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A novel species of amides formed from degradation of one of the most important key intermediates in Maillard hexose chemistry-1-deoxyhexo-2,3-diulose-was investigated. In 1-deoxyhexo-2,3-diulose/N(alpha)-t-BOC-lysine reaction mixtures four amides, N(epsilon)-acetyl lysine, N(epsilon)-formyl lysine, N(epsilon)-lactoyl lysine and N(epsilon)-glycerinyl lysine, were identified and their structures verified by authentic reference standards. Amides and corresponding carboxylic acids (acetic acid, formic acid, lactic acid and glyceric acid) accumulated over time. Both N(epsilon)-lysine amides and carboxylic acids were thus determined as stable Maillard end products. Results of model incubations suggested the synthesis of amides to be mechanistically closely related to the formation of their corresponding carboxylic acids by beta-dicarbonyl cleavage. Due to the different chemical properties of all the compounds monitored, various analytical strategies had to be carried out (LC-MS(2), GC-MS, GC-FID, enzymatic determination).

Originally published as:Wieloch, T., Helle, G., Heinrich, I., Voigt, M., Schyma, P. (2011): A novel device for batch-wise isolation of α-cellulose from small-amount wholewood samples. AbstractA novel device for the chemical isolation of α-cellulose from wholewood material of tree rings was designed by the Potsdam Dendro Laboratory. It allows the simultaneous treatment of up to several hundred micro samples. Key features are the batch-wise exchange of the chemical solutions, the reusability of all major parts and the easy and unambiguous labelling of each individual sample. Compared to classical methods labour intensity and running costs are significantly reduced.

The growth kinetics of ZnO nanorods in methanol is studied by a combination of scanning and high-resolution transmission electron microscopy and X-ray diffraction analysis. In the early stage of growth oriented attachment of 2−3 spheroidal crystallites to rod-like structures occurs. Later, rods of up to 90 nm in length with a hexagonal cross-section up to 18 nm in diameter form by ripening. Our main finding is that the growth follows a power law as a function of the ripening time with exponents of 0.32 to 0.39 for the length and 0.17 to 0.21 for the diameter. In contrast to previous studies on the growth of ZnO rods in alcohols our results indicate that the growth is dominated by anisotropic Ostwald ripening that is limited by volume diffusion.

Degradation of 1-deoxyhexo-2,3-diulose, a key intermediate in Maillard chemistry, in the presence of l-alanine under moderate conditions (37 and 50 degrees C) was investigated. Different analytical strategies were accomplished to cover the broad range of products formed and their differing chemical properties. These involved GC-MS analysis of trimethylsilyl and O-benzyloxime trimethylsilyl derivatives (after reaction with O-benzylhydroxylamine and N,O-bis(trimethylsilyl)acetamide), GC-FID analysis of the decyl ester of acetic acid (after reaction with decyl chloroformate), and HPLC-UV analysis of quinoxaline derivatives (after reaction with o-phenylenediamine). Among the compounds identified were carboxylic acids (glyceric acid and acetic acid) that can be seen as stable Maillard end-products. However, the formation of dicarbonyls (3,4-dihydroxy-2-oxobutanal, 1-hydroxybutane-2,3-dione, and 4-hydroxy-2-oxobutanal) and of hydroxycarbonyls (acetol) was verified presenting unstable, reactive Maillard intermediates. Results confirmed that beta-dicarbonyl cleavage is a very important pathway within the degradation of 1-deoxyhexo-2,3-diulose. Other reactions taking place include enolization, water elimination, and oxidation.

With this work, we report on further insights into the chemistry of 1-deoxy-D-erythro-hexo-2,3-diulose (1-deoxyglucosone, 1-DG). This alpha-dicarbonyl plays an important role as a highly reactive intermediate in the Maillard chemistry of hexoses. Degradation of 1-DG in the presence of the amino acid l-alanine led to the formation of several products. Lactic acid and glyceric acid were found to be major degradation products. Their formation was dependent on the presence of oxygen. Therefore, a mechanism is postulated based on oxidation leading to a tricarbonyl intermediate. Carbonyl cleavage of this structure should then give rise to carboxylic acids. This mechanism was supported by the isotope distribution observed during degradation of different (13)C-labeled D-glucose isotopomers. Furthermore, we identified 3,5-dihydroxy-6-methyl-2,3-dihydro-4H-pyran-4-one (gamma-pyranone) to be capable of rehydration forming 1-DG to a minor extent and therefore leading to the same degradation products. The formation of carboxylic acids from gamma-pyranone was also dependent on the presence of oxygen in agreement with the postulated oxidative fragmentation. Finally, we investigated the formation of aldehydes expected as retro-aldol products formed within the degradation of 1-DG. Results seemed to rule out this reaction as an important degradation pathway under the conditions investigated herein.

Zinc oxide thin-films are prepared either by spin coating of an ethanolic dispersion of nanoparticles (NP, diameter 5 nm) or by spray pyrolysis of a zinc acetate dihydrate precursor. High-resolution electron microscopy studies reveal a monolayer of particles for the low temperature spin coating approach and larger crystalline domains of more than 30 nm for the spray pyrolysis technique. Thin-film transistor devices (TFTs) based on spray pyrolysis films exhibit higher electron mobilities of up to 24 cm2 V(-1) s(-1) compared to 0.6 cm2 V(-1) s(-1) for NP based TFTs. These observations were dedicated to a reduced number of grain boundaries within the transistor channel.