Degradation kinetics of neostigmine in solution

The degradation kinetics of neostigmine were studied in aqueous solutions with varied pH from 1.5 to 9.9 under accelerated storage conditions. The stability of neostigmine in solutions containing propylene glycol or polyethylene glycol 400 was also investigated. The reaction order of neostigmine in these aqueous and solvent systems followed pseudo-first-order degradation kinetics. The degradation rates of neostigmine under various buffer concentrations within the investigated pH range were obtained. They indicated that the degradation was independent of the species of buffering agent. Maximum stability of neostigmine was determined at pH 5.0 buffer species conditions. The activation energy could be estimated from the Arrhenius plot as 15.72 kcal/mole. The half-life of 883.7 days was estimated at room temperature in 0.1 M, pH 4.9 acetate buffer solution (mu = 0.5). Ultraviolet (UV) irradiation at 254 nm of the neostigmine solutions in pH 4.9 acetate buffer showed an accelerated degradation in comparison with light-protected samples. Incorporation of propylene glycol into the neostigmine solution at pH 4.9 enhanced the stability; however, an adverse effect on the stability of neostigmine was noted when a polyethylene glycol 400 solvent system was used.     

Induction of apoptosis in HL-60 cells by skimmed milk digested with a proteolytic enzyme from the yeast Saccharomyces cerevisiae

Bovine skimmed milk digested with cell-free extract of the yeast Saccharomyces cerevisiae was found to exhibit proliferation inhibition activity towards human leukemia (HL-60) cells. The optimum pH for digestion of skimmed milk and production of the proliferation inhibition factor was pH 4.8. Nondigested skimmed milk exhibited little suppressive effect on the proliferation of HL-60 cells. An active enzyme involved in the production of cell proliferation inhibitory materials from skimmed milk was purified from the cell-free extract of S. cerevisiae by a series of column chromatographies: DEAE-Sephacel, D-tryptophan methyl ester-Sepharose 4B, Hiload Superdex G-200 and HPLC Mono Q. The homogeneous purified enzyme and exhibited a molecular mass of 33 kDa in sodium dodeceyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and was identified as protease B by N-terminal amino acid sequence analysis. Bovine skimmed milk digested with purified protease B was found to inhibit proliferation activity of HL-60 cells most strongly when digestion was conducted at pH 4.8. The cell proliferation inhibition activity induced by digested skimmed milk was shown to be due to the induction of apoptosis, demonstrated by the formation of apoptotic bodies and fragmentation of DNA in treated cells. The proliferation inhibition factors produced were recovered in the soluble fraction of 92% ethanol, suggesting that the factors were hydrophilic low molecular mass substances derived from skimmed milk.     

The effect of antioxidant deficiency on tissue lipid composition in the rat. III. Testes

Production of testicular degeneration in the antioxidant-deficient rat resembles encephalomalacia in the chick in its dependence on essential (ω6) fatty acids and is distinct from the generalized response to all polyunsaturated fatty acids seen in nutritional muscular dystrophy in the rat. The nonessential (ω3) polyunsaturated fatty acids, however, lower the essential fatty acid content of the testicular lipids only slightly, are not themselves incorporated into this tissue to any appreciable degree and thus do not show the inhibitory effect on production of the antioxidant-deficiency sign noted in the studies on encephalomalacia. A direct relationship between the essential fatty acid content of the testes and the rate of testicular degeneration was found, but no effects of biologically available selenium and sulfur amino acids were evident. As the liver and muscle, onset of antioxidant-deficiency is characterized by a decrease in the most highly unsaturated fatty acid in the tissue (22∶5–ω6 in this case) and a net increase in arachidonate.     

Effects of interface roughness on the spectral properties of thin films and multilayers

We introduce two parameters, large-scale and small-scale rms roughness, to take into account the interface properties of thin films and multilayers in the calculation of their specular reflectance and transmittance. A theoretical motivation for the introduction of these two parameters instead of a standard single rms roughness is provided. Experimental power spectral density functions of several samples are used to illustrate ways in which the parameters introduced can be evaluated.     

Determination of uronic acids in isolated hemicelluloses from kenaf using diffuse reflectance infrared fourier transform spectroscopy (DRIFTS) and the curve-fitting deconvolution method

Hemicellulose samples were isolated from kenaf (Hibiscus cannabinus L.). Hemicellulosic fractions usually contain a variable percentage of uronic acids. The uronic acid content (expressed in polygalacturonic acid) of the isolated hemicelluloses was determined by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and the curve-fitting deconvolution method. A linear relationship between uronic acids content and the sum of the peak areas at 1745, 1715, and 1600 cm(-1) was established with a high correlation coefficient (0.98). The deconvolution analysis using the curve-fitting method allowed the elimination of spectral interferences from other cell wall components. The above method was compared with an established spectrophotometric method and was found equivalent for accuracy and repeatability (t-test, F-test). This method is applicable in analysis of natural or synthetic mixtures and/or crude substances. The proposed method is simple, rapid, and nondestructive for the samples.     

Engineered superoxide dismutase monomers for superoxide biosensor applications

Because of its high reaction rate and specificity, the enzyme superoxide dismutase (SOD) offers great potential for the sensitive quantification of superoxide radicals in electrochemical biosensors. In this work, monomeric mutants of human Cu,Zn-SOD were engineered to contain one or two additional cysteine residues, which could be used to bind the protein to gold surfaces, thus making the use of promotor molecules unnecessary. Six mutants were successfully designed, expressed, and purified. All mutants bound directly to unmodified gold surfaces via the sulfur of the cysteine residues and showed a quasi-reversible, direct electron transfer to the electrode. Thermodynamic and kinetic parameters of the electron transfer were characterized and showed only slight variations between the individual mutants. For one of the mutants, the interaction with the superoxide radical was studied in more detail. For both partial reactions of the dismutation, an interaction between protein and radical could be shown. In an amperometric biosensorial approach, the SOD-mutant electrode was successfully applied for the detection of superoxide radicals. In the oxidation region, the electrode surpassed the sensitivity of the commonly used cytochrome c electrodes by approximately 1 order of magnitude while not being limited by interferences, but the electrode did not fully reach the sensitivity of dimeric Cu,Zn-SOD immobilized on MPA-modified gold.     

A smooth impact rotation motor using a multi-layered torsional piezoelectric actuator

A smooth impact rotation motor was fabricated and successfully operated using a torsional piezo actuator. Yoshida et al. reported a linear type smooth impact motor in 1997. This linear motor demonstrated a high output force and a long stroke. A superior feature of the smooth impact drive is a high positioning resolution compared with an impact drive. The positioning resolution of SIDM (smooth impact drive mechanism) is equal to the piezo displacement. The reported positioning resolution of the linear type was 5 nm. Our rotation motor utilized a torsional actuator containing multi-layered piezoelectric material. The torsional actuator was cylindrical in shape with an outer diameter of 15 mm, an inner diameter of 10 mm, and a length of 11 mm. Torsional vibration performance was measured with a laser Doppler vibrometer. The obtained torsional displacement agreed with the calculated values and was sufficient to drive a rotor. The rotor was operated with a saw-shaped input voltage (180 V; 8 kHz). The revolution direction was reversible. The maximum revolution speed was 27 rpm, and the maximum output torque was 56 gfcm. In general, smooth-impact drives do not show high efficiency; however, the level of efficiency of our results (max., 0.045%) could be increased by improving the contact surface material. In addition, we are studying quantitative consideration, for example, about the optimum pre-load or frictional force.     

Delta-sigma oversampled ultrasound beamformer with dynamic delays

The principles of oversampling are exploited in a simple beamforming architecture using a single bit delta-sigma (DeltaC) analog to digital converter (A/D) on every channel. The high sampling rate required for the single bit A/D provides adequate delay accuracy for high quality beamforming using elementary sample manipulations. Images produced with this beamformer exhibit significant artifacts directly related to dynamic focusing. However, a simple digital recording technique following delays permits dynamically focused beamforming without degrading image quality. The simplicity of this beamformer compared to conventional methods may facilitate very large channel count or low power beamformers suitable for 1.5-D arrays or portable scanners.