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91.
Gabriela Flores-Ramírez Manuel Rivera Alfredo Morales-Pablos Joel Osuna Xavier Soberón Paul Gaytán 《BMC chemical biology》2007,7(1):1
Background
The effect of single and multiple amino acid substitutions in the green fluorescent protein (GFP) from Aequorea victoria has been extensively explored, yielding several proteins of diverse spectral properties. However, the role of amino acid deletions in this protein -as with most proteins- is still unknown, due to the technical difficulties involved in generating combinatorial in-phase amino acid deletions on a target region. 相似文献92.
The system containing six benzylideneanilines (BA) has been studied: Group 1:
The crystal structures of Group 1 are isostructural. They crystallize in a monoclinic cell, space groupP21. They are rare examples of planar benzylideneanilines in a nondisordered crystal structure. The crystal structures exhibit an intermolecular ring containing five atoms and hal- - - hal. C-H- - - hal interactions, which may contribute to the planarity of the molecule. The structures in Group 2 crystallize in a monoclinic cell, space groupP21/c. The conformation is nonplanar and there are no intermolecular halogen- - -halogen interactions. The abovementioned five atom pattern ring does not occur in these structures. These two groups of structures show that the type and mode of molecular substitution can lead to specific intermolecular interactions which in turn stabilize an otherwise unfavorable molecular conformation. 相似文献
I: | N-(p-Chlorobenzylideneaniline)m-chloroaniline (BA, X=4-Cl, Y=3-Cl) |
II: | N-(p-Bromobenzylideneaniline)m-bromoaniline (BA, X=4-Br, Y=3-Br) |
III: | N-(p-Bromobenzylideneaniline)m-chloroaniline (BA, X=4-Br, Y=3-Cl) |
IV: | N-(p-Chlorobenzylideneaniline)m-bromoaniline (BA, X=4-Cl, Y=3-Br) Group 2: |
V: | N-(m-Chlorobenzylideneaniline)p-bromoaniline (BA, X=3-Cl, Y=4-Br) |
VI: | N-(m-Bromobenzylidencaniline)p-chloroaniline (BA, X=3-Br, Y=4-Br) |
93.
Jean Bricmont Jean-Raymond Fontaine Joel L. Lebowitz Thomas Spencer 《Communications in Mathematical Physics》1981,78(3):363-371
We consider perturbations of a massless Gaussian lattice field on ? d ,d≧3, which preserves the continuous symmetry of the Hamiltonian, e.g., $$ - H = \sum\limits_{< x,y > } {(\phi _x - \phi _y )^2 + T(\phi _x - \phi _y )^4 ,\phi _x \in \mathbb{R}.} $$ It is known that for allT>0 the correlation functions in this model do not decay exponentially. We derive a power law upper bound for all (truncated) correlation functions. Our method is based on a combination of the log concavity inequalities of Brascamp and Lieb, reflection positivity and the Fortuin, Kasteleyn and Ginibre (F.K.G.) inequalities. 相似文献
94.
Oxidation of quadruply bonded metal-metal dimers in the presence of good π-accepting ligands results in the formation of MoV---MoV compounds of the type [MO2(μ-X)2(Y)(Y′)]2+ (X = O or S; Y,Y′ = O,O; S,S; O,S). Reaction of MO2(O2CCH3)4 with oxygen in the presence of Na2mnt (mnt = 1,2-dicyanoethylene-2,2-dithiolate) gives [MO2(μ-S)2(O)(S)(mnt)2]2− (1). The compound crystallizes in the monoclinic space group P21/c, with cell dimensions a = 19.547(4), b = 15.210(4), c = 18.754(6) Å, β = 101.69(2)°, V= 5460(2) Å3, and Z = 4. Similarly, oxidation of o-dichlorobenzene solutions of Mo2Cl4(CH3CN)4 and 4,4′-dimethyl-2,2′-dipyridyl (dmpby) or, more directly, the reaction of Mo2Cl4(dmbpy)2 with oxygen leads to the formation of a red solid, which was characterized by X-ray crystallography to be Mo2(μ-O)2(O)2(Cl)2(dmbpy)2 (2). Red diamond crystals, prepared by slow evaporation of CH3CN solutions of 2, are trigonal and in the space group P3121 with cell dimensions a = 16.135(4), b = 16.135(4), c = 10.709(3) Å, V = 2414.4(13) Å3 and Z = 3. In both structures, the geometry about each of the molybdenum atoms is a distorted square pyramid with terminal oxygen or sulphur atoms at the apices and in a syn conformation. The molybdenum-molybdenum bond distances of 2.858(1) Å and 2.562(2) Å in structures of 1 and 2, respectively, are typical of other MoV---MoV dimers and indicative of a single Mo---Mo bond. 相似文献
95.
96.
The effect on heats of formation, of conjoined or proximate functional groups which can interact via polar or resonance effects, is examined using the –CF3 group as a standard. Two metrics are applied: the difference in heat of formation of G–CF3 and G–CH3, where –G is a wide range of functional groups, and also the deviation of the heat of formation of G–CF3 from the average of the heats of formation of G–G and CF3–CF3. This latter metric reveals both stabilizing and destabilizing effects on the heat of formation, of up to 60 kcal/mol, depending on the polar and resonance nature of the –G structure. The possibility of using such metrics as a correction the group additivity values is examined. 相似文献
97.
Maja Ponikvar-Svet Diana N. Zeiger Loryn R. Keating Joel F. Liebman 《Structural chemistry》2013,24(6):2101-2114
The contents of issues 1 and 2 for the calendar year 2013 are summarized in the current review of the journal Structural Chemistry. In addition, a brief thermochemical commentary is added to the summary of each paper. 相似文献
98.
This essay is the introductory paper for a special issue of Structural Chemistry explicitly dedicated to the premier Spanish calorimetrist and thermochemist, our colleague and friend, María Victoria Roux. The studies in this issue were written on the occasion of her recent retirement from the CSIC Institute of Physical Chemistry “Rocasolano,” Madrid. 相似文献
99.
In this paper we report a simple methodology for obtaining (+) trans - 1,2 - epoxylimonene (1b) in high purity (>99% HRGC) and reasonable quantity. The mixture of 1a and 1b in CH2Cl2 is stirred with 1M NaHSO3 in water. Under these conditions 1a is completely destroyed, while 1b is only partially destroyed. 相似文献
100.
Joel A. Tropp 《Probability Theory and Related Fields》2012,153(3-4):759-769
This note demonstrates that it is possible to bound the expectation of an arbitrary norm of a random matrix drawn from the Stiefel manifold in terms of the expected norm of a standard Gaussian matrix with the same dimensions. A related comparison holds for any convex function of a random matrix drawn from the Stiefel manifold. For certain norms, a reversed inequality is also valid. 相似文献