System of Estimating the Cross-Sectional Area of a Molecule for Use in the Prediction of Ion Mobility

Abstract

A method of estimating the cross-sectional area of a molecule for use in the prediction of ion mobility gives gas phase interaction radii determination and cross-sectional algorithm computation to provide separation and characterisation of structurally related isomers. More specifically, the invention provides a method of correlating the differences in the molecular structures with differences in anti-cancer activity of pre-determined anti-cancer drugs by utilizing a new algorithm for estimating the cross-sectional area of the molecules of such drugs.

1 . A system for determining characteristics of predetermined molecules, the system comprising:
 a sufficiently programmed computer;   an ion mobility cell;   a mass spectrometer; and   a processor programmed or configured to determine experimentally, values of a range of molecular structures and compare the values of the range with those derived by a method of estimating a cross-sectional area of a molecule of interest so as to correlate differences in the molecular structures with differences in selected predetermined activity of those molecules wherein said method of estimating the cross sectional area of a molecule of interest comprises the steps of:   A) Developing a predicted geometric structure of the molecule of interest;   B) Assigning a value for a cross sectional area of each atom within the molecule;   C) Calculating a sum of values of the cross sectional area for each atom within the molecule;   D) Randomly selecting an orientation of the predicted geometric structure of said molecule of interest;   E) Randomly selecting a number of atoms K with a probability proportional to the atom's cross sectional area;   F) Randomly selecting a position within the cross sectional area of each of the number of atoms K;   G) Identifying a number of atoms whose cross sectional area includes said position;   H) Calculating a value for the cross sectional area of said molecule of interest at said orientation based on the sum of values of the cross sectional area for each atom within the molecule divided by the number of atoms K times the number of atoms m;   I) Calculating an averaged cross sectional area over all said randomly selected orientations; and   J) Iterating steps D) to I) for at least N iterations or until M independent calculations of the averaged cross sectional area agree within a predetermined range R for X iterations wherein at least steps D) to I) are preformed with the sufficiently programed computer.   
     
     
         2 . The system according to  claim 1 , wherein the value of N is between 1 and 50, the value of M is between 1 and 20, the value of R is between 1 and 20% and the value of X is between 1 and 20. 
     
     
         3 . A system for determining characteristics of predetermined molecules, the system comprising:
 a sufficiently programmed computer;   an ion mobility cell;   a mass spectrometer; and   a processor programmed or configured to determine experimentally with a combined ion mobility-mass spectrometry (IM-MS) technique a range of molecular structures and compare the values of the range with those derived by a method of estimating a cross-sectional area of a molecule of interest so as to correlate differences in the molecular structures with differences in selected predetermined activity of those molecules wherein said method of estimating the cross sectional area of a molecule of interest comprises the steps of:   A) Developing a predicted geometric structure of the molecule of interest;   B) Assigning a value for a cross sectional area of each atom within the molecule;   C) Calculating a sum of values of the cross sectional area for each atom within the molecule;   D) Randomly selecting an orientation of the predicted geometric structure of said molecule of interest;   E) Randomly selecting a number of atoms K with a probability proportional to the atom's cross sectional area;   F) Randomly selecting a position within the cross sectional area of each of the number of atoms K;   G) identifying a number of atoms whose cross sectional area includes said position;   H) Calculating a value for the cross sectional area of said molecule of interest at said orientation based on the sum of values of the cross sectional area for each atom within the molecule divided by the number of atoms K times the number of atoms m;   I) Calculating an averaged cross sectional area over all said randomly selected orientations; and   J) Iterating steps D) to I) for at least N iterations or until M independent calculations of the averaged cross sectional area agree within a predetermined range R for X iterations wherein at least steps D) to I) are preformed with an sufficiently programed computer.   
     
     
         4 . The system according to  claim 3  wherein the method correlates the differences in the molecular structures with differences in the activity of drugs. 
     
     
         5 . The system according to  claim 4  wherein said drugs are organometallic based drugs. 
     
     
         6 . The system according to  claim 5  wherein said organometallic based drugs are anti-cancer drugs. 
     
     
         7 . The system according to  claim 5  wherein the organometallic based drugs are isomeric Ru-based. 
     
     
         8 . The system according to  claim 3  wherein the ion mobility cell generates a travelling wave and the IM-MS technique includes travelling wave (T-wave) mobility separation. 
     
     
         9 . A system for determining characteristics of predetermined molecules, the system comprising:
 an ion mobility cell;   a mass spectrometer; and   a processor programmed or configured to determine experimentally, values of a range of molecular structures and compare the values of the range with those derived by a method of estimating a cross-sectional area of a molecule of interest so as to correlate differences in the molecular structures with differences in selected predetermined activity of those molecules.