Spectrophotometric assay of superoxide anion formed in Maillard reaction based on highly water-soluble tetrazolium salt.

A novel highly water-soluble tetrazolium salt, WST-1 (4-[3-(4-iodophenyl)-2-(4-nitrophenyl)-2H-5-tetrazolio]-1,3-benzene disulfonate sodium salt), can be reduced to water-soluble formazan with a superoxide anion. Here, the WST-1 assay was applied to detect the superoxide anion generated during the Maillard reaction. A sample solution containing carbonyl compounds such as glyceraldehyde and glycolaldehyde (5 mM) and Na-acetyl-L-lysine (10 mM) was incubated for 2 days at 37 degrees C. The detection of a superoxide anion generated in the sample was performed by the WST-1 assay, and the result was compared with the cytochrome c assay. The reduction of WST-1 was almost perfectly (86-96%) inhibited by the addition of the superoxide dismutase (SOD). On the contrary, the reduction of cytochrome c was slightly (20-25%) inhibited by the addition of SOD. A similar result was observed for the addition of 4,5-dihydroxy-1,3-benzene disulfonic acid (Tiron). These results mean that the specificity of WST-1 to the superoxide anion was superior to that of cytochrome c. It was also possible to continuously monitor superoxide anion generation during the Maillard reaction by the coexistence of WST-1 in the reaction solution.     

Copper-catalyzed, one-pot, three-component synthesis of benzimidazoles by condensation and C-N bond formation

Benzimidazoles were synthesized by the copper-catalyzed, one-pot, three-component reaction of 2-haloanilines, aldehydes, and NaN(3). The reaction was optimized when 2-iodo- or 2-bromoanilines (1.0 equiv), aldehydes (1.2 equiv), NaN(3) (2.0 equiv), 5 mol% of CuCl, and 5 mol % of TMEDA were reacted in DMSO at 120 °C for 12 h. Good yields resulted, and the reaction showed tolerance toward functional groups such as ester, nitro, and chloro. Aliphatic and heteroaromatic aldehydes also afforded the desired products in moderate to good yields.     

Primitive chain network simulations for comb-branched polymer under step shear deformations

The damping of the relaxation modulus under step shear deformation is weaker for multi-branched polymers such as comb polymers than for linear polymers. This weak damping has been related to the hierarchical relaxation, the branched arm relaxation occurring prior to the backbone relaxation and dilating the entanglement network for the backbone relaxation/contraction. A corresponding model has been proposed and favorably compared with the data for the damping function. However, the enhancement of dilation due to large deformation, known to occur for linear polymers to affect the chain contraction rate, was not considered in the model. Thus, in this paper, we investigated the dilation for a comb polymer under deformation with the aid of a 3D multichain sliplink simulation that naturally accounts for the dilation due to the constraint release through the many chain dynamics. The simulation was confirmed, to the first time, to reproduce the linear and nonlinear viscoelastic data for a comb polyisoprene (Kirkwood et al., Macromolecules 42:9592–9608, 2009). A magnitude of dilation under deformation was examined for the survival probability of the sliplinks. It turned out that the dilation for the comb backbone activated by the arm relaxation is enhanced by the deformation at short times but not at long times where the backbone relaxes and the damping function is defined. This result lends support to the conventional model.     

p-Diethynylbenzene-based molecular wires, Fe-CC-p-C6H2X2-CC-Fe [Fe = Fe(η-C5Me5)(dppe)]: Synthesis, substituent effects and unexpected formation of benzodifuran complex

A series of p-diethynylbenzene-based molecular wires, Fe-CC-p-C₆H₂X₂-CC-Fe (3) (Fe = FeCp^∗(dppe)), is prepared and their wire-like performance is estimated on the basis of the K_C and V_ab values. It has been revealed that electron-donating substituents (X) improve the performance. The benzodifuran complex 4 unexpectedly formed from the derivative with X = OH shows the performance comparable to 3.     

Oil in water emulsions stabilized by maillard conjugates of sodium caseinate-locust bean gum

Conjugates composed by sodium caseinate and locust bean gum (LBG) were produced through Maillard reaction in order to enhance their emulsifying properties. The reactions were performed (80?°C/76% relative humidity) at three protein/polysaccharide ratios (0.3, 0.6, 1.2), and the conjugates were added in emulsions at two pH values (3.5 and 7). The formation of protein-polysaccharide conjugates was confirmed by SDS-polyacrylamide gel electrophoresis and by FTIR spectra. At both pH values, the conjugates subjected to longer reaction times presented less emulsifying capability, probably due to insoluble compounds formation. Furthermore, the conjugates provided high stability in O/W emulsions at pH 7 due to the electrostatic repulsion of protein charged groups. However, even though the conjugates were not charged at pH 3.5, the stabilization process occurred at this condition probably due to the formation of a thicker interfacial layer, which provided an increase in steric repulsion between the droplets. Thus, the conjugates formed by sodium caseinate and locust bean gum can be characterized as a good emulsifying agent to be applied in different pH conditions.     

Versatile Synthetic Route to Cycloheximide and Analogues That Potently Inhibit Translation Elongation

Cycloheximide (CHX) is an inhibitor of eukaryotic translation elongation that has played an essential role in the study of protein synthesis. Despite its ubiquity, few studies have been directed towards accessing synthetic CHX derivatives, even though such efforts may lead to protein synthesis inhibitors with improved or alternate properties. Described here is the total synthesis of CHX and analogues, and the establishment of structure–activity relationships (SAR) responsible for translation inhibition. The SAR studies aided the design of more potent compounds, one of which irreversibly blocks ribosomal elongation, preserves polysome profiles, and may be a broadly useful tool for investigating protein synthesis.     

Rate coefficients for the gas‐phase reactions of OH radicals with methylbutenols at 298 K

The relative‐rate method has been used to determine the rate coefficients for the reactions of OH radicals with three C₅ biogenic alcohols, 2‐methyl‐3‐buten‐2‐ol (k₁), 3‐methyl‐3‐buten‐1‐ol (k₂), and 3‐methyl‐2‐buten‐1‐ol (k₃), in the gas phase. OH radicals were produced by the photolysis of CH₃ONO in the presence of NO. Di‐n‐butyl ether and propene were used as the reference compounds. The absolute rate coefficients obtained with the two reference compounds agreed well with each other. The O₃ and O‐atom reactions with the target alcohols were confirmed to have a negligible contribution to their total losses by using two kinds of light sources with different relative rates of CH₃ONO and NO₂ photolysis. The absolute rate coefficients were obtained as the weighted mean values for the two reference compound systems and were k₁ = (6.6 ± 0.5) × 10^?11, k₂ = (9.7 ± 0.7) × 10^?11, and k₃ = (1.5 ± 0.1) × 10^?10 cm³ molecule^?1 s^?1 at 298 ± 2 K and 760 torr of air. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 379–385 2004     

Palladium-catalyzed cross-coupling reaction: Direct allylation of aryl bromides with allyl acetate

Various aryl bromides underwent a palladium-catalyzed cross-coupling reaction with allyl acetate in the presence of hexa-n-butylditin to give the allylated products in very high yields.     

Ruthenium-catalyzed alkoxylation of a hydrodisilane without SiSi bond cleavage

Transition metal-catalyzed synthesis of alkoxydisilanes via dehydrogenative coupling of a hydrodisilane with alcohols is reported. During the reaction, the SiSi bond is preserved effectively when [RuCl₂(p-cymene)]₂ is used as a catalyst. Various alcohols can be used in this alkoxylation.