Dimethylsulfoxide oxidizes glutathione in vitro and in human erythrocytes:kinetic analysis by 1H NMR

The interaction of dimethylsulfoxide (Me2SO) with glutathione was investigated under non-equilibrium conditions in solution using 1H NMR and in intact erythrocytes using 1H spin-echo NMR. In solution the reaction was observed to follow second-order kinetics (Rate = k1[glutathione][Me2SO]) at 300 K pH 7.4, ksol = 4.7 × 10-5 mol -1 L1 s-1. In intact erythrocytes the rate constant for the cellular environment, kcell, was found to be slightly larger at 8.1 × 10-5 mol-1 L1 s-1. Furthermore, the reaction of Me2SO with erythrocyte glutathione showed a biphasic dependence on the Me2SO concentration, with little oxidation of glutathione occurring until the Me2SO concentration exceeded 0.5 mol L-1. The results suggest that at lower concentrations, Me2SO can be effectively removed, most probably by reaction with glutathione, which is regenerated by glutathione reductase, although preferential reaction with other cellular components (e.g., membrane or cellular thiols) cannot be ruled out. Thus the concentrations of Me2SO that are commonly used in cryopreservation of mammalian cells (∼1.4 mol L-1) can cause oxidation of intracellular glutathione.

Drying kinetic analysis of municipal solid waste using modified page model and pattern search method

This work studied the drying kinetics of the organic fractions of municipal solid waste (MSW) samples with different initial moisture contents and presented a new method for determination of drying kinetic parameters. A series of drying experiments at different temperatures were performed by using a thermogravimetric technique. Based on the modified Page drying model and the general pattern search method, a new drying kinetic method was developed using multiple isothermal drying curves simultaneously. The new method fitted the experimental data more accurately than the traditional method. Drying kinetic behaviors under extrapolated conditions were also predicted and validated. The new method indicated that the drying activation energies for the samples with initial moisture contents of 31.1 and 17.2 % on wet basis were 25.97 and 24.73 kJ mol−1. These results are useful for drying process simulation and industrial dryer design. This new method can be also applied to determine the drying parameters of other materials with high reliability.

Renal dopamine and salt-retaining states

Although generally regarded as a neurotransmitter, dopamine is also known to be secreted by the kidney whereby it promotes sodium excretion in its role as a natriuretic honnone. Peripheral dopamine may be formed by two alternative pathways; the decarboxylation of circulating L-Dopa by L-aromatic amino acid decarboxylase (LAAAD), and the desulphation of dopamine sulphate by arylsulphatase A (ASA), the latter being poorly represented in the literature. In many conditions and diseases with which sodium retention is associated, a reduced urinary excretion of dopamine has been noted implicating the involvement of dopamine in the maintenance of sodium homeostasis.This study investigates renal dopamine production via the desulphation of dopamine sulphate in a sample cohort during normal unregulated dietary sodium intake and following a low sodium regimen. After dietary salt restriction urinary dopamine sulphate levels were significantly increased, indicating that dopamine sulphate is indeed a physiological reservoir of active free dopamine, the necessity for which is reduced during self depletion. This confirmed the dopamine/dopamine sulphate pathway as one which may be relevant to the maintenance of sodium homeostasis. The activity of urinary ASA was investigated in diabetes mellitus as an example of a sodium-retaining state, and compared with that in a matched normal control group. A decreased ASA activity was anticipated, given the blunted dopamine excretion observed in many sodium-retaining states, however an unexpected increase in activity in the diabetic group was observed. Enzyme kinetic analysis of ASA showed that this was not due to the existence of an isoform having an altered affinity for dopamine sulphate. This rather paradoxical situation, that urinary-dopamine is decreased while ASA activity is increased, may be explained by the sequestering of free dopamine by autoxidation to 6-hydroxydopamine as has been hypothesised recently to occur in diabetes mellitus. To confirm the homogeneity of ASA in the normal and diabetic groups, four amplicons spanning the 3637bp intronic and exonic regions of the gene were generated by PCR. These were sequence utilising a fluorescent-dye terminator reaction using the forward PCR primer as sequencing primer. Although single nucleotide polymorphisms were observed between the two groups these occurred either in intronic regions or, when exonic, generated silent mutations, supporting the enzyme kinetic data. The expression of ASA was investigated to determine the basis of the increased activity observed in diabetes mellitus. Although a validated comparative RT-PCR assay was developed for amplification of arsa transcripts from fresh blood samples, expression analysis from archived paraffin-embedded renal tissue was complicated by the low yield and degradation of unprotected mRNA. Suggestions for the development of this work using renal cell-culture are discussed.

Stability studies on pencillin derivatives

Current analytical assay methods for ampicillin sodium and cloxacillin sodium are discussed and compared, High Performance Liquid Chromatography (H.P.L.C.) being chosen as the most accurate, specific and precise. New H.P.L.C. methods for the analysis of benzathine cloxacillin; benzathine penicillin V; procaine penicillin injection B.P.; benethamine penicillin injection; fortified B.P.C.; benzathine penicillin injection; benzathine penicillin injection, fortified B.P.C.; benzathine penicillin suspnsion; ampicillin syrups and penicillin syrups are described. Mechanical or chemical damage to column packings is often associated with H.P.L.C. analysis. One type, that of channel formation, is investigated. The high linear velocity of solvent and solvent pulsing during the pumping cycle were found to be the cause of this damage. The applicability of nonisotherrnal kinetic experiments to penicillin V preparations, including formulated paediatric syrups, is evaluated. A new type of nonisotherrnal analysis, based on slope estimation and using a 64K Random Access Memory (R.A.M.) microcomputer is described. The name of the program written for this analysis is NONISO. The distribution of active penicillin in granules for reconstitution into ampicillin and penicillin V syrups, and its effect on the stability of the reconstituted products, are investigated. Changing the diluent used to reconstitue the syrups was found to affect the stability of the product. Dissolution and stability of benzathine cloxacillin at pH2, pH6 and pH9 is described, with proposed dissolution mechanisms and kinetic analysis to support these mechanisms. Benzathine and cloxacillin were found to react in solution at pH9, producing an insoluble amide.

Adsorption of dimethyl ether (DME) on zeolite molecular sieves

In recent years there has been growing interest in the use of dimethyl ether (DME) as an alternative fuel. In this study, the adsorption of DME on molecular sieves 4Å (Mol4A) and 5Å (Mol5A) has been experimentally investigated using the volumetric adsorption method. Data on the adsorption isotherms, heats of adsorption, and adsorption kinetic have been obtained and used to draw conclusions and compare the performance of the two adsorbents. Within the conditions considered, the adsorption capacity of Mol5A was found to be around eight times higher than the capacity of Mol4A. Low temperature adsorption and thermal pre-treatment of the adsorbents in vacuum were observed to be favourable for increased adsorption capacity. The adsorption isotherms for both adsorbent were fitted to the Freundlich model and the corresponding model parameters are proposed. The adsorption kinetic analysis suggest that the DME adsorption on Mol5A is controlled by intracrystalline diffusion resistance, while on Mol4A it is mainly controlled by surface layering resistance with the diffusion only taking place at the start of adsorption and for a very limited short time. The heats of adsorption were calculated by a calorimetric method based on direct temperature measurements inside the adsorption cell. Isosteric heats, calculated by the thermodynamic approach (Clasius-Clapeyron equation), have consistently shown lower values. The maximum heat of adsorption was found to be 25.9kJmol-1 and 20.1kJmol-1 on Mol4A and Mol5A, respectively; thus indicating a physisorption type of interactions. © 2014 Elsevier B.V.

Heterogeneous catalysis in an oscillatory baffled flow reactor

The first demonstration of heterogeneous catalysis within an oscillatory baffled flow reactor (OBR) is reported, exemplified by the solid acid catalysed esterification of organic acids, an important prototypical reaction for fine chemicals and biofuel synthesis. Suspension of a PrSOH-SBA-15 catalyst powder is readily achieved within the OBR under an oscillatory flow, facilitating the continuous esterification of hexanoic acid. Excellent semi-quantitative agreement is obtained between OBR and conventional stirred batch reaction kinetics, demonstrating efficient mixing, and highlighting the potential of OBRs for continuous, heterogeneously catalysed liquid phase transformations. Kinetic analysis highlights acid chain length (i.e. steric factors) as a key predictor of activity. Continuous esterification offers improved ester yields compared with batch operation, due to the removal of water by-product from the catalyst, evidencing the versatility of the OBR for heterogeneous flow chemistry and potential role as a new clean catalytic technology. © The Royal Society of Chemistry 2013.

Using apparent activation energy as a reactivity criterion for biomass pyrolysis

The reactivity of chemically isolated lignocellulosic blocks, namely, α-cellulose, holocellulose, and lignin, has been rationalized on the basis of the dependence of the effective activation energy (Eα) upon conversion (α) determined via the popular isoconversional kinetic analysis, Friedman’s method. First of all, a detailed procedure for the thermogravimetric data preparation, kinetic calculation, and uncertainty estimation was implemented. Resulting Eα dependencies obtained for the slow pyrolysis of the extractive-free Eucalyptus grandis isolated α-cellulose and holocellulose remained constant for 0.05 < α < 0.80 and equal to 173 ± 10, 208 ± 11, and 197 ± 118 kJ/mol, thus confirming the single-step nature of pyrolysis. On the other hand, large and significant variations in Eα with α from 174 ± 10 to 322 ± 11 kJ/mol in the region of 0.05 and 0.79 were obtained for the Klason lignin and reported for the first time. The non-monotonic nature of weight loss at low and high conversions had a direct consequence on the confidence levels of Eα. The new experimental and calculation guidelines applied led to more accurate estimates of Eα values than those reported earlier. The increasing Eα dependency trend confirms that lignin is converted into a thermally more stable carbonaceous material.

Kinetic study of the pyrolysis of miscanthus and its acid hydrolysis residue by thermogravimetric analysis

The kinetic parameters of the pyrolysis of miscanthus and its acid hydrolysis residue (AHR) were determined using thermogravimetric analysis (TGA). The AHR was produced at the University of Limerick by treating miscanthus with 5 wt.% sulphuric acid at 175 °C as representative of a lignocellulosic acid hydrolysis product. For the TGA experiments, 3 to 6 g of sample, milled and sieved to a particle size below 250 μm, were placed in the TGA ceramic crucible. The experiments were carried out under non-isothermal conditions heating the samples from 50 to 900 °C at heating rates of 2.5, 5, 10, 17 and 25 °C/min. The activation energy (EA) of the decomposition process was determined from the TGA data by differential analysis (Friedman) and three isoconversional methods of integral analysis (Kissinger–Akahira–Sunose, Ozawa–Flynn–Wall, Vyazovkin). The activation energy ranged from 129 to 156 kJ/mol for miscanthus and from 200 to 376 kJ/mol for AHR increasing with increasing conversion. The reaction model was selected using the non-linear least squares method and the pre-exponential factor was calculated from the Arrhenius approximation. The results showed that the best fitting reaction model was the third order reaction for both feedstocks. The pre-exponential factor was in the range of 5.6 × 1010 to 3.9 × 10+ 13 min− 1 for miscanthus and 2.1 × 1016 to 7.7 × 1025 min− 1 for AHR.

Kinetic study on thermal decomposition of woods in oxidative environment

The purpose of this work is to gain knowledge on kinetics of biomass decomposition under oxidative atmospheres, mainly examining effect of heating rate on different biomass species. Two sets of experiments are carried out: the first set of experiments is thermal decomposition of four different wood particles, namely aspens, birch, oak and pine under an oxidative atmosphere and analysis with TGA; and the second set is to use large size samples of wood under different heat fluxes in a purpose-built furnace, where the temperature distribution, mass loss and ignition characteristics are recorded and analyzed by a data post-processing system. The experimental data is then used to develop a two-step reactions kinetic scheme with low and high temperature regions while the activation energy for the reactions of the species under different heating rates is calculated. It is found that the activation energy of the second stage reaction for the species with similar constituent fractions tends to converge to a similar value under the high heating rate.

Time scale analysis for fluidized bed melt granulation I: granule-granule and granule-droplet collision rates

Fluidized bed spray granulators (FBMG) are widely used in the process industry for particle size growth; a desirable feature in many products, such as granulated food and medical tablets. In this paper, the first in a series of four discussing the rate of various microscopic events occurring in FBMG, theoretical analysis coupled with CFD simulations have been used to predict granule–granule and droplet–granule collision time scales. The granule–granule collision time scale was derived from principles of kinetic theory of granular flow (KTGF). For the droplet–granule collisions, two limiting models were derived; one is for the case of fast droplet velocity, where the granule velocity is considerable lower than that of the droplet (ballistic model) and another for the case where the droplet is traveling with a velocity similar to the velocity of the granules. The hydrodynamic parameters used in the solution of the above models were obtained from the CFD predictions for a typical spray fluidized bed system. The granule–granule collision rate within an identified spray zone was found to fall approximately within the range of 10-2–10-3 s, while the droplet–granule collision was found to be much faster, however, slowing rapidly (exponentially) when moving away from the spray nozzle tip. Such information, together with the time scale analysis of droplet solidification and spreading, discussed in part II and III of this study, are useful for probability analysis of the various event occurring during a granulation process, which then lead to be better qualitative and, in part IV, quantitative prediction of the aggregation rate.

Pryolytic and kinetic study of Chlorella Vulgaris under isothermal and non-isothermal conditions

Algae are a new potential biomass for energy production but there is limited information on their pyrolysis and kinetics. The main aim of this thesis is to investigate the pyrolytic behaviour and kinetics of Chlorella vulgaris, a green microalga. Under pyrolysis conditions, these microalgae show their comparable capabilities to terrestrial biomass for energy and chemicals production. Also, the evidence from a preliminary pyrolysis by the intermediate pilot-scale reactor supports the applicability of these microalgae in the existing pyrolysis reactor. Thermal decomposition of Chlorella vulgaris occurs in a wide range of temperature (200-550°C) with multi-step reactions. To evaluate the kinetic parameters of their pyrolysis process, two approaches which are isothermal and non-isothermal experiments are applied in this work. New developed Pyrolysis-Mass Spectrometry (Py-MS) technique has the potential for isothermal measurements with a short run time and small sample size requirement. The equipment and procedure are assessed by the kinetic evaluation of thermal decomposition of polyethylene and lignocellulosic derived materials (cellulose, hemicellulose, and lignin). In the case of non-isothermal experiment, Thermogravimetry- Mass Spectrometry (TG-MS) technique is used in this work. Evolved gas analysis provides the information on the evolution of volatiles and these data lead to a multi-component model. Triplet kinetic values (apparent activation energy, pre-exponential factor, and apparent reaction order) from isothermal experiment are 57 (kJ/mol), 5.32 (logA, min-1), 1.21-1.45; 9 (kJ/mol), 1.75 (logA, min-1), 1.45 and 40 (kJ/mol), 3.88 (logA, min-1), 1.45- 1.15 for low, middle and high temperature region, respectively. The kinetic parameters from non-isothermal experiment are varied depending on the different fractions in algal biomass when the range of apparent activation energies are 73-207 (kJ/mol); pre-exponential factor are 5-16 (logA, min-1); and apparent reaction orders are 1.32–2.00. The kinetic procedures reported in this thesis are able to be applied to other kinds of biomass and algae for future works.

Comparative analysis of experimental and modelling of gas-solid flow hydrodynamics:effect of friction and interparticle cohesion forces

The effect of friction and interparticle cohesion forces on the gas-solid flow hydrodynamics was discussed. A proposed interparticle cohesion and frictional force terms have been tested in a continuum fully developed flow model to investigate their effect on the general hydrodynamic features of vertical duct flow. It was observed that both terms have direct effect on lowering the material carryover, which implies a reduced bed expansion in freely bubbling column. The parametric analysis shows that cohesion and frictional forces are high when compared to kinetic stress and hence it can play a major role in describing the hydrodynamics features of the flow.

Alternative exon usage in the single CPT1 gene of Drosophila generates functional diversity in the kinetic properties of the enzyme:differential expression of alternatively spliced variants in drosophila tissues

The Drosophila melanogaster genome contains only one CPT1 gene (Jackson, V. N., Cameron, J. M., Zammit, V. A., and Price, N. T. (1999) Biochem. J. 341, 483-489). We have now extended our original observation to all insect genomes that have been sequenced, suggesting that a single CPT1 gene is a universal feature of insect genomes. We hypothesized that insects may be able to generate kinetically distinct variants by alternative splicing of their single CPT1 gene. Analysis of the insect genomes revealed that (a) the single CPT1 gene in each and every insect genome contains two alternative exons and (ii) in all cases, the putative alternative splicing site occurs within a small region corresponding to 21 amino acid residues that are known to be essential for the binding of substrates and of malonyl-CoA in mammalian CPT1A.Weperformed PCR analyses of mRNA from different Drosophila tissues; both of the anticipated splice variants of CPT1mRNAwere found to be expressed in all of the tissues tested (both in larvae and adults), with the expression level for one of the splice variants being significantly different between flight muscle and the fat body of adult Drosophila. Heterologous expression of the full-length cDNAs corresponding to the two putative variants of Drosophila CPT1 in the yeast Pichia pastoris revealed two important differences between the properties of the two variants: (i) their affinity (K 0.5) for one of the substrates, palmitoyl-CoA, differed by 5-fold, and (ii) the sensitivity to inhibition by malonyl-CoA at fixed, higher palmitoyl-CoA concentrations was 2-fold different and associated with different kinetics of inhibition. These data indicate that alternative splicing that specifically affects a structurally crucial region of the protein is an important mechanism through which functional diversity of CPT1 kinetics is generated from the single gene that occurs in insects. © 2010 by The American Society for Biochemistry and Molecular Biology, Inc.