private void eTargetPosition_Leave(object sender, EventArgs e)
 {
     if (Motif == null)
     {
         eTargetAminoAcid.Text = "";
         return;
     }
     keyPosition = 0;
     keyAA       = ' ';
     if (Int32.TryParse(eTargetPosition.Text, out keyPosition))
     {
         if (keyPosition <= 0 || keyPosition > Motif.PeptideLength)
         {
             MessageBox.Show("The target position should be within the length of the motif.", Analyzer.ProgramName);
         }
         if (keyPosition > 0)
         {
             keyAA = Motif.GetKeyChar(keyPosition - 1);
         }
     }
     eTargetAminoAcid.Text = keyAA.ToString().Trim();
 }