Inducing a pH-dependent conformational response by competitive binding to Zn2+ of a series of chiral ligands of disparate basicity.

Molecules that change shape in response to environmental conditions are central to biological molecular communication devices and their synthetic chemical analogues. Here we report a molecular system in which a series of chiral anionic ligands of differing basicity are selectively protonated according to the pH of the medium. A cationic circular dichroism (CD) reporter complex responds to anion binding by selecting one of two alternative enantiomeric conformations. Exploiting the principle that less basic anions have, in general, weaker electrostatic interactions than more basic anions, a set of three chiral acids with large (>5 unit) pK a differences and differing configurations were sequentially deprotonated in acetonitrile by addition of base, allowing the most basic anion in the mixture at any time to bind to the reporter complex. A characteristic CD output resulted, which changed in sign as the next-most basic anion was revealed by the next deprotonation in the series. Four cycles of switching between three ligand-bound states were achieved with minimal changes in signal magnitude, by alternating addition of base and acid. The pH-dependent conformational response was used to transduce a signal by appending to the binding site a 2-aminoisobutyric acid (Aib) oligomer, whose M or P helical conformation depended on the chirality of the bound ligand, and was reported by a remote 13C-labelled NMR reporter group. The multicomponent system thus converts a pH signal into a programmable conformational response which induces a remote spectroscopic effect.

Frontal fibrosing alopecia: survey of severity assessment methods in routine clinical practice and validation of the International Frontal Fibrosing Alopecia Cooperative Group measurement guidance.

BACKGROUND: The lack of validated and responsive outcome measures in the management of frontal fibrosing alopecia (FFA) significantly limits assessment of disease progression and treatment response over time. AIM: To understand how FFA extent and progression is currently assessed in UK specialist centres, to validate components of the International FFA Cooperative Group (IFFACG) statement on FFA assessment, and to identify pragmatic advice to improve FFA management in clinic. METHODS: Consultant dermatologists with a specialist interest in hair loss (n = 17) were invited to take part. Preferred FFA assessment methods were explored using questionnaires and clinical scenarios. Participants were asked to identify and mark the current hairline in 10 frontal and 10 temporal hairline images (Questionnaire 1), with assessment repeated 3 months later to assess intraindividual variability (Questionnaire 2) and 12 months later to test whether interindividual accuracy could be improved with simple instruction (Questionnaire 3). RESULTS: All 17 clinicians (100%) completed the questionnaire at each time interval. We identified a wide variation in assessment techniques used by our experts. Measurements were perceived as the most accurate method of assessing frontal recession whereas photography was preferred for temporal recession. Inter-rater reliability between clinicians measuring the frontal hairline scenarios indicated a moderate strength of agreement [intraclass coefficient (ICC) = 0.61; 95% CI 0.40-0.85], yet intrarater reliability was found to be poor with wide limits of agreement (-8.71 mm to 9.92 mm) on follow-up. Importantly, when clear guidance was provided on how the hairline should be identified (Questionnaire 3), inter-rater reliability improved significantly, with ICC = 0.70, suggesting moderate agreement (95% CI 0.51-0.89; P < 0.001). A similar pattern was seen with temporal hairline measurements, which again improved in accuracy with instruction. CONCLUSION: We found that accuracy of measurements in FFA can be improved with simple instruction and we have validated components of the IFFACG measurement recommendations.

Molecular Recognition by Zn(II)-Capped Dynamic Foldamers.

Two α-aminoisobutyric acid (Aib) foldamers bearing Zn(II)-chelating N-termini have been synthesized and compared with a reported Aib foldamer that has a bis(quinolinyl)/mono(pyridyl) cap (BQPA group). Replacement of the quinolinyl arms of the BQPA-capped foldamer with pyridyl gave a BPPA-capped foldamer, then further replacement of the linking pyridyl with a 1,2,3-triazole gave a BPTA-capped foldamer. Their ability to relay chiral information from carboxylate bound to Zn(II) at the N-terminus to a glycinamide-based NMR reporter of conformational preference at the C-terminus was measured. The importance of the quinolinyl arms became readily apparent, as the foldamers with pyridyl arms were unable to report on the presence of chiral carboxylate in acetonitrile. Low solubility, X-ray crystallography and 1H NMR spectroscopy suggested that interfoldamer interactions inhibited carboxylate binding. However changing solvent to methanol revealed that the end-to-end relay of chiral information could be observed for the Zn(II) complex of the BPTA-capped foldamer at low temperature.

Remote conformational responses to enantiomeric excess in carboxylate-binding dynamic foldamers.

A crystallographically characterised zinc(ii)-capped foldamer can sense the enantiomeric excess of scalemic carboxylate solutions, including those produced by enantioselective organocatalysis, and can relay this input signal along the foldamer body to a remote glycinamide group, which then provides an NMR spectroscopic output.

Dibenzazepinyl ureas as dual NMR and CD probes of helical screw-sense preference in conformationally equilibrating dynamic foldamers.

Conformationally mobile oligomers with helical structures, or 'dynamic foldamers', may populate a mixture of screw-sense conformers whose relative proportion has been used as a means of communicating information on a molecular scale. The dibenzazepinyl urea provides a means of quantifying both the sense and degree of this screw-sense preference through a combination of circular dichroism (CD) and NMR spectroscopy. The dibenzazepinyl urea probe is synthetically versatile, readily accessible, and easy to introduce to the terminus of an amide or a urea foldamer.

A tendril perversion in a helical oligomer: trapping and characterizing a mobile screw-sense reversal.

Helical oligomers of achiral monomers adopt domains of uniform screw sense, which are occasionally interrupted by screw-sense reversals. These rare, elusive, and fast-moving features have eluded detailed characterization. We now describe the structure and habits of a screw-sense reversal trapped within a fragment of a helical oligoamide foldamer of the achiral quaternary amino acid 2-aminoisobutyric acid (Aib). The reversal was enforced by compelling the amide oligomer to adopt a right-handed screw sense at one end and a left-handed screw sense at the other. The trapped reversal was characterized by X-ray crystallography, and its dynamic properties were monitored by NMR and circular dichroism, and modelled computationally. Raman spectroscopy indicated that a predominantly helical architecture was maintained despite the reversal. NMR and computational results indicated a stepwise shift from one screw sense to another on moving along the helical chain, indicating that in solution the reversal is not localised at a specific location, but is free to migrate across a number of residues. Analogous unconstrained screw-sense reversals that are free to move within a helical structure are likely to provide the mechanism by which comparable helical polymers and foldamers undergo screw-sense inversion.

Dynamic foldamer chemistry.

Foldamers can be made more than pieces of static, conformationally uniform molecular architecture by designing into their structure the conformational dynamism characteristic of functional molecular machines. We show that these dynamic foldamers display biomimetic properties reminiscent of allosteric proteins and receptor molecules. They can translate chemical signals into conformational changes, and hence into chemical outputs such as control of reactivity and selectivity. Future developments could see dynamic foldamers operating in the membrane phase providing artificial mechanisms for communication and control that integrate synthetic chemistry into synthetic biology.

Refoldable Foldamers: Global Conformational Switching by Deletion or Insertion of a Single Hydrogen Bond.

Small changes in the structure of a foldamer may lead to gross changes in conformational preference. We show that the simple insertion or deletion of a single hydrogen bond by changes in pH or by photochemical deprotection is sufficient to refold a helical oligomer, interconverting M and P screw-sense preference. As a consequence of the switch, information may be transmitted to a remote catalytic site, selectively directing the formation of either of two enantiomeric products by a reaction involving 1,22-remote intermolecular asymmetric induction.

Conformational cooperativity between helical domains of differing geometry in oligoamide-oligourea foldamer chimeras.

Linking together an oligourea and an oligoamide foldamer gives rise to a conformationally well-defined structure, despite the different hydrogen-bonding patterns in the two domains, provided the oligomers are ligated amide C terminus to urea N terminus. A powerful screw-sense preference induced at the N terminus of the resulting chimeric structure provides evidence for cooperative conformational interactions within the 'block co-foldamer'.

Flaws in foldamers: conformational uniformity and signal decay in achiral helical peptide oligomers.

Although foldamers, by definition, are extended molecular structures with a well-defined conformation, minor conformers must be populated at least to some extent in solution. We present a quantitative analysis of these minor conformers for a series of helical oligomers built from achiral but helicogenic α-amino acids. By measuring the chain length dependence or chain position dependence of NMR or CD quantities that measure screw-sense preference in a helical oligomer, we quantify values for the decay constant of a conformational signal as it passes through the molecular structure. This conformational signal is a perturbation of the racemic mixture of M and P helices that such oligomers typically adopt by the inclusion of an N or C terminal chiral inducer. We show that decay constants may be very low (<1% signal loss per residue) in non-polar solvents, and we evaluate the increase in decay constant that results in polar solvents, at higher temperatures, and with more conformationally flexible residues such as Gly. Decay constants are independent of whether the signal originates from the N or the C terminus. By interpreting the decay constant in terms of the probability with which conformations containing a screw-sense reversal are populated, we quantify the populations of these alternative minor conformers within the overall ensemble of secondary structures adopted by the foldamer. We deduce helical persistence lengths for Aib polymers that allow us to show that in a non-polar solvent a peptide helix, even in the absence of chiral residues, may continue with the same screw sense for approximately 200 residues.

Confronting the challenges of the menopausal transition.

Canada's Generation X is now entering the menopausal transition and pursuing effective therapy for bothersome vasomotor symptoms. They do so at a time when confusion about the safe and appropriate use of menopausal hormone therapy (MHT) has never been greater. Misplaced fears among women and their health care providers about MHT have, in many circumstances, led them to abandon this most effective therapy. This review discusses the physiology of the menopausal transition, the nature of symptoms related to withdrawal of ovarian estrogen production, and the potential benefits and risks of MHT. It is now clear that for most recently menopausal women the benefits of MHT outweigh the risks. The rationale for choosing different dosages, formulations, and regimens is reviewed.

International spinal cord injury upper extremity basic data set.

OBJECTIVE: To develop an International Spinal Cord Injury (SCI) Upper Extremity Basic Data Set as part of the International SCI Data Sets, which facilitates consistent collection and reporting of basic upper extremity findings in the SCI population. SETTING: International. METHODS: A first draft of a SCI Upper Extremity Data Set was developed by an international working group. This was reviewed by many different organisations, societies and individuals over several months. A final version was created. VARIABLES: The final version of the International SCI Upper Extremity Data Set contains variables related to basic hand-upper extremity function, use of assistive devices, SCI-related complications to upper extremity function and upper extremity/hand reconstructive surgery. Instructions for data collection and the data collection form are freely available on the ISCoS website (www.iscos.org.uk). CONCLUSION: The International SCI Upper Extremity Basic Data Set will facilitate consistent collection and reporting of basic upper extremity findings in the SCI population.

Controlling the sign and magnitude of screw-sense preference from the C-terminus of an achiral helical foldamer.

The global screw-sense preference of an achiral helical oligomer may be controlled by a single chiral monomer located at one terminus. Remarkably, maximal control is induced in oligomers of the achiral quaternary amino acid Aib by a single C-terminal alaninamide residue, probably because the Ala side chain, though small, is compatible with a 310 helical conformation. The presence or absence of a C-terminal hydrogen bond donor determines the screw sense of the entire oligomer.

Analysis of health stories in daily newspapers in the UK.

OBJECTIVES: To assess what makes a good piece of medical reporting in newspapers, to quantify what is being reported on in the major British newspapers, to identify the sources of the news threads, and to assess how these are reported. STUDY DESIGN: Development and validation of a tool to assess the quality of reporting of health-related articles, and assessment of the quality of these articles in British newspapers. METHODS: Eight national daily newspapers from the UK were reviewed for 20 days over a 2-month period. All articles reporting newly emerging research pertaining to health in humans were included and reviewed independently by two raters. A descriptive analysis was performed. Subsequently, a quality assessment tool for use by a non-expert was developed and validated to objectively assess the quality of a newspaper article on a health-related topic. RESULTS: The quality assessment tool was found to have good internal consistency and inter-rater reliability. The Daily Mail published almost twice as many articles as its nearest rival, The Daily Express, and over eight times as many articles as The Guardian. Articles in The Times were, on average, more than twice as long as those in The Sun and The Daily Telegraph. The highest quality articles were in The Times and The Independent, with the lowest quality articles in The Sun. The quality scores of anonymous articles were significantly lower than those attributed to named journalists. CONCLUSIONS: There are significant differences in the quality of reporting within and between major daily UK newspapers, with anonymous articles being the poorest quality, and widespread reliance on press releases from the major UK scientific journals.

Automated Illustration of Molecular Flexibility.

In this paper, we present an approach to creating illustrations of molecular flexibility using normal mode analysis (NMA). The output of NMA is a collection of points corresponding to the locations of atoms and associated motion vectors, where a vector for each point is known. Our approach abstracts the complex object and its motion by grouping the points, models the motion of each group as an affine velocity, and depicts the motion of each group by automatically choosing glyphs such as arrows. Affine exponentials allow the extrapolation of nonlinear effects such as near rotations and spirals from the linear velocities. Our approach automatically groups points by finding sets of neighboring points whose motions fit the motion model. The geometry and motion models for each group are used to determine glyphs that depict the motion, with various aspects of the motion mapped to each glyph. We evaluated the utility of our system in real work done by structural biologists both by utilizing it in our own structural biology work and quantitatively measuring its usefulness on a set of known protein conformation changes. Additionally, in order to allow ourselves and our collaborators to effectively use our techniques we integrated our system with commonly used tools for molecular visualization.

Iron-catalysed, hydride-mediated reductive cross-coupling of vinyl halides and Grignard reagents.

An iron-catalysed, hydride-mediated reductive cross-coupling reaction has been developed for the preparation of alkanes. Using a bench-stable iron(II) pre-catalyst, reductive cross-coupling of vinyl iodides, bromides and chlorides with aryl- and alkyl Grignard reagents successfully gave the products of formal sp(3)-sp(3) cross-coupling reactions.

Photopatch testing of 1155 patients: results of the U.K. multicentre photopatch study group.

BACKGROUND: Photoallergic contact dermatitis can be difficult to diagnose if not appropriately investigated. Currently, the most common U.K. photoallergens appear to be sunscreen chemicals. The investigation of choice is photopatch testing (PPT), which is probably underused. In part, this is due to differences in methodology and results interpretation. OBJECTIVES: To conduct PPT using a group of sunscreen chemicals, defined indications and a standardized methodology including interpretation and relevance of reactions in patients attending for investigation at 17 centres across the U.K., Ireland and the Netherlands. METHODS: Patients (n = 1155) who fulfilled the inclusion criteria were investigated with PPT using sunscreen chemicals in addition to suspected topical products. Readings were taken at 24, 48 and 72 h following standardized ultraviolet A irradiation (5 J cm(-2)). The clinical relevance of any reaction was recorded. RESULTS: Of the 1155, 130 had allergic reactions (11.3%). Of these, 51 had photoallergy (PA) (4.4%), 64 had contact allergy (CA) (5.5%), and 15 patients had combined PA and CA (1.3%). Multiple PA was seen in some. The most common photoallergen was benzophenone-3 (27 reactions; 21%). Most reactions (60%) were clinically relevant. The most common indication for testing in patients found to have PA was a history of reacting to a sunscreen (41%). The other 59% had an exposed-site dermatitis/skin problem or a photodermatosis. Some centres (n = 8) performed readings after the standard 48-h reading, and an extra 32 PA and 22 CA reactions were detected, which were not evident at 48 h. A new photoallergen (octyl triazone) was detected in two patients. CONCLUSIONS: Sunscreen PA and CA are probably equally uncommon. Most reactions, of both reaction types, were relevant clinically. A large proportion of patients (59%) found to have PA was unaware of reacting to a sunscreen chemical, suggesting that PA should be considered as an explanation in any exposed-site dermatitis. Although this study focused on reactions at 48 h postirradiation, readings performed up to 96 h, while inconvenient, add value by detecting additional relevant responses. A previously unknown photoallergen was found, highlighting the need for awareness of novel photoallergens in the marketplace. A standardized PPT method not only encourages more use of this investigation, but also facilitates comparison of results between centres and so will improve our understanding of PA.

Regulation of cutaneous drug-metabolizing enzymes and cytoprotective gene expression by topical drugs in human skin in vivo.

BACKGROUND: Individuality in the expression and regulation of hepatic drug-metabolizing enzymes (DMEs) and cytoprotective (CP) genes is an important determinant of treatment response. There is increasing evidence that many DMEs and CP genes are also expressed in human skin. Responses to topical drugs used to treat common skin diseases, such as psoriasis, are unpredictable and may potentially be rationalized, at least in part, by interindividual differences in cutaneous DME and CP gene expression. OBJECTIVES: We investigated whether three topical drugs [coal tar, all-trans retinoic acid (atRA) and clobetasol 17-propionate] used in routine clinical practice modulated the expression of a variety of DME and CP genes [cytochrome P450s, glutathione S-transferases (GSTs) and drug transporters] in healthy human skin in vivo. METHODS: Healthy adult volunteers (n = 30) were invited to participate in the study. Each subject was randomly allocated to receive two of the three study chemicals and one control site application. Crude coal tar (n = 13), atRA (n = 14) or clobetasol 17-propionate (n = 10) was applied under occlusion to photoprotected buttock skin for 96 h. A vehicle control (white soft paraffin) was also applied under the same conditions at an adjacent site in all subjects. Full-thickness punch biopsies (4-mm diameter) were then taken from treated and control sites. Total RNA was extracted and reverse transcribed into cDNA, which was used as a template in subsequent real-time polymerase chain reaction analysis, where fluorescent output was directly proportional to input cDNA concentration. Triplicate measurements of skin mRNA expression were made from each sample, and the arithmetic mean values taken. After logarithmic transformation, the paired t-test was used to compare values between treated and control skin. RESULTS: Cytochrome P450s CYP1A1, CYP1A2, CYP1B1, CYP2C18, quinone reductase (NQO-1), GSTP1, gamma-glutamyl cysteine synthetase (gamma-GCS), glutathione peroxidase-1 (GPx-1), cyclooxygenase-2 (COX-2) and haem oxygenase-1 (HO-1) were induced by coal tar; CYP26, NADPH P450 reductase (CPR), GSTP1 and HO-1 by atRA; and CYP3A5 by clobetasol 17-propionate. In contrast, CYP1A1 and CYP1A2 expression was suppressed by atRA, and gamma-GCS and MRP1 by clobetasol 17-propionate. Marked interindividual variation in gene regulation by topical drugs was seen for the majority of genes examined. CONCLUSIONS: These data demonstrate that topical drugs can modulate DME gene expression in human skin in vivo and indicate that variation in the expression and regulation of these genes may be a determinant of individuality in response to topical therapies for common skin diseases.