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ChemOffice.Com - CambridgeSoft

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The model display rotates the dihedral to the<br />

selected conformation.<br />

NOTE: The dihedral is rotated in 5 degree increments<br />

through 360 degrees for a total of 72 conformations to<br />

produce the graph. You can view the minimized energy values<br />

for each point in the Output window.<br />

To rotate the other dihedral angle (other end of the<br />

bond):<br />

• Right-click in the Dihedral Driver window and<br />

choose Exchange.<br />

Rotating two dihedrals<br />

To rotate two dihedrals:<br />

1. Use Shift+click to select two adjacent bonds.<br />

In this case, the middle atom’s position<br />

remains fixed<br />

2. Choose Dihedral Driver from the Calculations<br />

menu.<br />

The Dihedral Driver window opens. When the<br />

computation is completed, a graph is displayed<br />

showing theta 1 vs. theta 2.<br />

NOTE: The graph is the result of rotating one angle<br />

through 360° in 15° increments while holding the other<br />

constant. The second angle is then advanced 15° and the<br />

operation is repeated.<br />

To view the conformation at any given point:<br />

• Click any block in the graph.<br />

The model display rotates both dihedrals to the<br />

selected conformation.<br />

Customizing the Graph<br />

You can use the right-click menu to set the rotation<br />

interval used for the computation. You can also<br />

select display colors for the graph, background,<br />

coordinates, and labels.<br />

You also use the right-click menu to copy the<br />

graph, or it’s data set, to other applications, or to<br />

save the data.<br />

Tutorial 6: Overlaying<br />

Models<br />

Overlays are used to compare structural similarities<br />

between models, or conformations of the same<br />

model. Chem3D provides two overlay techniques:<br />

• a “Fast Overlay” algorithm<br />

• the traditional “do it by hand” method based<br />

on minimization calculations<br />

This tutorial describes the Fast Overlay method.<br />

For the Minimization Method, see <strong>Com</strong>paring<br />

Models by Overlay on page 105. The Minimization<br />

Method is more accurate, but the Fast Overlay<br />

algorithm is more robust. In both tutorial examples,<br />

you will superimpose a molecule of<br />

Methamphetamine on a molecule of Epinephrine<br />

(Adrenalin) to demonstrate their structural<br />

similarities.<br />

1. From the File menu, choose New Model. Open<br />

the Model Explorer if it is not already open.<br />

2. Choose the Text tool from the Building<br />

Toolbar and click in the model window.<br />

A text box appears.<br />

3. Type Epinephrine and press the Enter key.<br />

<strong>ChemOffice</strong> 2005/Chem3D Chem3D Tutorials • 39<br />

Tutorial 6: Overlaying Models

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