Wednesday, 31 December 2008

DOSY-shift reagents

A well-known procedure to separate resonances that would otherwise overlap in crowded NMR spectra is by adding to the sample some paramagnetic substance, the so-called shift-reagent. The most commonly used shift reagents are complexes of paramagnetic lanthanide ions such as europium(III) for down field shifts and praseodymium(III) for upfield shifts.
A similar approach has been recently reported to resolve mixture components via DOSY-NMR. It’s not very uncommon that in some mixture analyses, 2 or more compounds have diffusion coefficients so similar that they cannot be resolved by any mathematical procedure. For example, the figure below shows a synthetic DOSY spectrum (based on Figure 2 of the original article) of a mixture of two peptides, Trp-Gly and Leu-Met having D values nearly identical

M. E. Zielinski and K. F. Morris proposed in their article to add perdeuterated surfactant micelles to the mixture. Analogous to the chemical offsets induced by shift reagents, the molecules in the mixture under analysis interact differentially with the micelles and thus have different Diffusion values.

Using perdeuterated surfactant micelles to resolve mixture components in diffusion-ordered NMR spectroscopy
Matthew E. Zielinski, Kevin F. Morris, Magnetic Resonance in Chemistry
Volume 47 Issue 1, Pages 53 - 56

Sunday, 21 December 2008

Microreview on NMR structural elucidation

A nice short review presenting practical strategies for the elucidation of small organic molecules with NMR spectroscopy has been published a few months ago. I highly recommend it as a reference for organic chemists engaged in structural elucidation tasks.

Eugene E. Kwan, Shaw G. Huang, Structural Elucidation with NMR Spectroscopy: Practical Strategies for Organic Chemists European Journal of Organic Chemistry, 2008 (16), 2671-2688

DOI: 10.1002/ejoc.200700966

Thursday, 18 December 2008

Better NMR Processing and Analysis with Mnova 5.3.0

I’m pleased to announce the release of the latest version of Mnova (version 5.3.0), our software for the efficient processing, analysis and prediction of NMR spectra.
With the unveiling of version 5.3.0 come a multitude of enhancements over previous releases . Here I’d just like to highlight some key new features which I’m very proud of as I think they represent a substantial enhancement in the software’s capabilities and, in some cases, new breakthroughs in the world of NMR software:

  • Bayesian DOSY Processing
  • Whitening algorithm for 2D automatic Phase Correction
  • Prediction of X-Nuclides spectra
  • Spin Simulation module with support for scalar, dipolar and quadrupolar interactions and its unique classification of transitions feature
  • Covariance NMR: Direct, Indirect and Unsymmetrical by means of the Advanced Arithmetic Module
  • Multipoint (manual) Baseline Correction

We have also greatly improved some algorithms such as peak picking, automatic noise estimation, resolution booster, integration, etc.
It’s also worth mentioning that most of the new dialog boxes in the program are modeless. For example, now while phase correcting a spectrum, you can zoom in to a particular spectral region without having to quit the phase correction dialog.
There are many other new features in this new version, and many more to come shortly in forthcoming updates. I will be featuring some of them in future posts.
I would like to take this opportunity to congratulate our development team on the fantastic work they have done. Big thanks, guys!

Note. This version will be available for download from our web site Friday 19th