PLO, PLOT

NAME
PLO, PLOT - draw averaged hydrophobicity and/or hydrophobic moment.

SYNOPSIS
PLO HYD
PLO HYD start_index end_index
PLO MOM
PLO MOM start_index end_index
PLO HYD MOM
PLO HYD MOM start_index end_index
PLO OFF
PLOT HYDROPHOBICITY
PLOT HYDROPHOBICITY start_index end_index
PLOT MOMENT
PLOT MOMENT start_index end_index
PLOT HYDROPHOBICITY MOMENT
PLOT HYDROPHOBICITY MOMENT start_index end_index
PLOT OFF

DESCRIPTION
Draw averaged hydrophobicity and/or hydrophobic moment. The averaged hydrophobicity and hydrophobic moment will be calculated using the sequence from the main sequence buffer, the current sliding window width and the current hydrophobicity scale. To calculate the hydrophobic moment one more parameter is required: the rotation angle between adjacent residues.

The averaged hydrophobicity will be shown as red line, while the hydrophobic moment will be shown as blue line. The information about the residue below or above the pointer (mouse) will be visible in the output window (bottom right corner of the main window), while the sequence neighborhood of the current residue will be visible above the plot (top of the main window).

If the entire sequence is used for calculation, there is a chance that plot will contain the straight line at the end. This portion of the plot refers to solvent molecules, which are typically stored to the end of PDB file. This trailing line may be easily removed by adjusting the residue range. Here are two examples:

The first image was prepared using all residues from 200 to the last one, including solvent molecules.



The second image was prepared using residues from 200 to 280, omitting the solvent molecules.



KEYWORDS
KEYWORD
(SHORT) 		KEYWORD
(LONG) 		DESCRIPTION
OFF OFF Return to the main drawing mode (draw atomic coordinates).
Instead using this command, you can hit the ESCAPE key.
HYD HYDROPHOBICITY Draw averaged hydrophobicity.
MOM MOMENT Draw hydrophobic moment.

PARAMETERS
PARAMETER
(SHORT) 		DESCRIPTION
start_index Serial index of the first residue.
end_index Serial index of the last residue.

MOUSE USAGE
Mouse may be used to retrieve the information about averaged hydrophobicity and hydrophobic moment for a given residue. This residue is treated as the central residue of the current sliding window. The numerical data, along with residue name and serial number will be visible in the output window (bottom right corner). The sequence neighborhood of this residue will be visible above the plot. The information will be associated with the residue which has the same horizontal position (x coordinate) as the mouse pointer.



EXAMPLES
COMMAND DESCRIPTION
load 2por.pdb
seq from 1
scale eis
win 7
angle 180
plot hyd mom 1-300 		Load porin coordinates, copy sequence to
the main sequence buffer, select Eisenberg
hydrophobicity scale, set window width to 7
and set angle to 180 degrees. Draw averaged
hydrophobicity and hydrophobic moment for
residues from 1 to 300.
seq load sample.fasta
scale eis
angle 100
plot mom 		Read the file sample.fasta, which contains
the protein sequence in FASTA format (one
letter code), select Eisenberg scale, set
angle to 100 and draw hydrophobic moment.
plot off Return to default drawing mode.
Instead using this command, you can hit the ESCAPE key.

MATHEMATICAL BACKGROUND
Both the averaged hydrophobicity and the hydrophobic moment are calculated using a rectangular sliding window. If there are N residues in the sliding window, the averaged hydrophobicity is equal to:

Hydrophobic moment is equal to:

If you are searching for amphipatic alpha helices, set alpha to 100 degrees. To identify amphipatic beta strands, use 180 degrees. You can change alpha by using the command ANGLE.

NOTES
(1) Instead using the command PLOT OFF, the ESCAPE key may be pressed to return to the main drawing mode.

(2) PLOT uses only the sequence stored to the main sequence buffer. Read description of the command SEQ (SEQUENCE) to learn how to initialize this buffer.

(3) If you plot both the averaged hydrophobicity and the hydrophobic moment, the output window (bottom right corner) will contain the hydrophobic moment of the central residue.

(3) Every time you change hydrophobicity scale, don't forget to refresh the plot (i.e., execute the command PLOT once more).

RELATED COMMANDS
SEQUENCE is used to copy, define or load the sequence. ANGLE defines the rotation angle between adjacent residues. SCALE is used to specify the hydrophobicity scale. WINDOW is used to set the sliding window width.