A high-temperature water vapor equilibration method to determine non-exchangeable hydrogen isotope ratios of sugar, starch and cellulose.

The analysis of the non-exchangeable hydrogen isotope ratio (δ2 Hne ) in carbohydrates is mostly limited to the structural component cellulose, while simple high-throughput methods for δ2 Hne values of non-structural carbohydrates (NSC) such as sugar and starch do not yet exist. Here, we tested if the hot vapor equilibration method originally developed for cellulose is applicable for NSC, verified by comparison with the traditional nitration method. We set up a detailed analytical protocol and applied the method to plant extracts of leaves from species with different photosynthetic pathways (i.e., C3 , C4 and CAM). δ2 Hne of commercial sugars and starch from different classes and sources, ranging from -157.8 to +6.4‰, were reproducibly analysed with precision between 0.2‰ and 7.7‰. Mean δ2 Hne values of sugar are lowest in C3 (-92.0‰), intermediate in C4 (-32.5‰) and highest in CAM plants (6.0‰), with NSC being 2 H-depleted compared to cellulose and sugar being generally more 2 H-enriched than starch. Our results suggest that our method can be used in future studies to disentangle 2 H-fractionation processes, for improving mechanistic δ2 Hne models for leaf and tree-ring cellulose and for further development of δ2 Hne in plant carbohydrates as a potential proxy for climate, hydrology, plant metabolism and physiology.

doGlycans-Tools for Preparing Carbohydrate Structures for Atomistic Simulations of Glycoproteins, Glycolipids, and Carbohydrate Polymers for GROMACS.

Carbohydrates constitute a structurally and functionally diverse group of biological molecules and macromolecules. In cells they are involved in, e.g., energy storage, signaling, and cell-cell recognition. All of these phenomena take place in atomistic scales, thus atomistic simulation would be the method of choice to explore how carbohydrates function. However, the progress in the field is limited by the lack of appropriate tools for preparing carbohydrate structures and related topology files for the simulation models. Here we present tools that fill this gap. Applications where the tools discussed in this paper are particularly useful include, among others, the preparation of structures for glycolipids, nanocellulose, and glycans linked to glycoproteins. The molecular structures and simulation files generated by the tools are compatible with GROMACS.

An evaluation of peptide-bond isosteres.

Peptide-bond isosteres can enable a deep interrogation of the structure and function of a peptide or protein by amplifying or attenuating particular chemical properties. In this Minireview, the electronic, structural, and conformational attributes of four such isosteres-thioamides, esters, alkenes, and fluoroalkenes-are examined in detail. In particular, the ability of these isosteres to partake in noncovalent interactions is compared with that of the peptide bond. The consequential perturbations provide a useful tool for chemical biologists to reveal new structure-function relationships, and to endow peptides and proteins with desirable attributes.

Bimodal concentration-dependent reactivity pattern of a glycosyl donor: Is the solution structure involved?

Changes in concentration (0.001-0.1 M) of an arabinofuranosyl donor (1) have been shown to modulate the temperature T at which activation of 1 occurs (from -23 °C to +7 °C), the reaction time (from 1.5 h to 3 days) and the yield of the disaccharide formed (from 14% to 82%). At concentrations exceeding 0.01 M, these parameters, as well as the specific optical rotation of the solution of 1, virtually do not depend on concentration suggesting formation of reacting species (supramers) of glycosyl donor with similar structures, hence reactivities, but considerably different from those formed in more dilute solutions. The found critical concentration (0.01 M) separates two concentration ranges of reaction solutions corresponding to two types of solution structure that are featured by the presence of fundamentally different supramers of glycosyl donor, which have distinct chemical properties. These results allow a fresh look at the problems of reactivity of chemical compounds and selectivity of the reactions in which they participate.

AuCl3-AgOTf promoted O-glycosylation using anomeric sulfoxides as glycosyl donors at room temperature.

Activation of sulfoxide as glycosyl donors using AuCl3/AgOTf reagent system has been described. Under optimal reaction conditions, both armed and disarmed glycosyl sulfoxide donors were found to react with a range of primary, secondary, and tertiary alcohol acceptors, and sugar derived glycosyl acceptors to afford the corresponding glycosides in moderate to good yields with predictable selectivity. The reactions are quick (20-60 min), facile at room temperature and the reactions conditions tolerate acid sensitive groups.

Cellulose oligomers production and separation for the synthesis of new fully bio-based amphiphilic compounds.

Cellulose oligomers are water-soluble, on the contrary to cellulose, which greatly increase their application range. In this study, cellulose oligomers were obtained from the acidic hydrolysis of cellulose with phosphoric acid. The global yield in water-soluble oligomers was around 23% with polymerization degree (DP) ranging from 1 to 12. The cellulose oligomers DP distribution was successfully reduced by differential solubilisation in methanol as one of the goals of this work was to avoid the use of a time-consuming full chromatographic separation. The methanol-soluble oligomers were mainly low DP (≤3). The oligomers of higher molar mass, composed of 42% of cellotetraose and 36% of cellopentaose, were then functionalized and coupled with stearic acid through azide-alkyne click chemistry to obtain amphiphilic compounds. The self-assembly of these new bio-based compounds was finally investigated by dynamic light scattering (DLS) and transmission electron microscopy (TEM) and their critical micellar concentration (CMC) was found to be in the same range as alkylmaltosides and alkylglucosides.

Preparation of drug-in-cyclodextrin-in-liposomes at a large scale using a membrane contactor: Application to trans-anethole.

The present study aimed to prepare liposomes loaded with cyclodextrin/drug inclusion complexes at a pilot scale based on the ethanol injection technique. Anethole (ANE), a major component of anise and fennel essential oils, was used as a model of a volatile and highly hydrophobic drug. Membrane contactor (600mL) and a pilot plant (3L) were used for liposome production. The liposome preparations obtained were characterized for size, polydispersity index, zeta potential, morphology, stability and ANE release rate. All experimental set-ups were shown to be appropriate for the preparation of small, multilamellar vesicles with narrow size distribution and good stability at 4°C. The drug release study showed that only a small amount of ANE was released from liposome formulations after 21days of storage at 4°C. The loading rate of ANE was higher when ethanol was evaporated directly on the pilot plant compared to a rotary evaporation.

Trehalose has a protective effect on human brain-type creatine kinase during thermal denaturation.

We investigated the effects of trehalose on thermal inactivation and aggregation of human brain-type creatine kinase (hBBCK) in this study. In the presence of 1.0 M trehalose, the midpoint temperature of thermal inactivation (T (m)) of hBBCK increased by 4.6 °C, and the activation energy (E (a)) for thermal inactivation increased from 29.7 to 41.1 kJ mol(-1). Intrinsic fluorescence spectra also showed an increase in the apparent transition temperature (T (1/2)) of hBBCK from 43.0 °C to 46.5 °C, 47.7 °C, and 49.9 °C in 0, 0.6, 0.8, and 1.2 M trehalose, respectively. In addition, trehalose significantly blocked the aggregation of hBBCK during thermal denaturation. Our results indicate that trehalose has potential applications as a thermal stabilizer and may aid in the folding of other enzymes in addition to hBBCK.

Variability of cell wall polysaccharides composition and hemicellulose enzymatic profile in an apple progeny.

The genetic variability of apple cell walls polysaccharides chemical composition and structure was assessed in a progeny of 141 individuals harvested over 2 years. The variability of the hemicelluloses oligosaccharides released by glucanase was analyzed by MALDI-TOF MS. The genetic contribution was distinguished from harvest year as well as from parental crossing patterns and scab resistance selection. Results showed that harvest year had a major impact on cell wall polysaccharide composition and structure. Within each harvest, genetic effect impact more significantly cell wall polysaccharide chemistry than does reciprocal crossing or early scab selection. Uronic acids, glucose, galactose and xylose contents as well as some glucomannan and xyloglucan structures have a high heritability. This first cell wall chemotyping of an apple progeny opens the way for future searches of genetic markers for the chemical variability of cell wall polysaccharides.