Accurate Extraction of Nanometer Distances in Multimers by Pulse EPR

Pulse electron paramagnetic resonance (EPR) is gaining increasing importance in structural biology. The PELDOR (pulsed electron–electron double resonance) method allows extracting distance information on the nanometer scale. Here, we demonstrate the efficient extraction of distances from multimeric systems such as membrane‐embedded ion channels where data analysis is commonly hindered by multi‐spin effects.     

Synthesis and Isolation of the Titanium–Scandium Endohedral Fullerenes—Sc2TiC@Ih‐C80, Sc2TiC@D5h‐C80 and Sc2TiC2@Ih‐C80: Metal Size Tuning of the TiIV/TiIII Redox Potentials

The formation of endohedral metallofullerenes (EMFs) in an electric arc is reported for the mixed‐metal Sc–Ti system utilizing methane as a reactive gas. Comparison of these results with those from the Sc/CH₄ and Ti/CH₄ systems as well as syntheses without methane revealed a strong mutual influence of all key components on the product distribution. Whereas a methane atmosphere alone suppresses the formation of empty cage fullerenes, the Ti/CH₄ system forms mainly empty cage fullerenes. In contrast, the main fullerene products in the Sc/CH₄ system are Sc₄C₂@C₈₀ (the most abundant EMF from this synthesis), Sc₃C₂@C₈₀, isomers of Sc₂C₂@C₈₂, and the family Sc₂C_{2 n} (2 n=74, 76, 82, 86, 90, etc.), as well as Sc₃CH@C₈₀. The Sc–Ti/CH₄ system produces the mixed‐metal Sc₂TiC@C_{2 n} (2 n=68, 78, 80) and Sc₂TiC₂@C_{2 n} (2 n=80) clusterfullerene families. The molecular structures of the new, transition‐metal‐containing endohedral fullerenes, Sc₂TiC@I_h‐C₈₀, Sc₂TiC@D_5h‐C₈₀, and Sc₂TiC₂@I_h‐C₈₀, were characterized by NMR spectroscopy. The structure of Sc₂TiC@I_h‐C₈₀ was also determined by single‐crystal X‐ray diffraction, which demonstrated the presence of a short Ti=C double bond. Both Sc₂TiC‐ and Sc₂TiC₂‐containing clusterfullerenes have Ti‐localized LUMOs. Encapsulation of the redox‐active Ti ion inside the fullerene cage enables analysis of the cluster–cage strain in the endohedral fullerenes through electrochemical measurements.     

Cationic Xylan Derivatives with High Degree of Functionalization

Xylan from birch wood was characterized regarding both the supramolecular structure (X-ray, CP/MAS ¹³C-NMR) and the sugar composition. The reaction of the birch wood xylan with 2,3-epoxypropyltrimethylammonium chloride in 1,2-dimethoxyethane as slurry medium yields water-soluble, cationic 2-hydroxypropyltrimethylammonium xylan derivatives with high degree of substitution (DS). The DS values up to 1.6 can be controlled by adjusting the molar ratio in a one step synthesis. The structure of the cationic xylan derivatives was confirmed by means of DEPT(135) NMR spectroscopy. Film forming properties of cationic xylan derivatives were investigated with SEM measurements.     

Laccase-catalyzed carbon-carbon bond formation: oxidative dimerization of salicylic esters by air in aqueous solution

The laccase catalyzed oxidative dimerization of salicylic esters, a rare example of a laccase-catalyzed carbon-carbon bond formation, was studied. This reaction allows the use of air as stoichiometric oxidant and proceeds in aqueous solution. The preparative scope and the mechanism of the method, which provides a new and convenient access to functionalized biaryls under mild conditions, were investigated.     

Using freezing and drying techniques of emulsions for the microencapsulation of fish oil to improve oxidation stability

Epidemiological investigations show that n-3-polyunsaturated fatty acids (PUFA) have a protective effect with respect to coronary heart disease. For a long time fish oil has been known as a source of PUFA. The successful incorporation of fish oil into the normal food components offers an opportunity to increase the intake of PUFA, but fish oil has to be protected against oxidation preferably by microencapsulation. The high temperatures during the traditional spray-drying microencapsulation process lead to an increased oxidation of the PUFA. The authors demonstrate the application of a freeze-drying technique with respect to the production of dried microencapsulated fish oil with high quality and oxidation stability. The influence of emulsion parameters, freezing parameters and formulation on the stability of a dried fish oil emulsion is presented and illustrated. The used procedure gave a product with a good oxidation stability which is available as pellets or powder. It was found that the stability was mainly influenced by the freezing rate and the used encapsulation carbohydrate, whereby the powder showed a better shelf life than the pellets. Concluding, it can be summarized that the production of microencapsulated fish oil by freezing and subsequent freeze-drying offers an opportunity to achieve a product with a good oxidation stability.     

Cycloaddition Reactions and Dendritic Polymer Architectures – A Perfect Match

Summery: The potential of cycloaddition (CA) reactions for the synthesis of dendritic polymers is pointed out. The [4 + 2] Diels Alder cycloaddition as well as 1,3-dipolar CA reactions including “click chemistry” are addressed, and the advantages of these reactions like high selectivity, thus high tolerance towards additional functionalities, high yields and synthesis under mild reaction conditions are highlighted. New perfectly branched dendrimers as well as hyperbranched polymers have been prepared and modified using the 1,3-dipolar cycloaddition reaction of azines with alkynes. The 1,3-dipolar CA reaction of bisazine with maleimides results in hyperbranched and thus, irregular and broadly distributed polymers though with a degree of branching of 100% due to special intermediate formation. The [4 + 2] Diels Alder cycloaddition was successfully applied for the synthesis of highly branched polyphenylene structures using the AB₂ + AB and the A₂ + B₃ approach. CA reactions are also very suitable for highly efficient polymer analogous reactions and thus, they can also be used to prepare complex polymer architectures like dendronized polymers.     

Microwave-Assisted One-Pot Lipid Extraction and Glycolipid Production from Oleaginous Yeast Saitozyma podzolica in Sugar Alcohol-Based Media

Glycolipids are non-ionic surfactants occurring in numerous products of daily life. Due to their surface-activity, emulsifying properties, and foaming abilities, they can be applied in food, cosmetics, and pharmaceuticals. Enzymatic synthesis of glycolipids based on carbohydrates and free fatty acids or esters is often catalyzed using certain acyltransferases in reaction media of low water activity, e.g., organic solvents or notably Deep Eutectic Systems (DESs). Existing reports describing integrated processes for glycolipid production from renewables use many reaction steps, therefore this study aims at simplifying the procedure. By using microwave dielectric heating, DESs preparation was first accelerated considerably. A comparative study revealed a preparation time on average 16-fold faster than the conventional heating method in an incubator. Furthermore, lipids from robust oleaginous yeast biomass were successfully extracted up to 70% without using the pre-treatment method for cell disruption, limiting logically the energy input necessary for such process. Acidified DESs consisting of either xylitol or sorbitol and choline chloride mediated the one-pot process, allowing subsequent conversion of the lipids into mono-acylated palmitate, oleate, linoleate, and stearate sugar alcohol esters. Thus, we show strong evidence that addition of immobilized Candida antarctica Lipase B (Novozym 435^®), in acidified DES mixture, enables a simplified and fast glycolipid synthesis using directly oleaginous yeast biomass.