Molecular, labeling orientation

The development of IMS has provided an invaluable tool to the field of molecular analysis. Direct analysis of tissues or individual cells offers a mechanism to determine molecular spatial orientation and to evaluate molecular signatures indicative of disease. The technology is commercially available and is widely used as a discovery tool to monitor the spatial distribution of elements, Upids, pharmaceuticals, metabolites, peptides, and proteins and to evaluate molecular activities in biological processes. Assessment of a variety of compounds can be performed in parallel, without the use of isotopic labeling. The potential of IMS has driven methodology and instrumentation developments such as... 

The label liquid crystal seems to be a contradiction in tenns since a crystal cannot be liquid. However, tire tenn refers to a phase fonned between a crystal and a liquid, witli a degree of order intennediate between tire molecular disorder of a liquid and tire regular stmcture of a crystal. Wlrat we mean by order here needs to be defined carefully. The most important property of liquid crystal phases is tliat tire molecules have long-range orientational order. For tliis to be possible tire molecules must be anisotropic, whetlier tliis results from a rodlike or disclike shape. 

It is relatively easy to understand the significance of the non-coincident matrix axes in these cases. For the Co2C2 cluster, the C2v molecular symmetry permits a specific prediction of the possible matrix axis orientations. The g-matrix principal axes must be coincident with the molecular symmetry axes. The two cobalt nuclei are located in a reflection plane (which we label xz) so that symmetry requires the y-axis to be a principal axis for all three matrices. The other two axes may be rotated, relative to the molecular x- and z-axes, by /J. (Since the two nuclei are symmetrically equivalent, the rotations must be equal and opposite.)... 

Pi Each pi bond has one axial nodal plane (p-like shape) and the longitudinal profile, (Figs. 4.24(b) and (c)) to be expected from 7t-type overlap of d orbitals. The two pi bonds are labeled 7tw(o) (out of plane) or 7Tww(l) (in plane) to distinguish their orientation with respect to the molecular plane. 

Multi-dimensional DFT calculations show that the PES actually varies considerably with molecular orientation and impact point on the surface [21,23]. Universally, barriers for dissociation are substantially lower with molecular bonds nearly parallel to the surface. V is also laterally corrugated in the unit cell, both in magnitude and in location relative to the surface plane. The variation in the magnitude of V with X,Y has been labeled energetic corrugation, while the variation in its position... 

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