Analysis and validation of carbohydrate three-dimensional structures.
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ABSTRACT:
SUBMITTER: Lutteke T
PROVIDER: S-EPMC2631634 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:BackgroundG protein-coupled receptors (GPCRs) are abundant, activate complex signalling and represent the targets for up to approximately 60% of pharmaceuticals but there is a paucity of structural data. Bovine rhodopsin is the first GPCR for which high-resolution structures have been completed but significant variations in structure are likely to exist among the GPCRs. Because of this, considerable effort has been expended on developing in silico tools for refining structures of individual GPCRs. We have developed REPIMPS, a modification of the inverse-folding software Profiles-3D, to assess and predict the rotational orientation and vertical position of helices within the helix bundle of individual GPCRs. We highlight the value of the method by applying it to the Baldwin GPCR template but the method can, in principle, be applied to any low- or high-resolution membrane protein template or structure.Results3D models were built for transmembrane helical segments of 493 GPCRs based on the Baldwin template, and the models were then scored using REPIMPS and Profiles-3D. The compatibility scores increased significantly using REPIMPS because it takes into account the physicochemical properties of the (lipid) environment surrounding the helix bundle. The arrangement of helices in the helix bundle of the 493 models was then altered systematically by rotating the individual helices. For most GPCRs in the set, changes in the rotational position of one or more helices resulted in significant improvement in the compatibility scores. In particular, for most GPCRs, a rotation of helix VII by 240-300 degrees resulted in improved scores. Bovine rhodopsin modelled using this method showed 3.31 A RMSD to its crystal structure for 198 Calpha atom pairs, suggesting the utility of the method even when starting with idealised structures such as the Baldwin template.ConclusionWe have developed an in silico tool which can be used to test the validity of, and refine, models of GPCRs with respect to helix rotation and vertical position based on the physicochemical properties of amino acids and the surrounding environment. The method can be applied to any multi-pass membrane protein and potentially can be used in combination with other high-throughput methodologies to generate and refine models of membrane proteins.
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Project description:The title compounds, [(1R,3R,4R,5R,6S)-4,5-bis-(acet-yloxy)-7-oxo-2-oxabi-cyclo[4.2.0]octan-3-yl]methyl acetate, C14H18O8, (I), [(1S,4R,5S,6R)-5-acet-yloxy-7-hy-droxy-imino-2-oxobi-cyclo-[4.2.0]octan-4-yl acetate, C11H15NO6, (II), and [(3aR,5R,6R,7R,7aS)-6,7-bis-(acet-yloxy)-2-oxo-octa-hydro-pyrano[3,2-b]pyrrol-5-yl]methyl acetate, C14H19NO8, (III), are stable bicyclic carbohydrate derivatives. They can easily be synthesized in a few steps from commercially available glycals. As a result of the ring strain from the four-membered rings in (I) and (II), the conformations of the carbohydrates deviate strongly from the ideal chair form. Compound (II) occurs in the boat form. In the five-membered lactam (III), on the other hand, the carbohydrate adopts an almost ideal chair conformation. As a result of the distortion of the sugar rings, the configurations of the three bicyclic carbohydrate derivatives could not be determined from their NMR coupling constants. From our three crystal structure determinations, we were able to establish for the first time the absolute configurations of all new stereocenters of the carbohydrate rings.
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Project description:Although various higher-order protein structure prediction methods have been developed, almost all of them were developed based on the three-dimensional (3D) structure information of known proteins. Here we predicted the short protein structures by molecular dynamics (MD) simulations in which only Newton's equations of motion were used and 3D structural information of known proteins was not required. To evaluate the ability of MD simulationto predict protein structures, we calculated seven short test protein (10-46 residues) in the denatured state and compared their predicted and experimental structures. The predicted structure for Trp-cage (20 residues) was close to the experimental structure by 200-ns MD simulation. For proteins shorter or longer than Trp-cage, root-mean square deviation values were larger than those for Trp-cage. However, secondary structures could be reproduced by MD simulations for proteins with 10-34 residues. Simulations by replica exchange MD were performed, but the results were similar to those from normal MD simulations. These results suggest that normal MD simulations can roughly predict short protein structures and 200-ns simulations are frequently sufficient for estimating the secondary structures of protein (approximately 20 residues). Structural prediction method using only fundamental physical laws are useful for investigating non-natural proteins, such as primitive proteins and artificial proteins for peptide-based drug delivery systems.
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Project description:Microfluidic devices are gaining extensive interest due to their potential applications in wide-ranging areas, including lab-on-a-chip devices, fluid delivery, and artificial vascular networks. Most current microfluidic devices are in a planar design with fixed configurations once formed, which limits their applications such as in engineered vascular networks in biology and programmable drug delivery systems. Here, shape-programmable three-dimensional (3D) microfluidic structures, which are assembled from a bilayer of channel-embedded polydimethylsiloxane (PDMS) and shape-memory polymers (SMPs) via compressive buckling, are reported. 3D microfluidics in diverse geometries including those in open-mesh configurations are presented. In addition, they can be programmed into temporary shapes and recover their original shape under thermal stimuli due to the shape memory effect of the SMP component, with fluid flow in the microfluidic channels well maintained in both deformed and recovered shapes. Furthermore, the shape-fixing effect of SMPs enables freestanding open-mesh 3D microfluidic structures without the need for a substrate to maintain the 3D shape as used in previous studies. By adding magnetic particles into the PDMS layer, magnetically responsive 3D microfluidic structures are enabled to achieve fast, remote programming of the structures via a portable magnet. A 3D design phase diagram is constructed to show the effects of the magnetic PDMS/SMP thickness ratio and the volume fraction of magnetic particles on the shape programmability of the 3D microfluidic structures. The developed shape-programmable, open-mesh 3D microfluidic structures offer many opportunities for applications including tissue engineering, drug delivery, and many others.
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Project description:Amyloids are highly ordered protein aggregates that are associated with both disease (including PrP prion, Alzheimer's, and Parkinson's) and biological function. The amyloid structure is composed of the cross-β-sheet entity, which is an almost indefinitely repeating two-layered intermolecular β-sheet motif. The three-dimensional (3D) structure is unique among protein folds because it folds only upon intermolecular contacts (for a folding to occur, only short sequences of amino acid residues are required), and the structure repeats itself at the atomic level (i.e., every 4.7 Å). As a consequence of this structure, among others, it can grow by recruiting corresponding amyloid peptide/protein and thus has the capacity to be an infectious protein (i.e., a prion). Furthermore, its repetitiveness can translate what would be a nonspecific activity as monomer into a potent one through cooperativity. Because of these and other properties, the activities of amyloids are manifold and include peptide storage, template assistance, loss of function, gain of function, generation of toxicity, membrane binding, infectivity, and more. This review summarizes the structural nature of the cross-β-sheet motif on the basis of a few high-resolution structural studies of amyloids in the context of potential biological activities.
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Project description:Polarization as an important degree of freedom for light plays a key role in optics. Structured beams with controlled polarization profiles have diverse applications, such as information encoding, display, medical and biological imaging, and manipulation of microparticles. However, conventional polarization optics can only realize two-dimensional polarization structures in a transverse plane. The emergent ultrathin optical devices consisting of planar nanostructures, so-called metasurfaces, have shown much promise for polarization manipulation. Here we propose and experimentally demonstrate color-selective three-dimensional (3D) polarization structures with a single metasurface. The geometric metasurfaces are designed based on color and phase multiplexing and polarization rotation, creating various 3D polarization knots. Remarkably, different 3D polarization knots in the same observation region can be achieved by controlling the incident wavelengths, providing unprecedented polarization control with color information in 3D space. Our research findings may be of interest to many practical applications such as vector beam generation, virtual reality, volumetric displays, security, and anti-counterfeiting.
| S-EPMC9576785 | biostudies-literature
Project description:The complete mol-ecules of the title compounds, N2,N5-bis-(pyridin-2-ylmeth-yl)pyrazine-2,5-dicarboxamide, C18H16N6O2 (I), 3,6-dimethyl-N2,N5-bis-(pyridin-2-yl-meth-yl)pyrazine-2,5-dicarboxamide, C20H20N6O2 (II), and N2,N5-bis-(pyridin-4-ylmeth-yl)pyrazine-2,5-dicarboxamide, C18H16N6O2 (III), are generated by inversion symmetry, with the pyrazine rings being located about centres of inversion. Each mol-ecule has an extended conformation with the pyridine rings inclined to the pyrazine ring by 89.17 (7)° in (I), 75.83 (8)° in (II) and by 82.71 (6)° in (III). In the crystal of (I), mol-ecules are linked by N-H⋯N hydrogen bonds, forming layers lying parallel to the bc plane. The layers are linked by C-H⋯O hydrogen bonds, forming a three-dimensional supra-molecular structure. In the crystal of (II), mol-ecules are also linked by N-H⋯N hydrogen bonds, forming layers lying parallel to the (10-1) plane. As in (I), the layers are linked by C-H⋯O hydrogen bonds, forming a three-dimensional supra-molecular structure. In the crystal of (III), mol-ecules are again linked by N-H⋯N hydrogen bonds, but here form corrugated sheets lying parallel to the bc plane. Within the sheets, neighbouring pyridine rings are linked by offset π-π inter-actions [inter-centroid distance = 3.739 (1) Å]. The sheets are linked by C-H⋯O hydrogen bonds, forming a three-dimensional supra-molecular structure. Compound (I) crystallizes in the monoclinic space group P21/c. Another monoclinic polymorph, space group C2/c, has been reported on by Cockriel et al. [Inorg. Chem. Commun. (2008), 11, 1-4]. The mol-ecular structures of the two polymorphs are compared.
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Project description:Selective 2'-hydroxyl acylation analyzed by primer extension (SHAPE) is a facile technique for quantitative analysis of RNA secondary structure. In general, low SHAPE signal values indicate Watson-Crick base-pairing, and high values indicate positions that are single-stranded within the RNA structure. However, the relationship of SHAPE signals to structural properties such as non-Watson-Crick base-pairing or stacking has thus far not been thoroughly investigated. Here, we present results of SHAPE experiments performed on several RNAs with published three-dimensional structures. This strategy allows us to analyze the results in terms of correlations between chemical reactivities and structural properties of the respective nucleotide, such as different types of base-pairing, stacking, and phosphate-backbone interactions. We find that the RNA SHAPE signal is strongly correlated with cis-Watson-Crick/Watson-Crick base-pairing and is to a remarkable degree not dependent on other structural properties with the exception of stacking. We subsequently generated probabilistic models that estimate the likelihood that a residue with a given SHAPE score participates in base-pairing. We show that several models that take SHAPE scores of adjacent residues into account perform better in predicting base-pairing compared with individual SHAPE scores. This underscores the context sensitivity of SHAPE and provides a framework for an improved interpretation of the response of RNA to chemical modification.
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Project description:It is of interest to fabricate curved surfaces in three dimensions from homogeneous material in the form of flat sheets. The aim is not just to obtain a surface which has a desired intrinsic Riemannian metric, but to get the desired embedding in R3 up to translations and rotations. In this paper, we demonstrate three generic methods of moulding a flat sheet of thermo-responsive plastic by selective contraction induced by targeted heating. These methods do not involve any cutting and gluing, which is a property they share with origami. The first method is inspired by tailoring, which is the usual method for making garments out of plain pieces of cloth. Unlike usual tailoring, this method produces the desired embedding in R3 . The second method just aims to bring about the desired new Riemannian metric via an appropriate pattern of local contractions, without directly controlling the embedding. The third method is based on triangulation, and seeks to induce the desired local distances. This results in getting the desired embedding in R3 . The second and the third methods, and also the first method for the special case of surfaces of revolution, are algorithmic in nature. We explain these methods and show examples.
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