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A New Graduate Student!


Last Friday we had a new graduate student when our very own Marco Antonio Diaz defended his BSc thesis on the in silico design of drug carriers based on calix[n]arenes. During his thesis he performed around 160 different calculations regarding the interaction energy of our host-guest inclusion complexes, both using the supramolecular method and the NBODel procedure available in NBO3.1 as provided with Gaussian 09. One of the main targets of this work was to assess both methods -with the proper BSSE corrections- in their capabilities for the calculation of interaction energies.

We found that the NBODel method consistently generates interaction energies that are similar to those of the SM method + the BSSE correction (as opposed to SM – BSSE which is the proper correction). Marco and I are still in the process of writing the article so maybe it will be published in early 2018. In this case we’re using calixarenes to deliver three drugs: warfarine, furosemide, phenylbutazone to compite with ocratoxin-A (OTA) for the binding site in Human Serum Albumin (HSA).

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This project is undertaken in collaboration with my good friend Dr. Sándor Kunsági-Máté in Pécsi Tudomanyegyetem in Hungary.

Congratulations to Marco from all of us here at the lab!

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A new chemist is graduated


It is with great pleasure that I announce the graduation of another member of our research group: Luis Enrique “Kike” Aguilar defended his BSc thesis yesterday and is now counting the days left for the Autumn when he’ll move to the Netherlands for a masters in computational chemistry.

Luis Enrique, Kike, calculated the interaction energies of 144 different inclusion complexes where calix and thia-calix[n]arenes were once again the chosen hosts (36 of them) and two drugs for the treatment of chronic myeloid leukemia (CML), namely Sorafenib and Bosutinib, were the guests.

The publication of the corresponding article in which we once again were fortunate enough to count with the collaboration of Dr. Rodrigo Galindo from Utah University in the molecular dynamics section, is still pending but we’re confident enough that it wont take much longer until it’s out there.

Kike is a very diligent student with great learning skills, I’m sure he’ll succeed in any enterprise he sets himself off.  Congratulations, Kike! Thanks for being a part of our research but more importantly for being a part of our community.


    

WATOC 2014 – Virtual edition


I had a blast last week at WATOC2014 in Santiago de Chile! It was a wonderful opportunity to find old friends, meet new ones and listen to some exciting research done around the world, as well as some of the classics such as Pekka Pyykkö, who was awarded the Schrödinger medal. I decided to share my talk on SlideShare.com but also here because I found at WATOC that many many people seem to like this little space of mine! I was shocked, flattered but mostly happy to know that this little blog of mine is well regarded.

So, without further ado, here is my presentation at WATOC2014, please read the captions on each image for context. Feel free to make any comments, sharing or liking. Thanks for clicking!

Self explanatory :)

Self explanatory 🙂

Administration of a drug follows one of these two extreme pharmacokinetic pathways. Either way, drugs accumulate in non-target tissues, are wasted and cause undesired secondary effects.

Administration of a drug follows one of these two extreme pharmacokinetic pathways. Either way, drugs accumulate in non-target tissues, are wasted and cause undesired secondary effects.

Ideally, a drug should arrive to the target tissue. Several polymolecular drug carriers have been developed.

Ideally, a drug should arrive to the target tissue. Several polymolecular drug carriers have been developed.

In terms of monomolecular carriers, cyclodextrines have shown moderate success.

In terms of monomolecular carriers, cyclodextrines have shown moderate success.

Calixarenes offer a more chemically-tunable alternative.

Calixarenes offer a more chemically-tunable alternative.

We decided to go with drugs for the treatment of chronic myeloid leukemia

We decided to go with drugs for the treatment of chronic myeloid leukemia

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Interaction energies were calculated with the NBODel approach, in which elements of the Fock Matrix common to two molecular fragments are deleted

Interaction energies were calculated with the NBODel approach, in which elements of the Fock Matrix common to two molecular fragments are deleted

This deletion yields a new Fock matrix which is re-diagonalized; the increase in energy is ascribed to the interaction between both fragments.

This deletion yields a new Fock matrix which is re-diagonalized; the increase in energy is ascribed to the interaction between both fragments.

GTP was a small place to start (chemical space blocked due to animation lost in translation)

GTP was a small place to start (chemical space blocked due to animation lost in translation)

Interaction energies obtained

Interaction energies obtained

Hydrogen bonds and pi - pi interactions account for the large interaction energies

Hydrogen bonds and pi – pi interactions account for the large interaction energies

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Detail of the interactions in some of the obtained geometries

 

 

MD simulations show the progress of the "release" process.

MD simulations show the progress of the “release” process.

So we moved to a larger drug with more degrees of freedom (and a comercial one too)

So we moved to a larger drug with more degrees of freedom (and a comercial one too)

Chemical space increased regard to the one used with GTP.

Chemical space increased regard to the one used with GTP.

In both cases, two insertion modes were considered.

In both cases, two insertion modes were considered.

Some results...

Some results…

100ns of MD show three kinds of structures (inserted, partially released and totally released)

100ns of MD show three kinds of structures (inserted, partially released and totally released)

PMF US - the profile of release tells us if the carrier is way too strong to be a carrier at all.

PMF US – the profile of release tells us if the carrier is way too strong to be a carrier at all.

Where do we go from here?

Where do we go from here?

Second generation CML drugs; however Bosutinib poses a funny challenge

Second generation CML drugs; however Bosutinib poses a funny challenge

A comercial error has released two isomers to the market, only one of them actually works. CAN WE GENERATE A RECOGNITION AGENT??

A comercial error has released two isomers to the market, only one of them actually works. CAN WE GENERATE A RECOGNITION AGENT??

I know, some results need  some attention, I know, trust me.

I know, some results need some attention, I know, trust me.

Also, Imatinib is cardiotoxic. We research now the competence between allegedly affected enzymes and the carriers to at least delay the toxic effect.

Also, Imatinib is cardiotoxic. We research now the competence between allegedly affected enzymes and the carriers to at least delay the toxic effect.

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Thanks to all of these wonderful guys who made all publications possible (and also those who gave the money)

Thanks to all of these wonderful guys who made all publications possible (and also those who gave the money)

(The view from my office in Toluca) Any questions?

(The view from my office in Toluca, Mexico) ANY QUESTIONS? Write it in the comments section!

 

If you made it this far, let me tell you that this is also available at Slideshare.com 🙂

Thanks for reading, commenting and sharing!

New paper in Journal of Chemical Theory and Computation


Happy new year to all my readers!

Having a new paper published is always a matter of happiness for this computational chemist but this time I’m excedingly excited about anouncing the publishing of a paper in the Journal of Chemical Theory and Computation, which is my highest ranked publication so far! It also establishes the consolidation of our research group at CCIQS as a solid and competitive group within the field of theoretical and computational chemistry. The title of our paper is “In Silico design of monomolecular drug carriers for the tyrosine kinase inhibitor drug Imatinib based on calix- and thiacalix[n]arene host molecules. A DFT and Molecular Dynamics study“.

In this article we aimed towards finding a suitable (thia-) calix[n]arene based drug delivery agent for the drug Imatinib (Gleevec by Novartis), which is a broadly used powerful Tyrosine Kinase III inhibitor used in the treatment of Chronic Myeloid Leukaemia and, to a lesser extent, Gastrointestinal Stromal Tumors; although Imatinib (IMB) exhibits a bioavailability close to 90% most of it is excreted, becomes bound to serum proteins or gets accumulated in other tissues such as the heart causing several undesired side effects which ultimately limit its use. By using a molecular capsule we can increase the molecular weight of the drug thus increasing its retention, and at the same time we can prevent Imatinib to bind, in its active form, to undesired proteins.

We suggested 36 different calix and thia-calix[n]arenes (CX) as possible candidates; IMB-CX complexes were manually docked and then optimized at the B97D/6-31G(d,p) level of theory; Stephan Grimme’s B97D functional was selected for its inclusion of dispersion terms, so important in describing π-π interactions. Intermolecular interaction energies were calculated under the Natural Bond Order approximation; a stable complex was needed but a too stable complex would never deliver its drug payload! This brings us to the next part of the study. A monomolecular drug delivery agent must be able to form a stable complex with the drug but it must also be able to release it. Molecular Dynamics simulations (+100 ns) and umbrella sampling methods were used to analyse the release of the drug into the aqueous media.

Optimized geometries for all complexes under study (B97D/6-31G*)

Optimized geometries for the 20 most stable complexes under study (B97D/6-31G*)

Potential Mean Force profiles for the four most stable complexes for position N1 and  N2 from the QM simulations are shown below (Red, complexes in the N1 position, blue, N2 position). These plots, derived from the MD simulations  give us an idea of the final destination of the drug respect of the calixarene carrier. In the next image, the three preferred structures (rotaxane-like; inside; released) for the final outcome of the delivery process are shown. The stability of the complexes was also assessed by calculating the values of ΔG binding through the use of the Poisson equations.

PMF for the most stable compounds

PMF for the most stable compounds

General MD simulation final structures

General MD simulation final structures

Thanks to my co-authors Maria Eugenia Sandoval-Salinas and Dr. Rodrigo Galindo-Murillo for their enormous contributions to this work; without their hard work and commitment to the project this paper wouldn’t have been possible.

XIth Mexican Reunion on Theoretical Physical Chemistry


For over a decade these meetings have gathered theoretical chemists every year to share and comment their current work and to also give students the opportunity to interact with experienced researchers, some of which in turn were even students of Prof. Robert Parr, Prof. Richard Bader or Prof. Per Olov Löwdin. This year the Mexican Meeting on Theoretical Physical Chemistry took place last weekend in Toluca, where CCIQS is located. You can find links to this and previous meetings here. We participated with a poster which is presented below (in Spanish, sorry) about our current research on the development of calixarenes and tia-calixarenes as drug carriers. In this particular case, we presented our study with the drug IMATINIB (Gleevec as branded by Novartis), a powerful tyrosinkynase inhibitor widely employed in the treatment of Leukaemia.

The International Journal of Quantum Chemistry is dedicating an issue to this reunion. As always, this meeting posed a great opportunity to reconnect with old friends, teachers, and colleagues as well as to make new acquaintances; my favourite session is still the beer session after all the seminars! Kudos to María Eugenia “Maru”  Sandoval-Salinas for this poster and the positive response it generated.

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