubilities with the Setschenow equation. Caffeine k(s) values were smaller than the Setschenow constants (K) indicating that, for caffeine, K is not simply a salting-in/out parameter. Distribution data were used to characterize caffeine self-association using either a dimerization model (k(d), dimerization constant) or an isodesmic model (k(iso), stepwise association constant). Caffeine self-association constants (k(d) or k(iso)) decreased with NaClO(4) or NaSCN and increased with Na(2)SO(4) or NaCl.

Topics: Bromates; Caffeine; Chlorates; Phosphodiesterase Inhibitors; Salts; Sodium Chloride; Sodium Compounds; Solubility; Solutions; Sulfates; Thiocyanates

The dissociation of two peripheral spinach (Spinacia oleracea L.) thylakoid membrane proteins, coupling factor CF1 and ferredoxin-NADP+-oxidoreductase, in the presence of chaotropic sodium salts has been investigated, using monospecific antibodies against the proteins as probes. Release of both proteins followed the Hofmeister series of anions (Cl- < NO3- < Br- < I- < SCN-). In mixtures, the different salts had an additive effect. In addition, there were also qualitative differences in the action of the anions, such that NaI and NaSCN led to a different concentration and time dependence of the dissociation of the peripheral proteins from thylakoids. An analysis of the temperature dependence of protein release showed that the more chaotropic ions reduced the activation energy required for the dissociation of the proteins from their binding sites on the membrane. The addition of sugars (glucose, sucrose, or trehalose) reduced the amount of protein released from the membranes in the presence of NaI or NaSCN.

Topics: Binding Sites; Bromates; Chloroplasts; Intracellular Membranes; Membrane Proteins; Nitrates; Plant Proteins; Sodium Chloride; Sodium Compounds; Sodium Iodide; Solubility; Spinacia oleracea; Thiocyanates