Spin is the fundamental unit of information used by CARA to describe the chemical shift of a particular spin. It is stored together with all other spins in the SpinBase?.
The properties stored with each spin are:
- SpinId Each Spin has a unique integer to identify it. Whenever a new spin is created, the next available integer is assigned to it. The SpinId of a spin cannot be changed.
- Atom represents the Atom nucleus type of the spin (e.g. H1, C13)
- Shift represents the chemical shift in ppm
- Label representing the Atom the spin is assigned to (e.g. CA, CB) This is normally an IUPAC name (as defined in the ResidueType library). It can optionally start with a ? which indicates a tentative assignment, or ! to indicate a stereospecific assignment. It is possible to give spins labels that do not conform to th ResidueType librarym, but these spins will not give rise to peaks generated by PeakInference? and PathwaySimulation?.
If you give the spin a label ? it will be treated (for the generation of Peaks with PeakInference?) as if it could have any valid label of the ResidueType that applies to the spinsystem it is assigned to.
- SpinSystem? Usually a spin is associated with a particular spinsystem when it is created. This might change for example if "Eat System" is applied, or if user decides to assign it to a different SpinSystem?.
- Aliases Although CARA works under the premise that the chemical shift of a given spin is the same in all spectra, it is possible to assign the spin a different shift in a given spectrum by defining an alias shift.
See more on Spins in the entry SpinBase?