Mono-6-Substituted Cyclodextrins—Synthesis and Applications

Cyclodextrins are well known supramolecular hosts used in a wide range of applications. Monosubstitution of native cyclodextrins in the position C-6 of a glucose unit represents the simplest method how to achieve covalent binding of a well-defined host unit into the more complicated systems. These derivatives are relatively easy to prepare; that is why the number of publications describing their preparations exceeds 1400, and the reported synthetic methods are often very similar. Nevertheless, it might be very demanding to decide which of the published methods is the best one for the intended purpose. In the review, we aim to present only the most useful and well-described methods for preparing different types of mono-6-substituted derivatives. We also discuss the common problems encountered during their syntheses and suggest their optimal solutions.

Quantification of Starch Order in Physically Modified Rice Flours Using Small-Angle X-ray Scattering (SAXS) and Fourier Transform Infrared (FT-IR) Spectroscopy

The purpose of this study was to understand the ordered structure of starch in rice flour based on a physical modification with non-heating, milling, and water sorption through the structural evaluation of rice flour using small-angle X-ray scattering (SAXS) and infrared spectroscopy within the 4000–100 cm−1 region. The SAXS pattern of the samples with low moisture contents subjected to milling yield a band within the 0.4–0.9 nm−1 of the q range owing to a lamellar repeat of starch with an ordered structure in rice flour. We proposed an order parameter using the intensity of the SAXS band to quantify the order structure of starch in rice flour, and the true density was negatively correlated with the order parameter. Infrared band at 990 cm−1 in COH bending mode applied to the hydroxyl group of C6 shifted to a low wavenumber corresponding to the order parameter. A linear correlation was found between the order parameter and the 990 cm−1 and band at 861 cm−1 owing to COC symmetrical stretching of glycoside bond and CH2 deformation of the glucose unit of starch, 572, 472, and 436 cm−1, owing to the pyranose ring in the glucose unit of starch. The identified infrared bands are effective for quantifying the ordered structure of starch at the lamellar level. When subjected to water sorption, the band position at 990 cm−1 shifted to a higher wavenumber above a water activity of 0.7. This result revealed that the water-induced transition of glass to rubber of starch in rice flour can be clearly evaluated through infrared spectroscopy using the band at 990 cm−1. In addition, the band at 861 cm−1 also shifted to a higher wavenumber, whereas those at 572 and 436 cm−1 did not show a significant shift. These results indicate that water sorption slightly affects the internal structure and may mainly affect the surface of starch.

GlycanGUI: Automated Glycan Annotation and Quantification Using Glucose Unit Index

The retention time provides critical information for glycan annotation and quantification from the Liquid Chromatography Mass Spectrometry (LC-MS) data. However, the variation of the precise retention time of glycans is highly dependent on the experimental conditions such as the specific separating columns, MS instruments and/or the buffer used. This variation hampers the exploitation of retention time for the glycan annotation from LC-MS data, especially when inter-laboratory data are compared. To incorporate the retention time of glycan across experiments, Glucose Unit Index (GUI) can be computed using the dextrin ladder as internal standard. The retention time of glycans are then calibrated with respect to glucose units derived from dextrin ladders. Despite the successful application of the GUI approach, the manual calibration process is quite tedious and often error prone. In this work, we present a standalone software tool GlycanGUI, with a graphic user interface to automatically carry out the GUI-based glycan annotation/quantification and subsequent data analysis. When tested on experimental data, GlycanGUI reported accurate GUI values compared with manual calibration, and thus is ready to be used for automated glycan annotation and quantification using GUI.

Thermostable α-Glucan Phosphorylase-catalyzed Enzymatic Chain-elongation to Produce 6-Deoxygenated α(1γ4)-Oligoglucans

: Herein, the synthesis of 6-deoxygenated α(1γ4)-oligoglucans via thermostable αglucan phosphorylase (from Aquifex aeolicus VF5)-catalyzed enzymatic chain-elongation is reported from a maltotriose primer using a non-native substrate, 6-deoxy-α-D-glucose 1- phosphate. The enzymatic reaction of the two substrates mainly produced a tetrasaccharide with one 6-deoxy-α-D-glucose unit at the non-reducing end, together with a minor pentasaccharide with two 6-deoxy-α-D-glucose units. The enzymatic chain-elongation from the primer in the presence of 6-deoxy-α-D-glucose 1-phosphate and a native substrate, α-D-glucose 1- phosphate, afforded 6-deoxygenated α(1γ4)-oligoglucans with varying degrees of polymerization. This enzymatic chain-elongation catalyzed by thermostable α-glucan phosphorylase is an efficient method to produce non-natural oligosaccharides, that is, 6-deoxygenated α(1γ4)- oligoglucans.

Antibacterial Properties of Glycosylated Surfaces: Variation of the Glucosidal Moiety and Fatty Acid Conformation of Grafted Microbial Glycolipids

<div>Glycosylated surfaces can display antimicrobial properties. It has been shown that sophorolipids can be used to develop biocidal coatings against Gram-positive and Gramnegative bacteria, but with a limited efficiency so far. Therefore, it appears necessary to further investigate the surface antibacterial activity of a broader set of structurally related glycolipids.</div><div>The present work explores the influence of the glucosidic moiety (gluco-, sophoro-, cellobio-)</div><div>and the fatty acid backbone (saturated, cis or trans monounsaturated). We show that the fatty</div><div>acid backbone plays an important role: cis derivative of sophorolipids (SL) grafted onto model</div><div>gold surfaces has better biocidal properties than saturated (SL0) and trans monounsaturated</div><div>(SLt) molecules, which appear to be inefficient. The number of glucose units is also a key factor:</div><div>a one-third decrease in antibacterial activity is observed when having one glucose unit (GL)</div><div>compared to two (SL).Sugar acetylation (SLa) does not seem to have an impact on the biocidal</div><div>properties of surfaces. These results are not limited to sophorolipids, cellobioselipids (CL)</div><div>leading to similar antibacterial observations. </div>

Antibacterial Properties of Glycosylated Surfaces: Variation of the Glucosidal Moiety and Fatty Acid Conformation of Grafted Microbial Glycolipids

<div>Glycosylated surfaces can display antimicrobial properties. It has been shown that sophorolipids can be used to develop biocidal coatings against Gram-positive and Gramnegative bacteria, but with a limited efficiency so far. Therefore, it appears necessary to further investigate the surface antibacterial activity of a broader set of structurally related glycolipids.</div><div>The present work explores the influence of the glucosidic moiety (gluco-, sophoro-, cellobio-)</div><div>and the fatty acid backbone (saturated, cis or trans monounsaturated). We show that the fatty</div><div>acid backbone plays an important role: cis derivative of sophorolipids (SL) grafted onto model</div><div>gold surfaces has better biocidal properties than saturated (SL0) and trans monounsaturated</div><div>(SLt) molecules, which appear to be inefficient. The number of glucose units is also a key factor:</div><div>a one-third decrease in antibacterial activity is observed when having one glucose unit (GL)</div><div>compared to two (SL).Sugar acetylation (SLa) does not seem to have an impact on the biocidal</div><div>properties of surfaces. These results are not limited to sophorolipids, cellobioselipids (CL)</div><div>leading to similar antibacterial observations. </div>

Antibacterial Properties of Glycosylated Surfaces: Variation of the Glucosidal Moiety and Fatty Acid Conformation of Grafted Microbial Glycolipids

<div>Glycosylated surfaces can display antimicrobial properties. It has been shown that sophorolipids can be used to develop biocidal coatings against Gram-positive and Gramnegative bacteria, but with a limited efficiency so far. Therefore, it appears necessary to further investigate the surface antibacterial activity of a broader set of structurally related glycolipids.</div><div>The present work explores the influence of the glucosidic moiety (gluco-, sophoro-, cellobio-)</div><div>and the fatty acid backbone (saturated, cis or trans monounsaturated). We show that the fatty</div><div>acid backbone plays an important role: cis derivative of sophorolipids (SL) grafted onto model</div><div>gold surfaces has better biocidal properties than saturated (SL0) and trans monounsaturated</div><div>(SLt) molecules, which appear to be inefficient. The number of glucose units is also a key factor:</div><div>a one-third decrease in antibacterial activity is observed when having one glucose unit (GL)</div><div>compared to two (SL).Sugar acetylation (SLa) does not seem to have an impact on the biocidal</div><div>properties of surfaces. These results are not limited to sophorolipids, cellobioselipids (CL)</div><div>leading to similar antibacterial observations. </div>

Properties of Carboxymethylated-Cassava and Sago Starches Prepared by using Sodium Monochloroacetate

In the present study, carboxymethyl starch (CMC) were produced from different sources of starch and their physico-chemical properties were evaluated. Carboxymethylation was performed using different concentrations of sodium monochloroacetate (1.1, 1.3 and 1.5 mol/mol of anhydrous glucose units) in a three-necked round-bottom flask (250 mL) for approximately 3 h (250 rpm and 40°C) in a two-stage reaction comprising alkalization and etherification. The introduction of carboxymethyl groups was confirmed in the results by the appearance of a new peak in the FTIR spectrum in 1650.10-1649.76 cm-1 region. In addition, degree of substitution (DS) of produced CMS was ranged from 0.53-0.60. An increase in the concentration of sodium monochloroacetate (1.1, 1.3 and 1.5 mol/mol of anhydrous glucose unit) resulted in greater paste clarity, higher solubility and greater swelling than native starch. Furthermore, cassava starch (tapioca) produced a CMS exhibited greater swelling than sago starch, however by contrast, CMS-sago was more soluble and clearer than CMS-cassava.