sodium-chlorate and sodium-sulfate

A new stepwise self-assembly procedure is described for the preparation of functional cyclodextrin-modified electrodes. The approach is based on the formation of alkanethiol/lipoylamide-beta-cyclodextrin monolayers with the thiol component responsible for blocking of the electrode surface and lipoylamide-beta-cyclodextrin molecules-for controlled opening of the access of the electroactive probe to the electrode. Functionalization of the electrode is achieved by means of a new cyclodextrin derivative-mono(6-deoxy-6-lipoylamide)-per-2,3,6-O-acetyl-beta-cyclodextrin-prepared in the peracetyl form and deacetylated directly on the electrode surface following the cyclodextrin self-assembly. The progress of deacetylation was monitored by the MALDI MS technique. Deacetylation caused opening of the active sites toward solution probes. The response toward ferrocene was found to be highly improved when ferrocene was added to the solution following self-assembly of cyclodextrin but prior to the thiol self-assembly step (imprinting method). The proposed synthesis and sequential monolayer formation scheme lead to well-organized and stable modified electrode surfaces with improved sensitivity toward solution species compared to other procedures of electrode modification with the cyclodextrin derivatives.

Topics: Algorithms; Amides; beta-Cyclodextrins; Biosensing Techniques; Chlorates; Cyclodextrins; Electrochemistry; Electrodes; Ferrous Compounds; Gold; Metallocenes; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Sulfates; Sulfhydryl Compounds; Thermodynamics; Thioctic Acid

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 biological significance of protein sulfation is poorly understood. To study a possible role of protein sulfation in the regulated secretory pathway, neurointermediate lobes (NIL) of the pituitary of South-African clawed toads (Xenopus laevis) were treated with chlorate, a potent in vivo inhibitor of protein sulfation. We monitored the fates of newly synthesized proopiomelanocortin (POMC), prohormone convertase (PC2), and secretogranin III (SgIII), which are sulfated and regulated secretory proteins. Inhibition of protein sulfation had no effect on the proteolytic processing of these precursor proteins and the kinetics of release of their cleavage products. The release was sensitive to apomorphine, a drug that blocks the release of proteins via the regulated secretory pathway, indicating that no missorting to the constitutive pathway had occurred. Our results suggest that protein sulfation is not required for the intracellular transport, sorting, and proteolytic processing of regulated secretory proteins.

Topics: Animals; Apomorphine; Biological Transport; Chlorates; Chromogranins; Dopamine Agonists; Furin; Methionine; Organ Culture Techniques; Pituitary Gland; Pro-Opiomelanocortin; Protein Processing, Post-Translational; Proteins; Subtilisins; Sulfates; Xenopus laevis