Colonic Protein Fermentation and Promotion of Colon Carcinogenesis by Thermolyzed Casein

Thermolyzed casein is known to promote the growth of aberrant crypt foci (ACF) and colon cancer when it is fed to rats that have been initiated with azoxymethane. We speculated that the promotion was a consequence of increased colonic protein fermentation (i.e., that the thermolysis of the casein decreases its digestibility, increases the amount of protein reaching the colon, and increases colonic protein fermentation and that the potentially toxic products of this fermentation promote colon carcinogenesis). We found that the thermolysis of casein reduces its digestibility and increases colonic protein fermentation, as assessed by fecal ammonium and urinary phenol, cresol, and indol-3-ol. Thermolysis of two other proteins, soy and egg white protein, also increases colonic protein fermentation with increased fecal ammonia and urinary phenols, and thermolysis of all three proteins increases the levels of ammonia and butyric, valeric, and i-valeric acids in the cecal contents. We found, however, that the increased protein fermentation observed with thermolysis is not associated with pro-motion of colon carcinogenesis. With casein, the kinetics of protein fermentation with increasing thermolysis time are clearly different from the kinetics of promotion of ACF growth. The formation of the fermentation products was highest when the protein was thermolyzed for one hour, whereas promotion was highest for protein that had been thermolyzed for two or more hours. With soy and egg white, thermolysis increased colonic protein fermentation but did not promote colon carcinogenesis. Thus, although thermolysis of dietary casein increases colonic protein fermentation, products of this fermentation do not appear to be responsible for the promotion of colon carcinogenesis. Indeed, the results suggest that protein fermentation products do not play an important role in colon cancer promotion

Fast method for the determination of short-chain-length polyhydroxyalkanoates (scl-PHAs) in bacterial samples by In Vial-Thermolysis (IVT)

none8siA new method based on the GC–MS analysis of thermolysis products obtained by treating bacterial samples at a high temperature (above 270 C) has been developed. This method, here named “In-Vial- Thermolysis” (IVT), allowed for the simultaneous determination of short-chain-length polyhydrox- yalkanoates (scl-PHA) content and composition. The method was applied to both single strains and microbial mixed cultures (MMC) fed with different carbon sources. The IVT procedure provided similar analytical performances compared to previous Py-GC–MS and Py- GC-FID methods, suggesting a similar application for PHA quantitation in bacterial cells. Results from the IVT procedure and the traditional methanolysis method were compared; the correlation between the two datasets was fit for the purpose, giving a R2 of 0.975. In search of further simplification, the rationale of IVT was exploited for the development of a “field method” based on the titration of thermolyzed samples with sodium hydrogen carbonate to quantify PHA inside bacterial cells. The accuracy of the IVT method was fit for the purpose. These results lead to the possibility for the on-line measurement of PHA productivity. Moreover, they allow for the fast and inexpensive quantification/characterization of PHA for biotechnological process control, as well as investigation over various bacterial communities and/or feeding strategies.mixedF. Abbondanzi; G. Biscaro; G. Carvalho; L. Favaro; P. Lemos; M. Paglione; C. Samorì; C. TorriF. Abbondanzi; G. Biscaro; G. Carvalho; L. Favaro; P. Lemos; M. Paglione; C. Samorì; C. Torr

Thermal Decomposition of Diphenyl Tetroxane in Chlorobenzene Solution

The thermal decomposition of Cyclic Diperoxide of Benzaldehyde 3,6-diphenyl-1,2,4,5-tetroxane, (DFT) in chlorobenzene solution in the studied temperature range (130°C - 166°C) satisfactorily satisfies a first order law up to 60% conversions of diperoxide. DFT would decompose through a mechanism in stages and initiated by the homolytic breakdown of one of the peroxidic bonds of the molecule, with the formation of the corresponding intermediate biradical. The concentration studied was very low, so that the effects of secondary reactions of decomposition induced by free radicals originated in the reaction medium can be considered minimal or negligible. The activation parameters for the unimolecular thermal decomposition reaction of the DFT are ΔH# = 30.52 ± 0.3 kcal·mol-1 and ΔS# = -6.38 ± 0.6 cal·mol-1 K-1. The support for a step-by-step mechanism instead of a process concerted is made by comparison with the theoretically calculated activation energy for the thermal decomposition of 1,2,4,5-tetroxane.Fil: Bordón, Alexander Germán. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas y Naturales y Agrimensura; ArgentinaFil: Pila, Andrea Natalia. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas y Naturales y Agrimensura; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Modelado e Innovación Tecnológica. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas Naturales y Agrimensura. Instituto de Modelado e Innovación Tecnológica; ArgentinaFil: Profeta, Mariela Inés. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas y Naturales y Agrimensura; ArgentinaFil: Jorge, María J.. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas y Naturales y Agrimensura; ArgentinaFil: Jorge, Lilian Cristina. Universidad Nacional del Nordeste. Facultad de Ciencias Veterinarias; ArgentinaFil: Romero, Jorge Marcelo. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas y Naturales y Agrimensura; ArgentinaFil: Jorge, Nelly Lidia. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas y Naturales y Agrimensura; Argentin

Thermal degradation of citrus pectin in low-moisture environment - Influence of acidic and alkaline pre-treatment

Pectin powder is degraded during storage and transport by demethoxylation and depolymerisation. The degradation mechanisms and especially the influence of pre-treatments on the degradation reactions are not completely understood. In this study, commercial citrus pectin was modified by either acidic or alkaline demethoxylation. The modified pectins, as well as the commercial pectin, were thermally degraded during four weeks of storage at 60 °C and 80% relative humidity. Demethoxylation and depolymerisation as well as colour alterations were examined during degradation, and the course of the reactions was monitored. It was found that the type of pre-treatment during modification determined the material properties and, thus, the water uptake of the modified pectin powders. The resulting water availability in the samples was crucial to the extent of demethoxylation and to the type and intensity of depolymerisation since some of these reactions competed for the water in the climate chamber. The pre-treatment also determined the content of neutral sugars and sodium ions of the modified pectins. High contents of these components limited the extent of degradation in different ways. A previously assumed third depolymerisation mechanism of pectins, beside backbone hydrolysis and β-elimination, was confirmed.DFG, 268547215, Strukturabhängige Abbaureaktionen von Pektinen und deren Auswirkungen auf nicht-enzymatische Bräunung und technologische Funktionalitä

Dehydroalanine and Lysinoalanine in Thermolyzed Casein do not Promote Colon Cancer in the Rat

Thermolysis of proteins produces xenobiotic amino-acids such as the potentially toxic lysinoalanine, and the alkylating agent, dehydro¬alanine, which have been considered possible health hazards. We observed that thermolysed casein promoted aberrant crypt foci (ACF) and colon cancer growth in rats initiated with azoxymethane and speculated that promotion might be due to the formation of these compounds. To test this notion we first measured the concentration of the modified amino acids as a function of thermolysis time. The concentration of dehydroalanine in the casein paralleled the degree of promotion, that of lysinoalanine did not. We then tested diets containing foods with high levels of dehydroalanine (thermolysed sodium-caseinate, cooked Swiss cheese) for their effect on ACF promotion. They decreased the number and/or size of ACF significantly, indicating that dehydroalanine did not promote, but protected rats against colon carcinogenesis. These results do not support the notion that lysinoalanine or dehydroalanine are a hazard with respect to colon carcinogenicity

Thermolabile protecting groups in metal-organic frameworks : a thesis presented in partial fulfilment of the requirements of the degree of Doctor of Philosophy in Chemistry at Massey University, Manawatu, New Zealand

Prior to the work carried out for this thesis, there were no publications in which bpy was used as a ligand backbone, or in which a carboxylate was incorporated into a MOF using a TPG. Also, to the best of our knowledge there are no examples in the literature of an ethyl carbamate TPG in MOFs. In this thesis the range of TPG protected ligands has been expanded to include 1,4-bdc (Chapter 2) and bpy (Chapters 4 and 5). The bpy-NHBoc and bpy-TBE materials are the first examples of N-donor type ligands protected by TPGs. Furthermore, the bpy-TBE ligand is the first example of a TPG protected carboxylate in a MOF. In Chapter 2, 1,4-bdc-NH2 was protected as both the ethyl carbamate and the tert-butylcarbamate, giving 1,4-bdc-NHCOOEt and 1,4-bdc-NHBoc, which there then incorporated into a MOF-5-type framework. It was envisaged that thermolysis of the carbamate esters could generate an isocyanate group, though this was not expected for 1,4-bdc-NHBoc due to the tendency of tert-butylcarbamates to decompose to the amine. Despite thermolysis on the TGA apparatus only generating the amine, it was found that thermolysis under vacuum enabled not only enabled ~ 60 % conversion of the ethylcarbamate to 1,4-bdc-NCO, but also a ~20 % conversion of the tert-butylcarbamate to 1,4-bdc-NCO. The MOF-5 analogues in this work also proved sufficiently stable to survive the thermolysis conditions with little discernible effect on the porosity of the material. In Chapter 3, 1,3-bdc-NH2 was protected as both the ethyl carbamate and the tert-butylcarbamate, giving 1,3-bdc-NHCOOEt and 1,3-bdc-NHBoc, which there then incorporated into a lon-e-type framework. It became apparent the lon-e was a poor choice in MOF for use with TPGs as the framework was prone to collapse from desolvation, and it was not possible to thermolyse the materials without complete collapse of the MOFs. In Chapter 4, bpy-NH2 and bpy-CO2H were protected with TPGs to give bpy-NHBoc and bpy-TBE respectively. The ligands were combined with bpdc and zinc to obtain the BMOF-1-bpdc analogues MUF20-Aβ and MUF20-Aγ. Whilst the thermolysed materials MUF20-Aβt and MUF20-Aγt demonstrated significant gas uptakes compared to their protected counterparts, comparison of MUF20-Aβt with the directly synthesised material MUF20-Aβ’ revealed significantly higher uptakes than the thermolysed materials. This discrepancy indicates that the BMOF-1-bpdc/MUF20 framework is partially degraded under thermolysis conditions. These results strongly imply that this framework is not compatible with TPGs. However, TPGs did allow for the installation of a carboxylate group into the BMOF-1-bpdc/MUF20 framework which was not obtainable through direct synthesis methods. In Chapter 5, bpy-TBE was combined with btb and Zn/Cu to obtain Zn-DUT-23-TBE and Cu-DUT-23-TBE. These materials were then thermolysed to produce Zn/Cu-DUT-23-CO2H, materials that were not able to be directly synthesised using bpy-CO2H. Unfortunately, the thermolysed materials demonstrated significant decreases in uptakes compared to their protected counterparts. However, the TPG containing materials also had markedly lower uptakes than the parent Zn-DUT-23 and Cu-DUT-23 materials, which has been attributed to pore collapse. This partial pore collapse may have sufficiently weakened the MOF framework to increase its sensitivity to the thermolysis conditions, resulting in a much larger decrease in uptake than would have been the case with a defect free material. The results of this thesis revealed that MOF stability is a key factor in the compatibility of a material. Specifically, the MOF must be resistant to solvent removal and subsequent heating at elevated temperatures for extended periods. This is most clearly observed in Chapter 3, where the lon-e materials were very susceptible to solvent removal, and later were completely collapsed by thermolysis. These findings have led to the recommendations outlined in section 6.2 for the screening of MOFs for their compatibility with TPGs

Cinètica de la reacció de descomposició tèrmica de l’ascaridol en dissolució

Existen diferencias entre los valores de algunas propiedades físicas de ascaridol natural aislado del vegetal denominado vulgarmente «Paico» (Chenopodium ambrosioides L., Chenopodiaceae) y la sustancia sintética obtenida mediante la reacción de fotooxigenación de α-terpineno. Es más, el uso de decocciones de dicha planta, utilizadas como medicina antihelmíntica en los humanos, ha despertado un debate científico debido a las propiedades tóxicas atribuídas a su principio activo (ascaridol), el cual sería responsable de la muy conocida acción beneficiosa. En este trabajo se ha realizado la preparación de esa sustancia por el método de Schenck, pero trabajando a 0 ºC con alcohol isopropílico como solvente y efectuando su separación y purificación a temperatura ambiente por cromatografía en columna preparativa, a fin de prevenir su degradación térmica. De esta manera se obtuvieron excelentes rendimientos de ascaridol (ca. 99% GC-FID), de un alto grado de pureza (> 98% GC; RP-HPLC; 1 H y 13C RMN). Además, se informan aquí los parámetros de activación de la reacción de descomposición térmica de ascaridol en solución de n-hexano, alcohol isopropílico y metanol, en el ámbito de temperaturas de 120ºC a 170ºC. Es evidente también un efecto de solvente en la homólisis unimolecular de esa sustancia.Discrepancies exist between the values of some physical properties of ascaridole isolated from the vegetal named «Paico» (Chenopodium ambrosioides L., Chenopodiaceae) and the synthetic substance obtained by the photoxygenation reaction of α-terpinene. Moreover, the use of decoctions of the above mentioned plant as anthelmintic medicine in humans arouse a scientific debate because of toxic properties attributed to its main active drug (ascaridole), which would be responsible of the well-known beneficial action. This lead to perform here the preparation of that substance by Schenck’s method, but working at 0 ºC with isopropyl alcohol as solvent and doing its separation and purification at room temperature by preparative column chromatography to prevent its thermal degradation. Thus, excellent yields of ascaridole were obtained (ca. 99 % GC-FID) of high degree of purity (> 98% GC; RP-HPLC; 1 H and 13C NMR). Furthermore, the kinetics of the thermal stability of ascaridole in solution is now advanced, reporting the activation parameters values for their decomposition reactions in n-hexane, isopropyl alcohol and methanol, in the 120º170 ºC temperature range. A solvent effect on the unimolecular homolysis of that substance is also evident.  Hi ha diferències entre els valors d’algunes propietats fisiques de l’ascaridol natural, aïllat del vegetal dit vulgarment «Paico» (Chenopodium ambrosioides L., Chenopodiaceae), i la substància sintètica obtinguda mitjançant la reacció de fotooxigenació d’α-terpinè. Encara més, l’ús de decoccions de l’esmentada planta, emprades com a medicina antihelmíntica en humans, ha despertat un debat científic, donades les propietats tòxiques atribuïdes al seu principi actiu (ascaridol), que seria el responsable de la molt coneguda acció beneficiosa. En aquest treball, s’ha realitzat la preparació d’aquesta substància pel mètode de Schenck, però treballant a 0 ºC amb alcohol isopropílic com a dissolvent i efectuant la seva separació i purificació a temperatura ambient mitjançant cromatografia de columna preparativa, per tal de prevenir la seva degradació tèrmica. D’aquesta manera, s’obtenen excel.lents rendiments d’ascaridol (ca. 99% GC-FID), d’un alt grau de puresa (> 98% GC; RP-HPLC; 1 H i 13C RMN). A més, es presenten els paràmetres d’activació de la reacció de descomposició tèrmica de l’ascaridol en dissolució de n-hexà, alcohol isopropílic i metanol, en el marge de temperatures de 120ºC a 170 ºC. Així mateix, és evident un efecte del dissolvent en l’homòlisi unimolecular d’aquesta substància.Fil: Cafferata, Lazaro. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Química. Laboratorio de Estudio de Compuestos Orgánicos; ArgentinaFil: Jeandupeux, R.. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Química. Laboratorio de Estudio de Compuestos Orgánicos; ArgentinaFil: Cañizo, Adriana Ines. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Química. Laboratorio de Estudio de Compuestos Orgánicos; Argentin

Synthesis and Reactivity of Iridium(III) Dihydrido Aminocarbenes

Iridium complexes supported by the PNP amidophosphine scaffold (PNP = [N(2-PiPr2-4-Me-C6H3)2]−) perform the selective double C−H activation of methyl amines to produce iridium(III) dihydrido aminocarbenes. The reactivity of these complexes is presented and contrasted with that observed for the previously reported iridium(I) alkoxycarbenes

Thermal degradation of Cross-Linked Polyisoprene and Polychloroprene

Polyisoprene and polychloroprene have been cross-linked either in solution or in solid state using free radical initiators. In the comparable experimental conditions higher cross-linking density was observed in the solid state process. Independent of the cross-linking method, polychloroprene tended to give a higher gel content and cross-link density than does polyisoprene. Infrared characterization of the cross-linked materials showed cis-trans isomerization occurred in the polyisoprene initiated by benzoyl peroxide, whereas no isomerization was found in the samples initiated by dicumyl peroxide. Polyisoprene does not cross-link by heating in a thermal analyzer, whereas polychloroprene easily undergoes cross-linking in such conditions. Infrared spectroscopy showed that in the case of polyisoprene, rearrangements occur upon heating which lead to the formation of terminal double bonds, while polychloroprene loses hydrogen chlorine which leads to a conjugated structure. There is apparently some enhancement of the thermal and thermal oxidative stability of polyisoprene because of the cross-linking. Cross-linked polychloroprene is less thermally stable than the virgin polymer. Cross-linking promotes polymers charring in the main step of weight loss in air, which leads to enhanced transitory char