High-Precision, Fast and Automated Projection Spectroscopy

APSY experiments and software

APSY (Automated Projection Spectroscopy) automatically records and analyzes a series of projections of N-dimensional spectra (1). Projections spectroscopy (2, 3) measures the information content of high dimensional spectra in low dimensional projection spectra which results in a drastic reduction in acquisition time.
The output of an APSY experiment is a N-dimensional peak list that can be directly used by various protein assignment programs. During the APSY experiment the peak list is calculated continuously and the APSY experiment will automatically stop when the convergence criterion has been reached.
This means APSY can automatically create high-precision peak lists of your protein in the shortest possible time.

How to carry out an APSY experiment

The APSY command panel guidies the user, step-by-step, through the setup and the acquisition of an APSY experiment in Topspin. After the projection angles and GAPRO processing parameters for geometrical analysis of the projections have been defined, the APSY experiment begins and the resulting peak list can be inspected at any time during the APSY experiment.

APSY command panel: Enables ease-of-use of APSY
High Precision: Artifact-free peak lists of high precision
from an optimum number of projections
Fast computation: All calculations are based on peak lists resulting
in very fast computing time even for data of high dimensionality.

Peak lists of high precision

: The above table shows the differences of chemical shifts from a comparison of the peaks lists from a 4D-APSY-HNCOCA and a 6D-APSYHNCOCANH experiment of [13C,15N]-ubiquitin. The precision (standard deviation in Hz) is much better than the digital resolution in the indirect dimension, which allows good assignment.

Sequential assignment

: Sequential assignment of [13C,15N]-ubiquitin using the peaklist from a 6D-APSY-HNCOCANH experiment.

Visual Inspection of Results

: The final N-dimensional peak list can be projected and displayed on any projection spectrum. This allows for quick inspection of the ndimensional peak list and the success of the APSY experiment. A projection (A) and an expansion (B)

References:
(1) S. Hiller, F. Fiorito, K. Wüthrich & G. Wider, Proc. Natl. Acad. Sci. USA 102, 10876-10881 (2005).
(2) S. Kim & T. Szyperski, J. Am. Chem. Soc. 125, 1385 (2003)
(3) E. Kupce & R. Freeman, J. Am. Chem. Soc. 126, 6429 (2004))