Pure-shift IMPRESS EXSIDE:Easy measurement of ¹H-¹³C scalar coupling constants with increased sensitivity and resolution

Measuring long-range 1H–13C scalar coupling constants, nJCH, is made easier through improved sensitivity and resolution of the SelEXSIDE NMR experiment by incorporation of ‘pure-shift’ homonuclear decoupling and IMPRESS-Hadamard encoding.</p

Synergism of anisotropic and computational NMR methods reveals the likely configuration of phormidolide A.

Characterization of the complex molecular scaffold of the marine polyketide natural product phormidolide A represents a challenge that has persisted for nearly two decades. In light of discordant results arising from recent synthetic and biosynthetic reports, a rigorous study of the configuration of phormidolide A was necessary. This report outlines a synergistic effort employing computational and anisotropic NMR investigation, that provided orthogonal confirmation of the reassigned side chain, as well as supporting a further correction of the C7 stereocenter

Outreach:Impact on Skills and Future Careers of Postgraduate Practitioners Working with the Bristol ChemLabS Centre for Excellence in Teaching and Learning

Postgraduate engagement in delivering outreach activities is more commonplace than it once was. However, the impact on postgraduate students (typically studying for a Ph.D. degree) of participating in the delivery of these outreach activities has rarely, if ever, been recorded. The Bristol ChemLabS Outreach program has been running for ca. 17 years, and in that time, many postgraduate students have been involved (approximately 500), with around 250 typically for up to 3 years. We sought to investigate the impact of outreach engagement on postgraduate alumni who were involved in the program for over 3 years (32) and how the experiences and training of the outreach program had impacted on their careers postgraduation. Thirty of the 32 postgraduates engaged and ∼70% reported that their outreach experience had influenced their decision making on future careers. Many respondents reported that the skills and experiences gained through outreach participation had contributed to success in applying for and interviewing at their future employers. All respondents reported that outreach had helped them to develop key skills that were valued in the workplace, specifically, communication, teamwork, organizational skills, time planning, event planning, and event management. Rather than a pleasant distraction or an opportunity to supplement income, all participants noted that they felt there were many additional benefits and that this was time well spent. Outreach should not be viewed as a distraction to science research but rather an important enhancement to it provided that the program is well constructed and seeks to develop those delivering the outreach activities

Comparative performance of bio-based coatings formulated with cellulose, chitin, and chitosan nanomaterials suitable for fruit preservation

Sustainable nanomaterials (SNMs) from wood, sugarcane and crab shell were prepared and used to coat selected fruits. The properties of SNMs and selected fruits were characterized and strawberry was used as an example to test antifungal activity and freshness preservation of the SNMs. The SNMs with their nano-structured morphology form strong shear-thinning dispersions for easy spraying on fruit surfaces. The fruit surface free energy was influenced by its surface morphology, predominant surface wax components, and cutin monomers. The antifungal activity of SNMs was influenced by their surface functional groups and particle size (crystals vs fibers). The coblend of wood nanocrystals (WCNCs) and chitosan nanofiber (CSNFs) exhibited the best antifungal property, which was comparable with the performance of the fungicide thiabendazole (80 mg L). The weight loss and color change of the WCNC/CSNF coated strawberries decreased by nearly half compared with the control samples, showing coating effectiveness on preserving fruit freshness

Xylella fastidiosa modulates exopolysaccharide polymer length and the dynamics of biofilm development with a β-1,4-endoglucanase

ABSTRACT Xylella fastidiosa is a Gram-negative bacterium that causes disease in many economically important crops. It colonizes the plant host xylem and the mouthparts of its insect vectors where it produces exopolysaccharide (EPS) and forms robust biofilms. Typically, the ability to form a biofilm enhances virulence, but X. fastidiosa does not fit neatly into that paradigm. Instead, X. fastidiosa enters into biofilms to attenuate its movement in the xylem, which, in turn, slows disease progression. In most of its over 600 known plant hosts, X. fastidiosa behaves as a benign commensal, but in some hosts like Vitis vinifera grapevines, it acts as a pathogen. Its ability to attenuate its own virulence in susceptible hosts may be a remnant of its commensal lifestyle in other hosts. Here, we demonstrate that X. fastidiosa utilizes a β-1,4 endoglucanase to cleave its self-produced β-1,4-glucan exopolysaccharide polymer to process it from a higher molecular weight to a lower molecular weight polymer. This processing mediates surface adherence of the cells and ultimately governs overall biofilm architecture, indicating enzymatic pruning of the EPS plays a key role in biofilm-mediated attenuation of X. fastidiosa in planta and, thus, is a key vestige that links its commensal behaviors to its parasitic behaviors in specific hosts. IMPORTANCE It is well established that exopolysaccharide (EPS) is an integral structural component of bacterial biofilms necessary for assembly and maintenance of the three-dimensional architecture of the biofilm. However, the process and role of EPS turnover within a developing biofilm is not fully understood. Here, we demonstrated that Xylella fastidiosa uses a self-produced endoglucanase to enzymatically process its own EPS to modulate EPS polymer length. This enzymatic processing of EPS dictates the early stages of X. fastidiosa’s biofilm development, which, in turn, affects its behavior in planta. A deletion mutant that cannot produce the endoglucanase was hypervirulent, thereby linking enzymatic processing of EPS to attenuation of virulence in symptomatic hosts, which may be a vestige of X. fastidiosa’s commensal behavior in many of its other non-symptomatic hosts

Acetylation in Ionic Liquids Dramatically Increases Yield in the Glycosyl Composition and Linkage Analysis of Insoluble and Acidic Polysaccharides

Glycosyl composition and linkage analyses are important first steps toward understanding the structural diversity and biological importance of polysaccharides. Failure to fully solubilize samples prior to analysis results in the generation of incomplete and poor-quality composition and linkage data by gas chromatography–mass spectrometry (GC-MS). Acidic polysaccharides also do not give accurate linkage results, because they are poorly soluble in DMSO and tend to undergo β-elimination during permethylation. Ionic liquids can solubilize polysaccharides, improving their derivatization and extraction for analysis. We show that water-insoluble polysaccharides become much more amenable to chemical analysis by first acetylating them in an ionic liquid. Once acetylated, these polysaccharides, having been deprived of their intermolecular hydrogen bonds, are hydrolyzed more readily for glycosyl composition analysis or methylated more efficiently for glycosyl linkage analysis. Acetylation in an ionic liquid greatly improves composition analysis of insoluble polysaccharides when compared to analysis without acetylation, enabling complete composition determination of normally recalcitrant polysaccharides. We also present a protocol for uronic acid linkage analysis that incorporates this preacetylation step. This protocol produces partially methylated alditol acetate derivatives in high yield with minimal β-elimination and gives sensitive linkage results for acidic polysaccharides that more accurately reflect the structures being analyzed. We use important plant polysaccharides to show that the preacetylation step leads to superior results compared to traditional methodologies

pKa measurements for the SAMPL6 prediction challenge for a set of kinase inhibitor-like fragments

Determining the net charge and protonation states populated by a small molecule in an environment of interest or the cost of altering those protonation states upon transfer to another environment is a prerequisite for predicting its physicochemical and pharmaceutical properties. The environment of interest can be aqueous, an organic solvent, a protein binding site, or a lipid bilayer. Predicting the protonation state of a small molecule is essential to predicting its interactions with biological macromolecules using computational models. Incorrectly modeling the dominant protonation state, shifts in dominant protonation state, or the population of significant mixtures of protonation states can lead to large modeling errors that degrade the accuracy of physical modeling. Low accuracy hinders the use of physical modeling approaches for molecular design. For small molecules, the acid dissociation constant (pKa) is the primary quantity needed to determine the ionic states populated by a molecule in an aqueous solution at a given pH. As a part of SAMPL6 community challenge, we organized a blind pKa prediction component to assess the accuracy with which contemporary pKa prediction methods can predict this quantity, with the ultimate aim of assessing the expected impact on modeling errors this would induce. While a multitude of approaches for predicting pKa values currently exist, predicting the pKas of drug-like molecules can be difficult due to challenging properties such as multiple titratable sites, heterocycles, and tautomerization. For this challenge, we focused on set of 24 small molecules selected to resemble selective kinase inhibitors-an important class of therapeutics replete with titratable moieties. Using a Sirius T3 instrument that performs automated acid-base titrations, we used UV absorbance-based pKa measurements to construct a high-quality experimental reference dataset of macroscopic pKas for the evaluation of computational pKa prediction methodologies that was utilized in the SAMPL6 pKa challenge. For several compounds in which the microscopic protonation states associated with macroscopic pKas were ambiguous, we performed follow-up NMR experiments to disambiguate the microstates involved in the transition. This dataset provides a useful standard benchmark dataset for the evaluation of pKa prediction methodologies on kinase inhibitor-like compounds

Unequivocal structure confirmation of a breitfussin analog by anisotropic NMR measurements

Structural features of proton-deficient heteroaromatic natural products, such as the breitfussins, can severely complicate their characterization by NMR spectroscopy. For the breitfussins in particular, the constitution of the five-membered oxazole central ring cannot be unequivocally established via conventional NMR methods when the 4′-position is halogenated. The level of difficulty is exacerbated by 4′-iodination, as the accuracy with which theoretical NMR parameters are determined relies extensively on computational treatment of the relativistic effects of the iodine atom. It is demonstrated in the present study, that the structure of a 4′-iodo breitfussin analog can be unequivocally established by anisotropic NMR methods, by adopting a reduced singular value decomposition (SVD) protocol that leverages the planar structures exhibited by its conformers

Heavy metal contamination of cassava (Manihot esculentum) grown on quarry soils in Umunneochi Abia state and its health implications

Contamination of agricultural soils by quarry activities is posing serious challenges food security in greater parts of the Sub-Saharan Africa. This study determined the heavy metals in soils and cassava (Manihot esculentum) tubers obtained from three different quarry sites in Umunneochi, Abia State Nigeria. Samples of soil and cassava tubers were collected in replicates following the direction of natural drainage, while control samples were obtained against the direction of natural drainage from the quarry pits. Soil and cassava tuber samples were collected and subjected to standard physicochemical analyses. Heavy metal concentration in the quarry soil and cassava tubers varied significantly from the control except for Cd (mg/kg) at P&lt;0.05. All heavy metals identified in the soil were also present in the cassava tuber samples, with Al concentration in the quarry soils correlating positively (0.977**) with that of cassava tubers. The quarry activities contributed to the heavy metal levels of quarry soils and responsible for the accumulation of heavy metals in cassava tubers that could lead to food insecurity and public health concerns. This further brings to fore the challenges and need to review and update mining and quarry regulations in Nigeria