TRACT - TROSY for rotational correlation times
============================================

Original method:
D. Lee, C. Hilty, G. Wider, K. Wuthrich (2006).
Effective rotational correlation times of proteins from NMR relaxation
interference. Journal of Magnetic Resonance 178 (1), 72-76.
https://doi.org/10.1016/j.jmr.2005.08.014

Included original files (unchanged):
- tract.dl: Bruker pulse sequence; header credits D. Lee, November 2002.
- tract.xls: original Excel correlation-time worksheet.
- split_all_int.pl: legacy Perl splitter for interleaved Bruker ser data.

Experiment
----------
Calibrate pulses, gradients, carrier, and water suppression for the actual
instrument and sample. Read the sequence comments. Confirm compatibility
with the installed TopSpin release before running an experiment.

Data splitting
--------------
The Perl script reads ./ser. Its supplied configuration writes ./ser1 and
./ser2, with 20 delay points, 1024 direct-dimension points and 4 bytes per
data point. Inspect and adjust initnr, endnr, tdpoints and directtdpoints
for the acquisition format. This original script does not validate the
input size or preserve existing output files.

Run ONLY on a working copy, in a directory without existing ser1 or ser2
files. It overwrites files with those names. Do not run it on the sole
copy of experimental data. The original script is preserved for research
provenance; no instrument or processing compatibility is implied.

Worksheet
---------
The example uses a 750 MHz proton field, Rb = 64 /s and Ra = 13 /s.
Review the physical constants and input measured rates for your sample.
The worksheet presents a cubic equation in the correlation time. Check
the physically meaningful positive root and time units (seconds).
The stored tc value is an example and must not be mistaken for a newly
calculated result. The workbook contains an old external cubic-solver
link; availability of that third-party website is not guaranteed.

Interpretation
--------------
TRACT estimates an effective rotational correlation time. Internal motion,
anisotropic tumbling and experimental conditions affect interpretation.
It is not a direct molecular-weight measurement.

Verification
------------
SHA256SUMS.txt contains hashes of the three unchanged original files.
The 2026 website update packages existing files; it is not a new release
of the TRACT method or a validation of the legacy code.

Questions: dlee04@kbsi.re.kr