Microcalorimetric studies on catalase reaction and inhibition of catalase by cyanide ion

As Chance et al. [1, 2 and 3] proposed, the decomposition of hydrogen peroxide catalyzed by catalase is an overall first-order reaction. In this paper, we have studied this enzyme-catalyzed reaction with a thermokinetic method. The rate constant and the molar reaction enthalpy of this reaction have been measured. At 310.15 K and pH=8.2, k_cat=1.75×10⁶ l mol⁻¹ s⁻¹, Δ_rH_m=88.99 kJ mol⁻¹. Furthermore, we have studied the competitive inhibition of catalase by cyanide ion and reported some correlated parameters.     

Influence of macroscopic and microscopic interactions on kinetic rate constants: I. Role of the extended DLVO theory in determining the kinetic adsorption constant of proteins in aqueous media, using von Smoluchowski’s approach

In the case of adsorption in an aqueous medium of a hydrophilic protein (e.g. human serum albumin (HSA)) onto a hydrophilic solid substratum such as a clean glass surface, one has to deal with a macroscopic-level repulsion between HSA and glass at (generally) the majority of orientations of the protein molecules, and also a microscopic-level attraction between HSA and glass at (generally) the minority of orientations of the protein molecules. The first phenomenon represents von Smoluchowski’s improbability of adhesion or adsorption and the second represents the probability of adhesion or adsorption [1]. Both contingencies have to be taken into account in determining von Smoluchowski’s net probability factor, f of the kinetic association constant, k_a, pertaining to protein adsorption. In the exceptional case where both the protein and the solid substratum are hydrophobically/hydrophilically and electrostatically neutral, f=1, and the k_a-value is only proportional to the diffusion coefficient of the protein [2]. In order to determine the contributions of both the macroscopic repulsion and the microscopic attraction pertaining to the kinetics of protein adsorption, an extended DLVO analysis (XDLVO) needs to be done on these interactions at all distances and at all protein orientations. The XDLVO analysis comprises the Lewis acid–base interaction energies as a function of distance, in addition to the Lifshitz–van der Waals and the electrokinetic interaction energies [2, 3, 4 and 5].     

A new instrument for the measurement of very small electrophoretic mobilities using phase analysis light scattering (PALS)

A new instrument based on the principles of phase analysis light scattering (PALS) applied to the measurement of electrophoretic mobilities has been produced. Such measurements are particularly useful in the study of dispersions in non-polar media since for a given zeta potential, the mobility is proportional to the dielectric constant. It is also potentially useful where mobilities are low and the use of high electric fields (a traditional remedy) is inappropriate. This is the case when the ionic concentration and hence conductivity of the medium is high. The PALS configuration has been shown to be able to measure mobilities at least two orders of magnitudes lower than conventional LDE. The device is based on developments reported elsewhere (J. Miller et al., J. Colloid Interface Sci. 143 (2) (1991) [1]), but has a number of new features. In particular, all the signal processing is digital and the optical system a reference beam configuration.     

Control factors for hydrogen-atom abstraction from organic molecules in cryogenic solids

Hydrogen-atom transfer from organic molecules to free deuterium atoms and to methyl radicals in cryogenic organic solids due to quantum-mechanical tunneling of C–H hydrogen was studied for elucidating the control factors for the reaction. The following differences were found in comparison with regular thermal reactions: (1) The rate of hydrogen-atom tunneling decreases with increasing number and length of alkyl chains attaching to C–H carbon to be hydrogen-abstracted. This is due to the increase of steric hindrance to the deformation of the chemical bonds of the C–H carbon. The abstraction accompanies the change of the chemical bonds for the C–H carbon from sp³ to sp², so that prevention of the deformation by the alkyl chains causes the increase of the thickness of the potential barrier for the tunneling. The tunneling rate therefore decreases. (2) The rate of abstraction increases with the energy released by the reaction. The energy is used to excite the vibrational states of product molecules, which accelerates the tunneling from the initial reactant state to the final product state.     

Tetrametallic Group 13 ‘Mitsubishi’ Molecules

Under fairly disparate conditions tetrametallic aluminum complexes can be isolated that feature a central six-coordinate aluminum connected by bridging heteroatoms to three peripheral four-coordinate aluminum atoms. Based upon their striking resemblance to the Mitsubishi emblem these molecules will be given the name ‘Mitsubishi™’ [1]. This review will discuss the formation of these compounds and will seek to establish the guiding principles under which additional ‘Mitsubishi™’ compounds may be formed. The impact of these compounds on the formation of solid-state materials, particularly aluminum oxide, will be briefly discussed.     

Characterization of porous SiC by variable-energy positron beams

3C–SiC grown on n-type Si wafers by chemical vapor deposition (CVD) was anodized in a HF–ethanol solution. Positron annihilation Doppler broadening and lifetime measurements were carried out to characterize a porous structure formed in the SiC layer. In contrast to the case of porous Si, for which long-lived components with lifetimes 5–30 ns have been reported (Suzuki et al., 1994), a lifetime longer than 1 ns was not observed for the porous SiC. We discuss chemical effect in the pore surface based on the Doppler broadening spectrum in the high momentum region.     

Destruction of Ascaris ova by accelerated electron

We investigated the efficiency of radiation treatment to destroy Ascaris ova viability and found that no ova were viable after exposure to 0.75 kGy (D₉₀ at 0.39 kGy). Although the outer coat of the Ascaris ovum had a protective effect at low doses (0.20 kGy) no difference in ova viability was observed at 0.30 kGy. As the doses commonly used for sanitary treatment of wastewater are much higher, Ascaris ova should be effectively eliminated from sludge by the 10 kGy dose required by EPA regulations (U.S. EPA, 1993 Federal Register 58, 9248–9415).     

Predictive models to describe VLE in ternary mixtures water + ethanol + congener for wine distillation

The modeling of liquid–vapor equilibrium in ternary mixtures that include substances found in alcoholic distillation processes of wine and musts is analyzed. In particular, vapor–liquid equilibrium in ternary mixtures containing water + ethanol + cogener has been modeled using parameters obtained from binary mixture data only. The congeners are substances that although present in very low concentrations, of the order of part per million, 10⁻⁶ to 10⁻⁴ mg/L, are important enological parameters [1] and [2]. In this work two predictive models, the PSRK equation of state and the UNIFAC liquid phase model and two semipredictive activity coefficient models: NRTL and UNIQUAC have been used. The results given by these different models have been compared with literature data and conclusions about the accuracy of the models studied are drawn, recommending the best models for correlating and predicting the phase equilibrium in this type of mixtures.     

The quasi-ballistic model of electron mobility in liquid hydrocarbons : Effect of an external electric field

The quasi-ballistic model of electron transport in liquid hydrocarbons, introduced earlier by the author [A. Mozumder, Chem. Phys. Lett. 207 (1993) 245], has been extended to the field dependence of mobility, when the zero-field mobility is low. A sinh-type dependence is obtained, due mainly to the random direction of detrapping relative to the field. The length parameter is interpreted as the trap radius¹, in contradistinction to the jump length of the hopping model. Experimental data have been examined for six liquid hydrocarbons and a speculation is offered regarding the nature of the electron trap.     

“Model-free” kinetic analysis?

All kinetic analyses aim to determine a sufficient number of kinetic parameters, usually at least an apparent Arrhenius activation energy and pre-exponential factor, and a conversion function or kinetic model (making up a ‘kinetic triplet’), so that accurate extrapolations of kinetic behaviour can be made. “Model-free” methods of kinetic analysis postpone the problem of identifying a suitable kinetic model until an estimate of the activation energy has been made. A major reason for doing this is that misidentification of the kinetic model has a marked effect on the values obtained for the Arrhenius parameters in both isothermal and non-isothermal kinetic analyses. Some aspects of this problem are discussed.

The non-parametric kinetics (NPK) method [1 and 2] is a “model-free” method of kinetic analysis that does not seem to have received the attention that it deserves. This is probably because of its mathematical sophistication and the fact that the matrix and non-linear regression calculations involved are not readily automated. The principle of the method appears to be that of “forcing” a set of non-isothermal data into the set which should have been obtained if the experiments had been carried out isothermally. The method deserves wider testing and also raises some interesting aspects of the philosophy behind non-isothermal kinetic analysis.     

Anion and ion-pair receptor chemistry: highlights from 2000 and 2001

This review article highlights advances made in abiotic anion coordination chemistry in 2000 and 2001. The structure of this review is that similar to the previous reviews in this series that covered 1997, 1998 and 1999 [1 and 2]. The review also includes examples of ion-pair receptors. The first section examines anion receptors that do not contain metal ions. This is followed by a review of metal containing anion receptors in which the metal can function as: (i) a coordination site for the anion; (ii) an agent withdrawing electron density from the receptor; (iii) an organisational element in the receptor; (iv) a sensor; and (v) a co-bound guest in ion-pair receptor. Examples of the role of anions in directing the self-assembly of complex molecular architectures are presented in the final section.     

A new spline approach for data fitting

This paper presents an extension of the Modified Spline Technique (MST) formulation for data fitting named power spline, which gives consistent results for sets of data of concave and convex curves. This method is based on a technique which couples an implicit formulation of the maximum likelihood principle to the spline method, making the method suitable to fit data when no physical model is available. The MST method proved to be better than to the spline method and the extended spline fit technique (EST), because it provided accurate results for the first and second derivatives in sets of data where the EST solution developed inaccuracies. The EST method is a formulation that couples Least Squares to the spline method. There are, however, some sets of data where the MST method would show inconsistent solutions for the first and second derivatives. The power spline method eliminates these problems for concave or convex curves. Another improvement on the method is a more flexible choice for the interval boundaries.¹     

Description of the S1(ππ*) state and the reinterpretation of the (1+1) REMPI spectra of N-methylpyrrole as based on the ab intio calculation: a computational spectroscopy

The ab intio calculation was performed to establish the assignment of the title spectra by such as searching for stationary points belonging to lower excited states. The lowest excited state was confirmed to be of ππ* type with an A″ symmetry of a molecular point group C_s (against the previous assumption of πΣ* type) trapped in deep potential minima at the nonplanar staggered conformation (also against the current belief on the involvement of internal rotation). Thus, lower ‘vibrational’ levels in the S₁ state were shown to be tunnel-split levels with various symmetry species for a molecular symmetry group G₁₂. Based on this finding, the spectral data as reported by Philis [Chem. Phys. Lett. 353 (2002) 84] were reassigned while applying the formalism as will be presented in Appendix A.     

Measurement of atomic L shell fluorescence (ω1, ω2, ω3) and Auger (a1, a2 and a3) yields for some elements in the atomic number range 59≤Z≤85

A comprehensive set of theoretical Coster–Kronig and fluorescence yields are presented for atomic numbers 18≤Z≤100. These quantities are based on ab initio relativistic calculations. Agreement with experimental values is fair for ω₁ and generally good for ω₂, ω₃ (Z≥54) [1]. Therefore, atomic L shell fluorescence (ω₁, ω₂, ω₃) and Auger yields (a₁, a₂ and a₃) for some elements in the atomic number range 59≤Z≤85 were determined. These selected measured semi-empirical values were also fitted by least squares to polynomials in the Z of the form ∑_na_nZⁿ and compared with theoretical and with earlier fitted values.     

Electron solvation in methanol revisited

Suggestions for the mechanism of electron solvation in methanol during the last three decades were mostly based on limited time resolution measurements, or indirect observations. The two-channel solvation scheme proposed by Lewis and Jonah (1986) based on indirect observations in electron scavenging experiments is checked here to see if it is in accordance with recent sub-picosecond pump-and-probe laser experimental results. We confirm the applicability of this solvation mechanism and calculate quantitative kinetic and spectral parameters involved.     

Applications of life cycle assessment to NatureWorks™ polylactide (PLA) production

NatureWorks™ polylactide (PLA)¹ is a versatile polymer produced by Cargill Dow LLC. Cargill Dow is building a global platform of sustainable polymers and chemicals entirely made from renewable resources. Cargill Dow's business philosophy is explained including the role of life cycle assessment (LCA), a tool used for measuring environmental sustainability and identifying environmental performance-improvement objectives. The paper gives an overview of applications of LCA to PLA production and provides insight into how they are utilized. The first application reviews the contributions to the gross fossil energy requirement for PLA (54 MJ/kg). In the second one PLA is compared with petrochemical-based polymers using fossil energy use, global warming and water use as the three impact indicators. The last application gives more details about the potential reductions in energy use and greenhouse gasses. Cargill Dow's 5–8 year objective is to decrease the fossil energy use from 54 MJ/kg PLA down to about 7 MJ/kg PLA. The objective for greenhouse gasses is a reduction from +1.8 down to −1.7 kg CO₂ equivalents/kg PLA.     

The conformational composition of 3-buten-1-ol, the importance of intramolecular hydrogen bonding

The conformations of 3-buten-1-ol (1), and its model compounds cis-6-methyl-3-cyclohexen-1-ol (6), 3-cyclopenten-1-ol (7) and epicholesterol (9) have been investigated by FT-IR and ¹H NMR spectroscopy. The energies and geometries of 1, 6 and 7 were also investigated by molecular mechanics, semiempirical molecular orbital and ab initio calculations, while 9 was investigated by molecular mechanics only. The objective of the work was to study the conformational composition and importance of intramolecular OH…π hydrogen bonding for this composition in 1. Only two conformers of 1 have a geometrical possibility for intramolecular hydrogen bonding: Conformers 12 and 13 (Fig. 1). Compounds 6 and 7 were used as models for Conformer 12, while 9 was used as a model for Conformer 13. The investigations showed that Conformer 13 is the only hydrogen-bonded conformer, and that Conformer 12 is not intramolecularly hydrogen bonded. Conformer 13 was the most populated conformer, while Conformer 12 was hardly populated. The combination of experimental and theoretical data, and the use of model compounds was found necessary to obtain this conclusion.     

Structural phase transitions in organized organic thin films built of alkali stearates

Temperature-dependent structure modification of organised organic thin films (OOTF) built of sodium (NaSt) and lithium (LiSt) stearates was investigated by DSC and vibrational spectroscopy. Structural phases found for the bulk specimens of substances by DSC measurements, correspond to those previously known [1]. The pre-transitional structural changes observed for thin films in the first crystalline phase were investigated by using temperature dependent FTIR spectroscopy. Changes in orientation of stearate long axis and alkyl chain conformation in NaSt and LiSt thin films with temperature are reported. It was found that film heating from 20 up to 110°C leads to decrease of the tilt of alkyl radicals with respect to the surface for NaSt films. With temperature increasing, in the IR absorption spectra of NaSt and LiSt films, the frequency of methylene symmetric C-H stretching IR band change from 2849 to 2851 cm⁻¹ upon the temperature variation in the range 70–90°C and at 100°C, respectively. This indicates the onset of partial melting of the chains at this temperatures which are lower as compared to those of bulk specimens. It is suggested that this may be caused by a peculiar structural organisation of the films near the substrate surface.     

Non-isothermal thermoanalytical studies on the salt roasting of chalcopyrite using KCl

In an earlier study [1], the isothermal kinetics of salt roasting of chalcopyrite under an oxidizing atmosphere using KCl was studied in the temperature range 523–773 K. The salt roasting reaction was found to be chemically controlled at temperatures below 600 K both under static air and oxygen atmosphere. At higher temperatures, the process was not thermally activated because of a change in the chemistry of the process. In the present study, the salt roasting of chalcopyrite using KCl under oxygen and static air atmosphere was studied by non-isothermal thermoanalytical studies up to 723 K. The effect of salt content, heating rate and particle size on the salt roasting behavior was studied using TG/DTA techniques at a programmed linear heating rate. The TG and DTA studies reveal two distinct chemical processes, one operative up to 620 K and the other from 620 to 723 K. The integral method of Coats and Redfern was used for the treatment of non-isothermal kinetic data. The non-isothermal analysis confirmed the chemical control mechanism at temperatures below 620 K. However, the activation energy for the process derived from non-isothermal thermogravimetric analysis is almost twice as that deduced from isothermal measurements. In the temperature range 620–723 K, the kinetic data still obeys the interfacial reaction control model although the activation energy in this temperature range is very low.