Fraser J. Scott

Designing anti-inflammatory drugs from parasitic worms: a synthetic small molecule analogue of the Acanthocheilonema viteae product ES-62 prevents development of collagen-induced arthritis.

In spite of increasing evidence that parasitic worms may protect humans from developing allergic and autoimmune diseases and the continuing identification of defined helminth-derived immunomodulatory molecules, to date no new anti-inflammatory drugs have been developed from these organisms. We have approached this matter in a novel manner by synthesizing a library of drug-like small molecules based upon phosphorylcholine, the active moiety of the anti-inflammatory Acanthocheilonema viteae product, ES-62, which as an immunogenic protein is unsuitable for use as a drug. Following preliminary in vitro screening for inhibitory effects on relevant macrophage cytokine responses, a sulfone-containing phosphorylcholine analogue (11a) was selected for testing in an in vivo model of inflammation, collagen-induced arthritis (CIA). Testing revealed that 11a was as effective as ES-62 in protecting DBA/1 mice from developing CIA and mirrored its mechanism of action in downregulating the TLR/IL-1R transducer, MyD88. 11a is thus a novel prototype for anti-inflammatory drug development.

Amide isosteres in structure-activity studies of antibacterial minor groove binders.

Antibacterial minor groove binders related to the natural product, distamycin, are development candidates for novel antibiotics. Alkenes have been found to be effective substitutes for the isosteric amide links in some positions and alkyl groups larger than methyl have been found to increase binding to DNA in both selectivity and affinity. However the impact of other isosteres such as diazenes and the position of an alkyl group with respect to DNA binding and antibacterial activity are not known. The effects of some systematic variations in the structure of polyamide minor groove binders are investigated. Isosteres of the amide link (alkenes and diazenes) are compared: it is shown that all three are competent for binding to DNA but that alkene links give the tightest binding and highest antibacterial activity; no significant antibacterial activity was found for compounds with a diazene link. Within a series of alkene linked compounds, the effect of branched N-alkyl substituents on binding to DNA and antibacterial activity is investigated: it was found that C3 and C4 branched chains are acceptable at the central pyrrole residue but that at the pyrrole ring adjacent to the basic tail group, a C4 branched chain was too large both for DNA binding and for antibacterial activity. The active branched alkyl chain compounds were found to be especially active against Mycobacterium aurum, a bacterium related to the causative agent of tuberculosis.

Is mathematics to blame? An investigation into high school students' difficulty in performing calculations in chemistry

Mathematical ability is a major contributory factor to the success of a student in any science course. This paper aims to determine the source of the difficulty that students often find when performing calculations in chemistry. Through the design and analysis of a set of chemistry questions and analogous mathematics questions, set in a Standard Grade context, it is revealed that a basic grasp of mathematics is missing.

Design, synthesis and antibacterial activity of minor groove binders: the role of non-cationic tail groups.

The design and synthesis of a new class of minor groove binder (MGBs) in which, the cationic tail group has been replaced by a neutral, polar variant including cyanoguanidine, nitroalkene, and trifluoroacetamide groups. Antibacterial activity (against Gram positive bacteria) was found for both the nitroalkene and trifluoroacetamide groups. For the case of the nitroalkene tail group, strong binding of a minor groove binder containing this tail group was demonstrated by both DNA footprinting and melting temperature measurements, showing a correlation between DNA binding and antibacterial activity. The compounds have also been evaluated for binding to the hERG ion channel to determine whether non-cationic but polar substituents might have an advantage compared with conventional cationic tail groups in avoiding hERG binding. In this series of compounds, it was found that whilst non-cationic compounds generally had lower affinity to the hERG ion channel, all of the compounds studied bound weakly to the hERG ion channel, probably associated with the hydrophobic head groups.

An evaluation of minor groove binders as anti-Trypanosoma brucei brucei therapeutics

A series of 32 structurally diverse MGBs, derived from the natural product distamycin, was evaluated for activity against Trypanosoma brucei brucei. Four compounds have been found to possess significant activity, in the nanomolar range, and represent hits for further optimisation towards novel treatments for Human and Animal African Trypanosomiases. Moreover, SAR indicates that the head group linking moiety is a significant modulator of biological activity.

Novel TPP-riboswitch activators bypass metabolic enzyme dependency.

Riboswitches are conserved regions within mRNA molecules that bind specific metabolites and regulate gene expression. TPP-riboswitches, which respond to thiamine pyrophosphate (TPP), are involved in the regulation of thiamine metabolism in numerous bacteria. As these regulatory RNAs are often modulating essential biosynthesis pathways they have become increasingly interesting as promising antibacterial targets. Here, we describe thiamine analogs containing a central 1,2,3-triazole group to induce repression of thiM-riboswitch dependent gene expression in different E. coli strains. Additionally, we show that compound activation is dependent on proteins involved in the metabolic pathways of thiamine uptake and synthesis. The most promising molecule, triazolethiamine (TT), shows concentration dependent reporter gene repression that is dependent on the presence of thiamine kinase ThiK, whereas the effect of pyrithiamine (PT), a known TPP-riboswitch modulator, is ThiK independent. We further show that this dependence can be bypassed by triazolethiamine-derivatives that bear phosphate-mimicking moieties. As triazolethiamine reveals superior activity compared to pyrithiamine, it represents a very promising starting point for developing novel antibacterial compounds that target TPP-riboswitches. Riboswitch-targeting compounds engage diverse endogenous mechanisms to attain in vivo activity. These findings are of importance for the understanding of compounds that require metabolic activation to achieve effective riboswitch modulation and they enable the design of novel compound generations that are independent of endogenous activation mechanisms.

Exceptionally strong intermolecular association in hydrophobic DNA minor groove binders and their potential therapeutic consequences

An antibacterial DNA minor groove binder is shown by NOE experiments to self-associate in aqueous solution at temperatures up to 80 °C in an anti-parallel, head-to-tail orientation as found in binding to duplex DNA oligomers.

Selective anti-malarial minor groove binders

A set of 31 DNA minor groove binders (MGBs) with diverse structural features relating to both physical chemical properties and DNA binding sequence preference has been evaluated as potential drugs to treat Plasmodium falciparum infections using a chloroquine sensitive strain (3D7) and a chloroquine resistant strain (Dd2) in comparison with human embryonic kidney (HEK) cells as an indicator of mammalian cell toxicity. MGBs with an alkene link between the two N-terminal building blocks were demonstrated to be most active with IC50 values in the range 30-500nM and therapeutic ratios in the range 10->500. Many active compounds contained a C-alkylthiazole building block. Active compounds with logD7.4 values of approximately 3 or 7 were identified. Importantly the MGBs tested were essentially equally effective against both chloroquine sensitive and resistant strains. The results show that suitably designed MGBs have the potential for development into clinical candidates for antimalarial drugs effective against resistant strains of Plasmodia.

A simulated peer-assessment approach to improving student performance in chemical calculations

This paper describes the utility of using simulated, rather than real, student solutions to problems within a peer-assessment setting and whether this approach can be used as a means of improving performance in chemical calculations. The study involved a small cohort of students, of two levels, who carried out a simulated peer-assessment as a classroom activity and their improvement in performance and attitude towards the activity was measured. The results demonstrate that a simulated peer-assessment approach can be successfully used in lieu of standard peer-assessment and that student attitudes favour the simulated approach.

Evaluation of minor groove binders (MGBs) as novel anti-mycobacterial agents, and the effect of using non-ionic surfactant vesicles as a delivery system to improve their efficacy

Objectives The slow development of major advances in drug discovery for the treatment of Mycobacterium tuberculosis (Mtb) infection suggests a compelling need for evaluation of more effective drug therapies against TB. New classes of drugs are constantly being evaluated for anti-mycobacterial activity with currently a very limited number of new drugs approved for TB treatment. Minor groove binders (MGBs) have previously revealed promising antimicrobial activity against various infectious agents; however, they have not yet been screened against Mtb. Methods The mycobactericidal activity of 96 MGB compounds against Mtb was determined using an H37Rv-GFP microplate assay. MGB hits were screened for their intracellular mycobactericidal efficacy against the clinical Beijing Mtb strain HN878 in bone-marrow-derived macrophages using standard cfu counting. Cell viability was assessed by CellTiter-Blue assays. Selected MGBs were encapsulated into non-ionic surfactant vesicles (NIVs) for drug delivery system evaluation. Results H37Rv-GFP screening yielded a hit-list of seven compounds at an MIC99 of between 0.39 and 1.56 μM. MGB-362 and MGB-364 displayed intracellular mycobactericidal activity against Mtb HN878 at an MIC50 of 4.09 and 4.19 μM, respectively, whilst being non-toxic. Subsequent encapsulation into NIVs demonstrated a 1.6- and 2.1-fold increased intracellular mycobacterial activity, similar to that of rifampicin when compared with MGB-alone formulation. Conclusions MGB anti-mycobacterial activities together with non-toxic properties indicate that MGB compounds constitute an important new class of drug/chemical entity, which holds promise in future anti-TB therapy. Furthermore, the ability of NIVs to better deliver entrapped MGB compounds to an intracellular Mtb infection suggests further preclinical evaluation is warranted.