The Repository Chemotion: Infrastructure for Sustainable Research in Chemistry*.

The repository Chemotion provides solutions for current challenges to store research data in a feasible manner. A main advantage of Chemotion is the comprehensive functionality, offering options to collect, prepare, and reuse data with discipline-specific methods and data-processing tools.

Structure, dynamics and domain organization of the repeat protein Cin1 from the apple scab fungus.

Venturia inaequalis is a hemi-biotrophic fungus that causes scab disease of apple. A recently-identified gene from this fungus, cin1 (cellophane-induced 1), is up-regulated over 1000-fold in planta and considerably on cellophane membranes, and encodes a cysteine-rich secreted protein of 523 residues with eight imperfect tandem repeats of ~60 amino acids. The Cin1 sequence has no homology to known proteins and appears to be genus-specific; however, Cin1 repeats and other repeat domains may be structurally similar. An NMR-derived structure of the first two repeat domains of Cin1 (Cin1-D1D2) and a low-resolution model of the full-length protein (Cin1-FL) using SAXS data were determined. The structure of Cin1-D1D2 reveals that each domain comprises a core helix-loop-helix (HLH) motif as part of a three-helix bundle, and is stabilized by two intra-domain disulfide bonds. Cin1-D1D2 adopts a unique protein fold as DALI and PDBeFOLD analysis identified no structural homology. A (15)N backbone NMR dynamic analysis of Cin1-D1D2 showed that a short stretch of the inter-domain linker has large amplitude motions that give rise to reciprocal domain-domain mobility. This observation was supported by SAXS data modeling, where the scattering length density envelope remains thick at the domain-domain boundary, indicative of inter-domain dynamics. Cin1-FL SAXS data models a loosely-packed arrangement of domains, rather than the canonical parallel packing of adjacent HLH repeats observed in α-solenoid repeat proteins. Together, these data suggest that the repeat domains of Cin1 display a "beads-on-a-string" organization with inherent inter-domain flexibility that is likely to facilitate interactions with target ligands.

ChemSpectra: a web-based spectra editor for analytical data.

ChemSpectra, a web-based software to visualize and analyze spectroscopic data, integrating solutions for infrared spectroscopy (IR), mass spectrometry (MS), and one-dimensional 1H and 13C NMR (proton and carbon nuclear magnetic resonance) spectroscopy, is described. ChemSpectra serves as web-based tool for the analysis of the most often used types of one-dimensional spectroscopic data in synthetic (organic) chemistry research. It was developed to support in particular processes for the use of open file formats which enable the work according to the FAIR data principles. The software can deal with the open file formats JCAMP-DX (IR, MS, NMR) and mzML (MS) proposing these data file types to gain interoperable data. ChemSpectra can be extended to read also other formats as exemplified by selected proprietary mass spectrometry data files of type RAW and NMR spectra files of type FID. The JavaScript-based editor can be integrated with other software, as demonstrated by integration into the Chemotion electronic lab notebook (ELN) and Chemotion repository, demonstrating the implementation into a digital work environment that offers additional functionality and sustainable research data management options. ChemSpectra supports different functions for working with spectroscopic data such as zoom functions, peak picking and automatic peak detection according to a default or manually defined threshold. NMR specific functions include the definition of a reference signal, the integration of signals, coupling constant calculation and multiplicity assignment. Embedded into a web application such as an ELN or a repository, the editor can also be used to generate an association of spectra to a sample and a file management. The file management supports the storage of the original spectra along with the last edited version and an automatically generated image of the spectra in png format. To maximize the benefit of the spectra editor for e.g. ELN users, an automated procedure for the transfer of the detected or manually chosen signals to the ELN was implemented. ChemSpectra is released under the AGPL license to encourage its re-use and further developments by the community.

Synergistic transmembrane insertion of the heterodimeric PGLa/magainin 2 complex studied by solid-state NMR.

The skin secretions of amphibians are a rich source of antimicrobial peptides. The two antimicrobial peptides PGLa and magainin 2, isolated from the African frog Xenopus laevis, have been shown to act synergistically by permeabilizing the membranes of microorganisms. In this report, the literature on PGLa is extensively reviewed, with special focus on its synergistically enhanced activity in the presence of magainin 2. Our recent solid state (2)H NMR studies of the orientation of PGLa in lipid membranes alone and in the presence of magainin 2 are described in detail, and some new data from 3,3,3-(2)H(3)-L-alanine labeled PGLa are included in the analysis.

Cell-free synthesis and combinatorial selective 15N-labeling of the cytotoxic protein amoebapore A from Entamoeba histolytica.

Amoebapore A is a pore-forming protein produced by the pathogenic parasite Entamoeba histolytica, which causes human amoebic dysentery. The pore-forming activity of amoebapore A is regulated by pH-dependent dimerization, a prerequisite for membrane insertion and pore formation. Understanding of these important processes has been hampered by the cytotoxicity of amoebapore A, which prevents the production of this protein in cell-based expression systems. In this study, a protocol for the cell-free production of active recombinant amoebapore A is presented. Protein yields of approximately 500 microg/ml of cell-free reaction were achieved. Recombinant amoebapore A was purified using a three-step procedure. To facilitate the structural characterization of the dimeric and pore forms, we adapted the cell-free system to isotope label amoebapore A for NMR studies. The preliminary assignment of a 2D 1H-15N HSQC spectrum of a uniformly 13C/15N-labeled sample was achieved using a combinatorial selective 15N-labeling approach coupled with available 1H(N) chemical shift data, resulting in the unambiguous assignment of resonances from 55 of the 77 residues. To confirm these results and obtain the full sequence-specific assignments of the 2D 1H-15N HSQC spectrum, a 3D HNCA spectrum was recorded. These assignment data will be used to aid the characterization of amoebapore A dimer formation and membrane insertion.

Procedures for systematic capture and management of analytical data in academia.

Data management in universities is a challenging endeavor in particular due to the diverse infrastructure of devices and software in combination with limited budget. Nevertheless, in particular the analytical measurements and data sets need to be stored if possible digitally and in a well-organized manner. This manuscript describes how scientists can achieve a data management workflow focusing on data capture and storage by small adaptions to commonly used systems. The presented method includes data transfer options from ubiquitous devices like NMR instruments, GC (MS) or LC (MS), IR and Raman, or mass spectrometers to a central server and the visualization of the available data files in an electronic lab notebook (ELN). The given instruments were chosen according to the needs of synthetic chemists, in particular devices needed in organic, inorganic and polymer chemistry where single data files in the range of several megabytes per data set are produced. Altogether, three different data transfer systems were elaborated to allow a flexible handling of different devices running with different proprietary software: The first procedure allows data capture via the use of a mail server as data exchange point. With the second procedure, data are automatically mirrored from a local file folder to a central storage server where new files are monitored and processed. The third procedure was designed to transfer data with manual support to a central server which is supervised to register new information. All components that are necessary to install and use the herein elaborated functions are available as Open Source and the designed workflows are described step by step to facilitate the adaption of procedures in other universities accordingly if desired.

CHEMSCANNER: extraction and re-use(ability) of chemical information from common scientific documents containing ChemDraw files.

We developed CHEMSCANNER, a software that can be used for the extraction of chemical information from ChemDraw binary (CDX) or ChemDraw XML-based (CDXML) files and to retrieve the ChemDraw scheme from DOC, DOCX or XML documents. This can facilitate the reuse of chemical information embedded into diverse documents used as standard storage and communication instrument in chemical sciences (e.g. for student's theses, PhD theses, or publications). The extracted information is processed to reactions, molecules, as well as additional text and values and can be accessed via the CHEMSCANNER UI. CHEMSCANNER supports the export to Excel and CML, the direct import of the extracted data to the Open Source ELN Chemotion or the use via "copy and paste" of selected information. The software was designed with a focus on the processing of documents with embedded molecular structure information as CDX or CDXML as these are the most common file formats for chemical drawings. The project aims to support the chemists in their efforts to re-use chemistry research data by providing them missing tools for an automated assembly of reaction data.

Chemotion-ELN part 2: adaption of an embedded Ketcher editor to advanced research applications.

The Ketcher editor, available as an Open Source software package for drawing chemical structures, has been expanded to include several features that allow storage, management and application of templates, as well as the use of symbols for a planning and processing of solid phase synthesis. In addition, tools for the drawing of coordinative bonds to represent e.g. organometallic compounds were added. The editor has been implemented into an Electronic Lab Notebook (ELN) application which enables the use of the Ketcher editor for advanced operations in chemistry research. The developments of the ELN-integrated Ketcher (ketcher-rails) support the retrieval of identifiers and structure-related information from external databases and the molecule-based calculation of analytical values. The reworked editor can be used to generate molecular structures in reaction templates and to generate syntheses plans.

Conditions affecting the re-alignment of the antimicrobial peptide PGLa in membranes as monitored by solid state 2H-NMR.

The cationic antimicrobial peptide PGLa is electrostatically attracted to bacterial membranes, binds as an amphiphilic alpha-helix, and is thus able to permeabilize the lipid bilayer. Using solid state (2)H-NMR of non-perturbing Ala-d(3) labels on the peptide, we have characterized the helix alignment under a range of different conditions. Even at a very high peptide-to-lipid ratio (1:20) and in the presence of negatively charged lipids, there was no indication of a toroidal wormhole structure. Instead, PGLa re-aligns from a surface-bound S-state to an obliquely tilted T-state, which is presumably dimeric. An intermediate structure half-way between the S- and T-state was observed in fully hydrated multilamellar DMPC vesicles at 1:50, suggesting a fast exchange between the two states on the time scale of >50 kHz. We demonstrate that this equilibrium is shifted from the S- towards the T-state either upon (i) increasing the peptide concentration, (ii) adding negatively charged DMPG, or (iii) decreasing the level of hydration. The threshold concentration for re-alignment in DMPC is found to be between 1:200 and 1:100 in oriented samples at 96% humidity. In fully hydrated multilamellar DMPC vesicles, it shifts to an effective peptide-to-lipid ratio of 1:50 as some peptides are able to escape into the bulk water phase.

Chemotion ELN: an Open Source electronic lab notebook for chemists in academia.

The development of an electronic lab notebook (ELN) for researchers working in the field of chemical sciences is presented. The web based application is available as an Open Source software that offers modern solutions for chemical researchers. The Chemotion ELN is equipped with the basic functionalities necessary for the acquisition and processing of chemical data, in particular the work with molecular structures and calculations based on molecular properties. The ELN supports planning, description, storage, and management for the routine work of organic chemists. It also provides tools for communicating and sharing the recorded research data among colleagues. Meeting the requirements of a state of the art research infrastructure, the ELN allows the search for molecules and reactions not only within the user's data but also in conventional external sources as provided by SciFinder and PubChem. The presented development makes allowance for the growing dependency of scientific activity on the availability of digital information by providing Open Source instruments to record and reuse research data. The current version of the ELN has been using for over half of a year in our chemistry research group, serves as a common infrastructure for chemistry research and enables chemistry researchers to build their own databases of digital information as a prerequisite for the detailed, systematic investigation and evaluation of chemical reactions and mechanisms.

Synergistic transmembrane alignment of the antimicrobial heterodimer PGLa/magainin.

The antimicrobial activity of amphipathic alpha-helical peptides is usually attributed to the formation of pores in bacterial membranes, but direct structural information about such a membrane-bound state is sparse. Solid state (2)H-NMR has previously shown that the antimicrobial peptide PGLa undergoes a concentration-dependent realignment from a surface-bound S-state to a tilted T-state. The corresponding change in helix tilt angle from 98 to 125 degrees was interpreted as the formation of PGLa/magainin heterodimers residing on the bilayer surface. Under no conditions so far, has an upright membrane-inserted I-state been observed in which a transmembrane helix alignment would be expected. Here, we have demonstrated that PGLa is able to assume such an I-state in a 1:1 mixture with magainin 2 at a peptide-to-lipid ratio as low as 1:100 in dimyristoylphosphatidylcholine/dimyristoylphosphatidylglycerol model membranes. This (2)H-NMR analysis is based on seven orientational constraints from Ala-3,3,3-d(3) substituted in a non-perturbing manner for four native Ala residues as well as two Ile and one Gly. The observed helix tilt of 158 degrees is rationalized by the formation of heterodimers. This structurally synergistic effect between the two related peptides from the skin of Xenopus laevis correlates very well with their known functional synergistic mode of action. To our knowledge, this example of PGLa is the first case where an alpha-helical antimicrobial peptide is directly shown to assume a transmembrane state that is compatible with the postulated toroidal wormhole pore structure.

Solid-state NMR analysis of the PGLa peptide orientation in DMPC bilayers: structural fidelity of 2H-labels versus high sensitivity of 19F-NMR.

The structure and alignment of the amphipathic alpha-helical antimicrobial peptide PGLa in a lipid membrane is determined with high accuracy by solid-state 2H-NMR. Orientational constraints are derived from a series of eight alanine-3,3,3-d3-labeled peptides, in which either a native alanine is nonperturbingly labeled (4x), or a glycine (2x) or isoleucine (2x) is selectively replaced. The concentration dependent realignment of the alpha-helix from the surface-bound "S-state" to a tilted "T-state" by 30 degrees is precisely calculated using the quadrupole splittings of the four nonperturbing labels as constraints. The remaining, potentially perturbing alanine-3,3,3-d3 labels show only minor deviations from the unperturbed peptide structure and help to single out the unique solution. Comparison with previous 19F-NMR constraints from 4-CF3-phenylglycine labels shows that the structure and orientation of the PGLa peptide is not much disturbed even by these bulky nonnatural side chains, which contain CF3 groups that offer a 20-fold better NMR sensitivity than CD3 groups.