Fructose Chemistry

Fructose is a six-carbon ketose monosaccharide. In aqueous solution and in the crystalline form, the majority of the molecules form ring structures. Of these, the six-membered pyranose form is the most abundant; however, about one-quarter of the molecules are in the five-membered, furanose form. While many of its reactions are similar to those of glucose, the presence of a ketone group in the chain, and the relative ease with which the molecule forms a five-membered furanose ring affects its chemistry and biochemistry. Specific pathways are required to enable organisms to exploit fructose in energy metabolism; these require the enzyme fructokinase and involve the conversion of fructose to glycolytic intermediates. Similarly, specific pathways for the biosynthesis of fructose and fructose-containing polymers, such as inulin, are required. Non-enzymatic glycation (fructation) by fructose has not been as extensively studied as the corresponding reactions with glucose. Nevertheless, especially in diabetic patients and fructose-rich foodstuffs, this reaction is likely to be important.

Observation of an optical phonon band in situ in TiO electrochemistry:A possible indicator of strongly trapped intermediates in the O evolution reaction

This Letter reports in situ Fourier transform infrared (FTIR) spectroscopic data on thermal TiO films fabricated by heating titanium plates in air at 475, 700 and 800 °C. The films were studied in the dark and under UV-irradiation in aqueous 0.1MNaClO in the presence and absence of 0.1 M Na(OOC) and at 10, 25 and 50 °C. The film fabricated at 800 °C showed a broad feature near 1580cm under UV-irradiation that was not observed in the dark, whilst the films fabricated at lower temperatures, 475 and 700 °C, showed no such feature. This feature appears to be associated with the accumulation of surface-mobile holes at the complex, porous film-electrolyte interface and the capacity of such holes to enhance the absorption cross-section of optical phonons characteristic of the rutile crystal form at and near the surface of the TiO/electrolyte interface. © 2001 Elsevier Science B.V.

High-density lipoprotein subfractions display proatherogenic properties in overweight and obese children

BACKGROUND: In adults, obesity-driven inflammation can lead to increased cardiovascular disease (CVD). However, information regarding childhood obesity and its inflammatory sequelae is less well defined. Serum amyloid-A (SAA) is an inflammatory molecule that rapidly associates with high-density lipoproteins (HDLs) and renders them dysfunctional. Therefore, SAA may be a useful biomarker to identify increased CVD potential in overweight and obese children.

METHODS: Young Hearts 2000 is a cross-sectional cohort study in which 92 children who were obese were matched for age and sex with 92 overweight and 92 lean children. HDL2 and HDL3 (HDL2&3) were isolated from plasma by a three-step rapid-ultracentrifugation procedure. SAA was measured in serum and HDL2&3 by an enzyme-linked immunosorbent assay procedure, and the activities of cholesterol ester transfer protein (CETP) and lecithin cholesteryl acyltransferase (LCAT) were measured by fluorimetric assays.

RESULTS: Trends across the groups indicated that SAA increased in serum and HDL2&3 as BMI increased, as did HDL2-CETP and HDL2-LCAT activities.

CONCLUSION: These results have provided evidence that overweight and obese children are exposed to an inflammatory milieu that impacts the antiatherogenic properties of HDL and that could increase CVD risk. This supports the concept that it is important to target childhood obesity to help minimize future cardiovascular events.

Use of immunosorbent-purified antigens of Fasciola hepatica in enzyme immunoassays

A monoclonal antibody specific for the T1 tegumental antigen of Fasciola hepatica was used as a solid-phase immunosorbent for the purification of T1 antigen from homogenised mature F hepatica. Material fractionated by this technique was successfully used in enzyme-linked immunoassays to detect antibodies to F hepatica in sera from sheep and cattle. Species differences in response to infection by F hepatica were demonstrated.

Identification of two focal adhesion targeting sequences in the adapter molecule p130(Cas)

The adapter molecule CAS is localized primarily within focal adhesions in fibroblasts. Because many of the cellular functions attributed to CAS are likely to be dependent on its presence in focal adhesions, this study was undertaken to identify regions of the protein that are involved in its localization. The SH3 domain of CAS, when expressed in isolation from the rest of the protein, was able to target to focal adhesions, whereas a variant containing a point mutation that rendered the SH3 domain unable to associate with FAK remained cytoplasmic. However, in the context of full-length CAS, this mutation did not prevent CAS localization to focal adhesions. Two other variants of CAS that contained deletions of either the SH3 domain alone, or the SH3 domain together with an adjoining proline-rich region, also retained the capacity to localize to focal adhesions. A second focal adhesion targeting region was mapped to the extreme carboxy terminus of CAS. The identification of this second focal adhesion targeting domain in CAS ascribes a previously unknown function to the highly conserved C terminus of CAS. The regulated targeting of CAS to focal adhesions by two independent domains may reflect the important role of CAS within this subcellular compartment.

Regulation of apoptotic protease activating factor-1 oligomerization and apoptosis by the WD-40 repeat region

Apoptotic protease activating factor-1 (Apaf-1) has been identified as a proximal activator of caspase-9 in cell death pathways that trigger mitochondrial damage and cytochrome c release. The mechanism of Apaf-1 action is unclear but has been proposed to involve the clustering of caspase-9 molecules, thereby facilitating autoprocessing of adjacent zymogens. Here we show that Apaf-1 can dimerize via the CED-4 homologous and linker domains of the molecule providing a means by which Apaf-1 can promote the clustering of caspase-9 and facilitate its activation. Apaf-1 dimerization was repressed by the C-terminal half of the molecule, which contains multiple WD-40 repeats, but this repression was overcome in the presence of cytochrome c and dATP. Removal of the WD-40 repeat region resulted in a constitutively active Apaf-1 that exhibited greater cytotoxicity in transient transfection assays when compared with full-length Apaf-1. These data suggest a mechanism for Apaf-1 function and reveal an important regulatory role for the WD-40 repeat region.

An assay for angiotensin-converting enzyme using capillary zone electrophoresis

A sensitive and rapid method was developed for angiotensin-converting enzyme (ACE) activity determination by capillary zone electrophoresis. Hippuryl-View the MathML source-histidyl-View the MathML source-leucine, a synthetic tripeptide, was used as the ACE-specific substrate. Capillary zone electrophoresis was employed to separate the products of the enzymatic reaction and the ACE activity was determined by quantification of hippuric acid, a result of the enzymatic reaction on the tripeptide. The capillary electrophoresis was performed in a 27 cm × 75 μm i.d. fused-silica capillary using 200 mM boric acid–borate buffer (pH 9.0) as a run buffer with an applied voltage of 8.1 kV at a capillary temperature of 23°C. The electrophoresis was monitored at 228 nm. Each electrophoretic run requires only a nanoliter of the enzymatic reactant solution, at only 6 min, rendering a powerful tool for the ACE assay.

The Role of Water and Adsorbed Hydroxyls on Ethanol Electrochemistry on Pd: New Mechanism, Active Centers and Energetics for Direct Ethanol Fuel Cell Running in Alkaline Medium

First principles calculations with molecular dynamics are
utilized to simulate a simplified electrical double layer formed in the
active electric potential region during the electrocatalytic oxidation of
ethanol on Pd electrodes running in an alkaline electrolyte. Our
simulations provide an atomic level insight into how ethanol oxidation
occurs in fuel cells: New mechanisms in the presence of the simplified
electrical double layer are found to be different from the traditional
ones; through concerted-like dehydrogenation paths, both acetaldehyde
and acetate are produced in such a way as to avoid a variety of
intermediates, which is consistent with the experimental data obtained
from in situ FTIR spectroscopy. Our work shows that adsorbed OH on
the Pd electrode rather than Pd atoms is the active center for the
reactions; the dissociation of the C−H bond is facilitated by the
adsorption of an OH− anion on the surface, resulting in the formation
of water. Our calculations demonstrate that water dissociation rather than H desorption is the main channel through which
electrical current is generated on the Pd electrode. The effects of the inner Helmholtz layer and the outer Helmholtz layer are
decoupled, with only the inner Helmholtz layer being found to have a significant impact on the mechanistics of the reaction. Our
results provide atomic level insight into the significance of the simplified electrical double layer in electrocatalysis, which may be
of general importance.

Cathelicidin LL-37:a defense molecule with a potential role in psoriasis pathogenesis

Epidermal keratinocytes produce and secrete antimicrobial peptides (AMPs) that subsequently form a chemical shield on the skin surface. Cathelicidins are one family of AMPs in skin with various further immune functions. Consequently, dysfunction of these peptides has been implicated in the pathogenesis of inflammatory skin disease. In particular, the cathelicidin LL-37 is overexpressed in inflamed skin in psoriasis, binds to extracellular self-DNA released from dying cells and converts self-DNA in a potent stimulus for plasmacytoid dendritic cells (pDCs). Subsequently, pDCs secrete type I interferons and trigger an auto-inflammatory cascade. Paradoxically, therapies targeting the vitamin D pathway such as vitamin D analogues or UVB phototherapy ameliorate cutaneous inflammation in psoriasis but strongly induce cathelicidin expression in skin at the same time. Current evidence now suggests that self-DNA present in the cytosol of keratinocytes is also pro-inflammatory active and triggers IL-1β secretion in psoriatic lesions through the AIM2 inflammasome. This time, however, binding of LL-37 to self-DNA neutralizes DNA-mediated inflammation. Hence, cathelicidin LL-37 shows contrasting roles in skin inflammation in psoriasis and might serve as a target for novel therapies for this chronic skin disease.

Macrophage migration inhibitory factor (MIF) expression in human malignant gliomas contributes to immune escape and tumour progression

Macrophage migration inhibitory factor (MIF), which inhibits apoptosis and promotes angiogenesis, is expressed in cancers suppressing immune surveillance. Its biological role in human glioblastoma is, however, only poorly understood. We examined in-vivo expression of MIF in 166 gliomas and 23 normal control brains by immunohistochemistry. MIF immunoreactivity was enhanced in neoplastic astrocytes in WHO grade II glioma and increased significantly in higher tumour grades (III-IV). MIF expression was further assessed in 12 glioma cell lines in vitro. Quantitative RT-PCR showed that MIF mRNA expression was elevated up to 800-fold in malignant glioma cells compared with normal brain. This translated into high protein levels as assessed by immunoblotting of total cell lysates and by ELISA-based measurement of secreted MIF. Wild-type p53-retaining glioma cell lines expressed higher levels of MIF, which may be connected with the previously described role of MIF as a negative regulator of wild-type p53 signalling in tumour cells. Stable knockdown of MIF by shRNA in glioma cells significantly increased tumour cell susceptibility towards NK cell-mediated cytotoxicity. Furthermore, supernatant from mock-transfected cells, but not from MIF knockdown cells, induced downregulation of the activating immune receptor NKG2D on NK and CD8+ T cells. We thus propose that human glioma cell-derived MIF contributes to the immune escape of malignant gliomas by counteracting NK and cytotoxic T-cell-mediated tumour immune surveillance. Considering its further cell-intrinsic and extrinsic tumour-promoting effects and the availability of small molecule inhibitors, MIF seems to be a promising candidate for future glioma therapy.

VDR and MEK-ERK dependent induction of the antimicrobial peptide cathelicidin in keratinocytes by lithocholic acid

Cathelicidin is an antimicrobial peptide (AMP) and signaling molecule in innate immunity and a direct target of 1,25-dihydroxyvitamin D3 (1,25D3) in primary human keratinocytes (NHEK). The expression of cathelicidin is dysregulated in various skin diseases and its regulation differs depending on the epithelial cell type. The secondary bile acid lithocholic acid (LCA) is a ligand of the vitamin D receptor (VDR) and can carry out in vivo functions of vitamin D3. Therefore we analyzed cathelicidin mRNA- and peptide expression levels in NHEK and colonic epithelial cells (Caco-2) after stimulation with LCA. We found increased expression of cathelicidin mRNA and peptide in NHEK, in Caco-2 colon cells no effect was observed after LCA stimulation. The VDR as well as MEK-ERK signaled the upregulation of cathelicidin in NHEK induced by LCA. Collectively, our data indicate that cathelicidin induction upon LCA treatment differs in keratinocytes and colonic epithelial cells. Based on these observations LCA-like molecules targeting cathelicidin could be designed for the treatment of cutaneous diseases that are characterized by disturbed cathelicidin expression.