Posts Tagged ‘representative’

The “Accessible” in FAIR (data).

Thursday, April 18th, 2019

In a previous post, I looked at the Findability of FAIR data in common chemistry journals. Here I move on to the next letter, the A = Accessible.

The attributes of A[1] include:

  1. (meta)data are retrievable by their identifier using a standardized communication protocol.
  2. the protocol is open, free and universally implementable. 
  3. the protocol allows for an authentication and authorization procedure.
  4. metadata are accessible, even when the data are no longer available. 
  5. The metadata should include access information that enables automatic processing by a machine as well as a person.

Items 1-2 are covered by associating a DOI (digital object identifier) with the metadata. Item 3 relates to data which is not necessarily also OPEN (FAIR and OPEN are complementary, but do not mean the same).

Item 4 mandates that a copy of the metadata be held separately from the data itself; currently the favoured repository is DataCite (and this metadata way well be duplicated at CrossRef, thus providing a measure of redundancy). It also addresses an interesting debate on whether the container for data such as a ZIP or other compressed archive should also contain the full metadata descriptors internally, which would not directly address item 4, but could do so by also registering a copy of the metadata externally with eg DataCite.

Item 4 also implies some measure of separation between the data and its metadata, which now raises an interesting and separate issue (introduced with this post) that the metadata can be considered a living object, with some attributes being updated post deposition of the data itself. Thus such metadata could include an identifier to the journal article relating to the data, information that only appears after the FAIR data itself is published. Or pointers to other datasets published at a later date. Such updating of metadata contained in an archive along with the data itself would be problematic, since the data itself should not be a living object.

Item 5 is the need for Accessibility to relate both to a human acquiring FAIR data and to a machine. The latter needs direct information on exactly how to access the data. To illustrate this, I will use data deposited in support of the previous post and for which a representative example of metadata can be found at (item 4) a separate location at:
data.datacite.org/application/vnd.datacite.datacite+xml/10.14469/hpc/5496

This contains the components:

  1. <relatedIdentifier relatedIdentifierType="URL" relationType="HasMetadata" relatedMetadataScheme="ORE"schemeURI="http://www.openarchives.org/ore/
    ">https://data.hpc.imperial.ac.uk/resolve/?ore=5496</relatedIdentifier>
  2. <relatedIdentifier relatedIdentifierType="URL" relationType="HasPart" relatedMetadataScheme="Filename" schemeURI="filename://aW5wdXQuZ2pm">https://data.hpc.imperial.ac.uk/resolve/?doi=5496&file=1</relatedIdentifier>

Item 6 is an machine-suitable RDF declaration of the full metadata record. Item 7 allows direct access to the datafile. This in turn allows programmed interfaces to the data to be constructed, which include e.g. components for immediate visualisation and/or analysis. It also allows access on a large-scale (mining), something a human is unlikely to try. 

It would be fair to say that the A of FAIR is still evolving. Moreover, searches of the DataCite metadata database are not yet at the point where one can automatically identify metadata records that have these attributes. When they do become available, I will show some examples here.

Added: This search: https://search.test.datacite.org/works?
query=relatedIdentifiers.relatedMetadataScheme:ORE shows how it might operate.

References

  1. M.D. Wilkinson, M. Dumontier, I.J. Aalbersberg, G. Appleton, M. Axton, A. Baak, N. Blomberg, J. Boiten, L.B. da Silva Santos, P.E. Bourne, J. Bouwman, A.J. Brookes, T. Clark, M. Crosas, I. Dillo, O. Dumon, S. Edmunds, C.T. Evelo, R. Finkers, A. Gonzalez-Beltran, A.J. Gray, P. Groth, C. Goble, J.S. Grethe, J. Heringa, P.A. ’t Hoen, R. Hooft, T. Kuhn, R. Kok, J. Kok, S.J. Lusher, M.E. Martone, A. Mons, A.L. Packer, B. Persson, P. Rocca-Serra, M. Roos, R. van Schaik, S. Sansone, E. Schultes, T. Sengstag, T. Slater, G. Strawn, M.A. Swertz, M. Thompson, J. van der Lei, E. van Mulligen, J. Velterop, A. Waagmeester, P. Wittenburg, K. Wolstencroft, J. Zhao, and B. Mons, "The FAIR Guiding Principles for scientific data management and stewardship", Scientific Data, vol. 3, 2016. https://doi.org/10.1038/sdata.2016.18

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The "Accessible" in FAIR (data).

Thursday, April 18th, 2019

In a previous post, I looked at the Findability of FAIR data in common chemistry journals. Here I move on to the next letter, the A = Accessible.

The attributes of A[1] include:

  1. (meta)data are retrievable by their identifier using a standardized communication protocol.
  2. the protocol is open, free and universally implementable. 
  3. the protocol allows for an authentication and authorization procedure.
  4. metadata are accessible, even when the data are no longer available. 
  5. The metadata should include access information that enables automatic processing by a machine as well as a person.

Items 1-2 are covered by associating a DOI (digital object identifier) with the metadata. Item 3 relates to data which is not necessarily also OPEN (FAIR and OPEN are complementary, but do not mean the same).

Item 4 mandates that a copy of the metadata be held separately from the data itself; currently the favoured repository is DataCite (and this metadata way well be duplicated at CrossRef, thus providing a measure of redundancy). It also addresses an interesting debate on whether the container for data such as a ZIP or other compressed archive should also contain the full metadata descriptors internally, which would not directly address item 4, but could do so by also registering a copy of the metadata externally with eg DataCite.

Item 4 also implies some measure of separation between the data and its metadata, which now raises an interesting and separate issue (introduced with this post) that the metadata can be considered a living object, with some attributes being updated post deposition of the data itself. Thus such metadata could include an identifier to the journal article relating to the data, information that only appears after the FAIR data itself is published. Or pointers to other datasets published at a later date. Such updating of metadata contained in an archive along with the data itself would be problematic, since the data itself should not be a living object.

Item 5 is the need for Accessibility to relate both to a human acquiring FAIR data and to a machine. The latter needs direct information on exactly how to access the data. To illustrate this, I will use data deposited in support of the previous post and for which a representative example of metadata can be found at (item 4) a separate location at:
data.datacite.org/application/vnd.datacite.datacite+xml/10.14469/hpc/5496

This contains the components:

  1. <relatedIdentifier relatedIdentifierType="URL" relationType="HasMetadata" relatedMetadataScheme="ORE"schemeURI="http://www.openarchives.org/ore/
    ">https://data.hpc.imperial.ac.uk/resolve/?ore=5496</relatedIdentifier>
  2. <relatedIdentifier relatedIdentifierType="URL" relationType="HasPart" relatedMetadataScheme="Filename" schemeURI="filename://aW5wdXQuZ2pm">https://data.hpc.imperial.ac.uk/resolve/?doi=5496&file=1</relatedIdentifier>

Item 6 is an machine-suitable RDF declaration of the full metadata record. Item 7 allows direct access to the datafile. This in turn allows programmed interfaces to the data to be constructed, which include e.g. components for immediate visualisation and/or analysis. It also allows access on a large-scale (mining), something a human is unlikely to try. 

It would be fair to say that the A of FAIR is still evolving. Moreover, searches of the DataCite metadata database are not yet at the point where one can automatically identify metadata records that have these attributes. When they do become available, I will show some examples here.

Added: This search: https://search.test.datacite.org/works?
query=relatedIdentifiers.relatedMetadataScheme:ORE shows how it might operate.

References

  1. M.D. Wilkinson, M. Dumontier, I.J. Aalbersberg, G. Appleton, M. Axton, A. Baak, N. Blomberg, J. Boiten, L.B. da Silva Santos, P.E. Bourne, J. Bouwman, A.J. Brookes, T. Clark, M. Crosas, I. Dillo, O. Dumon, S. Edmunds, C.T. Evelo, R. Finkers, A. Gonzalez-Beltran, A.J. Gray, P. Groth, C. Goble, J.S. Grethe, J. Heringa, P.A. ’t Hoen, R. Hooft, T. Kuhn, R. Kok, J. Kok, S.J. Lusher, M.E. Martone, A. Mons, A.L. Packer, B. Persson, P. Rocca-Serra, M. Roos, R. van Schaik, S. Sansone, E. Schultes, T. Sengstag, T. Slater, G. Strawn, M.A. Swertz, M. Thompson, J. van der Lei, E. van Mulligen, J. Velterop, A. Waagmeester, P. Wittenburg, K. Wolstencroft, J. Zhao, and B. Mons, "The FAIR Guiding Principles for scientific data management and stewardship", Scientific Data, vol. 3, 2016. https://doi.org/10.1038/sdata.2016.18

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WATOC2014 Conference report. Emergent themes.

Thursday, October 9th, 2014

This second report highlights two “themes”, or common ideas that seem to emerge spontaneously from diversely different talks. Most conferences do have them.

The first is “embedding“, which in this context means treating different parts of a probably complex molecular system at different levels of theory. Thus Emily Carter in her plenary described how a periodic crystal treated by density functional theory, or DFT could have an embedded component in which the electronic structures are described instead by multi-reference correlated wave functions (CAS-PT2). She illustrated this by discussing what happens when a triplet state oxygen molecule approaches the surface of an aluminium crystal, and (mostly) dissociates into surface bound oxygen atoms with Al-O bonds. The spin state of the oxygen changes smoothly to an overall singlet, with a rapid transfer of charge at the saddle point in the potential energy surface. The numbered of embedded Al atoms had to be at least a cluster of 14 to reproduce the observed reaction barriers (DFT on its own gets a zero barrier!). This sort of study is important in understanding the details of what is happening in metal surface catalysis.

Arieh Warshel then addressed the same theme with his own talk entitled Multiscale Modeling of Complex Biological Systems and Processes. Here you got quantum embedding in a mechanical force field description of some very large molecules. This was a broad brush talk, but what I did get out of it was the concept of asymmetry in molecular systems. Whereas an organic chemist thinks of asymmetry as often relating to just a single chiral carbon centre in a molecule, nature operates on vaster scales. Thus the enzyme ATPase has a molecular axle or spindle, which rotates to assemble the phosphate groups one at a time. This spindle rotates asymmetrically, i.e. always in a specific direction, and Warshel attempts to describe the origins of this rotational asymmetry at a molecular level. Well, this is Nobel prize winning stuff! He followed this up with filaments that “walk” along surfaces in one (asymmetric) direction, first lifting up one point of attachment, and then re-attaching at a different point such that the filament develops a clear sense of direction in its walk. This of course is all done with molecular dynamics, and (I think) has its origins in subtle electrostatics.

Stefan Grimme in his plenary also described dynamic processes, this time those that happen in a mass spectrometer when a molecule is ionised by electron impact. Removal of an electron produces a complex set of ionised states, in which many different single bonds may be weakened due to this ionisation. He developed simplified  DFT (sDFT) methods that can be applied to molecular dynamics, and assembled a “black box” which predicts the expected fragmentations over a time scale of a ps or so. By sampling the trajectories, he estimated the intensities of the various positively charged species and overlaid this on the observed EI-MS. The agreement was often spectacular. A particularly interesting example was the fragmentation of taxol. Here, no molecular ion is found, only much lighter ions. The molecular dynamics shows that rather than consecutive single-bond fragmentations, you instead get multiple bonds more or less all fragmenting at the same time. Tougher was to reproduce rearrangements, such as the McLafferty. Here, the semi-empirical method OM2 was more successful. His work means you can just “dial-a-mass-spectrum” and he speculates whether getting a good fit with the observed spectrum could tell you subtle aspects of the gas-phase molecular species, what its tautomeric state might be or perhaps even its conformation. He also described large-scale (800+) atom simulations of electronic circular dichroism (ECD) spectra of organometallic systems. Octahedral complexes can be prepared in chiral form, and this theoretical ECD treatment allows determination of absolute configuration of these often non-crystalline systems. Here you often need to compute 1000 or more electronic states, and if you have ever tried such ECD simulations, you will know that this is a lot of states!

We had been expecting Stefan to talk about dispersion effects in molecules, another emerging theme. Instead lots of other people mentioned them. In my talk I showed how including a D3-dispersion correction could dramatically change the predicted enantioselectivity of a chiral aldol condensation.[1]

The above observations of course cannot be in the least representative; typical of a modern conference there are five parallel sessions and 400+ posters, and so it represents a highly personal and selective snapshot.

References

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    Posted in Interesting chemistry, WATOC reports | 1 Comment »

    The weirdest bond of all? Laplacian isosurfaces for [1.1.1]Propellane.

    Wednesday, July 21st, 2010

    In this post, I will take a look at what must be the most extraordinary small molecule ever made (especially given that it is merely a hydrocarbon). Its peculiarity is the region indicated by the dashed line below. Is it a bond? If so, what kind, given that it would exist sandwiched between two inverted carbon atoms?

    1.1.1 Propellane

    One (of the many) methods which can be used to characterize bonds is the QTAIM procedure. This identifies the coordinates of stationary points in the electron density ρ(r) (at which point ∇ρ(r) = 0) and characterises them by the properties of the density Hessian at this point. At the coordinate of a so-called bond critical point or BCP, the density Hessian has two negative eigenvalues and one positive one. The sum, or trace of the eigenvalues of the density Hessian at this point, denoted as ∇2ρ(r), provides in this model a characteristic indicator of the type of bond, according to the following qualitative partitions:

    1. ρ(r) > 0, ∇2ρ(r) < 0; covalent
    2. ρ(r) ~0, ∇2ρ(r) > 0; ionic
    3. ρ(r) > 0, ∇2ρ(r) > 0; charge shift

    The third category of bond was first characterised by Shaik, Hiberty and co. using valence-bond theory1 and they went on to propose [1.1.1] propellane (above, along with F2) as an exemplar of this type.2 Matching the conclusions drawn from VB theory was the value of the Laplacian. As defined above, for the central C-C bond, both ρ(r) and  ∇2ρ(r) have been calculated to be positive, supporting the identification of this interaction as having charge-shift character.3

    The Laplacian represents one of those properties where quantum mechanics meets experiment, in that its value (and that of ρ(r) itself) can be measured by (accurate) X-ray techniques.4 This was recently accomplished for propellane,5 with the same conclusion that the Laplacian in the central C-C region has the significantly positive value of +0.42 au. The electron density ρ(r) at this point was measured as 0.194 au. Calculations5 at the B3LYP/6-311G(d,p) level report ρ(r) as ~0.19 and ∇2ρ(r) as +0.08 au. Whilst the former is in good agreement with experiment, the latter is calculated as rather smaller than expected. This was originally interpreted as indicating that the “the experimental bond path has a stronger curvature [in ρ(r)] than the theoretical” although more recent thoughts are that both experimental and theoretical uncertainty may account for the discrepancy.5,6 An experiment worth repeating?

    A hitherto largely unexplored aspect of characterising a bond using the Laplacian is whether the value at the bond critical point is fully representative of the bond as a whole. The Laplacian is related to two components of the electronic energy by the Virial theorem;

    2G(r) + V(r) = ∇2ρ(r)/4; H(r) = V(r) + G(r)

    where G(r) is the kinetic energy density, V(r) is the potential energy density and H(r) the energy density. Charge-shift bonds exhibit a large value of the (repulsive) kinetic energy density, a consequence of which is that ∇2ρ(r) is more likely to be positive rather than negative. The relationships above hold not just for the specific coordinate of a bond critical point, but for all space. Accordingly, another way therefore of representing the Laplacian ∇2ρ(r) is to plot the function as an isosurface, including both the negative surface (for which |V(r)| > 2G(r)) and the positive surface [for which |V(r)| < 2G(r)].

    Such an analysis is the purpose of this post, using wavefunctions evaluated at the CCSD/aug-cc-pvtz level (see DOI: 10042/to-5012). The values of ρ(r) and ∇2ρ(r) at the bcp for the central bond are 0.188 and +0.095 au, which compares well with previous calculations. The values for the wing C-C bonds are 0.242 and -0.491 respectively (and were measured5 as 0.26 and -0.48). Laplacian isosurfaces corresponding to ± 0.49 (the value at the wing C-C bcp), ± 0.47 and ± 0.2 (which reveals prominent regions of +ve values for the Laplacian) can be seen in the figures below (and can be obtained as rotatable images by clicking).


    Laplacian isosurface contoured at ± 0.49

    		 –

    Laplacian isosurface contoured at ± 0.47. Red = -ve, blue= +ve.

    Laplacian isosurface contoured at ± 0.20

    A significant feature is the isosurface at -0.47, which corresponds to the lowest contiguous Laplacian isovalued pathway connecting the two terminal carbon atoms (and which coincidentally is similar in magnitude to that reported5 as measured for these two atoms). Three such bent pathways of course connect the two carbon atoms. The energy density H(r) shows a minimum value of -0.21 au along any of these pathways. It is significantly less negative (-0.13) for the direct pathway taken along the axis of the C-C bond.

    Energy density H(r) @-0.21

    Energy density H(r) @-0.13

    ELF isosurface @0.7

    A useful comparison with this result is the ELF isosurface. This too is computed at the correlated CCSD/aug-cc-pVTZ using a new procedure recently described by Silvi.7 Contoured at an isosurface of +0.7, the ELF function is continuous between the two terminal atoms, much in the manner of Laplacian. Significantly, the ELF function at the bcp appears at the very much lower threshold value of 0.54, and forms a basin with a tiny integration for the electrons (0.1e). Since both methods provide a measure of the Pauli repulsions via the excess kinetic energy, the similarity of the Laplacian to the ELF function is probably not coincidental.

    The issue then is whether a bond must be defined by the characteristics of the electron density distribution along the axis connecting that bond, or whether other, non-least-distance pathways can also be considered as being part of the bond.8 The former criterion defines a pathway involving a positive Laplacian (+0.095) and would be interpreted as indicating charge shift character for that bond. The latter involves three (longer) pathways for which the Laplacian is strongly -ve, and which would therefore per se imply more conventional covalent character for the interaction. Considered as a linear (straight) bond, it has charge shifted character; considered as three “banana” bonds, it may be covalent. Weird!

    1. Shaik, S.; Danovich, D.; Silvi, B.; Lauvergnat, D. L.; Hiberty, P. C., “Charge-Shift Bonding – A Class of Electron-Pair Bonds That
      Emerges from Valence Bond Theory and Is Supported by the Electron Localization Function Approach,” Chem. Eur. J., 2005,
      11, 6358-6371, DOI: 10.1002/chem.200500265 and references cited therein.
    2. W. Wu, J. Gu, J. Song, S. Shaik, and P. C. Hiberty, “The Inverted Bond in [1.1.1]Propellane is a Charge-Shift Bond,” Angew. Chem. Int. Ed., 2008,
      DOI: 10.1002/anie.200804965; 10.1002/cphc.200900633
    3. S. Shaik, D. Danovich, W. Wu & P. C. Hiberty, “Charge-shift bonding and its manifestations in chemistry”, Nature Chem, 2009, 1, 443-3439. DOI: 10.1038/nchem.327
    4. P. Coppens, “Charge Densities Come of Age”, Angew. Chemie Int. Ed., 2005, 44, 6810-6811. DOI: 10.1002/anie.200501734
    5. M. Messerschmidt, S. Scheins, L. Grubert, M. Pätzel, G. Szeimies, C. Paulmann, P. Luger. “Electron Density and Bonding at Inverted Carbon Atoms: An Experimental Study of a [1.1.1]Propellane Derivative, Angew. Chemie Int. Ed., 2005, 44, 3925-3928. DOI: 10.1002/anie.200500169
    6. L. Zhang, W. Wu, P. C. Hiberty, S. Shaik, “Topology of Electron Charge Density for Chemical Bonds from Valence Bond Theory: A Probe of Bonding Types”, Chem. Euro. J., 2009, 15, 2979-2989. DOI: 10.1002/chem.200802134
    7. F. Feixas , E. Matito, M. Duran, M. Solà and B. Silvi, submitted for publication. See also this abstract.
    8. See for example the work of R. F. Nalewajski

    Rzepa, Henry S. The weirdest bond of all? Laplacian isosurfaces for [1.1.1]Propellane. 2010-07-21. URL:http://www.ch.ic.ac.uk/rzepa/blog/?p=2251. Accessed: 2010-07-21. (Archived by WebCite® at http://www.webcitation.org/5rOFp6EuM)

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    Posted in Hypervalency, Interesting chemistry | 4 Comments »

    (Hyper)activating the chemistry journal.

    Monday, September 7th, 2009

    The science journal is generally acknowledged as first appearing around 1665 with the Philosophical Transactions of the Royal Society in London and (simultaneously) the French Academy of Sciences in Paris. By the turn of the millennium, around 10,000 science and medical journals were estimated to exist. By then, the Web had been around for a decade, and most journals had responded to this new medium by re-inventing themselves for it. For most part, they adopted a format which emulated paper (Acrobat), with a few embellishments (such as making the text fully searchable) and then used the Web to deliver this new reformulation of the journal. Otherwise, Robert Hooke would have easily recognized the medium he helped found in the 17th century.

    In 1994, a small group of us thought that one could, and indeed should go further than emulated paper. We argued [1] that journals should be activated by delivering not merely the logic of a scientific argument, but also the data on which it might have been based. Of course, we encountered the usual problem; doing this might cost publishers more in production resources, and in the absence of a market prepared to pay the extra, the business model did not make sense (to the publishers). Well, 15 years later, and most publishers are indeed now thinking about how their journals can be enhanced. A number of interesting projects (the RSC’s Project Prospect is one which strives to bring science alive) have emerged. Another is the topic of this blog; the activation of the journal with molecular coordinates and data using the Jmol applet.

    Initially (~2005), this project met with resistance from publishers, and the issue really amounted to what the definitive version of a scientific article should be. Should that definitive version be printable? That model, after all had served the community well for more than 300 years! And journals from the very beginning are still as readable now as when first published. In other words, print lasts! But print is pretty limiting after all. For a start, it is limited to 2D static representations. Molecules, by and large, do their magic in a dynamic three dimensions (4D in an Einsteinian sense). But print is also expensive; not merely to produce, but to transport paper around the world.

    From the turn of the millennium, a number of publishers, amongst them the American Chemical Society, started to evolve the scientific article such that the pre-eminent version would now be considered to be the HTML form (perhaps as a prelude to phasing out print entirely? See an interesting commentary by a journal editor) and perhaps a digital Acrobat form which would be deemed to loose some of its functionality once printed (again see here for how Acrobat can be used to enhance things). Again however, a chicken-and-egg scenario resulted. To enhance the articles with extra functionality (such as data), they would need to find authors prepared to put the extra work into preparing the material. In fact, most authors already do that, but they call it supporting information. This is often highly data rich, covering materials such as spectra, coordinates and other information nowadays provided to researchers for analysis. Unfortunately, what has been missing is the education of authors to provide this information in a proper digital form which can be easily re-used by others, and on a Web page, converted automatically to nice interactive models. Most spectra which form part of the supporting information are in fact still scanned versions of printed spectra!

    Enter computational chemists. Nowadays, they live in a world that truly does not need printing! Almost all of their data is already suitably digital. So perhaps it is no surprise to find that when enhanced journal articles started appearing around 2005, many were produced by this group of chemists. By now perhaps you are wondering what such an article might look like. Well, the remainder of this blog will be devoted to listing some examples. You will also notice that they come exclusively from our own publications. Perhaps someone will find the time to collect a far more representative set to better illustrate the diversity of this form, and how it is evolving. Meanwhile, you might wish to take a look at the following.

    Part 1: The early days: 1994 onwards

    These examples all relied on a browser plugin called Chime, which is no longer with us! Hence the pages designed to invoke it no longer display properly. But the data associated with the articles is still there!

    1. An early 1994 example of (hyper)activating a journal article can be seen here as the preliminary communication and
    2. in 1995 here as the final full article. I am told that this was the article that actually inspired the developers of Chime to enhance (Netscape) with a chemical plugin.
    3. This one from 1998 illustrates how articles can decay in functionality when Chime is no longer available.
    4. An ab initio and MNDO-d SCF-MO Computational Study of Stereoelectronic Control in Extrusion Reactions of R2I-F Iodine (III) Intermediates, M. A. Carroll, S. Martin-Santamaria, V. W. Pike, H. S. Rzepa and D. A. Widdowson, Perkin Trans. 2, 1999, 2707-2714 with the supporting information here.
    5. Huckel and Mobius Aromaticity and Trimerous transition state behaviour in the Pericyclic Reactions of [10], [14], [16] and [18] Annulenes. Sonsoles Martên-Santamarêa, Balasundaram Lavan and H. S. Rzepa, J. Chem. Soc., Perkin Trans 2, 2000, 1415. with the supporting information here.
    6. Peter Murray-Rust, H. S. Rzepa and Michael Wright, “Development of Chemical Markup Language (CML) as a System for Handling Complex Chemical Content”, New J. Chem., 2001, 618-634. DOI: 10.1039/b008780g. This article broke new ground in that the supporting information was something of a misnomer. It was expressed entirely in XML, including all the chemistry data, and used XSLT transforms on the fly to regenerate the article. In that sense, it was actually a superset of the published article. It would be fair to say that this article was rather ahead of its time (although it does seem appropriate to publish it in a new journal!).
    7. M. Jakt, L. Johannissen, H. S. Rzepa, D. A. Widdowson and R. Wilhelm, “A Computational Study of the Mechanism of Palladium Insertion into Alkynyl and Aryl Carbon-Fluorine bonds”, Perkin Trans. 2, 2002, 576-581 and supporting information.
    8. P. Murray-Rust and H. S. Rzepa, chapter in “Handbook of Chemoinformatics. Part 2. Advanced Topics.”, ed. J. Gasteiger and T. Engel, 2003, Vol 1, was not enhanced per se, but did lay out the principles of how it might/should be done.
    9. K. P. Tellmann, M. J. Humphries, H. S. Rzepa and V. C. Gibson, “An experimental and computational study of β-H transfer between organocobalt complexes and 1-alkenes”, Organometallics, 2004, 23, 5503-5513. DOI: 10.1021/om049581h and supporting information.

    Part 2: 2005.

    These four examples all now invoke Jmol, which downloads upon request and hence does not rely on the presence of any browser plugin. The four articles were submited with supporting information in the form of HTML. These were associated with the main article, but were not formal part of that article. In that sense, they represent an incarnation of the traditional model, with all the data firmly resident in the supporting information.

    1. Gibson, Vernon C.; Marshall, Edward L.; Rzepa, H. S. ” A computational study on the ring-opening polymerization of lactide initiated by β-diketiminate metal alkoxides: The origin of heterotactic stereocontrol”, J. Am. Chem. Soc., 2005, 127, 6048-6051. DOI: 10.1021/ja043819b and supporting information.
    2. H. S. Rzepa, Mobius aromaticity and delocalization”, Chem. Rev., 2005, 105, 3697 – 3715. DOI: 10.1021/cr030092l and supporting information.
    3. H. S. Rzepa, “Double-twist Mšbius Aromaticity in a 4n+2 Electron Electrocyclic Reaction”, 2005, Chem Comm, 5220-5222. DOI: 10.1039/b510508k The supporting information is also available directly.
    4. H. S. Rzepa, “A Double-twist Mobius-aromatic conformation of [14]annulene”, Org. Lett., 2005, 7, 637 – 4639. DOI: 10.1021/ol0518333 and supporting information.

    Part 3: 2006 onwards

    The supporting information has now been assimilated into the main body of the article proper, and within these confines contribute components such as enhanced figures or tables (i.e. enhanced with data)

    1. A. P. Dove, V. C. Gibson, E. L. Marshall, H. S. Rzepa, A. J. P. White and D. J. Williams, “Synthetic, Structural, Mechanistic and Computational Studies on Single-Site β-Diketiminate Tin(II) Initiators for the Polymerization of rac-Lactide”, J. Am. Chem. Soc., 2006,128, 9834-9843. DOI: 10.1021/ja061400a The enhancement can be seen in Figure 11.
    2. O. Casher and H. S. Rzepa, “SemanticEye: A Semantic Web Application to Rationalise and Enhance Chemical Electronic Publishing”, J. Chem. Inf. Mod., 2006, 46, 2396-2411. DOI: 10.1021/ci060139e
    3. H S. Rzepa and M. E. Cass, “A Computational Study of the Nondissociative Mechanisms that Interchange Apical and Equatorial Atoms in Square Pyramidal Molecules”, Inorg. Chem., 2006, 45, 3958–3963. DOI 10.1021/ic0519988. Interactive table at 10.1021/ic0519988/ic0519988.html
    4. M. E. Cass and H. S. Rzepa, “In Search of The Bailar Twist and Ray-Dutt mechanisms that racemize chiral tris-chelates: A computational study of Sc(III), V(III), Co(III), Zn(II) and Ga(III) complexes of a ligand analog of acetylacetonate”, Inorg. Chem., 2007, 49, 8024-8031. DOI: 10.1021/ic062473y The enhancement can be seen in Figure 2
    5. H. S. Rzepa, “Lemniscular Hexaphyrins as examples of aromatic and antiaromatic Double-Twist Möbius Molecules”, Org. Lett., 2008, 10, 949-952.DOI:10.1021/ol703129z The enhancement can be seen in Web Table 1.
    6. D. C. Braddock and H. S. Rzepa, “Structural Reassignment of Obtusallenes V, VI and VII by GIAO-based Density functional prediction”, J. Nat. Prod., 2008, DOI: 10.1021/np0705918 and WEO1.
    7. S. M. Rappaport and H S. Rzepa, “Intrinsically Chiral Aromaticity. Rules Incorporating Linking Number, Twist, and Writhe for Higher-Twist Möbius Annulenes”, J. Am. Chem. Soc., 2008, 130,, 7613-7619. DOI: 10.1021/ja710438j and WEO1 to 4
    8. C. S. M. Allan and H. S. Rzepa, “AIM and ELF Critical point and NICS Magnetic analyses of Möbius-type Aromaticity and Homoaromaticity in Lemniscular Annulenes and Hexaphyrins”, J. Org. Chem., 2008, 73, 6615-6622. DOI: 10.1021/jo801022b and WEO1
    9. C. S. M. Allan and H. S. Rzepa, “Chiral aromaticities. Möbius Homoaromaticity”, J. Chem. Theory. Comp., 2008, 4, 1841-1848. DOI: 10.1021/ct8001915 and WEO1
    10. C. S. M Allan and H. S. Rzepa, “The structure of Polythiocyanogen: A Computational investigation”, Dalton Trans., 2008, 6925 – 6932. DOI: 10.1039/b810147g and enhanced Table
    11. H. S. Rzepa, “Wormholes in Chemical Space connecting Torus Knot and Torus Link π-electron density topologies”, Phys. Chem. Chem. Phys., 2009, 1340-1345. DOI: 10.1039/b810301a and enhanced Table.
    12. H. S. Rzepa, “The Chiro-optical properties of a Lemniscular Octaphyrin”, Org. Lett., 2009, 11, 3088-3091. DOI: 10.1021/ol901172g
    13. C. S. Wannere, H. S. Rzepa, B. C. Rinderspacher, A. Paul, H. F. Schaefer III, P. v. R. Schleyer and C. S. M. Allan, “The geometry and electronic topology of higher-order Möbius charged Annulenes”, J. Phys. Chem., 2009, DOI: 10.1021/jp902176a and enhanced table
    14. H. S. Rzepa, “The distortivity of π-electrons in conjugated Boron rings.”, Phys. Chem. Chem. Phys., 2009, DOI: 10.1039/B911817A and enhanced table.
    15. H. S. Rzepa, “The importance of being bonded”, Nature Chem., 2009, DOI: 10.1038/nchem.373 and the exploratorium.
    16. King Kuok Hii, J.L.Arbour, H.S.Rzepa, A.J.P.White, “Unusual Regiodivergence in Metal-Catalysed Intramolecular Cyclisation of γ-Allenols”, Chem. Commun, 2009, DOI: 10.1039/b913295c and enhanced table.
    17. L. F. V. Pinto, P. M. C. Glória, M. J. S. Gomes, H. S. Rzepa, S. Prabhakar, A. M. Lobo. “A Dramatic Effect of Double Bond Configuration in N-Oxy-3-aza Cope Rearrangements – A simple synthesis of functionalised allenes”, Tet. Lett., 2009, 50, 3446-3449. DOI: 10.1016/j.tetlet.2009.02.228 and interactive table.
    18. H. S. Rzepa and C. S. M. Allan, “Racemization of isobornyl chloride via carbocations: a non-classical look at a classic mechanism”, J. Chem. Educ., 2010, DOI: 10.1021/ed800058c and interactive table.
    19. K. Abersfelder, A. J. P. White, H. S. Rzepa, and D. Scheschkewitz “A Tricyclic Aromatic Isomer of Hexasilabenzene”, Science, 2010, DOI: 10.1126/science.1181771 and interactive table.
    20. A. C. Spivey, L. Laraia, A. R. Bayly, H. S. Rzepa and A. J. P. White “Stereoselective Synthesis of cis- and trans-2,3-Disubstituted Tetrahydrofurans via Oxonium−Prins Cyclization: Access to the Cordigol Ring System”, Org. Lett., 2010, DOI 10.1021/ol9024259 and interactive table.
    21. J. Kong, P. v. R. Schleyer and H. S. Rzepa, “Successful Computational Modeling of Iso-bornyl Chloride Ion-Pair Mechanisms”, J. Org. Chem., 2010, DOI: 10.1021/jo100920e and interactive table.
    22. A. Smith, H. S. Rzepa, A. White, D. Billen, K. K. Hii, “Delineating Origins of Stereocontrol in Asymmetric Pd-Catalyzed α-Hydroxylation of 1,3-Ketoesters”, J. Org. Chem., 2010, 75, 3085-3096. DOI: 10.1021/jo1002906 and interactive table.
    23. H. S. Rzepa “The rational design of helium bonds”, Nature Chem., 2010, 2, 390-393. DOI: 10.1038/NCHEM.596 and web enhanced table.
    24. P. Rivera-Fuentes, J. Lorenzo Alonso-Gómez, A. G. Petrovic, P. Seiler, F. Santoro, N. Harada, N. Berova, H. S. Rzepa, and F. Diederich, “Enantiomerically Pure Alleno–Acetylenic Macrocycles: Synthesis, Solid-State Structures, Chiroptical Properties, and Electron Localization Function Analysis”, Chem. Eur. J., 2010, DOI: 10.1002/chem.201001087 and interactive figure
    25. H. S. Rzepa, “The Nature of the Carbon-Sulfur bond in the species H-CS-OH”, J. Chem. Theory. Comput., 2010, 49, DOI: 10.1021/ct100470g and interactive table.
    26. H. S. Rzepa, “Can 1,3-dimethylcyclobutadiene and carbon dioxide co-exist inside a supramolecular cavity?”, Chem. Commun., 2010, DOI: 10.1039/C0CC04023A and interactive table
    27. M. R. Crittall, H. S. Rzepa, and D. R. Carbery, “Design, Synthesis, and Evaluation of a Helicenoidal DMAP Lewis Base Catalyst”, Org. Lett., 2011, DOI: 10.1021/ol2001705 and interactive table
    28. H. S. Rzepa, “The past, present and future of Scientific discourse”, J. Cheminformatics, 2011, 3, 46. DOI: 10.1186/1758-2946-3-46 and interactive figure 3, figure 4 and figure 5.
    29. H. S. Rzepa, “A computational evaluation of the evidence for the synthesis of 1,3-dimethylcyclobutadiene in the solid state and aqueous solution”, Chem. Euro. J., 2012, in press.
    30. J. L. Arbour, H. S. Rzepa, L. A. Adrio, E. M. Barreiro, P. G. Pringle and K. K. (Mimi) Hii, “Silver-catalysed enantioselective additions of O-H and N-H to C=C bonds: Non-covalent interactions in stereoselective processes”, Chem. Euro. J., 2012, in press, Web table 1 and Web table 2.
    31. H. S. Rzepa, “Chemical datuments as scientific enablers”, J. Chemoinformatics, submitted.
    32. A. P. Buchard, F. Jutz, F. M. R. Kember, H. S. Rzepa, C. K. Williams, C.K., “Experimental and Computational Investigation of the Mechanism of Carbon Dioxide/Cyclohexene Oxide Copolymerization Using A Dizinc Catalyst”, in press. Interactivity box
    33. D. C. Braddock, D. Roy, D. Lenoir, E. Moore, H. S. Rzepa, J. I-Chia Wu and P. von R. Schleyer, “Verification of Stereospecific Dyotropic Racemisation of Enantiopure d and l-1,2-Dibromo-1,2-diphenylethane in Non-polar Media”, Chem. Comm., 2012, just published. DOI: 10.1039/C2CC33676F and interactivity box.
    34. K. Leszczyńska, K. Abersfelder, M. Majumdar, B. Neumann, H.-G. Stammler, H. S. Rzepa, P. Jutzi and D. Scheschkewitz, “The Cp*Si+ Cation as a Stoichiometric Source of Silicon, Chem. Comm., 2012, 48, 7820-7822. DOI: 10.1039/c2cc33911k. Cites links to 10042/to-13974, 10042/to-13982, 10042/to-13969, 10042/20028, 10042/to-13973, 10042/to-13985
    35. H. S. Rzepa, “A computational evaluation of the evidence for the synthesis of 1,3-dimethylcyclobutadiene in the solid state and aqueous solution”, Chem. Euro. J., 2013, 4932-4937. DOI: 10.1002/chem.201102942 and WebTable
    36. H. S. Rzepa, “Chemical datuments as scientific enablers”, J. Chemoinformatics, 2013, 4, DOI: 10.1186/1758-2946-5-6. The interactivity box is integrated into the body of the article.
    37. M. J. Cowley, V. Huch, H. S. Rzepa, D. Scheschkewitz, “A Silicon Version of the Vinylcarbene – Cyclopropene Equilibrium: Isolation of a Base-Stabilized Disilenyl Silylene”, 2013, Nature Chem., in press and Webtable.
    38. M. J. S. Gomes, L. F. V. Pinto, H. S. Rzepa, S. Prabhakar, A. M. Lobo, “N-Heteroatom Substitution Effects in 3-Aza-Cope Rearrangements”, Chemistry Central, 2013, 7:94. doi:10.1186/1752-153X-7-94 and Table.
    39. H. S. Rzepa and C. Wentrup, “Mechanistic Diversity in Thermal Fragmentation Reactions: a Computational Exploration of CO and CO2 Extrusions from Five-Membered Rings”, J. Org. Chem., DOI: 10.1021/jo401146k and Table.
    40. D. C. Braddock, J. Clarke and H. S. Rzepa “Epoxidation of Bromoallenes Connects Red Algae Metabolites by an Intersecting Bromoallene Oxide – Favorskii Manifold”, Chem. Comm., 2013, DOI: 10.1039/C3CC46720A and Table.
    41. M. J. Fuchter, Ya-Pei Lo and H. S. Rzepa, “Mechanistic and chiroptical studies on the desulfurization of epidithiodioxopiperazines reveal universal retention of configuration at the bridgehead carbon atoms”, J. Org. Chem., 2013, in press. doi: 10.1021/jo401316a and table.

    References

    1. H.S. Rzepa, B.J. Whitaker, and M.J. Winter, "Chemical applications of the World-Wide-Web system", Journal of the Chemical Society, Chemical Communications, pp. 1907, 1994. https://doi.org/10.1039/c39940001907

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