Aqueous Sodium Phosphate Buffer Research Articles

The preparation of the four monophosphates of α,α′-trehalose from trehalose and sodium phosphate

α,α′-Trehalose, when dried to a moisture content of ca. 5% from aqueous sodium phosphate buffer (with an initial pH ≤ 5.5), produces, after warming, a mixture containing the four isomeric monophosphate esters which can be isolated by anion-exchange chromatography. Their structures were deduced from their hydrolysis products (trehalose and inorganic orthophosphate) after treatment with alkaline phosphomonoesterase, and by 1H and 13C NMR spectroscopy which, in the case of the 6-isomer, gave spectra identical with those of authentic material. Under similar conditions, other saccharides, including glucose, sucrose, amylose, cyclodextrins, alditols and cyclitols (e.g., glycerol, mannitol, and inositol), also produce (as shown by chromatographic and enzymic analyses and, in some instances, from spectroscopic analysis of isolated products) their corresponding phosphate esters. The presence of higher phosphorylated species is indicated in chromatograms of the mixtures, especially when metaphosphate is used as the phosphorylating agent. The methodology described provides a simple and direct route to such phosphate esters.

Confirmation of the structure of nisin by complete 1H n.m.r. resonance assignment in aqueous and dimethyl sulphoxide solution

The chemical structure of the peptide antibiotic nisin has been confirmed by the unambiguous sequence-specific assignment of its 1H n.m.r. spectrum using a range of 2-D n.m.r. techniques. Nisin was examined in both aqueous (sodium phosphate buffer, pH 2.25) and dimethyl sulphoxide–trifluoroacetic acid solution. Amino acid spin systems were identified from observation of relayed connectivity patterns in the HOHAHA spectrum. Sequential assignments were accomplished with the aid of NOESY and relayed-NOESY spectra. In addition, the locations of the five thioether ring systems were confirmed. The detailed n.m.r. analysis provides strong evidence for the structure originally proposed on the basis of chemical degradation studies.

Optimization of the direct chiral separation of potential cytotoxic α-methylene-γ-butyrolactones and α-methylene-γ-butyrolactams by liquid chromatography

The direct enantiomeric resolution of a series of racemic α-methylene-γ-butyrolactones and α-methylene-γ-butyrolactams was carried out on various commercially available chiral stationary phases (CSPs). Particular interest was paid to compounds which exhibit physiological activity as cytotoxic agents. On a Pirkle-type column packed with ( R)-N-(3,5-dinitrobenzoyl)phenylglycine (DNBPG) covalently bonded to γ-aminopropylsilanized silica gel, only α-methylene-γ-lactams containing two aromatic groups were resolved; a chiral recognition mechanism is proposed. (+)-Poly-(triphenylmethyl methacrylate) (PTrMA) coated on silica gel [Chiralpak OT(+)] with methanol as eluent afforded fairly good selectivities (up to 1.8) especially for α-methylene γ-lactones. Temperature had a great influence on the resolution. Cellulose tribenzoate and triphenylcarbamate (Chiralcel OB and OC, respectively) coated on macroporous silica gel displayed selectivities from 1.1 to 1.3, but, because of the very poor efficiency of these CSPs, no baseline resolution was achieved. Investigations on two protein CSPs are reported, α 1-acid glycoprotein ( α 1-AGP) and bovine serum albumin (BSA) immobilized on microparticulate silica gel (Enantiopac and Resolvosil-BSA, respectively). The separations were performed using an aqueous sodium phosphate buffer as eluent and 2-propanol as organic modifier to regulate retention and selectivity. Both CSPs exhibited a good chiral recognition ability, especially towards cytotoxic solutes with resolution factors between 1 and 2.

Antiinflammatory polymer‐bound steroids for topical applications II. Controlled release of the steroids

AbstractThe release of hydrocortisone and dexamethasone due to hydrolysis of the carbonate linkage from the polymeric supports of poly(oxyethyleneglycol), hydroxypropyl cellulose, and N‐vinylpyrrolidone/hydrocortisone–21CH2–vinylcarbonate copolymer was observed in a living system, by induction of αGPDH activity in rat C6 glial cells, and in vitro by a kinetic study of release in aqueous sodium phosphate buffer medium. The glucocorticoid release is pH and temperature dependent and highly sensitive to steric hindrance. In vivo testing on antiinflammatory activity in rats with poly(oxyethyleneglycol) and hydroxypropyl cellulose bound dexamethasone was performed. However, it produced negative results probably due to difficulty in splitting the carbonate linkage in the inflammatory region of acidic pH values.

Circular dichroism of a membrane protein of Neurospora crassa

Membrane protein of a mutant of Neurospora crassa has been isolated in aqueous sodium phosphate buffer without employing a chemical agent such as urea, detergent, or organic solvent. The protein moved in a single band on sodium dodecyl sulfate gel electrophoresis and as well on non-SDS gel electrophoresis. The circular dichroism spectrum of the protein exhibited the characteristic low ellipticity but no red shift.