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Buffer Medium (buffer + medium)
Selected AbstractsDetecting active methanogenic populations on rice roots using stable isotope probingENVIRONMENTAL MICROBIOLOGY, Issue 3 2005Yahai Lu Summary Methane is formed on rice roots mainly by CO2 reduction. The present study aimed to identify the active methanogenic populations responsible for this process. Soil-free rice roots were incubated anaerobically under an atmosphere of H2/13CO2 or N2/13CO2 with phosphate or carbonate (marble) as buffer medium. Nucleic acids were extracted and fractionated by caesium trifluoroacetate equilibrium density gradient centrifugation after 16-day incubation. Community analyses were performed for gradient fractions using terminal restriction fragment polymorphism analysis (T-RFLP) and sequencing of the 16S rRNA genes. In addition, rRNA was extracted and analysed at different time points to trace the community change during the 16-day incubation. The Methanosarcinaceae and the yet-uncultured archaeal lineage Rice Cluster-I (RC-I) were predominant in the root incubations when carbonate buffer and N2 headspace were used. The analysis of [13C]DNA showed that the relative 16S rRNA gene abundance of RC-I increased whereas that of the Methanosarcinaceae decreased with increasing DNA buoyant density, indicating that members of RC-I were more active than the Methanosarcinaceae. However, an unexpected finding was that RC-I was suppressed in the presence of high H2 concentrations (80%, v/v), which during the early incubation period caused a lower CH4 production compared with that with N2 in the headspace. Eventually, however, CH4 production increased, probably because of the activity of Methanosarcinaceae, which became prevalent. Phosphate buffer appeared to inhibit the activity of the Methanosarcinaceae, resulting in lower CH4 production as compared with carbonate buffer. Under these conditions, Methanobacteriaceae were the prevalent methanogens. Our study suggests that the active methanogenic populations on rice roots change in correspondence to the presence of H2 (80%, v/v) and the type of buffer used in the system. [source] Mechanism of oxidation of alanine by chloroaurate(III) complexes in acid medium: Kinetics of the rate processesINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 7 2009Pratik K. Sen The kinetics of the oxidation of alanine by chloroaurate(III) complexes in acetate buffer medium has been investigated. The major oxidation product of alanine has been identified as acetaldehyde by 1H NMR spectroscopy. Under the experimental conditions, AuCl and AuCl3(OH), are the effective oxidizing species of gold(III). The reaction is first order with respect to Au(III) as well as alanine. The effects of H+ and Cl, on the second-order rate constant k2, have been analyzed, and accordingly the rate law has been deduced: k2, = (k1[H+][Cl,] + k3K4K5)/(K4K5 + [H+][Cl,]). Increasing dielectric constant of the medium has an accelerating effect on the reaction rate. Activation parameters associated with the overall reaction have been calculated. A mechanism involving the two effective oxidizing species of gold(III) and zwitterionic species of alanine, consistent with the rate law, has been proposed. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 473,482, 2009 [source] Influence of hydroxyvalerate composition of polyhydroxy butyrate valerate (PHBV) copolymer on bone cell viability and in vitro degradationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Hui Liu Abstract The objective of this study was to elucidate the role of hydroxyvalerate (HV) composition in polyhydroxy butyrate valerate (PHBV) copolymer film on the degradation of copolymer and osteoblastic cell activity. Degradation was studied by monitoring time-dependent changes in mass and chemical composition of the macroporous films. The mass loss of PHBV film upon 19 weeks of exposure to pH 7.4 phosphate buffer medium was found to range from 2.8% to 9.2% with a strong dependence on the original composition of the copolyester film and morphology. Tapping mode atomic force microscopy (TMAFM) was used to examine the roughness change of polyester films due to exposure to buffer medium. Chemical analysis of the degraded film was carried out using NMR to aid in the interpretation of the mass loss and TMAFM data. The NMR results showed a significant decrease in the mol % of HV content in the degraded PHBV film. Additionally, we established that UMR-106 cell proliferation on macroporous PHBV matrix is minimally enhanced by the HV content of PHBV copolymer. Information provided by this study can be used in the selection of appropriate PHBV copolymer for clinical use where the biopolymer needs to remain physically intact and chemically unchanged during the intended period of biomedical application. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Controlled application and removal of liposomal therapeutics: Effective elimination of pegylated liposomal doxorubicin by double-filtration plasmapheresis in vitroJOURNAL OF CLINICAL APHERESIS, Issue 2 2010Gerhard Pütz Abstract Introduction: Nanoscale particle-based drug delivery systems like long circulating liposomal doxorubicin show unique pharmacokinetic properties and improved toxicity profiles. Liposomal doxorubicin accumulates in tumor tissue due to the enhanced permeation and retention effect, but only a small fraction of a total dose reaches the tumor site. Accumulation of liposomal doxorubicin is much faster in tumor sites than in certain organs where dose limiting adverse effects occur. Finding a way to detoxify the predominant part of a given dose, circulating in the blood after accumulation is completed, will presumably reduce severe side effects during chemotherapy. Methods: Elimination properties of therapeutic used pegylated liposomal doxorubicin (Doxil®/Caelyx®) and therapeutic used double-filtration plasmapheresis systems were evaluated in vitro and in reconstituted human blood. Results: Liposomes can be filtered by appropriate membranes without leakage of doxorubicin up to a pressure of 1 bar. At higher pressures, liposomes (,85 nm) may squeeze through much smaller pores without significant leakage of doxorubicin, whereas decreasing pore size to ,8 nm leads to increased leakage of doxorubicin. With therapeutic used apheresis systems, liposomal doxorubicin can be efficiently eliminated out of buffer medium and reconstituted human blood. No leakage of doxorubicin was detected, even when liposomes were circulating for 48 h in human plasma before apheresis. Conclusions: Convenient apheresis techniques are capable of a safe and efficient elimination of therapeutic used liposomal doxorubicin in an experimental model system. J. Clin. Apheresis, 2010. © 2010 Wiley-Liss, Inc. [source] Solvent-mediated solid phase transformations of carbamazepine: Effects of simulated intestinal fluid and fasted state simulated intestinal fluidJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 3 2009Paula Lehto Abstract Solvent-mediated transformations of carbamazepine (CBZ) anhydrate form III were investigated in Simulated Intestinal Fluid, a simple USP buffer medium, and in FaSSIF, which contains sodium taurocholate (STC) and lecithin, important surfactants that solubilize lipophilic drugs and lipids in the gastrointestinal tract. Raman spectroscopy (in situ) was utilized to reveal the connection between the changes in solid phase composition and dissolution rate while simultaneously detecting the solid state and the dissolved amount of CBZ. Initial dissolution rate was clearly higher in FaSSIF, while the solid phase data revealed that the crystallization of CBZ dihydrate was inhibited in both the dissolution media, albeit by different mechanisms. In SIF this inhibition was related to extensive needle growth, which impeded medium contact with the solid surface by forming a sterical barrier leading to retarded crystallization rates. Morphological changes from the needle-like dihydrate crystals to plate-like counterparts in FaSSIF, combined with the information that the transformation process was leveled off, evidenced strong hydrogen bonding behavior between the CBZ and STC molecules. These results underline the importance of biologically representative dissolution media in linking the in vitro dissolution results of solids that are capable of hydrate formation to their in vivo dissolution behavior. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:985,996, 2009 [source] Resonance Rayleigh scattering method for the determination of chitosan with some anionic surfactantsLUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 3 2008Yu-Wei Wang Abstract In weak acidic buffer medium, chitosan binding with an anionic surfactant, such as sodium dodecyl benzene sulphonate (SDBS), sodium lauryl sulphate (SLS) or sodium dodecyl sulphonate (SDS), can result in a significant enhancement of resonance Rayleigh scattering (RRS) intensity. The results showed that under optimum conditions the enhanced RRS intensity is proportional to the concentration of chitosan in the range 0.10,20.0 µg/mL for SDBS, 0.27,15.0 µg/mL for SLS and 0.20,15.0 µg/mL for SDS. Among these, the sensitivity of SDBS is the highest and its detection limit for chitosan is 29 ng/mL, while those of SLS and SDS are 83 and 61 ng/mL, respectively. The method has good selectivity and was applied to the determination of trace amounts of chitosan in practical samples with satisfactory results. Therefore, a simple and convenient method with high sensitivity and selectivity for the determination of chitosan was established. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||