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NA-CDQuant — CD spectrum deconvolution

Decompose a CD spectrum into percentage contributions of elementary nucleic-acid structures (B-DNA, A-DNA, Z-DNA, quadruplex and i-motif folds, …) using forward-selected non-negative least squares, with optional bootstrap uncertainty bands and a semi-non-linear model for covalently-linked structural elements.

Spectrum (CSV with wavelength, CD[, HT] columns)

First column = wavelength (nm), second = CD signal (Δε). A third optional column (HT / high-tension) enables the tension cutoff below.

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Min wavelength (nm)

Max wavelength (nm)

Max HT / tension

Reference spectra to use

All None DNA only RNA only

DNA Parallel Double stranded RNA DNA Parallel Quadruplex Z-DNA Double stranded DNA RNA quadruplex rand_DNA_floppy rand_DNA_stacked rand_RNA_floppy rand_RNA_stacked DNA Cruciform DNA Hybrid Quadruplex DNA i-motif AU rich RNA DNA antiparallel quadruplex 1 DNA antiparallel quadruplex 2 AT rich DNA A-DNA

Fitting model

Linear only Both (linear + semi-non-linear) Auto-select (keep semi-non-linear only if AIC/BIC improves)

The linear model suits mixtures of structurally independent species; semi-non-linear suits covalently-linked structural elements where local CD responses couple (see NA-CDQuant discussion).

A collaboration between (IIMCB)| International Institute of Molecular and Cell Biology in Warsaw , (SOLEIL) Synchrotron, (CNRS) | Centre national de la recherche scientifique , (CEA)| French Alternative Energies and Atomic Energy Commission , Université Paris Cité