Spectroscopic, biochemical and computational studies of bioactive DNA minor groove binders targeting 5'-WGWWCW-3' motif.

Spectroscopic, biochemical, and computational modelling studies have been used to assess the binding capability of a set of minor groove binding (MGB) ligands against the self-complementary DNA sequences 5'-d(CGCACTAGTGCG)-3' and 5'-d(CGCAGTACTGCG)-3'. The ligands were carefully designed to target the DNA response element, 5'-WGWWCW-3', the binding site for several nuclear receptors. Basic 1D 1H NMR spectra of the DNA samples prepared with three MGB ligands show subtle variations suggestive of how each ligand associates with the double helical structure of both DNA sequences. The variations among the investigated ligands were reflected in the line shape and intensity of 1D 1H and 31P-{1H} NMR spectra. Rapid visual inspection of these 1D NMR spectra proves to be beneficial in providing valuable insights on MGB binding molecules. The NMR results were consistent with the findings from both UV DNA denaturation and molecular modelling studies. Both the NMR spectroscopic and computational analyses indicate that the investigated ligands bind to the minor grooves as antiparallel side-by-side dimers in a head-to-tail fashion. Moreover, comparisons with results from biochemical studies offered valuable insights into the mechanism of action, and antitumor activity of MGBs in relation to their structures, essential pre-requisites for future optimization of MGBs as therapeutic agents.

Bis(phosphine)hydridorhodacarborane Derivatives of 1,1'-Bis(ortho-carborane) and Their Catalysis of Alkene Isomerization and the Hydrosilylation of Acetophenone.

Deprotonation of [7-(1'-closo-1',2'-C2B10H11)-nido-7,8-C2B9H11]- and reaction with [Rh(PPh3)3Cl] results in isomerization of the metalated cage and the formation of [8-(1'-closo-1',2'-C2B10H11)-2-H-2,2-(PPh3)2-closo-2,1,8-RhC2B9H10] (1). Similarly, deprotonation/metalation of [8'-(7-nido-7,8-C2B9H11)-2'-(p-cymene)-closo-2',1',8'-RuC2B9H10]- and [8'-(7-nido-7,8-C2B9H11)-2'-Cp*-closo-2',1',8'-CoC2B9H10]- affords [8-{8'-2'-(p-cymene)-closo-2',1',8'-RuC2B9H10}-2-H-2,2-(PPh3)2-closo-2,1,8-RhC2B9H10] (2) and [8-(8'-2'-Cp*-closo-2',1',8'-CoC2B9H10)-2-H-2,2-(PPh3)2-closo-2,1,8-RhC2B9H10] (3), respectively, as diastereoisomeric mixtures. The performances of compounds 1-3 as catalysts in the isomerization of 1-hexene and in the hydrosilylation of acetophenone are compared with those of the known single-cage species [3-H-3,3-(PPh3)2-closo-3,1,2-RhC2B9H11] (I) and [2-H-2,2-(PPh3)2-closo-2,1,12-RhC2B9H11] (V), the last two compounds also being the subjects of 103Rh NMR spectroscopic studies, the first such investigations of rhodacarboranes. In alkene isomerization all the 2,1,8- or 2,1,12-RhC2B9 species (1-3, V) outperform the 3,1,2-RhC2B9 compound I, while for hydrosilylation the single-cage compounds I and V are better catalysts than the double-cage species 1-3.

Structural basis of DNA duplex distortion induced by thiazole-containing hairpin polyamides.

This manuscript reports the molecular basis for double-stranded DNA (dsDNA) binding of hairpin polyamides incorporating a 5-alkyl thiazole (Nt) unit. Hairpin polyamides containing an N-terminal Nt unit induce higher melting stabilisation of target dsDNA sequences relative to an archetypical hairpin polyamide incorporating an N-terminal imidazole (Im) unit. However, modification of the N-terminus from Im to Nt-building blocks results in an increase in dsDNA binding affinity but lower G-selectivity. A general G-selectivity trend is observed for Nt-containing polyamide analogues. G-selectivity increases as the steric bulk in the Nt 5-position increases. Solution-based NMR structural studies reveal differences in the modulation of the target DNA duplex of Nt-containing hairpin polyamides relative to the Im-containing archetype. A structural hallmark of an Nt polyamide•dsDNA complex is a more significant degree of major groove compression of the target dsDNA sequence relative to the Im-containing hairpin polyamide.

Sequence-Selective Minor Groove Recognition of a DNA Duplex Containing Synthetic Genetic Components.

The structural basis of minor groove recognition of a DNA duplex containing synthetic genetic information by hairpin pyrrole-imidazole polyamides is described. Hairpin polyamides induce a higher melting stabilization of a DNA duplex containing the unnatural P·Z base-pair when an imidazole unit is aligned with a P nucleotide. An NMR structural study showed that the incorporation of two isolated P·Z pairs enlarges the minor groove and slightly narrows the major groove at the site of this synthetic genetic information, relative to a DNA duplex consisting entirely of Watson-Crick base-pairs. Pyrrole-imidazole polyamides bind to a P·Z-containing DNA duplex to form a stable complex, effectively mimicking a G·C pair. A structural hallmark of minor groove recognition of a P·Z pair by a polyamide is the reduced level of allosteric distortion induced by binding of a polyamide to a DNA duplex. Understanding the molecular determinants that influence minor groove recognition of DNA containing synthetic genetic components provides the basis to further develop unnatural base-pairs for synthetic biology applications.

Structural and Kinetic Profiling of Allosteric Modulation of Duplex DNA Induced by DNA-Binding Polyamide Analogues.

A combined structural and quantitative biophysical profile of the DNA binding affinity, kinetics and sequence-selectivity of hairpin polyamide analogues is described. DNA duplexes containing either target polyamide binding sites or mismatch sequences are immobilized on a microelectrode surface. Quantitation of the DNA binding profile of polyamides containing N-terminal 1-alkylimidazole (Im) units exhibit picomolar binding affinities for their target sequences, whereas 5-alkylthiazole (Nt) units are an order of magnitude lower (low nanomolar). Comparative NMR structural analyses of the polyamide series shows that the steric bulk distal to the DNA-binding face of the hairpin iPr-Nt polyamide plays an influential role in the allosteric modulation of the overall DNA duplex structure. This combined kinetic and structural study provides a foundation to develop next-generation hairpin designs where the DNA-binding profile of polyamides is reconciled with their physicochemical properties.

Determination of the equilibrium constant of C60 fullerene binding with drug molecules.

We report a new analytical method that allows the determination of the magnitude of the equilibrium constant of complexation, Kh, of small molecules to C60 fullerene in aqueous solution. The developed method is based on the up-scaled model of C60 fullerene-ligand complexation and contains the full set of equations needed to fit titration datasets arising from different experimental methods (UV-Vis spectroscopy, 1H NMR spectroscopy, diffusion ordered NMR spectroscopy, DLS). The up-scaled model takes into consideration the specificity of C60 fullerene aggregation in aqueous solution and allows the highly dispersed nature of C60 fullerene cluster distribution to be accounted for. It also takes into consideration the complexity of fullerene-ligand dynamic equilibrium in solution, formed by various types of self- and hetero-complexes. These features make the suggested method superior to standard Langmuir-type analysis, the approach used to date for obtaining quantitative information on ligand binding with different nanoparticles.

Adding a Structural Context to the Deprotometalation and Trans-Metal Trapping Chemistry of Phenyl-Substituted Benzotriazole.

Organometallic bases are becoming increasingly complex, because mixing components can lead to bases superior to single-component bases. To better understand this superiority, it is useful to study metalated intermediate structures prior to quenching. This study is on 1-phenyl-1H-benzotriazole, which was previously deprotonated by an in situ ZnCl2 ⋅TMEDA/LiTMP (TMEDA=N,N,N',N'-tetramethylethylenediamine; TMP=2,2,6,6-tetramethylpiperidide) mixture and then iodinated. Herein, reaction with LiTMP exposes the deficiency of the single-component base as the crystalline product obtained was [{4-R-1-(2-lithiophenyl)-1H-benzotriazole⋅3THF}2 ], [R=2-C6 H4 (Ph)NLi], in which ring opening of benzotriazole and N2 extrusion had occurred. Supporting lithiation by adding iBu2 Al(TMP) induces trans-metal trapping, in which C-Li bonds transform into C-Al bonds to stabilise the metalated intermediate. X-ray diffraction studies revealed homodimeric [(4-R'-1-phenyl-1H-benzotriazole)2 ], [R'=(iBu)2 Al(µ-TMP)Li], and its heterodimeric isomer [(4-R'-1-phenyl-1H-benzotriazole){2-R'-1-phenyl-1H-benzotriazole}], whose structure and slow conformational dynamics were probed by solution NMR spectroscopy.

Shape-independent model (SHIM) approach for studying aggregation by NMR diffusometry.

NMR diffusometry has been gaining wide popularity in various areas of applied chemistry for investigating diffusion and complexation processes in solid and aqueous phases. To date, the application of this method to study aggregation phenomena proceeding beyond the dimer stage of assembly has been restricted by the need for a priori knowledge of the aggregates' shape, commonly difficult to know in practice. We describe here a comprehensive analysis of aggregation parameter-dependency on the type and shape selected for modeling assembly processes, and report for the first time a shape-independent model (designated the SHIM approach), which may be used as an alternative in cases when information on aggregates' shapes is unavailable. The model can be used for determining equilibrium aggregation parameters from self-diffusion NMR data including equilibrium self-association constant and changes in enthalpy, ΔH, and entropy, ΔS.

HOBS methods for enhancing resolution and sensitivity in small DNA oligonucleotide NMR studies.

(1) H NMR spectra from biopolymers give chemical shifts classified according to proton type and often suffer from signal degeneracy. Data from nucleic acids are particularly prone to this failing. Recent developments in proton broadband decoupling techniques with the promise of enhanced resolution at full sensitivity have allowed us to investigate the application of homonuclear band-selective (HOBS) decoupling to the study of small synthetic DNA molecules and to compare these with results from classical and pure shift techniques. Improved signal resolution at full sensitivity in both HOBS-1D (1) H and HOBS-2D [(1) H, (1) H] NOESY NMR data is reported for three example small DNA molecules. Comparisons of (1) H T1 and integrals of signals from HOBS-1D (1) H and HOBS-2D [(1) H, (1) H] NOESY NMR data with those of standard data collection methods are also reported. The results show that homonuclear HOBS-NOESY data are useful for data assignment purposes and have some merit for quantification purposes. In general, we show that resolution and sensitivity enhancement of (1) H NMR data for small DNA samples may be achieved without recourse to higher magnetic field strength at full sensitivity in a band-selected manner.

Effects of motives on reactions to safe sun messages.

We investigated whether appearance motive for sun exposure, which strongly predicts exposure behaviour, would predict reactions to safe sun messages. In a survey with an embedded experiment, 245 individuals completed measures of motives, read a safe sun message framed by incentive (appearance/health), tone (directive/nondirective) and valence (gain/loss), then completed measures of reactions. For participants high in appearance motive, an appearance-nondirective message was most persuasive. Regardless of individual's appearance motive, appearance messages produced lower reactance if phrased using nondirective language. To maximise persuasion and minimise reactance in individuals most motivated to sun expose, safe sun messages should focus on appearance using nondirective language.

Recognition of the DNA minor groove by thiazotropsin analogues.

Solution-phase self-association characteristics and DNA molecular-recognition properties are reported for three close analogues of minor-groove-binding ligands from the thiazotropsin class of lexitropsin molecules; they incorporate isopropyl thiazole as a lipophilic building block. Thiazotropsin B (AcImPy(iPr) ThDp) shows similar self-assembly characteristics to thiazotropsin A (FoPyPy(iPr) ThDp), although it is engineered, by incorporation of imidazole in place of N-methyl pyrrole, to swap its DNA recognition target from 5'-ACTAGT-3' to 5'-ACGCGT-3'. Replacement of the formamide head group in thiazotropsin A by nicotinamide in AIK-18/51 results in a measureable difference in solution-phase self-assembly character and substantially enhanced DNA association characteristics. The structures and associated thermodynamic parameters of self-assembled ligand aggregates and their complexes with their respective DNA targets are considered in the context of cluster targeting of DNA by minor-groove complexes.

Closing the Gap: How Psychological Distance Influences Willingness to Engage in Risky COVID Behavior.

Pandemics, and other risk-related contexts, require dynamic changes in behavior as situations develop. Human behavior is influenced by both explicit (cognitive) and implicit (intuitive) factors. In this study, we used psychological distance as a lens to understand what influences our decision-making with regard to risk in the context of COVID-19. This study was based on the rationale that our relational needs are more concrete to us than the risk of the virus. First, we explored the impact of social-psychological distance on participants' risk perceptions and behavioral willingness. As hypothesized, we found that close social relationships of agents promoted willingness to engage in risky behavior. In the second phase, we tested an intervention designed to increase the concreteness of information about virus transmission as a mechanism to mitigate the bias of social influence. We found that the concreteness intervention resulted in significantly reduced willingness to engage in risky behavior. As such, communications aimed at changing the behavior of citizens during times of increased risk or danger should consider conceptually concrete messaging when communicating complex risk, and hence may provide a valuable tool in promoting health-related behavior.

COVID-19 Personal Protective Behaviors during Large Social Events: The Value of Behavioral Observations.

Within the context of reopening society in the summer of 2021, as the UK moved away from 'lockdowns', the Government of Wales piloted the return of organized 'mass gatherings' of people at a number of test events. The current study reports behavioral observations that were made at two of the test events to inform this process. The researchers were particularly interested in four key factors: how (1) context within a venue, (2) environmental design, (3) staffing and social norms, and (4) time across an event, affected the personal protective behaviors of social distancing and face-covering use. Data collection was undertaken by trained observers. Adherence to protective behaviors was generally high, but there is clear evidence that these behaviors were shaped in a systematic way by the environment, situational cues, and the passage of time during the events. Some instances of large-scale non-adherence to personal protective behaviors were documented. An analysis within a dual-process framework suggests ways to understand and respond to supporting target health behaviors in groups of people where intervention is deemed valuable, such as in complex or ambiguous contexts. This is one of the first studies to include a 'true' behavioral measure in understanding human responses to COVID-19. It demonstrates that behavioral observations can add precision and granularity to understanding human behavior in complex real-world contexts. Given the significant physical and mental health burden created acutely and chronically by COVID-19, this work has implications for how governments and organizations support target populations in other complex challenges facing us today, such as in sustainability, and healthy lifestyle behaviors. An individual's intentions are not always matched by their actions, and so the findings support a balanced liberal paternalistic approach where system-level changes support appropriate individual-level decisions to engender collective responsibility and action.

C60 fullerene aggregation in aqueous solution.

In the present work we develop a novel approach for quantification of the energetics of C60 fullerene aggregation in aqueous media in terms of equilibrium aggregation constant KF. In particular, it is shown that the experimental determination of the magnitude of KF is possible only within the framework of the 'up-scaled aggregation model', considering the C60 fullerene water solution as a solution of fullerene clusters. Using dynamic light scattering (DLS) data we report the value, K(F) = 56,000 M(-1), which is in good agreement with existing theoretical estimates and the results of energetic analyses. It is suggested that the proposed 'up-scaled model' may be used in any instances of non-specific aggregation resulting in formation of large spherical particles. The measurement of the translational diffusion coefficient and the dimensions of the light scattering particles using a DLS approach with respect to C60 fullerene aggregates is found to contain significant systematic errors originating from the interaction effect that is well-known for micellar solutions. As a result, corrections to the equations associated with DLS data are proposed.

Multigramme synthesis and asymmetric dihydroxylation of a 4-fluorobut-2E-enoate.

Esters of crotonic acid were brominated on a multigramme scale using a free radical procedure. A phase transfer catalysed fluorination transformed these species to the 4-fluorobut-2E-enoates reproducibly and at scale (48-53%, ca. 300 mmol). Asymmetric dihydroxylation reactions were then used to transform the butenoate, ultimately into all four diastereoisomers of a versatile fluorinated C4 building block at high enantiomeric-enrichment. The (DHQ)2AQN and (DHQD)2AQN ligands described by Sharpless were the most effective. The development and optimisation of a new and facile method for the determination of ee is also described; (19)F{(1)H} spectra recorded in d-chloroform/diisopropyl tartrate showed distinct baseline separated signals for different enantiomers.

Nucleus accumbens response to food cues predicts subsequent snack consumption in women and increased body mass index in those with reduced self-control.

Individuals have difficulty controlling their food consumption, which is due in part to the ubiquity of tempting food cues in the environment. Individual differences in the propensity to attribute incentive (motivational) salience to and act on these cues may explain why some individuals eat more than others. Using fMRI in healthy women, we found that food cue related activity in the nucleus accumbens, a key brain region for food motivation and reward, was related to subsequent snack food consumption. However, both nucleus accumbens activation and snack food consumption were unrelated to self-reported hunger, or explicit wanting and liking for the snack. In contrast, food cue reactivity in the ventromedial prefrontal cortex was associated with subjective hunger/appetite, but not with consumption. Whilst the food cue reactivity in the nucleus accumbens that predicted snack consumption was not directly related to body mass index (BMI), it was associated with increased BMI in individuals reporting low self-control. Our findings reveal a neural substrate underpinning automatic environmental influences on consumption in humans and demonstrate how self-control interacts with this response to predict BMI. Our data provide support for theoretical models that advocate a 'dual hit' of increased incentive salience attribution to food cues and poor self-control in determining vulnerability to overeating and overweight.

Energetics of ligand binding to the DNA minor groove.

In the present work the decomposition of the total Gibbs free energy of ligand-DNA binding onto various physical terms was accomplished for the group of nine DNA minor groove binders (MGB ligands) differing in both structure and charge state. The decomposition protocol includes the analysis of the most complete set of physical factors known to contribute to the complexation process, viz. the net change in the number of degrees of freedom (translational, rotational, vibrations of the chemical bonds and vibrations of the ligand as a whole within the binding site), the conformational entropy, van der Waals, electrostatic and hydrophobic interactions, the polyelectrolyte contribution and the net effect of changes in the number of hydrogen bonds. All of these processes are further decomposed into the interaction with the solvent and the interaction of the ligand with DNA. The principal outcome of the decomposition is the possibility of performing a comparative analysis of the energetic contribution of various physical terms and provide an answer to the question concerning what physical factors stabilize or destabilize the complexes of MGB ligands with DNA.

Insights into the Spectrum of Activity and Mechanism of Action of MGB-BP-3.

MGB-BP-3 is a potential first-in-class antibiotic, a Strathclyde Minor Groove Binder (S-MGB), that has successfully completed Phase IIa clinical trials for the treatment of Clostridioides difficile associated disease. Its precise mechanism of action and the origin of limited activity against Gram-negative pathogens are relatively unknown. Herein, treatment with MGB-BP-3 alone significantly inhibited the bacterial growth of the Gram-positive, but not Gram-negative, bacteria as expected. Synergy assays revealed that inefficient intracellular accumulation, through both permeation and efflux, is the likely reason for lack of Gram-negative activity. MGB-BP-3 has strong interactions with its intracellular target, DNA, in both Gram-negative and Gram-positive bacteria, revealed through ultraviolet-visible (UV-vis) thermal melting and fluorescence intercalator displacement assays. MGB-BP-3 was confirmed to bind to dsDNA as a dimer using nano-electrospray ionization mass spectrometry and nuclear magnetic resonance (NMR) spectroscopy. Type II bacterial topoisomerase inhibition assays revealed that MGB-BP-3 was able to interfere with the supercoiling action of gyrase and the relaxation and decatenation actions of topoisomerase IV of both Staphylococcus aureus and Escherichia coli. However, no evidence of stabilization of the cleavage complexes was observed, such as for fluoroquinolones, confirmed by a lack of induction of DSBs and the SOS response in E. coli reporter strains. These results highlight additional mechanisms of action of MGB-BP-3, including interference of the action of type II bacterial topoisomerases. While MGB-BP-3's lack of Gram-negative activity was confirmed, and an understanding of this presented, the recognition that MGB-BP-3 can target DNA of Gram-negative organisms will enable further iterations of design to achieve a Gram-negative active S-MGB.

Why is RCM favoured over dimerisation? Predicting and estimating thermodynamic effective molarities by solution experiments and electronic structure calculations.

The thermodynamic effective molarities of a series of simple cycloalkenes, synthesised from α,ω-dienes by reaction with Grubbs' second generation precatalyst, have been evaluated. Effective molarities were measured from a series of small scale metathesis reactions and agreed well with empirical predictions derived from the number of rotors and the product ring strain. The use of electronic structure calculations (at the M06-L/6-311G** level of theory) was explored for predicting thermodynamic effective molarities in ring-closing metathesis. However, it was found that it was necessary to apply a correction to DFT-derived free energies to account for the entropic effects of solvation.

Appetitive motivational deficits in individuals with Parkinson's disease.

Parkinson's disease is known for its effects on sensorimotor coordination caused by degeneration of the nigrostriatal dopamine pathway. Dopamine-innervated areas of the ventral striatum also become compromised in Parkinson's disease, and little is known about the potential impact of this pathology on motivational processes mediated by the mesolimbic dopamine system. The current study tested the hypothesis that patients with Parkinson's disease would show a deficit in appetitive motivational arousal. Patients with Parkinson's disease and age-matched healthy controls completed a visual discrimination task in which control and appetitive food images (incidental to the task) were presented in the background. Response rate changes indicated appetitive motivational arousal. The healthy controls showed an increase in response rate on the task when appetitive food cues were present compared with control stimuli. In contrast, the Parkinson's disease group showed an inverse pattern to the healthy controls. The reduction in appetitive motivation correlated with an individual's Parkinsonian symptomology. Patients with Parkinson's disease demonstrated an impairment in appetitive motivational arousal consistent with the progression of dopaminergic degeneration across the course of the disease. Dysfunction of this system affects quality of life in Parkinson's disease, and a blunting of the anticipatory motivation may contribute to the high prevalence of depression in Parkinson's disease.