Adventures in Computational Chemistry

Returning to xleap again. The box I require this time has little tricky requirements. 1) The box should satisfy the molarity ratio for the solute: solvent. 2) Should be big enough that QMMM calculations can be carried out easily 3) combine sets of molecule-pairs which are interconvertible following a proton transfer. I have a pair of molecules say p(H)--i which can be converted to another set called P--I(H) following a proton transfer from p to i.So, p(H)--i <---> P-I(H) To fulfill condition (1), I initially created one molar box for p(H)--i called "PIN" and other box for P--I(H) called "PII" For condition (2) and (3), I created a bigger box with 7 PIN and 1 PII boxes. The idea is: after proton transfer from I to P, during the QMMM calculation, P--I(H) pair coming from "PII" should convert to p(H)--i pair like other pairs from "PIN" and the whole box should become homogeneous with 8 p(H)--i pairs. We begin with: PIN with ...

GNUPLOT can be used to generate histograms. The script below allows one to plot variations in angle from 0° to 180°. Each histogram box width correspond to 3° (covered here under bw option). To execute this script; type this in the terminal: gnuplot histogram.p You should be in the folder where below script is saved in a file name "histogram.p" and a dat file (here, it is N---H-O.dat) should be present. histogram.p ------------------ set term gif set output "angle_N---H-O.gif" set xrange [0.0:180.0] set boxwidth 2.0 absolute set style fill solid 1.0 border -1 set xtics 10 set title "molecule 3.0A Angle N---H-O" set ylabel "occurance" set xlabel "angle" bw = 3   # substitute what you want bin(x,width)=width*floor(x/width) plot 'N---H-O.dat' using (bin($2,bw)):(1.0) smooth freq with boxes ------------------ The dat file is an input file with data in the format: 0    23.680344 1    73.766251 2    67.4...

If Gabedit is installed and functioning on your system, type gabedit  in terminal. Gabedit will open and you can find an option "Geometry" in the tool bar. Select "Geometry"--> "Draw" After some trials and playing you will finally learn how to generate a structure. Once your structure is ready, you need to set the atom types and charges. For this click on "M" button in the top left of the "Draw Geometry" window and select options as: M-->"Set"--> "Atom Type & charge using PDB template" Here if you use "Atom Types using connection types", it helps. You can check if the atom type and charge has been set according to the amber requirements by an indirect method. Try to run a quick MM calculation. Run MM calculations by clicking: "M"-->Molecular Mechanics-->optimization It may sometimes end up with a pop up window that suggests that either atom type or charge is not...