Twisting motion

Figure 4 DynDom [67] analysis of the first two normal modes of human lysozyme. Dark grey and white indicate the two dynamic domains, separated by the black hinge bending region. The vertical line represents a hinge axis that produces a closure motion in the first normal mode. The horizontal line represents a hinge axis that produces a twisting motion in the second normal mode. (Adapted from Ref. 68.) The DynDom program is available from the Internet at http //md. chem.rug.nl/ steve/dyndom.html.

Are workstations and tools designed to prevent twisting motions ... 

The fluorescence lifetime of trans-4-[4-(dimethylamino-styryl]-l-methylpyridinium iodide trapped in water-containing AOT-reversed micelles has been found to be markedly influenced by R, implying a significant effect on its excited-state twisting motion [122],... 

The next-nearest-neighbor-orbital resonance integrals, /JI3, also remain unaffected by the pure twisting motion. We conclude that a pure twisting motion can therefore represent at best only a relatively small perturbation of the electronic structure of the polysilane chain, suitable for treatment by first-order perturbation theory. The perturbation is represented by changes in the resonance integrals between more distant hybrid orbitals, among which / 14 clearly is the most important. 

A number of fluorescent dyes with internal charge transfer mechanism allow the molecule to twist (rotate) between the electron donor and electron acceptor moieties of the fluorescent dipole. In most cases, the twisted conformation is energetically preferred in the excited Si state, whereas the molecule prefers a planar or near-planar conformation in the ground state. For this reason, photoexcitation induces a twisting motion, whereas relaxation to the ground state returns the molecule to the planar conformation. Moreover, the Si — So energy gap is generally smaller in the twisted conformation, and relaxation from the twisted state causes either a... 

First, use only enough to do the job Spread it thinly along the upper part of the joints, only. Push the joints together with a twisting motion. The joint should turn clear from one third to one half of the way down the joint. At no time should the entire joint clear This means you have too much grease and must start back at Preparation of the Joints. 

The twisting motion in the TICT mechanism is also a large-amplitude motion which is easily stopped by very high-viscosity conditions, and therefore TICT molecules with various rotating moieties can be used in the development of free volume... 

It is conceivable that the twisting motion experiences internal friction, by which is meant the occurrence of bumps or barriers in the potential surface along which the DNA deforms. This would cause y to exhibit a temperature (T) dependence differing from that due to the viscosity of water. Experimental results 4"1 give no indication of such anomalous T dependence, as shown subsequently. 

DNA unwinding in the above diagram occurs initially in the AT-rich regions of the DNA duplex (indicated as a above), and these local regions of disorder (shown in c and d ) require some twisting motions (shown in d ). As these areas grow ( e ), one reaches the point of nearly complete loss of local order ( f ), followed by formation of a large loop ( g )- As would be expected. 

If smart fibers began to be widely used, perhaps clothes and other fabrics would become more adaptable. Nature is one place to look for inspiration. Olivier Emile and Albert Le Floch of the Universite de Rennes in France and Fritz Vollrath at Oxford University in England studied why spiders rarely spin around when hanging from their silk threads. Most fibers turn and twist, as a climber dangling from a rope knows all too well, yet a suspended spider is stable. The researchers discovered that spider silk has a kind of shape memory in which it rapidly recovers its shape, resisting any twisting motion. This research, Shape Memory in Spider Draglines, was published in Nature in 2006. 

Structure for this compound. However, H-NMR experiments carried out at various temperatures and NOE measurements show that this picture is too simple the cavity of [Pd(24)]Cl2 is unstable and collapses via a twisting motion of the arms and the imidazolyl groups (Fig. 14). At room temperature a fast equilibrium exists between a left-handed and a right-handed twisted complex. At lower temperatures the dynamic equilibrium slows down, and at — 95 °C two separate imidazolyl proton signals can be observed in the H-NMR spectrum due to non-equivalence of the imidazolyl groups in a helically twisted structure. 

Fig. 14. Process of twisting motion in [Pd(24)]. (Reproduced with permission from the American Chemical Society)...

The next question to answer was the mechanism of closure of the channel. It is widely accepted now that the channel is closed by a rotational movement of the hexamer [Unwin and Ennis, 1984 Unwin and Zampighi, 1980] as illustrated in figure 5. This twisting motion closing the central channel is possible since the a-helix of the connexins, which is the part located within the lipid bilayer, is inclined with respect to the axis of the whole connexon [Milks et al., 1988]. 

Thus, the PNS structure becomes looser and more disordered by mutation, causing the twisting motion of the chromophore more random and the twisted state formation considerably slower, demonstrating the supreme importance of the well-ordered PNS for the ultrafast and highly efficient twisting reaction of the chromophore in PNS. 

At perpendicular geometries, this excited state of charge-separated nature usually exhibits an energy minimum.2,7,14,35 Thus, a molecule, which starts off in the planar conformation by Franck-Condon excitation, can spontaneously relax in the excited state by a twisting motion toward a... 

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