Controlled deposition of nanosize and microsize particles by spin-casting

The deposition of nanosize and microsize spherical particles on planar solid substrates by hydrodynamic-evaporative spin-casting is studied. The particles are dispersed in a volatile liquid, which evaporates during the process, and the particles are finally deposited on the substrate. Their coverage, Gamma, depends on the processing parameters (concentration by weight, particles size, etc.). The behavior of the particles during the spin-casting process and their final Gamma values are investigated. It is found that for up to particle diameters of a few micrometers, particle deposition can be described by a theoretical approach developed for the spin-casting of polymer solutions (Karpitschka, S.; Weber, C. M.; Riegler, H. Chem. Eng. Sci. 2015, 129, 243-248. Danglad-Flores, J.; Eickelmann, S.; Riegler, H. Chem. Eng. Sci. 2018, 179, 257-264). For large particles, this basic theory fails. The causes of this failure are analyzed, and a corrected, more general theoretical approach is presented. It takes into account particle size effects as well as particle sedimentation. In summary, we present new insights into the spin-cast process of particle dispersions, analyze the contributions affecting the final particle coverage, and present a theoretical approach which describes and explains the experimental findings

Transport phenomena in solid phase synthesis supported by cross-linked polymer beads

Solid phase synthesis (SPS) is a powerful tool for synthesizing oligomers, especially peptides, nucleic acids, and glycans. Since Merrifield developed solid phase peptide synthesis in 1963, organic chemistry and analytics have seen major advances. The need to optimize the process regarding cost, time, and energy consumption has renewed the research on previously overlooked transport phenomena. Here, we summarize the current understanding of momentum, heat, and mass transport in SPS reactors, highlighting the progress and identifying the urgent questions to be addressed

Parametric Analysis of Donor Activation for Glycosylation Reactions

The chemical synthesis of complex oligosaccharides relies on efficient and highly reproducible glycosylation reactions. The outcome of a glycosylation is contingent upon several environmental factors, such as temperature, acidity, the presence of residual moisture, as well as the steric, electronic, and conformational aspects of the reactants. Each glycosylation proceeds rapidly and with a high yield within a rather narrow temperature range. For better control over glycosylations and to ensure fast and reliable reactions, a systematic analysis of 18 glycosyl donors revealed the effect of reagent concentration, water content, protecting groups, and structure of the glycosyl donors on the activation temperature. With these insights, we parametrize the first step of the glycosylation reaction to be executed reliably and efficiently

Enabling Technologies in Carbohydrate Chemistry: Automated Glycan Assembly, Flow Chemistry and Data Science

The synthesis of defined oligosaccharides is a complex task. Several enabling technologies have been introduced in the last two decades to facilitate synthetic access to these valuable biomolecules. In this concept, we describe the technological solutions that have advanced glycochemistry using automated glycan assembly, flow chemistry and data science as examples. We highlight how the synergies between these different technologies can further advance the field, with progress toward the realization of a self‐driving lab for glycan synthesis

Design, Synthesis, and Characterization of Stapled Oligosaccharides

Stapling short peptides to lock specific conformations and thereby obtain superior pharmacological properties is well established. However, similar concepts have not been applied to oligosaccharides. Here, we describe the design, synthesis, and characterization of the first stapled oligosaccharides. Automated assembly of β-(1,6)-glucans equipped with two alkenyl side chains was followed by on-resin Grubbs metathesis for efficient ring closure with a variety of cross-linkers of different sizes. Oligosaccharide stapling increases enzymatic stability and cell penetration, therefore opening new opportunities for the use of glycans in medicinal chemistry

Producción de espumas sólidas de celulosa y Almidón de Yuca | Solid foam production of Cellulose and Cassava starch

 La reutilización de desechos sólidos es una alternativa viable por el potencial ahorro en energía, agua potable y materias primas indispensables para favorecer una economía de desarrollo sostenible. En este sentido, se llevó a cabo la producción de espumas sólidas utilizando celulosa a partir de papel Bond reciclado y gel de almidón de yuca como fase líquida, estabilizando el sistema con surfactantes (hidroxietilcelulosa como espesante y lauril sulfato de sodio como espumante). La espuma se formó mediante el método de Ross-Miller modificado, por aireación y mezclado con agitación fuerte a 10.000 rpm durante 5 min y secandola en un horno de bandeja. La formulación óptima correspondió a 15 g celulosa, 15 g almidón de yuca y 0,3 mol/L espumante; con las siguientes características estructurales, físicas y mecánicas: matriz sólida conformada por una microescruestructura de fibras de celulosa entrecruzadas con hojuelas de almidón; superficie externa sin desprendimiento de polvo al contacto ni olor apreciable; densidad y porosidad promedio de 173,49 kg/m3 y 73,22%, respectivamente; capacidad de absorción de agua de 512%; estabilidad térmica hasta 120°C y aislamiento térmico hasta un diferencial de 50°C. En cuanto a los parámetros indicativos de amortiguación, la resistencia a la compresión fue 3,99 kg/cm2 de área con poca deformación (20% de altura original). Estas propiedades hacen competitivas las espumas obtenidas a partir del almidón de yuca nacional y papel reciclado, respecto a las espumas importadas disponibles comercialmente, y hacen factible su uso como excelente material aislante y absorbente para diversas aplicaciones en construcción, embalaje y relleno.  Palabras clave: Papel reciclado, surfactante, aislante térmico. ABSTRACT Waste solids reutilization is an alternative to save energy, water and raw materials necessary for an eco-economy of sustainable development. In that sense, solid foams were produced using cellulose from recycled Bond paper and cassava starch gel as liquid phase, stabilizing the system with surfactants (hydroxyethylcellulose as thickener and sodium lauril sulfate as foaming). The foam was prepared through the modified Rosse-Miller method, by aeration and strong stirring at 10,000 rpm for 5 min, and drying it in a tray oven. The optimum formulation was 15 g of cellulose, 15 g of cassava starch and a concentration of 0.3 mol/L of foaming; with the following structural, physical and mechanical features: solid matrix with cross linked microstructure between cellulose fibers and starch flakes; outer surface without dusting at contact and odorless; average density and porosity 173.49 kg/m3 and 73.22%, respectively; 512% of swelling; thermal stability up to 120 °C and thermal insulation with 50 ºC of differential temperature. With respect to cushioning parameters, compression strength was 3.99 kg/cm2, with a slight deformation (20% from original height). These properties make the foams obtained from national cassava starch and recycled paper, competitive compared to imported commercially available foams, and make possible their use as excellent absorbent insulating material for various applications in construction, packaging and filling. Key words: Recycled paper, surfactant, thermal insulation.

Synthesis of a heparan sulfate tetrasaccharide using automated glycan assembly †

Herein we utilise automated glycan assembly to complete solid-phase synthesis of defined heparan sulfate oligosaccharides, employing challenging d-glucuronate disaccharide donors. Using an orthogonally protected d-GlcN-α-d-GlcA donor, milligram-scale synthesis of a heparan sulfate tetrasaccharide is completed in 18% yield over five steps. Furthermore, orthogonal protecting groups enabled regiospecific on-resin 6-O-sulfation. This methodology provides an important benchmark for the rapid assembly of biologically relevant heparan sulfate sequences