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Magnetic resonance imaging examinations are frequently carried out using contrast agents to improve the image quality. Practically all clinically used contrast agents are based on paramagnetic metals and lack in selectivity and specificity. A group of stable organic radicals, nitroxides, has raised interest as new metal-free contrast agents for MRI. Their structures can easily be modified to incorporate different functionalities. In the present study, a stable nitroxide TEEPO (2,2,6,6-tetraethylpiperidin-1-oxyl) was linked to a glucose moiety (Glc) to construct a water-soluble, potentially tumor-targeting compound with contrast-enhancing ability. The ability was assessed with in vivo MRI experiments. The constructed TEEPO-Glc agent proved to shorten the T 1 relaxation time in tumor, while the T 1 time in healthy brain tissue remained the same. The results indicate the potential of TEEPO-Glc as a valuable addition to the growing field of metal-free contrast enhancement in MRI-based diagnostics.

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Cancer is a widespread and life-threatening disease and its early-stage diagnosis is vital. One of the most effective, non-invasive tools in medical diagnostics is magnetic resonance imaging (MRI) with the aid of contrast agents. Contrast agents that are currently in clinical use contain metals, causing some restrictions in their use. Also, these contrast agents are mainly non-specific without any tissue targeting capabilities. Subsequently, the interest has notably increased in the research of organic, metal-free contrast agents. This study presents a new, stable organic radical, TEEPO-Met, where a radical moiety 2,2,6,6-tetraethylpiperidinoxide (TEEPO) is attached to an amino acid, methionine (Met), as a potentially tumour-targeting moiety. We describe the synthesis, stability assessment with electron paramagnetic resonance (EPR) spectroscopy and relaxation enhancement abilities by an in vitro nuclear magnetic resonance (NMR) and phantom MRI studies of TEEPO-Met. The new compound proved to be stable notably longer than the average imaging time in conditions mimicking a biological matrix. Also, it significantly reduced the relaxation times of water, making it a promising candidate as a novel tumour targeting contrast agent for MRI.

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This report describes an efficient procedure for the generation and isolation of various thymine and thymidine 5,6-epoxides from the corresponding trans-5,6-bromohydrins by reaction with triethylamine. The quantitative isolation of the epoxides, accomplished by solvent precipitation of triethylamine hydrobromide, enabled their regiospecific ring-opening at C6 position by organometallic nucleophiles. The reaction was amenable to a broad range of alkyl, aryl, alkenyl, and alkynyl organomagnesium, -zinc, -aluminum, or -boron reagents, although the reactivity was strongly affected by the electronic effects of N3 protecting group. Additionally, the reaction featured excellent cis-diastereoselectivity providing access to C6-carbon-functionalized dihydrothymidine cis-alcohols, which are synthetic derivatives of UV-induced DNA lesions, namely, thymidine (6-4) photoproducts.

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The synthesis and characterization of aminoacetyl cellulose and thioacetyl cellulose is presented in this paper. Cellulose was first chemically modified with chloroacetyl chloride using N,N-dimethylformamide (DMF) as reaction medium. The maximum substitution of hydroxyl groups of cellulose was achieved reacting in the presence of 6 equiv. of chloroacetyl chloride over 24 h at 60 °C. DMF were then recovered by fractional distillation of the media. In the next step, chloroacetyl cellulose was reacted with either secondary amines or thiols. The reactions were initially heterogeneous in hot DMF. As the reactions proceeded, homogenous mixtures were obtained. Highly substituted cellulose derivatives were achieved via this method. The success of the reactions was confirmed by ATR-IR and NMR spectroscopy. Various pulps were used as cellulose source. The resulting products were found to be thermally stable and have glass transition temperatures around 120 °C. Gel permeation chromatography (GPC) indicated that degradation of the cellulose backbone had occurred. The cellulose derivatives were then processed into films. Their potential, as packaging films, was then studied from the view-point of their moisture and oxygen barrier properties, as well as their tensile properties.

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NMR analysis of complex mixtures can be significantly simplified using polyethyleneglycol (PEG) as resolving additive in DOSY NMR technique, which allows the extraction of individual spectra of mixture components with differing polarity. Resolving power of PEG-assisted DOSY was demonstrated with natural product mixtures.

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Zn pyro-pheophorbide a and fulleronicotine form in nonpolar solvents a supramolecular self-assembled electron donor-acceptor dyad, which performs fast photoinduced charge separation (0.5 ps) and slow recombination (>1 ns) as evidenced by photochemical studies.

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A polymer assisted liquid state DOSY NMR technique, to extract the spectra of the individual components from mixtures in CDCl(3), is demonstrated. The enhancement of diffusion coefficient differences is achieved using a soluble polymer, polyvinylpyrrolidone, as the "stationary phase". The "separation" of analytes resembles normal-phase chromatography, for example, TLC. This method provides a fast, cheap, and simple technique to resolve the NMR spectra of complex mixtures.

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Pyrene mediated noncovalent attachment of a chlorophyll derivative, pyro-pheophorbide a, to a soluble single wall carbon nanotube is reported and the resultant CD, UV-Vis absorbance, fluorescence and 1H NMR spectra are discussed.

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