Self-Adaptive Synthesis of Non-Covalent Crosslinkers while Folding Single-Chain Polymers.

Peptide folding is a dynamic process driven by non-covalent cross-linking leading to functional nanostructures for essential biochemical activities. However, replicating this process in synthetic systems is challenging due to the difficulty in mimicking nature's real-time regulation of non-covalent crosslinking for single-chain polymer folding. Here, we address this by employing anionic dithiol building blocks to create macrocyclic disulfides as non-covalent crosslinkers that adapted to the folding process. Initially, small macrocycles facilitated a low degree folding of a polycation. Then, this preorganized structure catalysed the production of larger macrocycles that enhanced the folding conversely. The self-adaptive synthesis was verified through the encapsulation of an anticancer drug, showing an updated production distribution of non-covalent crosslinkers and maximizing drug-loading efficiency against drug-resistant cancer in vitro. Our research advances the understanding of molecular systems by exploring species evolution via the structural dynamics of polymer folding. Additionally, adaptive synthesis enables controlled, sequential folding of synthetic polymers, with the potential to mimic protein functions.

Visualizing Degradation of Cellulose Nanofibers by Acid Hydrolysis.

Cellulose hydrolysis is an extensively studied process due to its relevance in the fields of biofuels, chemicals production, and renewable nanomaterials. However, the direct visualization of the process accompanied with detailed scaling has not been reported because of the vast morphological alterations occurring in cellulosic fibers in typical heterogeneous (solid/liquid) hydrolytic systems. Here, we overcome this distraction by exposing hardwood cellulose nanofibers (CNFs) deposited on silica substrates to pressurized HCl gas in a solid/gas system and examine the changes in individual CNFs by atomic force microscopy (AFM). The results revealed that hydrolysis proceeds via an intermediate semi-fibrous stage before objects reminiscent of cellulose nanocrystals were formed. The length of the nanocrystal-like objects correlated well with molar mass, as analyzed by gel permeation chromatography, performed on CNF aerogels hydrolyzed under identical conditions. Meanwhile, X-ray diffraction showed a slight increase in crystallinity index as the hydrolysis proceeded. The results provide a modern visual complement to >100 years of research in cellulose degradation.

Challenges in Synthesis and Analysis of Asymmetrically Grafted Cellulose Nanocrystals via Atom Transfer Radical Polymerization.

When cellulose nanocrystals (CNCs) are isolated from cellulose microfibrils, the parallel arrangement of the cellulose chains in the crystalline domains is retained so that all reducing end-groups (REGs) point to one crystallite end. This permits the selective chemical modification of one end of the CNCs. In this study, two reaction pathways are compared to selectively attach atom-transfer radical polymerization (ATRP) initiators to the REGs of CNCs, using reductive amination. This modification further enabled the site-specific grafting of the anionic polyelectrolyte poly(sodium 4-styrenesulfonate) (PSS) from the CNCs. Different analytical methods, including colorimetry and solution-state NMR analysis, were combined to confirm the REG-modification with ATRP-initiators and PSS. The achieved grafting yield was low due to either a limited conversion of the CNC REGs or side reactions on the polymerization initiator during the reductive amination. The end-tethered CNCs were easy to redisperse in water after freeze-drying, and the shear birefringence of colloidal suspensions is maintained after this process.

Fast and quantitative compositional analysis of hybrid cellulose-based regenerated fibers using thermogravimetric analysis and chemometrics.

Cellulose can be dissolved with another biopolymer in a protic ionic liquid and spun into a bicomponent hybrid cellulose fiber using the Ioncell® technology. Inside the hybrid fibers, the biopolymers are mixed at the nanoscale, and the second biopolymer provides the produced hybrid fiber new functional properties that can be fine-tuned by controlling its share in the fiber. In the present work, we present a fast and quantitative thermoanalytical method for the compositional analysis of man-made hybrid cellulose fibers by using thermogravimetric analysis (TGA) in combination with chemometrics. First, we incorporated 0-46 wt.% of lignin or chitosan in the hybrid fibers. Then, we analyzed their thermal decomposition behavior in a TGA device following a simple, one-hour thermal treatment protocol. With an analogy to spectroscopy, we show that the derivative thermogram can be used as a predictor in a multivariate regression model for determining the share of lignin or chitosan in the cellulose hybrid fibers. The method generated cross validation errors in the range 1.5-2.1 wt.% for lignin and chitosan. In addition, we discuss how the multivariate regression outperforms more common modeling methods such as those based on thermogram deconvolution or on linear superposition of reference thermograms. Moreover, we highlight the versatility of this thermoanalytical method-which could be applied to a wide range of composite materials, provided that their components can be thermally resolved-and illustrate it with an additional example on the measurement of polyester content in cellulose and polyester fiber blends. The method could predict the polyester content in the cellulose-polyester fiber blends with a cross validation error of 1.94 wt.% in the range of 0-100 wt.%. Finally, we give a list of recommendations on good experimental and modeling practices for the readers who want to extend the application of this thermoanalytical method to other composite materials. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10570-021-03923-6.

Size-exclusion chromatography of xylan derivatives-the critical evaluation of macromolecular data.

Hydroxypropyl xylans with varying degrees of substitution were characterized by size-exclusion chromatography. Molar masses of the samples were determined using two approaches: by conventional calibration with molar mass standards and by a multi-detection method that utilizes the combination of static light scattering, viscometry, and differential refractive index detection. The molar mass results obtained by the multi-detection method were accurate, but required the determination of separate refractive index increments for each structurally different sample. The column calibration approach with standard pullulan samples gave biased results due to the differences in hydrodynamic volumes between pullulans and hydroxypropyl xylans with similar molar masses. The degree of hydroxypropylation affected the chain conformation and compactness of the polymer chains. Mark-Houwink parameters and persistence length values suggested that the hydroxypropyl substituents reduced the flexibility of the xylan chain and made the polymer chain more extended.

Size-exclusion chromatography of metal nanoparticles and quantum dots.

This review presents an overview of size-exclusion chromatographic separation and characterization of noble metal nanoparticles (NPs) and quantum dots (QDs) over the past 25 years. The properties of NPs and QDs that originate from quantum and surface effects are size dependent; to investigate these properties, a separation technique such as size-exclusion chromatography (SEC) is often needed to obtain narrow distribution NP populations that are also separated from the unreacted starting materials. Information on the size distributions and optical properties of NPs have been obtained by coupling SEC to detection methods such as ultraviolet-visible and/or fluorescence spectroscopy. Problems associated with the sorption of NPs and QDs onto various SEC stationary phases, employing both aqueous and organic eluents, are also discussed here.

Determining the core, corona, and total size of CdSeS/ZnS quantum dots by SEC/QELS and TEM.

The size (hydrodynamic or Stokes radius, R H) of non-functionalized CdSeS/ZnS (core/shell) quantum dots (QDs) was characterized by size-exclusion chromatography with on-line quasi-elastic light scattering (SEC/QELS). Accurate determination of the size of QDs is important, because many of the optical properties of these materials are size dependent. A clear advantage of SEC/QELS over many batch techniques (e.g., QELS without separation) is the capability of the hyphenated technique to characterize the entire size range of a disperse sample, rather than merely providing a statistical average of the sizes present. Here, the SEC/QELS-determined R H values of CdSeS/ZnS QDs are compared to those determined by a traditional SEC experiment employing a calibration curve based on polystyrene standards, providing for the first reported study on SEC/QELS of non-functionalized QDs while also demonstrating the shortcomings of the widely-employed calibration curve approach. Furthermore, combining the R H of the QDs obtained by SEC/QELS with core size measurements derived from transmission electron microscopy allowed further calculation of the size of the QDs' coronas. The latter result was found to be in close agreement to the previously measured dimension of the main corona constituent, as well as with the calculated size of this constituent.

AF4/MALS/QELS/DRI characterization of regular star polymers and their "span analogs".

Asymmetric flow field-flow fractionation (AF4) coupled with multi-angle static and quasi-elastic light scattering and differential refractive index detectors, was employed for the separation and characterization of regular star-shaped polystyrenes and their linear and span analogs in tetrahydrofuran. Stars with different arm lengths were separated from each other by employing a binary slope cross-flow gradient. Cross-flow optimization enabled fast separation of polystyrenes in two- and three-component blends. Macromolecular parameters were obtained by using light-scattering and refractive index detection, and properties of polystyrenes with different molecular architectures were compared. To our knowledge, this is the first report on the separation of star polymers by AF4. Novel characterization approaches for stars are important from both applied and fundamental standpoints, as these macromolecules are valued for their tribological, drug delivery, catalytic and coating capabilities, and also serve as model compounds for the structured study of long-chain branching and its effects in polymers.

Analysis of plant ribosomes with asymmetric flow field-flow fractionation.

Ribosome profiling is a technique used to separate ribosomal subunits, 80S ribosomes (monosomes), and polyribosomes (polysomes) from other RNA-protein complexes. It is traditionally performed in sucrose gradients. In this study, we used asymmetric flow field-flow fractionation (AsFlFFF) to characterize ribosome profiles of Nicotiana benthamiana plants. With the optimized running conditions, we were able to separate free molecules from ribosomal subunits and intact ribosomes. We used various chemical and enzymatic treatments to validate the positions of subunits, monosomes, and polysomes in the AsFlFFF fractograms. We also characterized the protein and RNA content of AsFlFFF fractions by gel electrophoresis and western blotting. The reverse transcription polymerase chain reaction (RT-PCR) analysis showed that ribosomes remained bound to messenger RNAs (mRNAs) during the analysis. Therefore, we conclude that AsFlFFF can be used for ribosome profiling to study the mRNAs that are being translated. It can also be used to study the protein composition of ribosomes that are active in translation at that particular moment.

Design of Fluoro-Free Surfaces Super-Repellent to Low-Surface-Tension Liquids.

Super-liquid-repellent surfaces feature high liquid contact angles and low sliding angles find key applications in anti-fouling and self-cleaning. While repellency for water is easily achieved with hydrocarbon functionalities, repellency for many low-surface-tension liquids (down to 30 mN m-1 ) still requires perfluoroalkyls (a persistent environmental pollutant and bioaccumulation hazard). Here, the scalable room-temperature synthesis of stochastic nanoparticle surfaces with fluoro-free moieties is investigated. Silicone (dimethyl and monomethyl) and hydrocarbon surface chemistries are benchmarked against perfluoroalkyls, assessed using model low-surface-tension liquids (ethanol-water mixtures). It is discovered that both hydrocarbon- and dimethyl-silicone-based functionalization can achieve super-liquid-repellency down to 40-41 mN m-1 and 32-33 mN m-1 , respectively (vs 27-32 mN m-1 for perfluoroalkyls). The dimethyl silicone variant demonstrates superior fluoro-free liquid repellency likely due to its denser dimethyl molecular configuration. It is shown that perfluoroalkyls are not necessary for many real-world scenarios requiring super-liquid-repellency. Effective super-repellency of different surface chemistries against different liquids can be adequately predicted using empirically verified phase diagrams. These findings encourage a liquid-centric design, i.e., tailoring surfaces for target liquid properties. Herein, key guidelines are provided for achieving functional yet sustainably designed super-liquid-repellency.

Functional and anionic cellulose-interacting polymers by selective chemo-enzymatic carboxylation of galactose-containing polysaccharides.

Carboxylated, anionic polysaccharides were selectively prepared using a combination of enzymatic and chemical reactions. The galactose-containing polysaccharides studied were spruce galactoglucomannan, guar galactomannan, and tamarind galactoxyloglucan. The galactosyl units of the polysaccharides were first oxidized with galactose oxidase (EC 1.1.3.9) and then selectively carboxylated, resulting in the galacturonic acid derivatives with good conversion and yield. The degrees of oxidation (DO) of the products were determined by gas chromatography-mass spectrometry (GC-MS). A novel feasible electrospray ionization-mass spectrometry (ESI-MS) method was also developed for the determination of DO. The solution properties and charge densities of the products were investigated. The interaction of the products with cellulose was studied by two methods, bulk sorption onto bleached birch kraft pulp and adsorption onto nanocellulose ultrathin films by quartz crystal microbalance with dissipation (QCM-D). To study the effect of the location of the carboxylic acid groups on the physicochemical properties, polysaccharides were also oxidized by 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated reaction producing polyuronic acids. The chemo-enzymatically oxidized galacturonic polysaccharides with an unmodified backbone had a better ability to interact with cellulose than the TEMPO-oxidized products. The selectively carboxylated polysaccharides can be further exploited, as such, or in the targeted functionalization of cellulose surfaces.

Enzymatic modification of oat globulin enables covalent interaction with procyanidin B2.

The effect of enzyme treatment on protein-tannin interactions was investigated using up-to-date analytical approaches for improving their physical properties. The formation of ligands between procyanidin B2 and native oat globulin (OG) was observed to be affected by the ratio of procyanidin B2 to OG and the availability of tryptophan. For the transglutaminase-treated OG, the results obtained from circular dichroism (CD) and size exclusion chromatography (SEC) revealed that procyanidin B2 acted as an acyl acceptor in the process of OG deamidation. Procyanidin B2 also inhibited the non-covalent protein-protein interactions occurring between the aromatic side-chains or sedimentation of tryptophan aggregates. For trypsin-treated OG, procyanidin B2 interacted with phenylalanine and the tryptophan side-chain of OG. The inhibition of procyanidin B2 towards protein-protein aggregation was proved by the observation of CD, SEC and asymmetric flow field-flow fractionation.

Behavior of polysaccharide assemblies in field-flow fractionation and size-exclusion chromatography.

Asymmetric flow field-flow fractionation (AsFlFFF) and high-performance size-exclusion chromatography (HPSEC) are techniques for separating and characterizing macromolecules; until now the latter is more utilized for analyzing polysaccharides. The demand for characterizing complex, high-molar-mass polysaccharides has raised interest in the use of AsFlFFF in analyzing polymeric carbohydrates in addition to HPSEC. In this paper, we compare the behavior of arabinoxylan aggregates present in aqueous solution in AsFlFFF and HPSEC and their effect on the obtained molecular characteristics (molar mass averages and size). Although the amount of aggregates in aqueous arabinoxylan solutions may be low, their role needs to be understood to avoid erroneous interpretations of AsFlFFF and HPSEC data. When these two separation systems were compared, AsFlFFF seemed to possess more separation power for the differentiation of aggregates from individual chains than HPSEC. To our knowledge, this is the first report on the characterization of xylans with AsFlFFF.

Cellulose-lignin composite fibres as precursors for carbon fibres. Part 1 - Manufacturing and properties of precursor fibres.

Cellulose-lignin composite fibres were spun from ionic liquid (IL) solutions by dry-jet wet spinning. Birch pre-hydrolysed Kraft (PHK) pulp and organosolv beech (BL) or spruce lignin (SL) were dissolved in the IL 1,5-diazabicyclo[4.3.0]non-5-enium acetate ([DBNH]OAc) to prepare spinning dopes. Fibres with lignin concentrations of up to 50 % were spun successfully. The fibres were analysed focusing on important properties for the production of carbon fibres (CF). Due to the higher molar mass of the SL compared to the BL, SL showed higher stability in the spinning process, giving higher lignin content in the final fibres. The CF yield after carbonization increased with increasing lignin content. The higher carbon content of SL compared to BL, resulted in moderately higher CF yield of the SL fibres, compared to fibres with BL. Overall, the produced cellulose-lignin composite fibres show great potential as precursors for CF production.

An efflux transporter PbrA and a phosphatase PbrB cooperate in a lead-resistance mechanism in bacteria.

The gene cluster pbrTRABCD from Cupriavidus metallidurans CH34 is thought to encode a unique, specific resistance mechanism for lead. However, the exact functions of these genes are unknown. In this study we examine the metal specificity and functions of pbrABCD by expressing these genes in different combinations and comparing their ability to restore Pb(2+), Zn(2+) and Cd(2+) resistance in a metal-sensitive C. metallidurans strain DN440. We show that lead resistance in C. metallidurans is achieved through the cooperation of the Zn/Cd/Pb-translocating ATPase PbrA and the undecaprenyl pyrophosphate phosphatase PbrB. While PbrA non-specifically exported Pb(2+), Zn(2+) and Cd(2+), a specific increase in lead resistance was observed when PbrA and PbrB were coexpressed. As a model of action for PbrA and PbrB we propose a mechanism where Pb(2+) is exported from the cytoplasm by PbrA and then sequestered as a phosphate salt with the inorganic phosphate produced by PbrB. Similar operons containing genes for heavy metal translocating ATPases and phosphatases were found in several different bacterial species, suggesting that lead detoxification through active efflux and sequestration is a common lead-resistance mechanism.

Colloidal features of softwood galactoglucomannans-rich extract.

Development of a sustainable bioeconomy requires valorization of renewable resources, such as wood hemicelluloses. The intra- and inter-molecular association of hemicelluloses within themselves or with other wood components can result in complex macromolecular features. These features exhibit functionality as hydrocolloids, however macromolecular characterization of these heterogeneous materials are challenging using conventional techniques such as size-exclusion chromatography. We studied galactoglucomannans (GGM) -rich softwood extracts at two grades of purity-as crude extract and after ethanol-precipitation. Asymmetrical flow field-flow fractionation (AF4) was optimized and utilized to fractionate size classes in GGM extracts, and subsequent characterization was performed with light scattering and microscopy techniques. Both GGM extracts contained polysaccharides of around 10,000 g/mol molar mass, and colloidal assemblies and/or particles in sub-micron size range. The optimized AF4 method facilitates the characterization of complex biomass-derived carbohydrates without pre-fractionation, and provides valuable understanding of their unique macromolecular features for their future application in food, pharmaceuticals, and cosmetics.

Comprehensive multidetector HPSEC study on solution properties of cereal arabinoxylans in aqueous and DMSO solutions.

The water-soluble arabinoxylans from wheat flour (high, medium, and low viscosity samples) and rye flour (high viscosity sample) were characterized by (1)H NMR spectroscopy and HPSEC with refractive index, light scattering, and viscometric detectors. These cereal arabinoxylans have recently been used as model arabinoxylans in various studies, but their solution properties have not been previously investigated. In this study, two HPSEC eluent systems were used: the water-based system and DMSO-based system. DMSO seemed to be a better solvent than water, especially for arabinoxylans containing a low amount of arabinose substituents. (1)H NMR spectroscopy indicated the structural differences between the analyzed arabinoxylan samples that also affected the hydrodynamic parameters obtained with HPSEC. Influence of arabinose side groups on the solution conformation of arabinoxylans could not be excluded based on our data, despite the role of arabinose substituents being questioned in previous investigations concerning arabinoxylan conformation in solution.

Knoevenagel Condensation for Modifying the Reducing End Groups of Cellulose Nanocrystals.

Herein, we demonstrate an effective approach toward functionalization of cellulose nanocrystal (CNC) reducing ends by means of a Knoevenagel condensation reaction with a reactive ß-diketone (acetylacetone). The end-wise modification was elucidated by advanced NMR analysis, which was facilitated by dissolving the CNCs in ionic liquid electrolyte and by the concomitant assignment of a model compound derived from d-cellobiose. The diffusion-edited 1H experiment afforded a simple method to identify the assigned model resonances in the reducing end-modified CNCs. The condensations can be carried out in aqueous bicarbonate solutions, avoiding the use of hazardous solvents. Under these preliminary aqueous conditions, end-group conversion of up to 12.5% could be confirmed. These results demonstrate the potential of ß-diketone chemistry and the Knoevenagel condensation for functionalizing cellulose reducing ends. Application of this liquid-state NMR method for confirming and quantifying reducing end conversion is also shown to be invaluable. Extension of this chemistry to other 1,3-dicarbonyl compounds and solvation conditions should allow for the topochemical and (axially) chirotopic installation of functional moieties to CNCs, paving the way to asymmetric cellulose-based nanomaterials with unique properties.

The effect of different sources of fish and camelina sativa oil on immune cell and adipose tissue mRNA expression in subjects with abnormal fasting glucose metabolism: a randomized controlled trial.

BACKGROUND/OBJECTIVES: Molecular mechanisms linking fish and vegetable oil intakes to their healthy metabolic effects may involve attenuation of inflammation. Our primary aim was to examine in a randomized controlled setting whether diets enriched in fatty fish (FF), lean fish (LF) or ALA-rich camelina sativa oil (CSO) differ in their effects on the mRNA expression response of selected inflammation-related genes in peripheral blood mononuclear cells (PBMCs) and subcutaneous adipose tissue (SAT) in subjects with impaired fasting glucose. SUBJECTS/METHODS: Samples from 72 participants randomized to one of the following 12-week intervention groups, FF (n = 19), LF (n = 19), CSO (n = 17) or a control group (n = 17), were available for the PBMC study. For SAT, 39 samples (n = 8, n = 10, n = 9, n = 12, respectively) were available. The mRNA expression was measured at baseline and 12 weeks by TaqMan® Low Density Array. RESULTS: In PBMCs, LF decreased ICAM1 mRNA expression (P < 0.05), which was different (P = 0.06, Bonferroni correction) from the observed increase in the FF group (P < 0.05). Also, compared to the control group, LF decreased ICAM1 mRNA expression (P < 0.05). Moreover, the change in ICAM1 mRNA expression correlated positively with the intake of FF (P < 0.05) and negatively with the intake of LF (P < 0.05), independently of study group. A diet enriched in CSO, a rich source of alpha-linolenic acid (ALA), decreased PBMC IFNG mRNA expression (P < 0.01). The intake of CSO in the CSO group, but not the increase in plasma ALA proportions, correlated inversely with the IFNG mRNA expression in PBMCs (P = 0.08). In SAT, when compared with the control group, the effect of FF on decreasing IL1RN mRNA expression was significant (P < 0.03). CONCLUSION: We propose that CSO intake may partly exert its benefits through immuno-inflammatory molecular regulation in PBMCs, while modulation of ICAM1 expression, an endothelial/vascular-related gene, may be more dependent on the type of fish consumed.

Safety considerations of plant polysaccharides for food use: a case study on phenolic-rich softwood galactoglucomannan extract.

A growing population and concern over the sufficiency of natural resources for feeding this population have motivated researchers and industries to search for alternative and complementary sources of food ingredients and additives. Numerous plant species and parts of plants are explored as raw materials for food production. An interesting example is wood; to date, only a few wood-based additives or ingredients are authorized for food use. Wood hemicelluloses, such as softwood galactoglucomannans (GGM), constitute an abundant bioresource that shows a high potential functionality in edible materials. Spruce GGM acts as a multi-functional emulsion stabilizer, and it could be used in various processed food products, replacing less effective, conventional emulsifiers. Before new materials can be released into the food market, their safety must be evaluated, according to the Novel Food regulation. This review focuses on the safety aspects that must be considered before polysaccharide- and phenolic-rich plant extracts can be awarded the status of authorized food ingredients. In this review, GGM is presented as a case study and examples are given of plant-based polysaccharides that are already authorized for food purposes. The legislation regarding Novel Food ingredients in Europe is also briefly reviewed.