# Heterophyllin B: Combining Isotropic and Anisotropic NMR for the Conformational Analysis of a Natural Occurring Cyclic Peptide

## TL;DR

The paper presents a new method combining isotropic and anisotropic NMR data to determine the 3D structure of the cyclic peptide heterophyllin B with high accuracy.

## Contribution

A novel computational-NMR framework is introduced for conformational analysis of cyclic peptides using isotropic and anisotropic NMR data.

## Key findings

- A minimal conformational ensemble of heterophyllin B was determined at DFT accuracy.
- The combined use of isotropic and anisotropic NMR data improves conformational sampling of flexible cyclic peptides.
- A new computational strategy using CREST and CENSO was proposed for efficient conformational analysis.

## Abstract

Heterophyllin B is a natural occurring cyclic peptide with diverse attributed bioactivities. NMR‐based conformational analysis of cyclic peptides often poses a challenge due to limited isotropic solution‐state NMR data. In this study, we combined isotropic and anisotropic NMR observables including J‐coupling, NOEs, amide proton temperature coefficients, and residual dipolar couplings (RDCs), which enabled the determination of a minimal conformational ensemble of heterophyllin B in methanol at density functional theory (DFT) accuracy. For conformational sampling of a cyclic peptide with a high degree of conformational freedom, we proposed a computational strategy that combines the Conformer–Rotamer Ensemble Sampling Tool (CREST) with the Commandline Energetic SOrting (CENSO). This combined computational and NMR‐based approach offers a robust framework for the conformational analysis of cyclic peptides.

A minimal conformational ensemble of cyclic peptide heterophyllin B is presented at the density functional theory accuracy using isotropic and anisotropic NMR.