Fitting of the beat pattern observed in NMR free-induction decay signals of concentrated carbohydrate-water solutions

J Magn Reson. 2004 Jun;168(2):278-83. doi: 10.1016/j.jmr.2004.03.013.

Abstract

A series of mathematical functions has been used to fit the proton free-induction decays (FIDs) of concentrated carbohydrate-water samples. For the solid protons, these functions included a sinc function, as well as the Fourier transforms of single and multiple Pake functions multiplied by a Gaussian broadening. The NMR signal from the mobile protons is described by an exponential function. It is found that in most cases the sinc function gives a satisfactory result and provides valuable information about the second moment M(2) and the ratio of solid to mobile protons (f(s) / f(m)). A good indication for using the sinc function is the presence of a beat in the FID. For high temperatures this approach breaks down, and a biexponential fit is more appropriate. If a clear dipolar splitting is observable in the NMR spectra, the Pake function (or a multiple Pake fit) should be used. In this case information about M(2) and f(s) / f(m) can also be obtained.

Publication types

  • Comparative Study
  • Evaluation Study
  • Research Support, Non-U.S. Gov't
  • Validation Study

MeSH terms

  • Algorithms*
  • Carbohydrates / analysis
  • Carbohydrates / chemistry*
  • Computers
  • Fourier Analysis
  • Glucose / analysis
  • Glucose / chemistry
  • Macromolecular Substances
  • Magnetic Resonance Spectroscopy / methods*
  • Mannose / analysis
  • Mannose / chemistry
  • Models, Chemical
  • Models, Molecular*
  • Molecular Conformation
  • Oscillometry / methods*
  • Water / analysis
  • Water / chemistry*

Substances

  • Carbohydrates
  • Macromolecular Substances
  • Water
  • Glucose
  • Mannose