Molecule bending

When the polypeptide chains of protein molecules bend and fold in order to assume a more compact three-dimensional shape, a tertiary (3°) level of structure is generated (Figure 5.9). It is by virtue of their tertiary structure that proteins adopt a globular shape. A globular conformation gives the lowest surface-to-volume ratio, minimizing interaction of the protein with the surrounding environment. 

It is unclear exactly how the two potential surfaces, and hence the interaction regions between them, behave as the parent molecules bend. Our experimental results indicate that the more bent the ozone molecules are as they dissociate the more effectively is the available energy channelled into the OA T, ) fragment vibration. It is possible that as the parent molecules bend, the crossing seams move to a region on the repulsive state that more strongly favors the production of vibrationally excited 02(3 ) fragments. 

The lnu orbitals in the linear case (these are the non-bonding 2px and 2p orbitals of the oxygen atom) lose their degeneracy when the molecule bends. The 2px orbital retains its non-bonding character, but the 2p orbital makes a very important contribution to the 3a, bonding MO of the bent molecule. It is this factor which is critical in determining the shape of the water molecule. The distortion of the linear molecule... 

Classical trajectory calculations on model ICN photodissociation. 464, 465 Effects of parent molecule bending and overall rotation Effects of product state anharmonicity in the theoretical descrip- 466 tion of the 234—266 nm photodissociation of ICN HgBr Rapid reaction of HgBr with Br shown to be responsible for 467... 

In analogy with the results of theoretical calculations on the dissociation path of CO on rhodium by De Koster and Van Santen [53], we visualize the rupture of the N-O bond as sketched in Fig. 5.12. Starting from a threefold position, the adsorbed NO molecule bends across a rhodium atom to the next threefold site. By stretching over the central rhodium atom, the antibonding NO orbitals have a strong interaction with the Rh d-orbitals, and the N-O bond is efficiently weakened. The picture implies that NO requires an ensemble of at least five atoms on the (111) surface of an fee transition metal in order to dissociate. This is in fair agreement with kinetic modelling, which indicates that three to four NO adsorption sites must be invoked to obtain realistic kinetic parameters [52]. 

When a lipid is unsaturated, as in Figure 23, the molecule bends wherever there is a double bond. This prevents the chains from packing close together, so these lipids tend to be liquid oHs such as olive or corn oH. 

DNA cleaving activity of PYML(6)-(4/ -APA)-distamycin was found to be more potent than that of PYML(6)-bleomycin and dramatic change in the base sequence specificity was observed. Evidently, PYML(6)-4R-APA)-distamycin predominantly cleaved AT rich regions which were not cleaved by BLM (Fig. 21B). The difference in the cleavage pattern between Dervan s compound and our compound remains to be explored in more detail. The inspection of the manmade BLM with a molecular model strongly suggests that the molecule bends at the 4R-APA linker to orient the metal center exactly to the observed cleavage site. 

The SO2 molecule contains two more valence electrons than CO2. If the stracture had been linear, the two additional electrons would have had to enter a 3c antibonding n orbital. When the molecule bends and the S atom is rehybridized, the three n orbitals in the molecular plane are converted into the three non-bonding a orbitals indicated at the left of Fig. 20.3. 

Trans fats contain a particular kind of unsaturated fatty acid. When there is a double bond between carbon atoms, the molecule bends in one of two ways the cis or the trans direction. In cis configuration, the carbon chain on both sides of the double bond bends in to the same side of the double bond (see stmcture). In the trans configuration, the chain on either side of the double bond bends toward opposite sides of the double bond (see structure). Most trans fats come from processing oils for prepared foods and from solid fats such as margarine. 

Nitrogen atoms at the ends of the molecule have lone pairs of electrons that can form coordinate covalent bonds. In forming a complex, the ethylenediamine molecule bends around so that both nitrogen atoms coordinate to the metal atom, M. 

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