β-Helical Polymers from Isocyanopeptides Jeroen J. L. M. Cornelissen; Jack J. J. M. Donners; de Gelder, René ...
Science (American Association for the Advancement of Science),
07/2001, Letnik:
293, Številka:
5530
Journal Article
Recenzirano
Polymerization of isocyanopeptides results in the formation of high molecular mass polymers that fold in a proteinlike fashion to give helical strands in which the peptide chains are arranged in ...β-sheets. The β-helical polymers retain their structure in water and unfold in a cooperative process at elevated temperatures. The peptide architecture in these polymers is a different form of the β-helix motif found in proteins. Unlike their natural counterparts, which contain arrays of large β-sheets stacked in a helical fashion, the isocyanopeptide polymers have a central helical core that acts as a director for the β-sheet-like arrangement of the peptide side arms. The helical structure of these isocyanopeptide polymers has the potential to be controlled through tailoring of the side branches and the hydrogen-bonding network present in the β-sheets.
U.K. HiGEM Shaffrey, L. C.; Stevens, I.; Norton, W. A. ...
Journal of climate,
04/2009, Letnik:
22, Številka:
8
Journal Article
Recenzirano
Odprti dostop
This article describes the development and evaluation of the U.K.’s new High-Resolution Global Environmental Model (HiGEM), which is based on the latest climate configuration of the Met Office ...Unified Model, known as the Hadley Centre Global Environmental Model, version 1 (HadGEM1). In HiGEM, the horizontal resolution has been increased to 0.83° latitude × 1.25° longitude for the atmosphere, and 1/3° × 1/3° globally for the ocean. Multidecadal integrations of HiGEM, and the lower-resolution HadGEM, are used to explore the impact of resolution on the fidelity of climate simulations.
Generally, SST errors are reduced in HiGEM. Cold SST errors associated with the path of the North Atlantic drift improve, and warm SST errors are reduced in upwelling stratocumulus regions where the simulation of low-level cloud is better at higher resolution. The ocean model in HiGEM allows ocean eddies to be partially resolved, which dramatically improves the representation of sea surface height variability. In the Southern Ocean, most of the heat transports in HiGEM is achieved by resolved eddy motions, which replaces the parameterized eddy heat transport in the lower-resolution model. HiGEM is also able to more realistically simulate small-scale features in the wind stress curl around islands and oceanic SST fronts, which may have implications for oceanic upwelling and ocean biology.
Higher resolution in both the atmosphere and the ocean allows coupling to occur on small spatial scales. In particular, the small-scale interaction recently seen in satellite imagery between the atmosphere and tropical instability waves in the tropical Pacific Ocean is realistically captured in HiGEM. Tropical instability waves play a role in improving the simulation of the mean state of the tropical Pacific, which has important implications for climate variability. In particular, all aspects of the simulation of ENSO (spatial patterns, the time scales at which ENSO occurs, and global teleconnections) are much improved in HiGEM.
Introduction and hypothesis
The objective was to compare the location and motion of pessaries between women with pelvic organ prolapse (POP) with a successful (fitting) and unsuccessful (non-fitting) ...pessary treatment on dynamic magnetic resonance imaging (dMRI).
Methods
A cross-sectional exploratory study of 15 women who underwent a mid-sagittal dMRI of the pelvic floor at rest, during contraction and during Valsalva with three different types of pessaries. The coordinates of the pessaries cross section, inferior pubic point (IPP) and sacrococcygeal junction (SCJ) were obtained and the location (position, orientation) and the motion (translation and rotation) were calculated. Differences between the groups and between the pessaries within the groups were compared.
Results
Nine women with a fitting pessary and 6 women with a non-fitting pessary were selected. In the non-fitting group, the pessaries were positioned more caudally and rotated more in clockwise direction and descended more, but not significantly, during Valsalva compared with the fitting group. The Falk pessary was positioned more anteriorly in the fitting group and more cranially in the non-fitting group compared with the ring and ring with support pessary.
Conclusions
A non-fitting pessary was positioned more caudally at rest; on Valsalva, it rotated more clockwise and moved more caudally, suggesting that the dynamic characteristics of the pessary might play an important role in its effectiveness. Findings of this study serve as a basis for the development of new pessary designs.
The design, synthesis, and characterization of "reverse" peptide amphiphiles (PAs) with free N-termini is described. Use of an unnatural amino acid modified with a fatty acid tail allows for the ...synthesis of this new class of PA molecules. The mixing of these molecules with complementary ones containing a free C-terminus results in coassembled structures, as demonstrated by circular dichroism and NOE/NMR spectroscopy. These assemblies show unusual thermal stability when compared to assemblies composed of only one type of PA molecule. This class of reverse PAs has made it possible to create biologically significant assemblies with free N-terminal peptide sequences, which were previously inaccessible, including those derived from phage display methodologies.
We describe a new approach to peptide-amphiphile (PA) nanofiber preparation that allows PAs with different bioactive amino acid sequences to be combined into a single fiber. Oppositely charged PAs ...are synthesized separately and then mixed to produce gels of nanofiber networks at physiological pH. Transmission electron microscopy reveals the formation of fibers approximately 7 nm in diameter and several micrometers long in these dimeric systems. On the basis of NMR and microscopy, we suggest that these nanofibers are cylindrical micelles of mixed composition, formed due to electrostatic attraction between the oppositely charged PAs. This strategy for self-assembly may be useful in cell therapies that can be implemented without invasive surgery or in in vitro tissue engineering.
Results are presented from a matrix of coupled model integrations, using atmosphere resolutions of 135 and 90 km, and ocean resolutions of 1° and 1/3°, to study the impact of resolution on simulated ...climate. The mean state of the tropical Pacific is found to be improved in the models with a higher ocean resolution. Such an improved mean state arises from the development of tropical instability waves, which are poorly resolved at low resolution; these waves reduce the equatorial cold tongue bias. The improved ocean state also allows for a better simulation of the atmospheric Walker circulation.
Several sensitivity studies have been performed to further understand the processes involved in the different component models. Significantly decreasing the horizontal momentum dissipation in the coupled model with the lower-resolution ocean has benefits for the mean tropical Pacific climate, but decreases model stability. Increasing the momentum dissipation in the coupled model with the higher-resolution ocean degrades the simulation toward that of the lower-resolution ocean.
These results suggest that enhanced ocean model resolution can have important benefits for the climatology of both the atmosphere and ocean components of the coupled model, and that some of these benefits may be achievable at lower ocean resolution, if the model formulation allows.
Objective
We investigated patients’ preferences for anterior colporrhaphy or mesh surgery as surgical correction of anterior vaginal wall prolapse.
Design
Labelled discrete choice experiment.
Setting
...Three Dutch teaching hospitals.
Population
Women with anterior vaginal wall prolapse Pelvic Organ Prolapse Quantification stage 2 or more, indicated for anterior colporrhaphy (n = 100).
Methods
Discrete choice experiments are an attribute‐based survey method for measuring preferences. In this experiment, women were asked to choose between two treatment scenarios, mesh surgery or anterior colporrhaphy. These surgical treatments differed in four treatment attributes: (i) recurrence rate, (ii) exposure rate, (iii) infection rate, (iv) dyspareunia. Data were analysed using a multinomial logit model.
Main outcome measures
Women's preferences for anterior colporrhaphy or mesh surgery for the repair of vaginal wall prolapse.
Results
All treatment attributes, i.e. recurrence, exposure, infection and dyspareunia, proved to be significant in the woman's decision to choose mesh surgery (P < 0.001), while only two attributes out of three, recurrence and infection, were significant for anterior colporrhaphy (P < 0.001). The relative importance data showed that with regards to the four statistically significant attributes for mesh, dyspareunia was the most important attribute, and of the two significant attributes for anterior colporrhaphy, the risk of infection. Based on the attributes and levels in our discrete choice experiment, anterior colporrhaphy was preferred in 74% as a primary correction of anterior vaginal wall prolapse, followed by a preference for mesh in 26% of all choices.
Conclusion
This study showed that next to the risk of recurrence, other aspects like risk of infection, dyspareunia and exposure play a role in the woman's preference for a surgical treatment. In addition, our results indicate that anterior colporrhaphy is preferred in the majority of the choices, followed by a preference for mesh surgery in a quarter of all choice sets. However, these results represent the average preference of a sample of women and cannot be taken as the preference of each individual. In the medical decision‐making context, information from the current study should be personalised to fit patient's unique circumstances. For patients to construct their own, individual preferences, they should be well informed about the existence and magnitude of the potential benefits and risks related to either anterior colporrhaphy or mesh surgery.
Introduction and hypothesis
National and international guidelines do not provide clear recommendations on the mode of delivery in a subsequent pregnancy after obstetric anal sphincter injury (OASI). ...The aim of this study was to investigate the opinion of gynecologists in The Netherlands on this choice and the extent to which this choice is affected by the gynecologist’s characteristics.
Methods
Of 973 gynecologists sent a questionnaire seeking their opinion on the mode of delivery in 16 different case descriptions, 234 (24%) responded. Factors influencing the opinion of the respondents on the mode of delivery, the presence of anal symptoms, the degree of OASI and the characteristics of the respondents were analyzed by univariate and multivariate logistic regression analysis.
Results
Recommendations on the mode of delivery in a subsequent pregnancy after OASI showed considerable variation. The recommendations depended on (previous) symptoms and the degree of OASI. For gynecologists who based their recommendations on endoanal ultrasonography outcomes (7–20% depending on the case), the degree of OASI and severity of (previous) symptoms were less important. Gynecologists basing their recommendations on endoanal ultrasonography recommended a primary cesarean section less often. Gynecologist’s characteristics (including years of experience, type of hospital and subspecialty) had a small effect on their recommendations on the mode of delivery.
Conclusions
Due to lack of evidence, recommendations of gynecologists in The Netherlands on the mode of delivery in a subsequent pregnancy after OASI vary widely and depend on (previous) symptoms and the degree of OASI. Gynecologists who based their recommendations on endoanal ultrasonography outcomes recommended cesarean section less often.
Alanyl-alanine-derived poly(isocyanide)s possess a helical structure that persists even in aqueous media. These rigid macromolecules possess a regular distribution of carboxylic acid-terminated side ...chains which for the first time allows the study of the templating process involved in biomineralization using a shape-persistent polymeric template. It is demonstrated that in the case where the polymer derived from l-Ala-d-Ala is used the formation of apple core-type calcite crystals is controlled both by nucleation of the (01.1) face and subsequent adsorption of the polymer to the {hk.0} faces of the growing crystal. A small change in the secondary structure of the template that is introduced by using the polymer derived from l-Ala-l-Ala is directly reflected in the lower degree of control over the crystallization process.
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