Solution structures of spinach acyl carrier protein with decanoate and stearate.
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Acyl carrier protein (ACP) is a cofactor in a variety of biosynthetic pathways, including fatty acid metabolism. Thus, it is of interest to determine structures of physiologically relevant ACP-fatty acid complexes. We report here the NMR solution structures of spinach ACP with decanoate (10:0-ACP) and stearate (18:0-ACP) attached to the 4'-phosphopantetheine prosthetic group. The protein in the fatty acid complexes adopts a single conformer, unlike apo- and holo-ACP, which interconvert in solution between two major conformers. The protein component of both 10:0- and 18:0-ACP adopts the four-helix bundle topology characteristic of ACP, and a fatty acid binding cavity was identified in both structures. Portions of the protein close in space to the fatty acid and the 4'-phosphopantetheine were identified using filtered/edited NOESY experiments. A docking protocol was used to generate protein structures containing bound fatty acid for 10:0- and 18:0-ACP. In both cases, the predominant structure contained fatty acid bound down the center of the helical bundle, in agreement with the location of the fatty acid binding pockets. These structures demonstrate the conformational flexibility of spinach ACP and suggest how the protein changes to accommodate its myriad binding partners. (+info)
Potential carcinogenicity of food additives and contaminants.
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The potential role in carcinogenesis of food additives and contaminants presents a complex problem in terms of assessing the risk to the general public. Long-term testing in laboratory animals is still the most feasible method for determining potential carcinogenicity of various chemicals. The disadvantages encountered in the present methods of animal testing are discussed and a review is made of the current status of particular food additives and contaminants under scrutiny as possible carcinogens. It is suggested that, since it may not be possible to remove all carcinogenic materials from the environment, methods to mitigate or neutralize their harmful effects should be sought. Greater cooperation is called for among food technologists, toxicologists, laboratory researchers, and epidemiologists in the decision-making process regarding the role of possibly carcinogenic additives and contaminants. (+info)
Antitumor activity and pharmacokinetics of liposomes containing lipophilic gemcitabine prodrugs.
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BACKGROUND: Gemcitabine is a deoxycytidine analogue that exhibits antitumoral activity against adenocarcinomas of the colon, lung and pancreas. After intravenous injection, gemcitabine is rapidly converted to the inactive metabolite 2'-deoxy-2',2'-difluorouridine by cytidine deaminase. MATERIALS AND METHODS: To improve the pharmacokinetic behavior and the antitumor activity of the drug, the gemcitabine prodrug, 4-(N)-stearoylgemcitabine (C18gem) was incorporated in liposomes and both the pharmacokinetic and the in vivo activity of this formulation intravenously or peritumorally administered in nude female CR1:Nu/Nu(CD-1)BR mice grafted with HT-29 and KB 396p cells were studied. RESULTS: The C18gem-liposomes showed both higher plasma half life and tumor regression than control and gemcitabine. CONCLUSION: The incorporation of C18gem-prodrug in liposomes increased the plasma half life of the drug resulting in increased accumulation in the tumor cells and a higher level of antitumoral efficacy. The results obtained with different tumors sensitive to gemcitabine support the efficacy of this proposed drug delivery system. (+info)
Efficient cytoplasmic protein delivery by means of a multifunctional envelope-type nano device.
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The potential for protein therapy, such as the use of antibodies, and vaccines is now well accepted. However, it is difficult to enhance efficiency in protein therapy without a suitable delivery system for delivering proteins to target sites. Here we describe the development of protein delivery system, which is capable of cytoplasmic delivery as well as efficient packaging. The multifunctional envelope-type nano device (MEND), which was originally developed for the delivery of nucleic acids such as plasmid DNA and oligodeoxynucleotides, can also be applied to protein delivery. In this study, the green fluorescent protein (GFP), a model protein, was condensed with stearyl octaarginine (stearyl R8) to form a nano particle, which was then coated with a lipid membrane, thus permitting R8 to be introduced for efficient cellular uptake and controlled intracellular trafficking. The packaging efficiency of the MEND was significantly higher than that of conventional liposomes, because the GFP can be encapsulated a condensed form. According to confocal laser scanning microscopy, the MEND is internalized efficiently and escapes from the acidic compartment to efficiently release GFP into the cytosol. These results indicate that the MEND can serve as a useful cytoplasmic delivery system for protein therapy. (+info)
Regulation of carbohydrate metabolism in lymphoid tissue. Nature of the endogenous substrates and their contribution to the respiratory fuel of the sliced rat spleen in vitro.
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1. Tissue glycogen contributes, maximally, only 10% of the respiratory fuel of the rat spleen slice in the absence of an added carbon source, and makes no significant contribution when glucose (3mM) is added. 2. The reserves of fatty acid in the form of triglyceride (35.5mumol of fatty acid/g dry wt. of tissue) fall by approx. 25% after incubation of spleen slices with or without added glucose for 2h, and , on this basis, account for 32% of the oxidative fuel. 3. In contrast, the total oxidative contribution of fatty acid reserves to the respiratory fuel, determined on the basis of inhibiton of respiration by 2-bromostearate, is 42-52%. This range includes tissue from both starved and well-fed animals and is not significantly altered by the presence of added glycose (3mM). 4. Large quantities of NH3 (31-35mumol//h per g dry wt. of tissue) are produced by spleen slices incubated in the absence of added substrates, and this value is suppressed by approx. 50% on incubation with glucose (3mM). Adenine nucleotide breakdown can account for only 17% of the total ammonia produced. 5. Individual free amino acid concentrations in spleen were determined, both in vivo and in slices before and after 60 min of incubation. Although the total free amino acid pool size increases by 45% during incubation, owing to protein breakdown, the tissue concentrations of aspartate, glutamate, glutamine and alanine do not increase. It is suggested that these amino acids areoxidized in a net sense to CO2 and water with the liberation of free NH3 via transamination reactions, glutaminase, the purine nucleotide cycle and the tricarboxylic acid cycle. 6. It is concluded that the normal endogenous metabolism of sliced rat spleen (43-52% due to lipids, 30% due to amino acids and 10% due to glycogen) is modified by added glycose only to the extent that glycogen oxidation and 50% of the contribtion made by ino acids are suppressed; endogenous lipid metabolism is unaffected. (+info)
Suppressed catalytic efficiency of plasmin in the presence of long-chain fatty acids. Identification of kinetic parameters from continuous enzymatic assay with Monte Carlo simulation.
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Ethanol contamination leads to Fatty acid ethyl esters in hair samples.
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The diagnosis of alcoholism is a topical subject of discussion; in fact, many studies have been published on the determination of biochemical markers useful to this target. Fatty acid ethyl esters (FAEE) are minor metabolites of ethanol, and their usefulness has been demonstrated by their detection in hair using a headspace solid-phase microextraction-gas chromatographic-mass spectrometric technique. Environmental contamination in the analysis of drugs of abuse is a well-known focus of discussion between scientists. In the same way, interference from the surroundings could be hypothesized in FAEE detection. To assess the influence of ethanol contamination, an in vitro experiment was performed, leaving hair in an atmosphere saturated with ethanol vapors for 15 days. The spontaneous production of FAEE was demonstrated by analyzing hair day by day. In fact, we observed a constant increase of ethyl myristate, palmitate, and stearate that reached very high concentrations at the end of the investigation. Although the experiment was managed in a stressed way and could not represent real life, its purpose was to focus the attention of researchers on the problem of hair contamination that can occur, for example, with ethanol-containing cosmetics. Therefore, care in interpretation must be taken into account, especially with such a volatile molecule. (+info)
Comparison of hydrogen bonding for chiral and racemic 1-monostearoylglycerols in solvent.
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Comparison of the hydrogen bonding of racemic RS-1-monostearoylglycerol and chiral S-1-monostearoylglycerol in benzene was carried out through the NMR measurement. In addition, the concentration dependence of a chirality of S-1-monostearoylglycerol in hexane was studied though UV and circular dichroism (CD) measurements. The chemical shifts of OH protons of the S- and RS-1- monostearoylglycerols indicated that the hydrogen bonding between the R- and S-form molecules of RS-1-monostearoylglycerol is stronger than that between the S- and S-form molecules of S-1-monostearoylglycerol in the low concentration region and that the difference in the strength of hydrogen-bonding between them becomes small in the high concentration region. The chirality of the S-1-monostearoyglycerol in hexane decreased with increasing its concentration. This suggests that the association of chiral S-1-monoacylglycerol arising from its increasing concentration reduces the chirality of S-1-monostearoylglycerol. (+info)