X-ray crystallography, Electron Microscopy (EM) and Nuclear Magnetic Resonance (NMR) spectroscopy are three experimental approaches for biological macromolecular structure determination, whereas NMR spectroscopy is the only technique providing detailed structure information of macromolecules in their natural solution state. To date, approximate 11,700 structures released are determined by NMR. Supported by NMR platform, Creative Biostructure offers customized gene-to-structure services for biological compounds including small proteins, peptides and their complexes.
NMR Experiments for Assignment and Structure Determination
NMR employs multidimensional nuclear magnetic resonance experiments to obtain structure information. Generally, the first experiment to be measured is a 2D heteronuclear single quantum coherence (HSQC) spectrum, such as 1H, 15N-HSQC, in which one signal is expected for each amino acid residue except proline. Analysis of HSQC spectra helps to determine the feasibility of subsequent experiments. In order to analyze the NMR data, it is necessary to get a resonance assignment for the protein of interest, which could be achieved by collecting of several different types of NMR experiments. For 13C and 15N double labeled protein, 3D resonance experiments including HNCO, HN(CA)CO, HNCA, HN(CO)CA, HNCACB and CBCA(CO)NH will be conducted for assignments; with the addition of TOCSY and NOESY experiments, a number of restraints such as distance restraints, angle restraints and orientation restraints are generated for structure calculation.
Structure Calculation and Validation
The most widely used computer programs for structure calculation includes GeNMR, CYANA and XPLOR-NIH. Restraints generated from NMR experiments and general properties of proteins such as bond lengths and angles are converted into energy terms by above-mentioned programs, and then results in an ensemble of structures. These protein structures are experimental models, which further validated by validation tools like PROCHECK, WHAT IF, CheShift or PSVS.
Our services include, but not limited to:
Efficient and reliable NMR structure determination demands acquisition of high quality experimental data, implementation of computational approaches and specialists experience for data interpretation and fine-tuning of the results. Backed by a team of scientists with extensive experience in NMR structure determination, Creative Biostructure provides services on isotope labeled sample preparation, structure determination of proteins and their complexes, as well as molecular modeling. Please feel free to consult with us through online inquiry.