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Functional genes can be introduced into mammalian cells in vitro by a variety of physical methods, including direct microinjection, electroporation, and co-precipitation with calcium phosphate. Most of these techniques, however, are impractical for delivering genes into tissues of intact animals. In contrast, receptor-mediated gene transfer has been shown to successfully introduce DNA into suitable recipient cells, both in vitro and in vivo (1-12). This procedure involves the formation of a complex between DNA and a polycation (such as poly-L-lysine), which bears a covalently linked ligand moiety specific for a given receptor on the surface of cells in the target tissue. The gene is internalized by the tissue, transported to the nucleus, and expressed in the cell for varying lengths of time (1,3,6,11). The overall level of expression of the transgene in the target tissue is dependent on several factors, such as the stability of the DNA/ligand⅐poly-L-lysine complex, the presence and number of specific receptors on the surface of the targeted cell, the receptor-DNA/ligand interaction, endocytosis of the DNA complex and the efficiency of gene transcription in the nucleus of the target cells.DNA in the nucleus of a higher eukaryote is intimately associated with basic nuclear proteins rich in lysine (i.e. histones) or arginine (i.e. protamines). The interaction of DNA with these basic proteins is responsible for the control of the condensation process that occurs upon chromosome formation during metaphase and is thought to play a role in the regulation of gene expression. DNA condensation, which occurs naturally in viruses, bacteria, and eukaryote nuclei, has been extremely difficult to reproduce in the laboratory (13,14). Due to the high negative charge of the DNA phosphate backbone, an increase in the degree of charge neutralization of the DNA theoretically results in extensive condensation and the separation of the DNA phase in the form of insoluble compact structures (15, 16). We have found, however, that the structure and stoichiometry of DNA⅐polycation complexes in solution can be manipulated by means of the process by which DNA⅐cationic polypeptide complexes are formed.Specific complexes of DNA (⌿-DNA) are formed with cationic homo-polypeptides (poly-L-lysine, poly-L-arginine, or poly-L-ornithine) after "annealing" both components in a step-down dialysis from NaCl concentrations of 3 to 0.010 M (11, 16). In contrast, direct addition of basic polypeptides to DNA at physiological salt concentrations results in reversible molecular aggregation and the formation of precipitates (7,17,18). Shapiro et al. (16) elucidated changes in DNA secondary structure in DNA⅐poly-L-lysine complexes prepared by directly mixing poly-L-lysine and DNA. The physical properties of the resulting soluble complexes were investigated by circular dichroism (CD) and optical rotatory dispersion. A change in the magnitude of the molar residue rotation was found, with a characteristic red shift and a strong negative rotatory transition center...

Xanthohumol (XN) is a unique prenylated flavonoid in hops (Humulus lupulus L.) and beer. XN alleviates hyperglycemia and has potential usage in the treatment of type 2 diabetes. In the present study, a series of in vitro experiments were performed to investigate whether XN was an effective inhibitor of α-glucosidase. The results showed that XN inhibited α-glucosidase in a reversible and noncompetitive manner, with an IC50 value of 8.8 μM and that XN inhibited the release of glucose from the maltose in the apical side of the Caco-2 cell monolayer. Fluorescence and circular dichroism spectra results indicated that XN directly bound to α-glucosidase and induced minor conformational changes of the enzyme. These results demonstrated that XN is a promising α-glucosidase inhibitor, which therefore could be used as functional food to alleviate postprandial hyperglycemia and as a potential candidate for the development of an antidiabetic agent.

Formation of seep carbonates along the makran convergent margin, northern Arabian sea and a molecular and isotopic approach to constrain the carbon isotopic composition of parent methane Formation of seep carbonates along the makran convergent margin, northern Arabian sea and a molecular and isotopic approach to constrain the carbon isotopic composition of parent methane, Chemical Geology (2015), AbstractAuthigenic carbonate deposits have been sampled with the remotely operated vehicle 'MARUM-QUEST 4000 m' from five methane seeps between 731 and 1823 m water depth along the convergent Makran continental margin, offshore Pakistan (northern Arabian Sea).Two seeps on the upper slope are located within the oxygen minimum zone (OMZ; ca. 100 to 1100 m water depth), the other sites are situated in oxygenated water below the OMZ (below 1100 m water depth). The carbonate deposits vary with regard to their spatial extent,sedimentary fabrics, and associated seep fauna: Within the OMZ, carbonates are spatially restricted and associated with microbial mats, whereas in the oxygenated zone below the OMZ extensive carbonate crusts are exposed on the seafloor with abundant metazoans (bathymodiolin mussels, tube worms, galatheid crabs). Aragonite and Mg-calcite are the dominant carbonate minerals, forming common early diagenetic microcrystalline cement and clotted to radial-fibrous cement. The δ 18 O carbonate values range from 1.3 to 4.2‰ V-PDB, indicating carbonate precipitation at ambient bottom-water temperature in shallow sediment depth. Extremely low δ 13 C carbonate values (as low −54.6‰ V-PDB) point to anaerobic oxidation of methane (AOM) as trigger for carbonate precipitation, with biogenic methane as dominant carbon source. Prevalence of biogenic methane in the seepage gas is corroborated by δ 13 C methane values ranging from −70.3 to −66.7‰ V-PDB, and also by back-calculationsconsidering δ 13 C methane values of carbonate and incorporated lipid biomarkers. These calculations (Δδ 13 C methane-carbonate , Δδ 13 C ANME-methane , Δδ 13 C MOX-methane ) prove to be useful to assess the carbon stable isotope composition of seeping methane if this has not been determined in the first place; such an approach represents a useful tool to reconstruct fluid composition of ancient seeps. AOM is also revealed by lipid biomarkers of anaerobic methane oxidizing archaea such as crocetane, pentamethylicosane (PMI), and sn2-hydroxyarchaeol strongly depleted in 13 C (δ 13 C values as low as −127‰ V-PDB). Biomarkers of sulphatereducing bacteria are also abundant, showing slightly less negative δ 13 C values, but still significantly 13 C-depleted (average values as low as −101‰). Other bacterial biomarkers, such as bacteriohopanepolyols (BHPs), hopanols, and hopanoic acids are detected in most carbonates, but are particularly common in seep carbonates from the non-OMZ sites. The BHP patterns of these carbonates and their low δ 13 C values resemble patterns of aerobic methanotrophic bacteria. In the shallower OMZ sites, BHPs revealed much lowe...