NMR structure determination of a segmentally labeled glycoprotein using in vitro glycosylation.

Although there is great interest in three-dimensional structures of glycoproteins and complex oligosaccharides, their structural determination have been hampered by inhomogeneous and incomplete glycosylation, poor expression, low tendency to crystallize, and severe chemical shift overlap. Using segmental labeling of the glycan and the protein component by in vitro glycosylation, we developed a novel method of NMR structural determination that overcomes some of these problems. Highly homogeneously glycosylated proteins in milligram amounts can be obtained. This allowed the determination of the structure of an N-linked glycoprotein from Campylobacter jejuni. The glycosylation acceptor site was found to be in a flexible loop. The presented methodology extends the observable NOE distance limit of oligosaccharides significantly over 4 A, resulting in a high number of distance restraints per glycosidic linkage. A well-defined glycan structure was obtained.

Collaborative development for setup, execution, sharing and analytics of complex NMR experiments.

Factory settings of NMR pulse sequences are rarely ideal for every scenario in which they are utilised. The optimisation of NMR experiments has for many years been performed locally, with implementations often specific to an individual spectrometer. Furthermore, these optimised experiments are normally retained solely for the use of an individual laboratory, spectrometer or even single user. Here we introduce a web-based service that provides a database for the deposition, annotation and optimisation of NMR experiments. The application uses a Wiki environment to enable the collaborative development of pulse sequences. It also provides a flexible mechanism to automatically generate NMR experiments from deposited sequences. Multidimensional NMR experiments of proteins and other macromolecules consume significant resources, in terms of both spectrometer time and effort required to analyse the results. Systematic analysis of simulated experiments can enable optimal allocation of NMR resources for structural analysis of proteins. Our web-based application (http://nmrplus.org) provides all the necessary information, includes the auxiliaries (waveforms, decoupling sequences etc.), for analysis of experiments by accurate numerical simulation of multidimensional NMR experiments. The online database of the NMR experiments, together with a systematic evaluation of their sensitivity, provides a framework for selection of the most efficient pulse sequences. The development of such a framework provides a basis for the collaborative optimisation of pulse sequences by the NMR community, with the benefits of this collective effort being available to the whole community.