NMR calculations

The subsequent NMR calculations occur in two sequential steps. The first step computes magnetic shielding and nuclear spin coupling constants for any selected nuclei of the molecular system, using a quantum mechanical description of the electronic structure. The second step calculates the frequencies and intensities of the NMR spectra from the results of step one (or from user-specified shieldings and couplings). The spectra are displayed graphically along with user-specified line widths. A variety of options for displaying the results of each of the two steps is available along with the ability to transfer the graphical spectra onto the Windows clipboard and into another application for incorporation into a manuscript.

HyperNMR calculates magnetic shielding for those atoms in a molecular system assigned a nuclear spin. It uses the gauge invariant atomic orbital (GIAO) self-consistent-field (SCF) perturbation theory with an external magnetic field as the perturbation. Nuclear spin coupling constants are calculated by the same rigorous SCF perturbation theory but with the Fermi contact interaction of a nuclear spin as the perturbation. The algorithms implemented in HyperNMR greatly improve the computational time over earlier methods and offer a tool for predicting NMR parameters and spectra for molecules from small organic systems to proteins.

NMR spectra can be simulated by HyperNMR based on the computed chemical shifts and spin coupling constants of step one, or chemical shifts and spin coupling constants obtained from elsewhere. There is no fixed limit on the number of nuclei in the NMR simulation: the maximum practical number of nuclei depends only computer memory. HyperNMR simulates the NMR spectra for spin 1/2 protons, C13, N15, F19, and P31.

NMR Spectral Presentation

• Display an NMR spectrum as individual peaks, as an envelope, or as peaks plus envelope
• Choose a Gaussian or Lorentzian distribution for line widths
• Select and deselect peaks interactively
• Zoom and pan
• Copy and paste spectra into other applications as Windows metafiles (resolution independent images)

HyperNMR uses two new SCF-MO methods for computing the electronic properties of molecules. These two methods, TNDO/1 and TNDO/2, include features from both conventional semiempirical quantum mechanical methods and molecular mechanics methods. They have shown great improvement in their chemical shift predictions compared to the conventional semiempirical SCF-MO methods. Principally, they incorporate the molecular mechanics concept of atom "type" and parameters specialized to atom type into quantum mechanical calculations.

• Choose from space-filling spheres, or sphere and cylinder (ball and stick) renderings. Use either flat or shaded spheres and cylinders
• Label atoms by element symbols, names, indices, types, or charges
• Rotate, Translate, and Zoom the molecular system
• Select and deselect an atom or some atoms or the whole molecular system

Sales of HyperNMR are restricted to the U.S. only.
Avalible for Windows 3.x, Windows 95, Windows NT