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Neurons differentiated from pluripotent stem cells using established neural culture conditions often exhibit functional deficits. Recently, we have developed enhanced media which both synchronize the neurogenesis of pluripotent stem cell‐derived neural progenitors and accelerate their functional maturation; together these media are termed SynaptoJuice. This pair of media are pro‐synaptogenic and generate authentic, mature synaptic networks of connected forebrain neurons from a variety of induced pluripotent and embryonic stem cell lines. Such enhanced rate and extent of synchronized maturation of pluripotent stem cell‐derived neural progenitor cells generates neurons which are characterized by a relatively hyperpolarized resting membrane potential, higher spontaneous and induced action potential activity, enhanced synaptic activity, more complete development of a mature inhibitory GABAA receptor phenotype and faster production of electrical network activity when compared to standard differentiation media. This entire process – from pre‐patterned neural progenitor to active neuron – takes 3 weeks or less, making it an ideal platform for drug discovery and disease modelling in the fields of human neurodegenerative and neuropsychiatric disorders, such as Huntington's disease, Parkinson's disease, Alzheimer's disease and Schizophrenia.

Notch signalling is an evolutionarily conserved pathway involved in cell-fate specification. The initiating event in this pathway is the binding of a Notch receptor to a DSL (Delta/Serrate/Lag-2) ligand on neighbouring cells triggering the proteolytic cleavage of Notch within its extracellular juxtamembrane region; a process known as proteolytic ‘shedding’ and catalysed by members of the ADAM (a disintegrin and metalloproteinase) family of enzymes. Jagged1 is a Notch-binding DSL ligand which is also shed by an ADAM-like activity raising the possibility of bi-directional cell–cell Notch signalling. In the present study we have unequivocally identified the sheddase responsible for shedding Jagged1 as ADAM17, the activity of which has previously been shown to be localized within specialized microdomains of the cell membrane known as ‘lipid rafts’. However, we have shown that replacing the transmembrane and cytosolic regions of Jagged1 with a GPI (glycosylphosphatidylinositol) anchor, thereby targeting the protein to lipid rafts, did not enhance its shedding. Furthermore, the Jagged1 holoprotein, its ADAM-cleaved C-terminal fragment and ADAM17 were not enriched in raft preparations devoid of contaminating non-raft proteins. We have also demonstrated that wild-type Jagged1 and a truncated polypeptide-anchored variant lacking the cytosolic domain were subject to similar constitutive and phorbol ester-regulated shedding. Collectively these data demonstrate that Jagged1 is shed by ADAM17 in a lipid-raft-independent manner, and that the cytosolic domain of the former protein is not a pre-requisite for either constitutive or regulated shedding.

Thiaalkane-bridge bis(benzimidazoles) varying both in the nature of the bridge and in the pendant groups attached to secondary nitrogen have been synthesised to assess metal selectivity in single and multiple phases. The single-phase studies (1H NMR, fast atom bombardment mass spectroscopy) and molecular modelling were intended primarily to rationalise the trends observed in the multiple-phase (bulk liquid-membrane) experiments. Selectivity for silver ion was studied by all of these techniques, whilst the membrane experiments were extended to assess selectivity for cadmium, zinc, lead and copper ions. All of these metal salts (as nitrates) were assessed in the membrane experiments or in pairwise competition experiments. Some useful separations were effected, the most striking being that for silver ions over lead. The lack of comparison amongst the results from the methods chosen indicates that a full understanding of the complex kinetics of three-phase transport is still to be attained.

Two new series of azapropeller crowns have been synthesised and investigated. The aza-propeller crowns 7,10-ditosylaza-1,4,13,16-tetraoxacyclooctadecane, (9a) and 4,7,10-tritosylaza-1,13-dioxacyclo-pentadecane, (11) have been shown by X-ray structure determination to have the propeller conformation matching that of the common isomer found previously in the polyether propeller crowns 1. The N-tosyl substituents, used as a probe of the movement of attached ring segments on the macrocyclic ring, rendered observable (in 1H NMR studies) the flipping of these segments, for which the calculated free energy of activation was typical of that for an unsubstituted propeller, ΔG‡217= 10.54 kcal mol–1 at the coalescence temperature for 9a, ΔG‡215= 10.74 kcal mol–1 for the analogous ring compound 10 with one additional methylene residue, and ΔG‡= 12.5 ± 0.4 kcal mol–1(at 230–240 K) for the tritosyl compound 11. These results and other NMR data show that the relatively slow switch of the propeller is the movement which mainly controls the observable process. Successful detosylation of 9a is reported. Two examples of a second series of propeller crowns having amide links in the macrocyclic ring have been prepared by two routes. Their selectivity for transport of silver and lead cations is described.

Metallomacrocycle 2, possessing an immobilized Lewis‐acidic uranyl cation, was synthesized by reaction of aldehyde 9 with 1,2‐cis‐cyclohexanediamine in the presence of Ba2+ as a template cation and subsequent transmetallation with UO22+. Docking experiments with barbituric acid revealed that a ‐(CH2)6– spacer between the salen‐uranyl and 2,6‐diamidopyridine moieties of 2 is optimal. According to 1H NMR titration experiments, the barbituric acid complex of 2 is up to 2.7 kcal · mol−1 more stable than the complexes with five disubstituted derivatives. The flux of barbituric acid through a supported liquid membrane is enhanced 3.7 times by carrier 2 mediated transport.

A series of bis benzimidazole ligands, bridged by additional donor groups (ether, thioether) and with pendant carboxylic amide groups, was prepared. In three-phase transport experiments using one quadridentate ligand and metal nitrates, the sequence Ag+≈ Cu2+ > Cd2+ > Zn2+ > Pb2+ was observed for rates of single-ion transport. In pairwise comparisons of mixtures of two salts, potentially useful discriminations between Ag+ and Pb2+, Ag+/Cu2+, Ag+/Zn2+, Ag+/Cd2+, Cu2+/Zn2+, and Cd2+/Zn2+ were also observed. The complexation behaviour of several ligands with Pb2+ and Ag+ in a single phase was further screened in an attempt to explain the observed discrimination between these cations, either in solid or solution, with 1H and 13C n.m.r., i.r., and fast atom bombardment (f.a.b.) mass spectrometric techniques. Evidence for complexes of Ag+ was found for each ligand, with each technique. However for Pb2+ only the ligands with benzimidazole plus ether donors showed any tendency to complex; although solids with a 1:1 ligand: metal salt composition could be isolated, only one could be verified as a complex in the f.a.b. experiment. Solid complexes with a 1:1 composition were isolated for the nitrate salts of Cd2+, Cu2+, and Zn2+.

Mixtures of cadmium salts and benzimidazoles have been examined by 1H, 13C and 113Cd NMR spectroscopy in dimethyl sulfoxide and in dimethyl sulfoxide–chloroform mixtures. Evidence of exchange processes both for cadmium entities and for ligand entities was obtained. Structure–shift relationships for 113Cd NMR signals were examined, but were found not to apply. The exchange was slowed in the mixed solvent and on cooling, permitting individual components to be identified (the cadmium entities with stoichiometry CdL3, CdL2, CdL, and solvated Cd, identified from the cadmium NMR spectra, and ligand-containing species CdL2 from proton spectra). Structural hypotheses relating to complexes are made and the role of these species in the observable exchange processes is explored.

Two new series of azapropeller crowns have been synthesised and investigated. The aza-propeller crowns 7,10-ditosylaza-1,4,13,16-tetraoxacyclooctadecane, (9a) and 4,7,10-tritosylaza-1,13-dioxacyclo-pentadecane, (11) have been shown by X-ray structure determination to have the propeller conformation matching that of the common isomer found previously in the polyether propeller crowns 1. The N-tosyl substituents, used as a probe of the movement of attached ring segments on the macrocyclic ring, rendered observable (in 1H NMR studies) the flipping of these segments, for which the calculated free energy of activation was typical of that for an unsubstituted propeller, ΔG‡217= 10.54 kcal mol–1 at the coalescence temperature for 9a, ΔG‡215= 10.74 kcal mol–1 for the analogous ring compound 10 with one additional methylene residue, and ΔG‡= 12.5 ± 0.4 kcal mol–1(at 230–240 K) for the tritosyl compound 11. These results and other NMR data show that the relatively slow switch of the propeller is the movement which mainly controls the observable process. Successful detosylation of 9a is reported. Two examples of a second series of propeller crowns having amide links in the macrocyclic ring have been prepared by two routes. Their selectivity for transport of silver and lead cations is described.

Thiaalkane-bridge bis(benzimidazoles) varying both in the nature of the bridge and in the pendant groups attached to secondary nitrogen have been synthesised to assess metal selectivity in single and multiple phases. The single-phase studies (1H NMR, fast atom bombardment mass spectroscopy) and molecular modelling were intended primarily to rationalise the trends observed in the multiple-phase (bulk liquid-membrane) experiments. Selectivity for silver ion was studied by all of these techniques, whilst the membrane experiments were extended to assess selectivity for cadmium, zinc, lead and copper ions. All of these metal salts (as nitrates) were assessed in the membrane experiments or in pairwise competition experiments. Some useful separations were effected, the most striking being that for silver ions over lead. The lack of comparison amongst the results from the methods chosen indicates that a full understanding of the complex kinetics of three-phase transport is still to be attained.

Some complexes of bridged bis(benzimidazole) ligands of various bridge types with Cu, Zn, and Cd have been examined as potential models of structure and mobility of biological metal binding sites. Two distinct (distorted trigonal bipyramidal and square-based pyramidal verging on distorted octahedral) environments have been found in crystal structures for-copper bromide and nitrate complexes of one ligand, 1,5-bis(benzimidazol-2-yl)-3-thiapentane. N.m.r. studies of the exchange of 1,6-bis(benzimidazol-2-yl)-2,5-dithiahexane [or its ring-methylated analogue 1,6-bis(5′,6′-dimethylbenzimidazolyl)-2,5-dithiahexane] in cadmium chloride mixtures show that it occurs via a rate-determining dissociative step, where there is cadmium salt in excess of a 1 : 1 ratio of M : L, but that bimolecular ligand exchange is rate-determining when the ratio M : L is less than unity. A hypothesis as to the minimum rearrangements necessary to explain the n.m.r. spectra is proposed. The crystal structure of 1,6-bis(1′-octylbenzimidazolyl)-2,5-dithiahexane was obtained. This ligand, lacking prototropy, served to test the role of protons in the hypothesis.

A series of bis benzimidazole ligands, bridged by additional donor groups (ether, thioether) and with pendant carboxylic amide groups, was prepared. In three-phase transport experiments using one quadridentate ligand and metal nitrates, the sequence Ag+≈ Cu2+ > Cd2+ > Zn2+ > Pb2+ was observed for rates of single-ion transport. In pairwise comparisons of mixtures of two salts, potentially useful discriminations between Ag+ and Pb2+, Ag+/Cu2+, Ag+/Zn2+, Ag+/Cd2+, Cu2+/Zn2+, and Cd2+/Zn2+ were also observed. The complexation behaviour of several ligands with Pb2+ and Ag+ in a single phase was further screened in an attempt to explain the observed discrimination between these cations, either in solid or solution, with 1H and 13C n.m.r., i.r., and fast atom bombardment (f.a.b.) mass spectrometric techniques. Evidence for complexes of Ag+ was found for each ligand, with each technique. However for Pb2+ only the ligands with benzimidazole plus ether donors showed any tendency to complex; although solids with a 1:1 ligand: metal salt composition could be isolated, only one could be verified as a complex in the f.a.b. experiment. Solid complexes with a 1:1 composition were isolated for the nitrate salts of Cd2+, Cu2+, and Zn2+.