Furan formation from vitamin C in a starch-based model system: Influence of the reaction conditions

in Food Chemistry (2010), 121(4), 1163-1170

The generation of furan from vitamin C during thermal treatment of a starch-based model system, which simulated baby food, was studied. Results indicated that the amount of sample heated in the vial ... [more ▼]

The generation of furan from vitamin C during thermal treatment of a starch-based model system, which simulated baby food, was studied. Results indicated that the amount of sample heated in the vial influenced the furan generation from ascorbic acid. Increasing the amount of heated sample from 5% to approximately 98% of the total vial volume, drastically reduced furan formation from 70 ppb to 16 ppb. Changes in ascorbic acid concentrations from 0.1 to 4.5 mg/g did not influence furan concentration nor did different ascorbic/dehydroascorbic acid molar ratios. Interestingly, waxy corn starch itself considerably enhanced furan generation from ascorbic acid. Under the same conditions, 13.2 ppb of furan was generated in starch-based samples, while in ascorbic acid buffered solutions only 0.4 ppb of furan was formed. Application of other matrices, in particular agar and hydrolysed starch, resulted in similar furan concentrations as for native starch, while in polyol solutions furan concentrations were comparable to those obtained for the buffered ascorbic acid solutions. [less ▲]

Structure-based design of selective high-affinity telomeric quadruplex-binding ligands

in Chemical Communications (2010), 46

A library of triazole-based telomeric quadruplex-selective ligands has been developed that mimic an established family of tri-substituted acridine-based ligands, using crystal structure data as a starting ... [more ▼]

A library of triazole-based telomeric quadruplex-selective ligands has been developed that mimic an established family of tri-substituted acridine-based ligands, using crystal structure data as a starting-point for computer-based design. Binding affinities, estimated by electrospray mass spectrometry, are in accord with the design concept [less ▲]

Electrospray Mass Spectrometry of Telomeric RNA (TERRA) Reveals the Formation of Stable Multimeric G-Quadruplex Structures

in Journal of the American Chemical Society (2010), 132(27), 93289334

We report on the self-assembled structures formed by 12-mer, 22-mer, and 45-mer telomeric RNA (telRNA/TERRA) sequences compared to their DNA analogues, as studied by electrospray mass spectrometry ... [more ▼]

We report on the self-assembled structures formed by 12-mer, 22-mer, and 45-mer telomeric RNA (telRNA/TERRA) sequences compared to their DNA analogues, as studied by electrospray mass spectrometry, circular dichroism, and thermal denaturation. The major difference between telomeric RNA and DNA sequences is the ability of telomeric RNA to form higher-order dimeric assemblies, initiated by cation-mediated stacking of two parallel G-quadruplex subunits. The 5′-5′ stacking had been observed recently by NMR for the r(GGGUUAGGGU) 10-mer (Martadinata, H.; Phan, A. T. J. Am. Chem. Soc. 2009, 131, 2570); the present work shows that stacking also occurs for the 22-mer containing four G-tracts and for the 45-mer containing eight G-tracts, suggesting a general structural feature of telomeric RNA. The importance of kinetic effects in multimer formation, unfolding, and structural rearrangements is also highlighted. [less ▲]

Importance of fat oxidation in starch-based emulsions in the generation of the process contaminant furan.

in Journal of Agricultural and Food Chemistry (2010), 58(17), 9579-86

The formation of the possibly carcinogenic process contaminant furan was studied in starch-based emulsions during heat treatments as applied for sterilization. Fresh and oxidized soybean, sunflower, high ... [more ▼]

The formation of the possibly carcinogenic process contaminant furan was studied in starch-based emulsions during heat treatments as applied for sterilization. Fresh and oxidized soybean, sunflower, high-oleic sunflower, olive, linseed, and rapeseed oils were compared. Results indicated that both the oil type, in particular, the fatty acid composition, and the oxidation degree of the oil determined the susceptibility of the oils to generate furan upon heating. Thus, oils containing the nutritionally relevant omega-3 unsaturated alpha-linolenic acid proved to be able to generate significant amounts of furan if the oils were oxidized. No clear relationship between p-anisidine values of various oils and the amount of generated furan could be observed. However, in the case of soybean oil, significantly more furan was produced upon an increase in oxidation degree. Surprisingly, furan formation in food-relevant systems containing fresh lipids proved to be a minor route (up to 1.5 ppb furan) compared to a previously studied vitamin C containing model system (up to 13 ppb furan). [less ▲]

Proteomic and functional characterization of a Chlamydomonas reinhardtii mutant lacking the mitochondrial alternative oxidase 1

in Journal of Proteome Research (2010)

In the present work we have isolated by RNA interference and characterized at the functional and the proteomic levels a Chlamydomonas reinhardtii strain devoid of the mitochondrial alternative oxidase ... [more ▼]

In the present work we have isolated by RNA interference and characterized at the functional and the proteomic levels a Chlamydomonas reinhardtii strain devoid of the mitochondrial alternative oxidase (AOX). The AOX-deficient strain displays a doubling of the cell volume and biomass without any alteration of the generation time, a significantly higher ROS production, no change in total respiration rate, and a slight decrease of the photosynthesis efficiency. In order to identify the molecular adaptation underlying these phenotypical effects, we carried out a comparative proteomic study at the level of the mitochondrial and cellular soluble proteomes. Our results indicate a strong up-regulation of the ROS scavenging systems and important modifications of proteins involved in the primary metabolism, namely an increase of enzymes involved in anabolic pathways and a concomitant general down-regulation of enzymes of the main catabolic pathways. [less ▲]

Tritrophic interactions among Macrosiphum euphorbiae aphids, their host plants and endosymbionts: investigation by a proteomic approach.

in Journal of Insect Physiology (2010), 56(6), 575-85

The Mi-1.2 gene in tomato confers resistance against certain clones of the potato aphid (Macrosiphum euphorbiae). This study used 2D-DIGE coupled with protein identification by MALDI-TOF-MS to compare the ... [more ▼]

The Mi-1.2 gene in tomato confers resistance against certain clones of the potato aphid (Macrosiphum euphorbiae). This study used 2D-DIGE coupled with protein identification by MALDI-TOF-MS to compare the proteome patterns of avirulent and semivirulent potato aphids and their bacterial endosymbionts on resistant (Mi-1.2+) and susceptible (Mi-1.2-) tomato lines. Avirulent aphids had low survival on resistant plants, whereas the semivirulent clone could colonize these plants. Eighty-two protein spots showed significant quantitative differences among the four treatment groups, and of these, 48 could be assigned putative identities. Numerous structural proteins and enzymes associated with primary metabolism were more abundant in the semivirulent than in the avirulent aphid clone. Several proteins were also up-regulated in semivirulent aphids when they were transferred from susceptible to resistant plants. Nearly 25% of the differentially regulated proteins originated from aphid endosymbionts and not the aphid itself. Six were assigned to the primary endosymbiont Buchnera aphidicola, and 5 appeared to be derived from a Rickettsia-like secondary symbiont. These results indicate that symbiont expression patterns differ between aphid clones with differing levels of virulence, and are influenced by the aphids' host plant. Potentially, symbionts may contribute to differential adaptation of aphids to host plant resistance. [less ▲]

New Advances in the Understanding of the In-Source Decay Fragmentation of Peptides in MALDI-TOF-MS.

in Journal of the American Society for Mass Spectrometry (2010), 21(11), 1906-17

In-source decay (ISD) is a rapid fragmentation occurring in the matrix-assisted laser desorption/ionization (MALDI) source before the ion extraction. Despite the increasing interest for peptides de novo ... [more ▼]

In-source decay (ISD) is a rapid fragmentation occurring in the matrix-assisted laser desorption/ionization (MALDI) source before the ion extraction. Despite the increasing interest for peptides de novo sequencing by ISD, the influence of the matrix and of the peptide itself is not yet fully understood. Here we compare matrices with high ISD efficiencies to gain deeper insight in the ISD fragmentation process(es). The major ISD fragments are the c- and z-ions, but other types of fragments are also observed, and their origin is studied here. Two main pathways lead to fragmentation in the source: a radical-induced pathway that leads to c-, z-, w-, and d-ions, and a thermally activated pathway that leads to y-, b-, and a-ions. A detailed analysis of the ISD spectra of selected peptides revealed that (1) the extents of the two in-source pathways are differently favored depending on the matrix used, that (2) the presence of a positive/negative charge on the radical-induced fragments is necessary for their observation in positive/negative mode, respectively, and that (3), for a same peptide, the patterns of the different types of fragments differ according to the matrix used. [less ▲]

Rapid Collapse into a Molten Globule Is Followed by Simple Two-State Kinetics in the Folding of Lysozyme from Bacteriophage lambda

in Biochemistry (2010), 49

Stopped-flow fluorescence and circular dichroism spectroscopy have been used in combination with quenched-flow hydrogen exchange labeling, monitored by two-dimensional NMR and electrospray ionization mass ... [more ▼]

Stopped-flow fluorescence and circular dichroism spectroscopy have been used in combination with quenched-flow hydrogen exchange labeling, monitored by two-dimensional NMR and electrospray ionization mass spectrometry, to investigate the folding kinetics of lysozyme from bacteriophage lambda (lambda lysozyme) at pH 5.6, 20 degrees C. The first step in the folding of lambda lysozyme occurs very rapidly (tau < 1 ms) after refolding is initiated and involves both hydrophobic collapse and formation of a high content of secondary structure but only weak protection from (1)H/(2)H exchange and no fixed tertiary structure organization. This early folding step is reflected in the dead-time events observed in the far-UV CD and ANS fluorescence experiments. Following accumulation of this kinetic molten globule species, the secondary structural elements are stabilized and the majority (ca. 88%) of refolding molecules acquire native-like properties in a highly cooperative two-state process, with tau = 0.15 +/- 0.03 s. This is accompanied by the acquisition of substantial native-like protection from hydrogen exchange. A double-mixing experiment and the absence of a denaturant effect reveal that slow (tau = 5 +/- 1 s) folding of the remaining (ca. 12%) molecules is rate limited by the cis/trans isomerization of prolines that are trans in the folded enzyme. In addition, native state hydrogen exchange and classical denaturant unfolding experiments have been used to characterize the thermodynamic properties of the enzyme. In good agreement with previous crystallographic evidence, our results show that lambda lysozyme is a highly dynamic protein, with relatively low conformational stability (DeltaG degrees (N-U) = 25 +/- 2 kJ.mol(-1)). [less ▲]

Biomarker for osteoarthritis and/or other ageing-related diseases, and use thereof

Patent (2009)

The invention relates to the identification of a biomarker whose abundance in bodily fluids is changed in subjects with osteoarthritis and/or other ageing-related diseases. The biomarker has applications ... [more ▼]

The invention relates to the identification of a biomarker whose abundance in bodily fluids is changed in subjects with osteoarthritis and/or other ageing-related diseases. The biomarker has applications in the diagnosis of osteoarthritis and/or other ageing-related diseases, in determining the prognosis for an individual diagnosed with osteoarthritis and/or other ageing-related diseases, and in monitoring the efficacy of treatment for osteoarthritis and/or other ageing-related diseases. [less ▲]

Ku proteins interact with activator protein-2 transcription factors and contribute to ERBB2 overexpression in breast cancer cell lines.

in Breast Cancer Research [=BCR] (2009), 11(6),

INTRODUCTION: Activator protein-2 (AP-2) alpha and AP-2 gamma transcription factors contribute to ERBB2 gene overexpression in breast cancer. In order to understand the mechanism by which the ERBB2 gene ... [more ▼]

INTRODUCTION: Activator protein-2 (AP-2) alpha and AP-2 gamma transcription factors contribute to ERBB2 gene overexpression in breast cancer. In order to understand the mechanism by which the ERBB2 gene is overexpressed we searched for novel AP-2 interacting factors that contribute to its activity. METHODS: Ku proteins were identified as AP-2 alpha interacting proteins by glutathione serine transferase (GST)-pull down followed by mass spectrometry. Transfection of the cells with siRNA, expression vectors and reporter vectors as well as chromatin immunoprecipitation (ChIP) assay were used to ascertain the implication of Ku proteins on ERBB2 expression. RESULTS: Nuclear proteins from BT-474 cells overexpressing AP-2 alpha and AP-2 gamma were incubated with GST-AP2 or GST coated beads. Among the proteins retained specifically on GST-AP2 coated beads Ku70 and Ku80 proteins were identified by mass spectrometry. The contribution of Ku proteins to ERBB2 gene expression in BT-474 and SKBR3 cell lines was investigated by downregulating Ku proteins through the use of specific siRNAs. Depletion of Ku proteins led to downregulation of ERBB2 mRNA and protein levels. Furthermore, reduction of Ku80 in HCT116 cell line decreased the AP-2 alpha activity on a reporter vector containing an AP-2 binding site linked to the ERBB2 core promoter, and transfection of Ku80 increased the activity of AP-2 alpha on this promoter. Ku siRNAs also inhibited the activity of this reporter vector in BT-474 and SKBR3 cell lines and the activity of the ERBB2 promoter was further reduced by combining Ku siRNAs with AP-2 alpha and AP-2 gamma siRNAs. ChIP experiments with chromatin extracted from wild type or AP-2 alpha and AP-2 gamma or Ku70 siRNA transfected BT-474 cells demonstrated Ku70 recruitment to the ERBB2 proximal promoter in association with AP-2 alpha and AP-2 gamma. Moreover, Ku70 siRNA like AP-2 siRNAs, greatly reduced PolII recruitment to the ERBB2 proximal promoter. CONCLUSIONS: Ku proteins in interaction with AP-2 (alpha and gamma) contribute to increased ERBB2 mRNA and protein levels in breast cancer cells. [less ▲]