potassium-bromide and sodium-sulfate

The free solution electrophoretic mobility of two DNA molecules of different molecular masses, 18 base pairs and 2686 base pairs, has been measured in isoelectric histidine buffers with and without added low-molecular-mass electrolytes. Extensive DNA-histidine complex formation is observed in isoelectric histidine buffer, as evidenced by distortion and splitting of the peaks in the electropherograms. Peak distortion and splitting can be decreased or eliminated by adding low-molecular-mass neutral salts to the solution, suggesting that the DNA-histidine complexes are stabilized by electrostatic interactions. The ability of various neutral salts to disrupt the DNA-histidine complexes depends on the molecular mass of the DNA and the concentration and type of added salt.

Topics: Anions; Base Pairing; Bromides; Buffers; Calcium Chloride; Cations, Divalent; DNA; Drug Stability; Electrophoresis, Capillary; Histidine; Magnesium Chloride; Molecular Weight; Osmolar Concentration; Potassium Compounds; Sodium Chloride; Static Electricity; Sulfates

Anhydrous sodium sulfate (Na2SO4) was analyzed at varying concentrations by infrared (ir) spectroscopy. A standard curve was obtained from a linear plot of sulfate (SO2-(4] concentration vs the weight of the ir band area of S = O stretching. Standard chondroitin 4-sulfate, chondroitin 6-sulfate, heparan sulfate, heparin, keratan sulfates, and various dermatan sulfates isolated from human and rat skins were also studied by ir spectroscopy. The spectrum of every glycosaminoglycan (GAG) displayed an ir band around 1230 cm-1 which originated from S = O stretching of sulfate esters. Therefore, the weight of the latter band was employed to quantify sulfate, by using the standard curve indicated above. Sulfate was also estimated quantitatively by the gelatin/BaCl2 method of K.S. Dodgson and R.G. Price (Biochem. J. 1962, 84, 106-110). The sulfate composition determined by ir spectroscopy ranged from 8.5 to 22.1% (w/w), and agreed closely with the values obtained chemically. In the ir spectroscopy method, sulfate was determined using the polymer forms of the GAGs. After analysis, these heteropolysaccharides were recovered unaffected in a yield greater than 95%. The data show that the infrared spectroscopy technique, in addition to being sensitive and reliable, is much more economical than the chemical procedures currently employed to quantify GAG sulfate.

Topics: Bromides; Cost-Benefit Analysis; Glycosaminoglycans; Humans; Potassium; Potassium Compounds; Sensitivity and Specificity; Spectrophotometry, Infrared; Sulfates

alpha-Chymotrypsin (alpha CT) was used as a model protein to study the effects of salt-induced precipitation on protein conformation. Process parameters investigated included the type and amount of salt used to induce precipitation. The salts studied included Na2SO4, NaCl, NaBr, KBr and KSCN. Precipitate secondary structure content was examined via laser Raman spectroscopy. Conventional and saturation transfer electron paramagnetic resonance spectroscopy were employed to probe the tertiary structure of the active site in spin-labelled alpha CT precipitates. As the molal surface tension increment of the inducing salt increased, the beta-sheet content increased and the alpha-helix content decreased. There was no significant variation in secondary structure with the amount of salt used. The fraction of precipitate that recovered activity on redissolution was correlated with the change in secondary structure content. Spin-labelled precipitate spectra indicated that the active site remains unaltered during precipitation. Molecular modelling was employed to investigate how physical property of alpha CT were affected by these types of conformational change. Estimated physical property changes could not account entirely for observed deviations from current equilibrium theory for salt-induced precipitation. The spectroscopic observations were also combined with activity/solubility results to propose a mechanism for the salt-induced precipitation of globular proteins.

Topics: Animals; Bromides; Chemical Precipitation; Chymotrypsin; Crystallography; Electron Spin Resonance Spectroscopy; Models, Molecular; Potassium; Potassium Compounds; Protein Conformation; Salts; Sodium; Sodium Chloride; Sodium Compounds; Spectrum Analysis, Raman; Structure-Activity Relationship; Sulfates; Thiocyanates