Water Effect on Peroxyoxalate Kinetics and Mechanism for Oxalic Esters with Distinct Reactivities

The peroxyoxalate reaction is being widely used for various analytical and bioanalytical applications, and however, few mechanistic studies are performed in aqueous media, important mainly for bioanalytical applications, where low chemiluminescence emission quantum yields are obtained. In this sense, we report here kinetic studies on the peroxyoxalate reaction, using two commercially available and widely utilized esters, bis(2,4-dinitrophenyl) oxalate (DNPO) and bis(2,4,6-trichlorophenyl) oxalate (TCPO), in 1,2-dimethoxyethane:water mixtures. The reaction of the much more reactive DNPO, in anhydrous and aqueous media, occurs by a direct nucleophilic attack of H₂ O₂ to the oxalic ester, not involving nucleophilic catalysis by imidazole. Contrary, in the reaction of the less reactive TCPO with H₂ O₂ , imidazole acts mainly as nucleophilic catalyst. For both esters, experimental conditions are established where precise kinetic data and emission quantum yields can be obtained. Interestingly, the quantum yields in 1,2-dimethoxyethane water mixtures increase up to a water concentration of 0.7 mol L^-1 and decrease significantly with higher concentrations.

Dry storage of mammalian spermatozoa and cells: state-of-the-art and possible future directions

This review provides a snapshot of the current state-of-the-art of drying cells and spermatozoa. The major successes and pitfalls of the most relevant literature are described separately for spermatozoa and cells. Overall, the data published so far indicate that we are closer to success in spermatozoa, whereas the situation is far more complex with cells. Critical for success is the presence of xeroprotectants inside the spermatozoa and, even more so, inside cells to protect subcellular compartments, primarily DNA. We highlight workable strategies to endow gametes and cells with the right combination of xeroprotectants, mostly sugars, and late embryogenesis abundant (LEA) or similar 'intrinsically disordered' proteins to help them withstand reversible desiccation. We focus on the biological aspects of water stress, and in particular cellular and DNA damage, but also touch on other still unexplored issues, such as the choice of both dehydration and rehydration methods or approaches, because, in our view, they play a primary role in reducing desiccation damage. We conclude by highlighting the need to exhaustively explore desiccation strategies other than lyophilisation, such as air drying, spin drying or spray drying, ideally with new prototypes, other than the food and pharmaceutical drying strategies currently used, tailored for the unique needs of cells and spermatozoa.

Improved Expression and Optimization of Trehalose Synthase by Regulation of Pglv in Bacillus subtilis

Trehalose synthase (TreS) converts maltose to trehalose, which has several important functions; therefore, enhancing TreS expression is desirable. Here, a recombinant Bacillus subtilis W800N (ΔamyE)-P_glv strain was constructed to achieve enhanced expression of TreS. Process optimization strategies were developed to improve the expression level of TreS in B. subtilis W800N (ΔamyE)-P_glv. Intracellular activity of TreS was induced using 60 g/L of maltose in shake flask culture. The protein activity reached 5211 ± 134 U/g at 33 °C and pH 7.0 in Luria-Bertani medium. A fed-batch fermentation strategy was applied in a 30 L fermenter containing 18 L terrific broth to achieve high cell density by replacing glycerol with high maltose syrup as a carbon source and an inducer. After 32 h of fermentation, recombinant B. subtilis W800N (ΔamyE)-P_glv activity reached 6850 ± 287 U/g dry cell weight. Our results demonstrate the efficiency of the P_glv promoter in increasing the expression of TreS in B. subtilis W800N (ΔamyE)-P_glv.

Quantification of the Disaccharide Trehalose from Biological Samples: A Comparison of Analytical Methods

Trehalose is a disaccharide that is biosynthesized by many different organisms subjected to extreme conditions, such as dehydration, heat, oxidative stress, and freezing. This disaccharide allows organisms to better survive these environmental stresses; however, the mechanisms by which trehalose exerts its protective effects are not well understood. Methods to accurately measure trehalose from different organisms will help us gain better understanding of these protective mechanisms. In this study, three experimental approaches for the quantification of trehalose from biological samples were compared: an enzymatic trehalose assay (Trehalose Assay Kit; Megazyme International), a high-performance liquid chromatography coupled with refractive index detection-based assay, and a liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based assay. Limits of detection and quantification for each assay were compared, as were the dynamic ranges for all three assays. The percent recoveries for known amounts of trehalose spiked into bacterial and mammalian cellular lysates were also determined for each of the assays. Finally, endogenous trehalose produced by Escherichia coli cells was detected and quantified using these assays. Results from this study indicate that an LC-MS/MS-based assay is the most direct and sensitive method for the quantification of low concentrations of trehalose from biological samples; however, the enzymatic assay is suitable for the rapid quantification of higher concentrations of trehalose when an LC-MS/MS is unavailable.