Aggregation-caused dual-signal response of gold nanoclusters for ratiometric optical detection of cysteine.

Designing ratiometric sensors for cysteine (Cys) monitoring with high accuracy is of great significance for disease diagnosis and biomedical studies. The current ratiometric methods mainly rely on multiplex probes, which not only complicates the operation but also increases the cost, making it difficult for quantitative Cys detection in resource-limited areas. Herein, one-pot prepared gold nanoclusters (Au NCs) that glow red fluorescent were synthesized by employing glutathione as the stabilizer and reducing agent. When Fe3+ is present with Au NCs, the fluorescence is quenched and the scattering is strong because of the aggregation of Au NCs. With introduction of Cys, Cys can efficiently compete with glutathione-modified Au NCs for Fe3+, which leads to increase of fluorescence and decrease of scattering. The ratiometric determination of Cys can be thereby realized by collecting the fluorescence and SRS spectrum simultaneously. The linear range for Cys was 5-30 µM with a detection limit of 1.5 µM. In addition, the sensing system exhibits good selectivity for Cys and shows potential application in biological samples.

Ratiometric optical detection of pyrophosphate based on aggregation-caused dual-signal response of gold nanoclusters.

Sensing of pyrophosphate ion (PPi) has received much attention due to the strong demand for clinical diagnostics. Here, based on gold nanoclusters (Au NCs), a ratiometric optical detection method for PPi is developed by simultaneously detecting the dual signals of fluorescence (FL) and second-order scattering (SOS). The PPi is detected by inhibiting the formation of aggregates of Fe3+ with Au NCs. Binding of Fe3+ to Au NCs causes aggregation of Au NCs, which leads to fluorescence quenching and scattering increasing. The presence of PPi can competitively bind Fe3+ to re-disperse the Au NCs and finally recover the fluorescence and reduce the scattering signal. The designed PPi sensor shows a high sensitivity with a linear range 5-50 µM and a detection limit of 1.2 µM. In addition, the assay has excellent selectivity for PPi, which makes its application in real biological samples extremely valuable.

Development of a Combination Fermentation Strategy to Simultaneously Increase Biomass and Enzyme Activity of D-amino Acid Oxidase Expressed in Escherichia coli.

D-amino acid oxidase (DAAO) is widely used in the industrial preparation of L-amino acids, and cultivating Escherichia coli (E. coli) expressing DAAO for the biosynthesis of L-phosphinothricin (L-PPT) is very attractive. At present, the biomass production of DAAO by fermentation is still limited in large-scale industrial applications because the expression of DAAO during the fermentation process inhibits the growth of host cells, which limits higher cell density. In this study, the factors that inhibit the growth of bacterial cells during a 5-L fed-batch fermentation process were explored, and the fermentation process was optimized by co-expressing catalase (CAT), by balancing the biomass and the enzyme activity, and by adding exogenous D-alanine (D-Ala) to relieve the limitation of DAAO on the cells and optimize fermentation. Under optimal conditions, the DO-STAT feeding mode with DO controlled at 30% ± 5% and the addition of 27.5 g/L lactose mixed with 2 g/L D-Ala during induction at 28 °C resulted in the production of 26.03 g dry cell weight (DCW)/L biomass and 390.0 U/g DCW specific activity of DAAO; an increase of 78% and 84%, respectively, compared with the initial fermentation conditions. The fermentation strategy was successfully scale-up to a 5000-L fermenter.

Explore the effects of Huang-Lian-Jie-Du-Tang on Alzheimer's disease by UPLC-QTOF/MS-based plasma metabolomics study.

Alzheimer's disease (AD) is a progressive neurodegenerative disease with neither definitive pathogenesis nor effective treatment method so far. Huang-Lian-Jie-Du-Tang (HLJDT) is a classic formula of traditional Chinese medicine (TCM) proven to have ameliorative effects on learning and memory deficits of dementia. Morris water maze (MWM) test and pathology analysis have demonstrated that HLJDT could ameliorate learning and memory deficits in AD mouse model, which may act via its anti-neuroinflammation properties. According to our previous studies, an UPLC-QTOF/MS-based metabolomics approach was performed to explore the potential mechanisms of HLJDT on preventing AD. As a result, a total of 23 potential metabolites (VIP >1, |Pcorr| >0.58, CUFjk excludes 0, P < 0.05) contributing to AD progress were identified. The metabolic pathway analysis with MetPA revealed that glycerophospholipid metabolism, sphingolipid metabolism, arachidonic acid metabolism, linoleic acid metabolism and tryptophan metabolism were disturbed in mouse model of AD. After HLJDT treatment, 14 metabolites were restored back to the control-like levels.

[Mechanism of treatment effect of Huanglian-Huangqin herb pairs on cerebral ischemia rats based on metabolomic approach].

The metabolic effect of Huanglian-Huangqin herb pairs on cerebral ischemia rats was studied by using metabolomic method. The rat model of ischemia reperfusion injury induced by introduction of transient middle cerebral artery occlusion (MCAO) followed by reperfusion. Ultra high performance liquid chromatography-series four pole time of flight mass spectrometry method（UPLC-Q-TOF/MS）, Markerlynx software, and principal component analysis and partial least-squares discriminant analysis were used to analyze the different endogenous metabolites among the urine samples of sham rats, cerebral ischemia model rats, Huanglian groups (HL), Huangqin groups (HQ) and Huanglian-Huangqin herb pairs groups (LQ) was achieved, combined with accurate information about the endogenous metabolites level and secondary fragment ions, retrieval and identification of possible biological markers, metabolic pathway which build in MetPA database. The 20 potential biomarkers were found in the urine of rats with cerebral ischemia, which mainly involved in the neurotransmitter regulation, amino acid metabolism, energy metabolism, lipid metabolism and so on. Those metabolic pathways were disturbed in cerebral ischemia model rats, the principal component analysis showed that the normal and cerebral ischemia model is clearly distinguished, and the compound can be given to the normal state of change after HL, HQ, LQ administration. This study index the interpretation of cerebral ischemia rat metabolism group and mechanism, the embodiment of metabonomics can reflect the physiological and metabolic state, which can better reflect the traditional Chinese medicine as a whole view, system view and the features of multi ingredient synergistic or antagonistic effects.

Affinity Purification of Hepatitis B Virus Surface Antigen Containing PreS1 Region.

The large protein of hepatitis B virus surface antigen (LHBs) contained an attachment site of HBV to liver cells and the antibodies to preS1 were virus-neutralizing. Therefore, vaccines containing preS1 would be more protective. However, One of the key problems in the preparation of gene-expressed proteins was the purification of the products. We have established a method of immuno-affinity chromatography with the anti-HBsAg-preS1 monoclonal antibody. Using this technique, We have successfully purified gene-expressed fusion protein of hepatitis B virus surface antigen containing preS1 (21-47). Results showed that this method was simple, effective and specific as compared to other methods, and might be useful in the future.

The Application of Monoclonal Antibodies to the Imunoaffinity Purification of Human Ferritin.

There was difference between the reactivities of anti-human ferritin monoclonal antibodies, 6D6 and A-hF-C with liver and heart ferritins. 6D6 reacts with liver and heart ferritin with similar intensity, while A-hF-C reacts preferentially with liver ferritin. Two affinity gels were made with 6D6 and A-hF-C respectively, and used to purify ferritins from crude extracts of human liver and heart ferritins. The results have showed that it is a simple and time-saving method for the purification of ferritin with high purity and yield.