Influence of TiO2 on prebiotic thermal synthesis of the Gly-Gln polymer.

The role of the titanium dioxide (rutile and anatase) with and without room light on the thermal synthesis of the glycine-L-glutamine (Gly-Gln) polymer is described. The efficiency in percentage of polymerization with room light was increased in 6% in the presence of rutile and in 23% in the presence of anatase. The thermal synthesis in the molten state was carried out in the absence and presence of both oxides. In all cases, the vibrational spectra showed characteristic group frequencies corresponding to a polypeptide structure. No spectral differences were observed by room light effect on the polymer on rutile. However, the polymer obtained in the presence of anatase and room light shows spectral changes associated with the formation of shorter new abundant and conformationally different species compared with the original polymer. The SEM-EDX characterization of the solid phase involved in the thermal synthesis showed that the morphology of the polypeptide is different in the presence of rutile compared to anatase. The SDS-PAGE and GPC results suggest that smaller chains are formed in the presence of both oxides and the distribution of the size and weight of each polymer molecule is completely different when the condensation is performed in the presence of anatase or rutile. Nuclear magnetic resonance analyses confirmed the incorporation of both Gly and Gln residues in the polymers, with a prevalence of Gly. Both possible sequences N-GlyGln-C and N-GlnGly-C were also detected.

Synthesis, biological evaluation, and pharmacophore generation of uracil, 4(3H)-pyrimidinone, and uridine derivatives as potent and selective inhibitors of parainfluenza 1 (Sendai) virus.

Several new 6-oxiranyl-, 6-oxiranylmethyluracils, and pyrimidinone derivatives, synthesized by lithiation-alkylation sequence of 1,3,6-trimethyluracil, 1,3-dimethyl-6-chloromethyluracil, and 2-alkoxy-6-methyl-4(3H)-pyrimidinones, showed a potent and selective antiviral activity against Sendai virus (SV) replication. To gain insight into the structural features required for SV inhibition activity, the new compounds were submitted to a pharmacophore generation procedure using the program Catalyst. The resulting pharmacophore model showed high correlation and predictive power. It also rationalized the relationships between structural properties and biological data of these inhibitors of SV replication.

A possible prebiotic synthesis of purine, adenine, cytosine, and 4(3H)-pyrimidinone from formamide: implications for the origin of life.

The synthesis of prebiotic molecules is a major problem in chemical evolution as well as in any origin-of-life theory. We report here a plausible new prebiotic synthesis of naturally occurring purine and pyrimidine derivatives from formamide under catalytic conditions. In the presence of CaCO(3) and different inorganic oxides, namely silica, alumine, kaolin, and zeolite (Y type), neat formamide undergoes the formation of purine, adenine, cytosine, and 4(3H)-pyrimidinone, from acceptable to good yields. The role of catalysts showed to be not limited to the improvement of the yield but it is also relevant in providing a high selectivity in the products distribution.

The reactivity of phenolic and non-phenolic residual kraft lignin model compounds with Mn(II)-peroxidase from Lentinula edodes.

Three phenolic model compounds representing bonding patterns of residual kraft lignin were incubated with manganese peroxidase from Lentinula edodes. Extensive degradation of all the phenolic models, mainly occurring via side-chain benzylic oxidation, was observed. Among the tested model compounds the diphenylmethane alpha-5 phenolic model was found to be the most reactive, yielding several products showing oxidation and fragmentation at the bridging position. The non-phenolic 5-5' biphenyl and 5-5' diphenylmethane models were found unreactive.

19F nuclear magnetic resonance spectroscopy for the quantitative detection and classification of carbonyl groups in lignins.

A novel method that permits the quantitative detection and classification of various carbonyl groups in lignins has been developed. The proposed method was optimized with the quantitative trifluoromethylation of a series of carbonyl-containing lignin-like model compounds. This effort was followed by (19)F NMR spectral analyses of the resulting fluorine derivatives allowing for a thorough understanding of their structure/(19)F chemical shift relationships. The various carbonyl groups present in lignins were also investigated by trifluoromethylating them in the presence of catalytic amounts of tetramethylammonium fluoride (TMAF), followed by hydrolysis with TMAF in tetrahydrofuran. By using a variety of selective reactions, it became possible to assign a number of prominent (19)F NMR signals to a variety of carbonyl groups present in lignins. These studies demonstrated that the proposed method can be applied to the quantitative determination of carbonyl groups that are present in soluble native and technical lignins.

Biomimetic degradation of lignin and lignin model compounds by synthetic anionic and cationic water soluble manganese and iron porphyrins.

The biomimetic oxidation of 5-5' condensed and diphenylmethane lignin model compounds with several water soluble anionic and cationic iron and manganese porphyrins in the presence of hydrogen peroxide is reported. The oxidative efficiency of manganese and iron meso-tetra(2,6-dichloro-3-sulphonatophenyl) porphyrin chloride (TDCSPPMnCl and TDCSPPFeCl, respectively), meso-tetra-3-sulphonatophenyl porphyrin chloride (TSPPMnCl) and manganese meso-tetra(N-methylpyridinio)porphyrin pentaacetate (TPyMePMn(CH3COO)5) was compared on the basis of the oxidation extent of the models tested. Manganese porphyrins were found more effective in degrading lignin substructures than iron ones. Among them the cationic TPyMePMn (CH3COO)5, never used before in lignin oxidation, showed to be the best catalyst. The catalytic activity of porphyrins in hydrogen peroxide oxidation of residual kraft lignin was also investigated. The use of quantitative 31P NMR allowed the focusing on the occurrence of different degradative pathways depending on the catalyst used. TPyMePMn(CH3COO)5 was able to perform the most extensive degradation of the lignin structure, as demonstrated by the decrease of aliphatic hydroxyl groups and carboxylic acids. Noteworthy, no significant condensation reactions occurred during manganese porphyrins catalyzed oxidations of residual kraft lignin, while in the presence of iron porphyrins a substantial increase of condensed substructures was detected.

Structural modifications induced during biodegradation of wheat lignin by Lentinula edodes.

The structural modifications occurring during wheat straw lignin biodegradation were evaluated by the concerted use of 31P-, 1H- and 2D homo- and heteronuclear NMR spectroscopies. Straw lignin was found to be oxidatively degraded via stereoselective side-chain oxidation as evidenced by a lower erythro/threo ratio. Significantly lower amounts of phenolic hydroxy and methoxy groups in the decayed lignin may be indicative that its structure after the fungal treatment contained a lower amount of aromatic units. In addition an increase in carboxylic acids content, that cannot be explained only on the basis of side-chain oxidation reactions, was also apparent. This evidence, coupled with pertinent data collected during this effort, suggests the occurrence of aromatic ring cleavage reactions. In fact the oxidative degradation of lignin model compounds by fungi has been reported to occur via the 3-oxoadipate pathway which is known to cause aromatic ring cleavage with the formation of aliphatic chains. The presence of aliphatic moieties in the decayed lignin was confirmed by detailed 1H- and 2D NMR spectroscopic analyses.

The biodegradation of recalcitrant effluents from an olive mill by a white-rot fungus.

Biodegradation of olive-mill wastewater (OMW) was performed by the polyurethane-immobilized mycelium of Lentinula edodes. Throughout three consecutive treatment cycles of the effluent significant abatements of its polluting characteristics were observed. In fact, its contents in total organic carbon, total phenols, total ortho-diphenol were dramatically reduced. In addition, a significant effluent decolorization was evident.

The early oxidative biodegradation steps of residual kraft lignin models with laccase.

A number of model compounds resembling the fundamental bonding patterns of residual kraft lignin, including a series of stilbenes, were incubated with laccase from Trametes versicolor in the presence and absence of delignification 'mediators' ABTS and HBT. The condensed kraft lignin model compounds seem to undergo initial degradation by laccase mainly via benzylic oxidation, demethylation and hydroxylation reactions. Phenolic 5-5', diphenylmethane and alpha-5 lignin models were found to be degraded mainly via side-chain oxidation reactions. Among the models studied, a phenolic stilbene was found to be the most reactive, yielding several products showing side-chain oxidation/transposition, demethoxylation and hydroxylation reactions. Non-phenolic 5-5', diphenylmethane and stilbene model compounds were found unreactive even in the presence of the laccase-mediator system.

A potent and selective inhibition of parainfluenza 1 (Sendai) virus by new 6-oxiranyl-, 6-methyloxiranyluracils, and 4(3H)-pyrimidinone derivatives.

Several new 6-oxiranyl-, 6-methyloxiranyluracils, and pyrimidinone derivatives, synthesized by the lithiation-alkylation sequence of 1,3,6-trimethyluracil, 1,3-dimethyl-6-chloromethyluracil, and 2-alkoxy-6-methyl-4(3H)-pyrimidinones, showed a potent and selective antiviral activity against the parainfluenza 1(Sendai) virus replication.

Mechanism of degradation of 2'-deoxycytidine by formamide: implications for chemical DNA sequencing procedures.

We describe the reaction of formamide with 2'-deoxycytidine to give pyrimidine ring opening by nucleophilic addition on the electrophilic C(6) and C(4) positions. This information is confirmed by the analysis of the products of formamide attack on 2'-deoxycytidine, 5-methyl-2'-deoxycytidine, and 5-bromo-2'-deoxycytidine, residues when the latter are incorporated into oligonucleotides by DNA polymerase-driven polymerization and solid-phase phosphoramidite procedure. The increased sensitivity of 5-bromo-2'-deoxycytidine relative to that of 2'-deoxycytidine is pivotal for the improvement of the one-lane chemical DNA sequencing procedure based on the base-selective reaction of formamide with DNA. In many DNA sequencing cases it will in fact be possible to incorporate this base analogue into the DNA to be sequenced, thus providing a complete discrimination between its UV absorption signal and that of the thymidine residues. The wide spectrum of different sensitivities to formamide displayed by the 2'-deoxycytidine analogues solves, in the DNA single-lane chemical sequencing procedure, the possible source of errors due to low discrimination between C and T residues.

Production and isolation of chitosan by submerged and solid-state fermentation from Lentinus edodes.

A method for the laboratory-scale production and isolation of chitosan (polyglucosamine) by liquid and solidstate fermentation from Lentinus edodes was developed. The yields of isolated chitosan were 120 mg/L of fermentation medium under liquid fermentation conditions and 6.18 g/kg of fermentation medium under solid-state fermentation conditions. The latter method, which gives up to 50 times yields than other chitosan production methods from fungi, provides a new flexible and easily scaledup procedure for the production of low acetylation degree chitosan.