A kinetic model for the sulphite inhibited Maillard reaction

The time-dependent concentrations of free and total sulphur(IV) oxoanion present during the sulphite inhibited Maillard reaction of glucose and glycine have been found to fit a simple kinetic model. The irreversible combination of the additive follows the scheme:

In this the sulphur(IV) oxoanion does not participate in the reactions involving k₁ and k₂. The former proceeds at constant rate when the concentrations of glucose and glycine are both high compared with the concentration of sulphur(IV) oxoanion, whilst the latter is of first order with respect to intermediate 1. When the reaction is carried out at pH 5·5 and 55°C and the initial concentrations of glucose and glycine are 1 m and 0·5 m, respectively, $\text{k}{}_1\text{= 3·2 × 10}{}^{\mathrm{?5}}\text{M}\text{h}{}^{\mathrm{?1}}\text{and}\text{k}{}_2\text{= 5·5 × 10}{}^{\mathrm{?3}}\text{h}{}^{\mathrm{?1}}$. Reversible binding of the additive takes place as a result of hydroxysulphonate formation with glucose and with the final product of reaction, 3,4-dideoxy-4-sulphohexosulose. The dissociation constant of the hydroxysulphonate of the latter is deduced to be 5 × 10^?3M under the reaction conditions stated above. The model does not include hydroxysulphonate formation involving intermediates in the reaction leading to irreversible combination of the additive, and fits concentration-time data with an initial sulphur(IV) oxoanion concentration of 0·039 m to 9-% loss of the additive, the latter representing the limit of the available experimental data.     

Adhesion of an Air Bubble to Quartz Surface in Aqueous Solution of Aliphatic Amine Hydrochloride

Measurements of the force of air bubble detachment from a quartz surface in aqueous solutions of decylamine hydrochloride (DAC1), dodecylamine hydrochloride (DDAC1) and tetradecylamine hydrochloride (TDAC1) were made in the concentration range from 0 to 200mg/dm³. At the same time, the instantaneous contact angle for the system quartz-air bubble-aqueous solution of aliphatic amine hydrochloride was photographed at the moment of detachment. Wetting contact angles for the system quartz-air bubble-aqueous solution of DDAC1 were also measured. On the basis of the measured values of the instantaneous angle and surface tension of the solutions studied, the changes of polar components of surface free energy of quartz/monolayer water film under the influence of adsorption of molecules of aliphatic amine hydrochloride (RAC1) from aqueous solution were calculated and compared with the literature data. Using these data, the force of air bubble detachment from the quartz surface in the presence of RAC1 was also calculated and compared with the measured force, obtaining a good agreement. From the studies and calculations it appears that a little addition of RAC1 to water considerably changes the stability of the system quartz-air bubble-solution, and that this change is first of all caused by reduction of a polar component of the surface free energy of quartz/monolayer water film as a result of adsorption of RAC1 molecules in the negative places of such a surface. As a result of RAC1 adsorption this surface becomes similar to that of paraffin.     

The effect of the droplet volume and hydrocarbon chain length on the detachment force in the sulphur/hydrocarbon drop/sulphur system

Using a device constructed in our laboratory, measurements of the detachment force of a small sulphur plate from hydrocarbon drops of various volumes located on a large sulphur plate were carried out. Eleven aliphatic hydrocarbons in the series from n-hexane to n-hexadecane were used. Using the literature data for hydrocarbon-water interfacial tensions and the contact angles for the system sulphur/hydrocarbon drop/water, the detachment force was also calculated from the Laplace equation. On the basis of the measured results it was found that the detachment force depends on the hydrocarbon drop volume and the type of hydrocarbon and that in the many cases there is a good agreement between the measured and calculated values of the detachment force. It was also found that there is a stepwise relationship between the detachment force and the number of carbon atoms in the hydrocarbon molecule.     

Quantitative Profiling of DNA Damage and Apoptotic Pathways in UV Damaged Cells Using PTMScan Direct

Traditional methods for analysis of peptides using liquid chromatography and tandem mass spectrometry (LC-MS/MS) lack the specificity to comprehensively monitor specific biological processes due to the inherent duty cycle limitations of the MS instrument and the stochastic nature of the analytical platform. PTMScan Direct is a novel, antibody-based method that allows quantitative LC-MS/MS profiling of specific peptides from proteins that reside in the same signaling pathway. New PTMScan Direct reagents have been produced that target peptides from proteins involved in DNA Damage/Cell Cycle and Apoptosis/Autophagy pathways. Together, the reagents provide access to 438 sites on 237 proteins in these signaling cascades. These reagents have been used to profile the response to UV damage of DNA in human cell lines. UV damage was shown to activate canonical DNA damage response pathways through ATM/ATR-dependent signaling, stress response pathways and induce the initiation of apoptosis, as assessed by an increase in the abundance of peptides corresponding to cleaved, activated caspases. These data demonstrate the utility of PTMScan Direct as a multiplexed assay for profiling specific cellular responses to various stimuli, such as UV damage of DNA.     

STABILITY OF COAL - AIR BUBBLE - WATER SYSTEM

Abstract

Measurements of the detachment force of an air bubble from the surface of various coal ranks were carried out in water. These values were compared with those calculated from the contact angle values measured in coal - air bubble - water system and from the values (from literature) of the dispersion and the nondispersion components of the surface free energy of the studied coals. On the basis of the obtained results we found that there is a good agreement among the measured and calculated values of the detachment force for given coal rank. The coals studied may be divided into three groups according to their ability to form the stable attachment with air bubble. The arithmetic weighted mean of the detachment forces were correlated with the natural flotability of coals and the linear relationship as obtained.     

Working of active carbon by attrition in a spouted bed

Many techniques have been developed to monitor the particle size distribution of latex and slurries, where the primary objective is to assure the uniformity and quality of the product. Unfortunately, most of the techniques which are adaptable to routine quality control, such as Beckman DU or Higher Order Tyndall Spectrum, do not have the ability to detect other important quality features such as outsize or flocculated particles in the system. Other methods such as disc centrifugation, are sensitive to outsize particles, but have other limitations.The newest method, intensity (or frequency) correlation spectroscopy, has been made commercially available in an instrument called the Coulter^® Nano-sizer. This instrument, at a cost of about $25,000.00, will give rapid (under 5 min) automatic and accurate values of the average size and polydispersity of a latex or slurry in the range from 40 to 3000 nm. It is the objective of this report to document the response of the method to various chemical types of latex, but also to latices containing outsize particles and two or more families of particles.The results of this study show that the Coulter^® Nano-sizer gives excellent particle size data correlations with other accepted methods, on lattices of narrow or broad distribution. Moreover, the method does display a sensitivity to outsize particle content, although this sensitivity varies with chemical type of latex.     

The reaction of an azo food dye with hydrogen sulphite ions

The kinetics of the reaction between carmoisine and hydrogen sulphite ions are reported in the pH range 4-5.3. The stoichiometry is 1:1 and the major sulphurcontaining product is sulphate ion. A mechanism consistent with experimental data is proposed.     

Multifrequency microwave thermograph for biomedical applications

This paper presents problems related to thermal radiation of human bodies in microwave range with respect to diagnosis of breast carcinoma. A mathematical model of thermal radiation transfer through tissues is introduced and methods of measurement of temperature, depth and size of a heat source, by means of multifrequency microwave thermograph are described. Theoretical considerations are supplemented by presentation of experimental results.     

A new method to prepare porous silk fibroin membranes suitable for tissue scaffolding applications

A new method to prepare porous silk fibroin (SF) membranes without dialysis is proposed. Silk fibers were degummed to remove sericin and the resultant fibroin was dissolved in a CaCl₂‐CH₃CH₂OH‐H₂O ternary solvent. Rather than undergoing dialysis, a fibroin salty solution was diluted in water and then submitted to a mechanical agitation that led to a phase separation through foam formation on the solution surface. This foam was continually collected and then compacted between plates to remove the excess of water. The membranes presented large pores with diameters of greater than 100 μm (as shown by scanning electron microscopy ‐ SEM), porosity of 68% and water content of 91% w/w. X‐ray diffraction (XRD) and infrared spectroscopy (FTIR‐ATR) indicated that the membranes present SF in a β‐sheet structure even before the ethanol treatment. A typical elastic deformation profile and degradation under temperature were observed using calorimetric analysis (DSC), thermal gravimetric analysis (TGA) and mechanical tests. As indicated by the in vitro cytotoxicity tests, these membranes present potential for use as scaffolds. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009