Evaluation of minimal processing of orange juice by automated data analysis of volatiles and nonvolatile polar compounds determined by gas chromatography coupled to mass spectrometry

The effects of minimal processing on the metabolite composition of orange juice were studied. Volatiles and nonvolatile polar compounds in Lane Late orange juices, with different pulp contents, treated by high-pressure homogenisation (HPH) at 150 MPa (at 58, 63 and 68 °C) and stored for 3 months at 3 °C were analysed by gas chromatography coupled to mass spectrometry (GC-MS) with automated data processing. A total of 92 volatiles and 22 polar components (trimethylsilyl, TMS, derivatives of sugars, organic acids and amino acids) were determined in fresh, processed and stored juices. Initially, concentration of fresh flavours (hydrocarbon terpenes and aldehydes) determined in the homogenised samples with the original pulp content was higher than that determined in fresh juice. During storage, desirable descriptors were better preserved in the juice processed at 68 °C with the lowest increase in off-flavours (alcohols and ketones). Generally, operations assayed did not exert a significant influence on polar metabolites, showing no effect on their decrease with time. Evaluation of minimally processed orange juice by high-throughput metabolite analysis.</p

Tumor targeting of functionalized quantum dot-liposome hybrids by intravenous administration

A strategy to target functionalized quantum dot-liposome (f-QD-L) hybrid vesicles in the solid tumor tissue of tumor-bearing mice is explored. Functionalized polyethylene glycol (PEG)-lipid coated QD (f-QD) were encapsulated into the aqueous core of 100 nm cationic (DOPC:Chol: DOTAP); sterically stabilized, fluid-phase (DOPC:Chol:DSPE-PEG2000); and sterically stabilized, gel-phase (DSPC:Chol:DSPE-PEG2000) liposome vesicles. Double tracking of f-QD-L in blood was performed at different time points after intravenous administration in B16F10 melanoma tumor-bearing C57BL6 mice. Cholesteryl [-1-14C] oleate lipids probed the vesicle membrane were followed by liquid scintillation counting while QD were determined independently by elemental (Cd2+) analysis using inductively coupled plasma mass spectrometry (ICP-MS). Rapid blood clearance was observed following intravenous administration of the cationic hybrid vesicles, while incorporation of PEG at the surface of zwitterionic vesicles dramatically prolonged their blood circulation half-life after systemic administration. The "rigid" PEGylated f-QD-L (DSPC:Chol:DSPE-PEG2000) hybrid vesicles led to rapid tumor accumulation of peak values (approximately 5% of injected dose per gram tissue) of QD compared to long-circulating f-QD that accumulated in the tumor tissue at longer time points. More interestingly, this hybrid vesicle tumor retention persisted for at least 24 h. For almost all types of systems, a preferential cadmium uptake by liver and spleen was obtained. Overall, f-QD-L hybrid vesicles offer great potential for tumor imaging applications due to their rapid accumulation and prolonged retention within the tumor. Furthermore, f-QD-L offer many opportunities for the development of combinatory therapeutic and imaging (theranostic) modalities by incorporating both drug molecules and QD within the different compartments of a single vesicle.</p

Manipulation of phytoene levels in tomato fruit: effects on isoprenoids, plastids, and intermediary metabolism

In tomato (Solanum lycopersicum), phytoene synthase-1 (PSY-1) is the key biosynthetic enzyme responsible for the synthesis of fruit carotenoids. To further our understanding of carotenoid formation in tomato fruit, we characterized the effect of constitutive expression of an additional tomato Psy-1 gene product. A quantitative data set defining levels of carotenoid/isoprenoid gene expression, enzyme activities, and metabolites was generated from fruit that showed the greatest perturbation in carotenoid content. Transcriptional upregulation, resulting in increased enzyme activities and metabolites, occurred only in the case of Psy-1, Psy-2, and lycopene cyclase B. For reactions involving 1-deoxy-d-xylulose5-phosphate synthase, geranylgeranyl diphosphate synthase, phytoene desaturase, zeta-carotene desaturase, carotene isomerase, and lycopene beta-cyclase, there were no correlations between gene expression, enzyme activities, and metabolites. Perturbations in carotenoid composition were associated with changes in plastid type and with chromoplast-like structures arising prematurely during fruit development. The levels of >120 known metabolites were determined. Comparison with the wild type illustrated that key metabolites (sucrose, glucose/fructose, and Glu) and sectors of intermediary metabolism (e.g., tricarboxylic [corrected] acid cycle intermediates and fatty acids) in the Psy-1 transgenic mature green fruit resembled changes in metabolism associated with fruit ripening. General fruit developmental and ripening properties, such as ethylene production and fruit firmness, were unaffected. Therefore, it appears that the changes to pigmentation, plastid type, and metabolism associated with Psy-1 overexpression are not connected with the ripening process

Creation of Libraries of Recurring Mass Spectra from Large Data Sets Assisted by a Dual-Column Workflow

An analytical methodology has been developed for extracting recurrent unidentified spectra (RUS) from large GC/MS data sets. Spectra were first extracted from original data files by the Automated Mass Spectral Deconvolution and Identification System (AMDIS; Stein, S. E. J. Am. Soc. Mass Spectrom. 1999, 10, 770–781) using settings designed to minimize spurious spectra, followed by searching the NIST library with all unidentified spectra. The spectra that could not be identified were then filtered to remove poorly deconvoluted data and clustered. The results were assumed to be unidentified components. This was tested by requiring each unidentified spectrum to be found in two chromatographic columns with slightly different stationary phases. This methodology has been applied to a large set of pediatric urine samples. A library of spectra and retention indices for derivatized urine components, both identified and recurrent unidentified, has been created and is available for download