Among the movements observed in some cellulosic structures produced by plants are those that involve the dispersion and burial of seeds, as for example in Erodium from the Geraniaceae plant family. Here we report on a simple and efficient strategy to isolate and tune cellulose-based hygroscopic responsive materials from Erodium awns' dead tissues. The stimuli-responsive material isolated forms left-handed (L) or right-handed (R) helical birefringent transparent ribbons in the wet state that reversibly change to R helices when the material dries. The humidity-driven motion of dead tissues is most likely due to a composite material made of cellulose networks of fibrils imprinted by the plant at the nanoscale, which reinforces a soft wall polysaccharide matrix. The inversion of the handedness is explained using computational simulations considering filaments that contract and expand asymmetrically. The awns of Erodium are known to present hygroscopic movements, forming R helices in the dry state, but the possibility of actuating chirality via humidity suggests that these cellulose-based skeletons, which do not require complicated lithography and intricate deposition techniques, provide a diverse range of applications from intelligent textiles to micro-machines.

An unprecedented approach towards oligosaccharides containing N-acetylglucosamine-N-acetylmuramic (NAG-NAM) units was developed. These novel bacterial cell wall surrogates were obtained from chitosan via a top down approach involving both chemical and enzymatic reactions. The chemical modification of chitosan using a molecular clamp based strategy, allowed obtaining N-acetylglucosamine-N-acetylmuramic (NAG-NAM) containing oligomers. Intercalation of NAM residues was confirmed through the analysis of oligosaccharide fragments from enzymatic digestion and it was found that this route affords NAG-NAM containing oligosaccharides in 33% yield. These oligosaccharides mimic the carbohydrate basic skeleton of most bacterial cell surfaces. The oligosaccharides prepared are biologically relevant and will serve as a platform for further molecular recognition studies with different receptors and enzymes of both bacterial cell wall and innate immune system. This strategy combining both chemical modification and enzymatic digestion provides a novel and simple route for an easy access to bacterial cell wall fragments – biologically important targets.

G-quadruplex (G4) is involved in many biological processes, such as telomere function, gene expression and DNA replication. The selective isolation of G4 using affinity ligands that bind tightly and selectively is a valuable strategy for discovering new G4 binders for the separation of G4 from duplexes or the discrimination of G4 structures. In this work, one affinity chromatographic support was prepared using a naphthalene amine as a G4 binder. The ligand was immobilized on epoxy-activated Sepharose CL-6B using a long spacer arm and was characterized by HR-MAS spectroscopy. The supercoiled (sc) isoform of pVAX1-LacZ and pVAX1-G4 was isolated from a native sample. Also, the recovery and isolation of the plasmid isoforms from Escherichia coli lysate samples were achieved using an ionic gradient with different concentrations of NaCl in 10 mM Tris-HCl (pH 7.4). The retention times of different DNA/single strand sequences that can form G4, such as, c-MYC, c-kit1, c-kit2, tetrameric, telomeric (23AG), thrombin aptamer (TBA) and 58Sγ3 in this support were evaluated. Our experimental results suggest that the support exhibits selectivity for parallel c-MYC and c-kit1 G4s. In vitro transcription was performed using purified sc pVAX1-G4 and pPH600 to induce G4 formation and circular dichroism (CD) analysis confirmed that both transcripts adopt a parallel G4 topology.

The present study focus on the preparation of chromatography supports for affinity-based chromatography of supercoiled plasmid purification. Three l-tryptophan based supports are prepared through immobilization on epoxy-activated Sepharose and characterized by HR-MAS NMR. The SPR is employed for a fast screening of l-tryptophan derivatives, as potential ligands for the biorecognition of supercoiled isoform, as well as, to establish the suitable experimental conditions for the chromatography. The results reveal that the overall affinity is high (KD = 10−9 and 10−8 M) and the conditions tested show that the use of HEPES 100 mM enables the separation and purification of supercoiled at T = 10 °C. The STD-NMR is performed to accomplish the epitope mapping of the 5′-mononucleotides bound to l-tryptophan derivatives supports. The data shows that the interactions between the three supports and the 5′-mononucleotides are mainly hydrophobic and π–π stacking. The chromatography experiments are performed with l-tryptophan support and plasmids pVAX-LacZ and pPH600. The supercoiled isoform separation is achieved at T = 10 °C by decreasing the concentration of (NH4)2SO4 from 2.7 to 0 M in HEPES for pVAX-LacZ and 2.65 M to 0 M in HEPES for pPH600.

Overall, l-tryptophan derivatives can be a promising strategy to purify supercoiled for pharmaceutical applications.

Fresh-cut fruit is an important segment in fruit market due to the increasing demand for healthy/convenient foods. However, processing promotes a decrease in fruits stability with faster physiological and microbiological deteriorations. Food stability is strongly attributed to its molecular dynamics and “water availability”. Understanding changes in water location/mobility is of utmost importance, since water dynamics profoundly influences physic-chemical and microbiological quality of foods. Nuclear magnetic resonance spectroscopy (NMR) is a methodology used to study the food constituents' molecular dynamics.

The aim of this study is to use NMR to evaluate changes in water mobility that occurred in fresh-cut pear tissues during storage, by measuring the transverse relaxation time (T2) parameter.

Results showed the existence of three water classes in the cells after processing, with T2 values of 10 ms, 187 ms and 3s for cellular wall, cytoplasm and vacuole, respectively. Also, the obtained results demonstrated that T2 was affected by processing and storage. Moreover, a relationship between T2, microstructure and the quality parameters was established. T2, maximum value increased with pear hardness as well as water activity. On the contrary, a decrease in total colour difference (TCD) was found with T2.

Results demonstrate the usefulness of the application of NMR relaxometry in food studies.

The developments in the use of plasmid DNA (pDNA) in gene therapy and vaccines have motivated the search and improvement of optimized purification processes. In this context, dipeptides l-tyrosine-l-tyrosine and l-tyrosine-l-arginine are synthetized to explore their application as affinity ligands for supercoiled (sc) plasmid DNA (pDNA) purification. The synthesis is based on the protection of N-Boc-l-tyrosine, followed by condensation with l-tyrosine or l-arginine methyl esters in the presence of dicyclohexylcarbodiimide (DCC), which after hydrolysis and acidification give the afforded dipeptides. The supports are then obtained by coupling l-tyrosine, l-tyrosine-l-tyrosine and l-tyrosine-l-arginine to epoxy-activated Sepharose and are characterized by high resolution magic angle spinning (HR-MAS) NMR and Fourier transform infrared spectroscopy (FTIR). Surface plasmon resonance (SPR) biosensor is used to establish the promising ligand to be used in the chromatographic experiments and ascertain experimental conditions. Sc isoform showed the highest affinity to the dipeptides, followed by linear (ln) pDNA, being the open circular (oc) the one that promoted the lowest affinity to l-tyrosine-l-arginine. Saturation transfer difference (STD)-NMR experiments show that the interaction is mainly hydrophobic with the majority of the 5'-mononucleotides, except for 5'-GMP with l-tyrosine-l-arginine Sepharose that is mainly electrostatic. The support l-tyrosine Sepharose used in chromatographic experiments promotes the separation of native pVAX1-LacZ and pcDNA3-FLAG-p53 samples (oc+sc) by decreasing the salt concentration. The results suggest that it is possible to purify different plasmids with the l-tyrosine Sepharose, with slight adjustments in the gradient conditions.

Molecular mobility is a fundamental parameter which reflects the dynamic properties of food components and contributes to food degradation reactions comprehension. Fresh-cut fruits have become an important food market segment. However, processing of fruits promotes faster its physiological deterioration, biochemical changes and microbial degradation. The purpose of this work was to use NMR methodology as a tool to evaluate fresh-cut fruit quality, during storage at refrigerated conditions. The fresh-cut melon transverse relaxation time (T-2) was measured for a period of 7 days of storage at 5 degrees C. The relationship between the obtained values, microstructure and quality parameters was investigated. In general, results show the existence of one class of water fluidity in the system, the one present in cells after processing. T-2, a measure of this fluidity, is affected by the processing and storage time. Also, it is possible to find a close relationships between T-2 and quality parameters of total colour difference (TCD), firmness and a(w). As T-2 increases TCD also increases, while firmness and aw decrease. These results highlight the usefulness of NMR methodology application in food science. (C) 2015 Elsevier Ltd. All rights reserved.

Foods are partially crystalline partially amorphous systems. Edible films are considered good models for food systems due to their interesting physical properties, quite straightforward matrices, and easy reproduction. Chitosan is a semicrystalline biopolymer, biocompatible, biodegradable, with antimicrobial activity and filmogenic properties, thoroughly used in edible films' studies. This work aims to investigate the relationship between chitosan films' molecular relaxation time, their microstructure (crystallinity) and functional properties. Analyses were carried out using data on chitosan/glycerol films prepared with different polymer/plasticisant concentrations. Results demonstrate that there is a relationship between macroscopic properties and water and glycerol relaxation times. Moreover, results show that while water is free in the matrix, glycerol is linked to the chitosan polymeric chains, decreasing intermolecular attractions and increasing free volume, thus facilitating molecular migration. Also the data analysis reveals the usefulness of NMR and molecular mobility studies in the matrix for characterisation and development of polymeric structures. Industrial relevance: NMR spectroscopy is currently one of the key methods for food characterisation. Foodstuff is a complex matrix including many different compounds with different chemical structures, concentrations, solubility, properties and nutritional values. From a fundamental perspective, foods are mainly edible and digestible biopolymers that are partially crystalline/partially amorphous and thus edible films, specifically chitosan/glycerol films can be very interesting food model systems for mobility and microstructure studies. Studies on water and solids' mobility and thermo-mechanical properties in food systems (real or model systems),are fundamental to fully attain food physical properties and stability. These studies may be extremely useful for food product and process design, safety and sensorial attributes and also for better understanding and predicting, for example, food storage stability conditions. (C) 2015 Elsevier Ltd. All rights reserved.

This study was developed with the purpose to investigate the effect of polysaccharide/plasticiser concentration on the microstructure and molecular dynamics of polymeric film systems, using transmission electron microscope imaging (TEM) and nuclear magnetic resonance (NMR) techniques. Experiments were carried out in chitosan/glycerol films prepared with solutions of different composition. The films obtained after drying and equilibration were characterised in terms of composition, thickness and water activity. Results show that glycerol quantities used in film forming solutions were responsible for films composition; while polymer/total plasticiser ratio in the solution determined the thickness (and thus structure) of the films. These results were confirmed by TEM. NMR allowed understanding the films molecular rearrangement. Two different behaviours for the two components analysed, water and glycerol were observed: the first is predominantly moving free in the matrix, while glycerol is mainly bounded to the chitosan chain.