Determination of methylene blue release in plasma virus inactivation bag by fluorescence energy transfer method / 中国输血杂志

【Objective】 To establish a simple, economical and rapid method for the determination of methylene blue (MB) release in virus inactivation bag. 【Methods】 Based on the fluorescence energy transfer between MB and BSA-stabilized gold nanoclusters (BSA-AuNCs), the standard curve of MB determination was established by measuring the fluorescence quenching degree of MB to BSA-AuNCs in different concentrations to conduct the determination of MB release in virus inactivation bag. 【Results】 There was a good linear relationship between the MB concentration (cMB) and the fluorescence quenching degree of BSA-AuNCs[ (I0-I)/I0=0.018cMB+ 0.021(r=0.996)] when the fluorescence emission wavelength was about 620 nm and the cMB was in the range of (0.9-36) μmoL/L. The recovery of MB was 98.00% -101.95 % when applied to determine MB at high, medium, and low concentrations, the obtained intra-day variation coefficients were 0.73%, 0.81% and 0.77% respectively, and the obtained inter-day variation coefficients were 3.92%, 3.81%, and 4.73% respectively. There was no significant difference between the results measured by this method and those measured by combination of solid-phase extraction and spectrophotometry(P>0.05). 【Conclusion】 The fluorescence energy transfer method could achieve simple and rapid determination of MB release in virus inactivation bag with accurate and reliable results.

Environments of ethidium binding to allosteric Dna: II. Accessibility, mobility and mode of binding

DNA binding compounds were previously shown to bind to the right-handed DNA forms and hybrid B-Z forms in a highly cooperative manner and indicate that structural specificity plays a key role in a ligand binding to DNA. In this study, the modes of binding and structural specificity of agents to unusual DNA are examined by a variety of fluorescence techniques (intensity, polarization and quenching, etc.) to explore a reliable method to detect the association environment of ligands to deoxyoligonucleotides initially containing a B-Z junction between the left-handed Z-DNA and right-handed B-DNA. The results of fluorescence energy transfer measurement demonstrated that the ligand molecules bind to the allosterically converted DNA structures by intercalation. In the absence of high-resolution structural data, this fluorescence energy transfer measurement allowed reliable measures and infer the binding environment of ligands to the allosteric DNA structures.

Conformational and ion-binding properties of cyclolinopeptide A isolated from linseed.

The conformation of the cyclic nonapeptide from linseed, cyclolinopeptide A in methanol and in acetonitrile has been elucidated by one- and two-dimensional nuclear magnetic resonance. The molecule is folded in a ß-turn conformation. Cyclolinopeptide A interacts and weakly complexes with Tb3+ (a Ca2+ mimic ion) with the metal ion positioned proximally to the Phe residue, but with no substantial structural alteration upon metal binding. Cyclolinopeptide A is also seen to aid the translocation of Pr3+ (another Ca2+ mimic) across unilamellar liposomes. However, cyclolinopeptide A does not phase transfer or act as an ionophore of calcium ion myself. Experiments using lanthanide ions thus do not necessarily indicate any ionophoretic ability of the complexone towards calcium ions.