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71.
Gregor Hagelueken Dr. W. John Ingledew Dr. Hexian Huang Biljana Petrovic‐Stojanovska Chris Whitfield Prof. Hassane ElMkami Dr. Olav Schiemann Dr. James H. Naismith Prof. 《Angewandte Chemie (International ed. in English)》2009,48(16):2904-2906
Distance fingerprinting : Pulsed electron–electron double resonance spectroscopy (PELDOR) is applied to the octameric membrane protein complex Wza of E. coli. The data yielded a detailed distance fingerprint of its periplasmic region that compares favorably to the crystal structure. These results provide the foundation to study conformation changes from interaction with partner proteins.
72.
Huawei Li Hong Liu C Eduardo Corrales Jessica R Risner Jeff Forrester Jeffrey R Holt Stefan Heller Albert SB Edge 《BMC neuroscience》2009,10(1):122
Background
Neural differentiation of embryonic stem (ES) cells is usually achieved by induction of ectoderm in embryoid bodies followed by the enrichment of neuronal progenitors using a variety of factors. Obtaining reproducible percentages of neural cells is difficult and the methods are time consuming. 相似文献73.
The space group symmetry and crystal structure of Tl3SbS3−xSex compounds in the composition range 0 < x < 3 have been determined by a combination of powder X-ray diffraction, electron diffraction, and high-resolution electron microscopy. The incongruently melting compound Tl3SbSe3 has been shown to crystallize in cubic space group P213 with a = 9.435Å in a structure related to that of Langbeinite. The convergent beam electron diffraction pattern of Tl3SbS3 is in accord with the space group R3m determined by X-ray diffraction. The cubic Langbeinite-type structure is found for Tl3SbS3−xSex for 0.5 < x < 3 and for Tl3SbyAs1−ySe3 for 0.077 < y < 1.0. A five-component compound Tl3Sb0.5As0.5Se1.5S1.5 was also found to be cubic. 相似文献
74.
Alba Sicher Dr. Richard Whitfield Dr. Jan Ilavsky Prof. Dr. Vinodkumar Saranathan Prof. Dr. Athina Anastasaki Prof. Dr. Eric R. Dufresne 《Angewandte Chemie (International ed. in English)》2023,62(16):e202217683
Synthetic methods to control the structure of materials at sub-micron scales are typically based on the self-assembly of structural building blocks with precise size and morphology. On the other hand, many living systems can generate structure across a broad range of length scales in one step directly from macromolecules, using phase separation. Here, we introduce and control structure at the nano- and microscales through polymerization in the solid state, which has the unusual capability of both triggering and arresting phase separation. In particular, we show that atom transfer radical polymerization (ATRP) enables control of nucleation, growth, and stabilization of phase-separated poly-methylmethacrylate (PMMA) domains in a solid polystyrene (PS) matrix. ATRP yields durable nanostructures with low size dispersity and high degrees of structural correlations. Furthermore, we demonstrate that the length scale of these materials is controlled by the synthesis parameters. 相似文献
75.
Panitkin SY Ajitanand NN Alexander J Anderson M Best D Brady FP Case T Caskey W Cebra D Chance J Chung P Cole B Crowe K Das A Draper J Gilkes M Gushue S Heffner M Hirsch A Hjort E Huo L Justice M Kaplan M Keane D Kintner J Klay J Krofcheck D Lacey R Lauret J Lisa MA Liu H Liu YM McGrath R Milosevich Z Odyniec G Olson D Pinkenburg C Porile N Rai G Ritter HG Romero J Scharenberg R Schroeder LS Srivastava B Stone NT Symons TJ Wang S Wells R Whitfield J Wienold T Witt R Wood L Yang X Zhang WN 《Physical review letters》2001,87(11):112304
We report a particle source imaging analysis based on two-pion correlations in high multiplicity Au+Au collisions at beam energies between 2A and 8A GeV. We apply the imaging technique introduced by Brown and Danielewicz, which allows a model-independent extraction of source functions with useful accuracy out to relative pion separations of about 20 fm. The extracted source functions have Gaussian shapes. Values of source functions at zero separation are almost constant across the energy range under study. Imaging results are found to be consistent with conventional source parameters obtained from a multidimensional Hanburg-Brown-Twiss analysis. 相似文献
76.
Ionescu AR Bérces A Zgierski MZ Whitfield DM Nukada T 《The journal of physical chemistry. A》2005,109(36):8096-8105
The conformation of the six-membered ring of pyranosyl sugars has pronounced effects on the physical and chemical properties of carbohydrates. We present a method to determine key features of the potential energy surfaces, such as transition states associated with the inversion pathways of the model compounds cyclohexane, tetrahydropyran, p-dioxane, m-dioxane, s-trioxane, and 2-oxanol. Finally, we make the first determination of the pathways for inversion of penta-O-methyl-alpha-D-glucopyranose and penta-O-methyl-beta-D-glucopyranose. For both anomers, a transition state with five coplanar atoms with appreciable (O)E character was found. The method is based on constrained Car-Parrinello ab initio molecular dynamics, as implemented in the projector augmented-wave (PAW) method. The constraints are derived from the normal modes of six-membered rings and are described in terms of the canonical conformations (1)C(4) chair, (1,4)B boat, and (O)S(2) skew-boat. The PAW derived trajectories are in agreement with previous suggestions in the literature that pseudorotation is an important feature of such conformational interconversions. The dynamic nature as well as the internal coordinate-based constraints provide a method which can reliably accommodate pseudorotation. To determine semiquantitative energies, we recalculate key conformations using standard quantum mechanical calculations while keeping the ring dihedral angles frozen at their values found in the dynamics. In all cases where experimental barriers are known, our results are in excellent agreement. 相似文献
77.
[reaction: see text]. A trisaccharide donor containing a cis-Galpalpha(1-->4)Galp linkage was prepared using a synthetic strategy based on chemoenzymatic oligosaccharide synthesis on a soluble polymeric support. Significantly, only retaining glycosyltransferases gave complete reactions, whereas inverting enzymes showed little or no activity with poly(ethylene glycol) (MPEG)-bound lactose as an acceptor. The MPEG-attached trisaccharide was shown to bind to Verotoxin-1 by transfer NOE studies through the Galpalpha(1-->4)Galp portion of the molecule. 相似文献
78.
79.
Dihydroedulan I and II, two trace components of the juice of the passionfruit Passiflora edulis Sims, have been shown by synthesis to be the epimeric 2,3,4,4a,5,6-hexahydro-2,5,5,8a-tetramethyl-(8aH)-1-benzopyrans 2b and 2a. 相似文献
80.
Bérces A Enright G Nukada T Whitfield DM 《Journal of the American Chemical Society》2001,123(23):5460-5464
Static and dynamical Density Functional Theory studies of 2,6-di-O-acetyl-3,4-O-isopropylidene-D-galactopyranosyl cation have shown that this cation can exist in two conformers characterized as (2)S(O) and B(2,5), respectively. The (2)S(O) conformer has the O-2 acyl group equatorial with the carbonyl syn to H-2 and is populated by monocyclic oxocarbenium ions. These conformational features are present in the structurally related glycosyl donor ethyl 2,6-di-O-benzoyl-3,4-O-isopropylidene-beta-D-galactothiopyranoside as determined by X-ray diffraction studies. The B(2,5) conformer has O-2 axial and allows the carbonyl to rotate and close the five-membered ring to form a bicyclic dioxolenium ion. Constraints based on natural internal coordinates were implemented to study this conformational transition. In this way the barrier to interconversion has been determined to be 34 kJ mol(-)(1) with a transition state characterized as (O)S(2) and a pathway involving pseudorotation. Thus, for the first time the structures and energetics of the key ions postulated to be involved in neighboring group assisted glycosylation reactions have been determined. 相似文献