Enzymatic degradation of poly(epsilon-caprolactone) film in phosphate buffer solution containing lipases

The enzymatic degradation of poly(epsilon-caprolactone) (PCL) films in phosphate buffer solution containing lipases has been studied by DSC, WAXD and SEM. Three lipases, pseudomonas lipase (PS), porcine pancreatic lipase (PP), and candida cylindracea lipase (AY), were used. The results showed that the degradation of PCL films in phosphate buffer solution containing PP or AY was very slow: no weight loss could be found within 1 week. However, PCL film could degrade rapidly and completely within 4 days in phosphate buffer solution containing PS lipase. (C) 1997 Elsevier Science Limited.

Study of the miscibility and thermodynamics of cellulose diacetate-poly(vinyl pyrrolidone) blends

The miscibility of blends of cellulose diacetate (CDA) and poly(vinyl pyrrolidone) (PVP) was extensively studied by means of differential thermal analysis and dynamic mechanical thermal analysis, tensile test, measuring viscosity of diluted and concentrated solutions of blends in acetone-ethanol mixture and morphological observations. A single glass transition temperature is observed, which is intermediate between the glass transition temperatures associated with each component and depends on composition. A synergism in mechanical properties of blends was found. The absolute viscosity and the intrinsic viscosity of solutions of blends are much higher than the weight average values of solutions of CDA and PVP. Optically clear and thermodynamically stable films were formed in the composition range of CDA/PVP = 100/0 to 50/50w/w. Fourier transform infrared was used to investigate the nature of CDA-PVP interaction. Hydrogen bonds were formed between hydroxyl groups of CDA and carbonyl groups of PVP. Heats of solutions of CDA/PVP blends and their mechanical mixtures were measured by using a calorimeter. Mixing enthalpy obtained with Hess's law approach was used to quantify interaction parameters of this blending system. It was found that mixing enthalpies and interaction parameters were negative and composition dependent. (C) 1997 Elsevier Science Ltd.

Lanthanide metal complexes for the hydrolysis of ribonucleoside 3',5'-cyclic phosphate and deoxyribonucleoside 3',5'-cyclic phosphate

Ytterbium(III) and praseodymium(III) complexes of 2-carboxyethylgermanium sesquioxide (Ge-132) can hydrolyze the phosphodiester linkage of 3',5'-cyclic adenosine monophosphate (cAMP) and 3',5'-cyclic deoxyadenosine monophosphate (dcAMP). Both cAMP and dcAMP are hydrolyzed with high selectivity, yielding predominantly 3'-monophosphates. The selectivity and activity for hydrolyzing cAMP and dcAMP by lanthanide metal(III) complexes and lanthanide metal ions are compared.

Efficient cleavage of ribonucleoside 3',5'-cyclic phosphates and deoxyribonucleoside 3',5'-cyclic phosphate by lanthanides

The cleavage of 3',5'-cAMP, 3',5'-cGMP and 3',5'-dcAMP by lanthanides has been investigated by HPLC and H-1 NMR. Rapid cleavage of cAMP, cGMP and dcAMP by Ce(III) under air at pH 8 and 37 degrees C has been observed. Regioselective cleavage of P-O(5') bond in cAMP, cGMP and dc;aMP tu give the corresponding 3'-AMP, 3'-GMP and 3'-dAMP by lanthanide chlorides has been achieved, and 3'-AMP and 3'-GMP are cleaved to adenosine(A) and guanosine(CT) more slowly, respectively, The notable difference in reactivity between Ce(III) and the other lanthanide ions under air has also been studied. The cleavage is enhanced with the increase in the molar fraction of Ce(IV). The fast cleavage of cAMP by Ce(III) under air at pH 8 is ascribed to the resultant Ce(IV) in the reaction mixture.

A new phosphate, KMgY(PO4)(2), isostructural with xenotime

A new phosphate, KMgY(PO4)(2), isostructural with xenotime, was firstly reported in detail. It crystallizes in tetragonal system with space group I4(1)/amd (No. 141). The cell parameters were obtained from X-ray powder diffraction data with a=0.6886, c=0.6025 nm, 2=2. The proposed structure of KMgY(PO4)(2) was further confirmed by its vibrational spectra, IR and Raman spectra, which were also compared with those of iso-structural YPO4.

OPTICAL AND STRUCTURAL INVESTIGATION OF KMGLA(PO4)(2) PHOSPHATE DOPED WITH EUROPIUM

A new compound KMgLa(PO4)(2), isotypic with monoclinic LaPO4, is reported. Its cell parameters have been determined from X-ray powder diffraction data. Crystallization occurs in the monoclinic space group P2(1)/n (No. 14) with a = 6.839(3) Angstrom, b = 7.066(1) Angstrom, c = 6.523(3) Angstrom, beta = 103.42(4)degrees, and Z = 2. It was found that the KMgLa(PO4)(2) phase was isostructural with monoclinic LaPO4. The difference between them was that half of the La atoms in LaPO4 were couplingly substituted with the same amount of Mg and K atoms. This isomorphous substitution was confirmed by IR and Eu3+-doped excitation and emission spectra and by elemental analysis of single crystals. The spectroscopic data were compared with those of LaPO4:Eu3+. (C) 1995 Academic Press, Inc.

Cloning and Comparative Studies of Seaweed Trehalose-6-Phosphate Synthase Genes

The full-length cDNA sequence (3219 base pairs) of the trehalose-6-phosphate synthase gene of Porphyra yezoensis (PyTPS) was isolated by RACE-PCR and deposited in GenBank (NCBI) with the accession number AY729671. PyTPS encodes a protein of 908 amino acids before a stop codon, and has a calculated molecular mass of 101,591 Daltons. The PyTPS protein consists of a TPS domain in the N-terminus and a putative TPP domain at the C-terminus. Homology alignment for PyTPS and the TPS proteins from bacteria, yeast and higher plants indicated that the most closely related sequences to PyTPS were those from higher plants (OsTPS and AtTPS5), whereas the most distant sequence to PyTPS was from bacteria (EcOtsAB). Based on the identified sequence of the PyTPS gene, PCR primers were designed and used to amplify the TPS genes from nine other seaweed species. Sequences of the nine obtained TPS genes were deposited in GenBank (NCBI). All 10 TPS genes encoded peptides of 908 amino acids and the sequences were highly conserved both in nucleotide composition (>94%) and in amino acid composition (>96%). Unlike the TPS genes from some other plants, there was no intron in any of the 10 isolated seaweed TPS genes.