Archive for the ‘Hot articles’ Category

Insights into temperature controlled enantioselectivity in asymmetric catalysis

The rare phenomenon of enantioselectivity reversal, using a simple change in reaction temperature control, is presented in the latest HOT article published in OBC.

The ability to mimic nature’s stereochemical control in the production of complex molecules has been a longstanding challenge in chemistry. There are numerous strategies chemists have implemented to generate stereochemically complex structures, however, with the advent of asymmetric catalysis, highly stereoselective reactions can be achieved using chiral reagents and catalysts.

In a recent OBC publication by Prof. Kenso Soai of Tokyo University and researchers from Merck, one of the very few examples in which the enantioselective outcome of a reaction is controlled through temperature was presented. Gaining enantioselective control by changing simple reaction parameters has been an attractive and long sought after advancement within the field of asymmetric catalysis. While there are examples of enantioselective control using solvent, metals and additives, very few examples exist that use temperature alone.

The study outlines the effect of temperature on the asymmetric autocatalysis of pyrimidal alkanol in the addition reaction of diisopropyl zinc to the pyrimidine-5-carbaldehyde. After reaction initiation using a chiral initiator, the product alkanol behaves as an asymmetric catalyst for its own formation and infers its chirality to the product in an autocatalytic cycle. When the reaction was performed at 0 ºC in the presence of (S)-1-phenyl-ethyl alcohol, as expected, (S)-pyrimidal alkanol was afforded in high enantiomeric excess. Interestingly, when the reaction was cooled to -44 ºC, the opposite enantioselectivity was observed though with a slightly lower enantiomeric excess of the desired alkanol.

The exact mechanism through which this reversal happens is still unclear however, it’s speculated that the relationship between temperature and the relative enthalpic vs. entropic contributions to free energy may play a part or the temperature dependent aggregation of zinc alkoxide may also be involved.

It’s important to remember that the temperature effect on reactions involving organozinc reagents is not always straight forward and may not always lead to the best outcome.

Regardless, this study provides interesting insight into temperature controlled enantioselectivity that may lead to a more detailed understanding of such processes and how they can be synthetically exploited.

To find out more see:

Unusual reversal of enantioselectivity in the asymmetric autocatalysis of pyrimidyl alkanol triggered by chiral aromatic alkanols and amines
Arimasa Matusmoto, Satoshi Fujiwara, Yui Hiyoshi,aKerstin Zawatzky, Alexey A. Makarov, Christopher J. Welch and Kenso Soai
DOI: 10.1039/C6OB02415G


Victoria Corless is currently completing her Ph.D. in organic chemistry with Prof. Andrei Yudin at The University of Toronto. Her research is centred on the synthesis of kinetically amphoteric molecules, which offer a versatile platform for the development of chemoselective transformations with particular emphasis on creating novel biologically active molecules.

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Enhancing nonlinear optical imaging through porphyrin-based dyes

Over the past several decades, advances in cell imaging have dramatically transformed biology and medicine. Fluorescence spectroscopy and microscopy are currently the most popular imaging techniques however, there are intrinsic limitations; many substrates are non-fluorescent or weakly fluorescent, fluorescent labels are often perturbative for small molecules and peptides and, perhaps most importantly, labelling or staining with fluorophores are not recommended for in vivo medicinal applications in humans. Hence, the search for highly sensitive optical imaging methods is increasingly desirable in biomedical and material sciences.

Nonlinear optical imaging is an emerging technology that encompasses a range of optical phenomena. In a recent study by Prof. Koen Clays of the University of Leuven and Prof. Harry Anderson of Oxford University, a new group of chromophores based on pyropheophorbide-a methyl ester (PPa-OMe) was developed for the linear and nonlinear optical imaging of membrane potentials as well as biological imaging of structures through two-photon excited fluorescence (TPEF) and second harmonic generation (SGH) microscopy.

In TPEF, a fluorophore is excited by the simultaneous absorption of two photons in the infrared spectral range. In conventional one-photon fluorescence, the same transition to higher energy levels requires photons in the ultraviolet or visible range. The longer incident wavelength in TPEF leads to improved depth penetration in tissues, with reduced potential for photolytic damage. SHG, on the other hand, is a nonlinear process where two photons interact with a nonlinear material and are effectively combined to generate new photons with twice the energy. This process does not involve absorption of photons but relies on virtual energy states and can only occur in materials that exhibit a non-centrosymmetric structure.

Unlike incoherent processes such as fluorescence, coherent nonlinear optical spectroscopies generate different optical signals depending on the underlying processes. They have broad utility as biomedical tools, offering contrasting mechanisms to fluorescence emissions and provide a useful alternative to label-based imaging.

In this OBC publication, the electronic structure of PPa-OMe (1a) was altered to tune it’s linear and nonlinear optical properties. Porphyrins and related porphyrinoid chromophores inherently possess excellent linear and nonlinear optical properties due to their large, conjugated π-system. By incorporating both electron-donating and –accepting groups, a push-pull type system was generated in which greater SHG intensity was observed due to the increased polarization of its π-system. A hydrophilic group, bis-triethyleneglycol (TEG) amide, was attached to make PPa-OMe amphiphilic and was then suspended in lipid-based water in oil monolayer droplets—a simple model system used to probe potentials across cellular membranes. TPEF and SHG images of the bis-TEG amide attached dyes revealed that the TPEF and SHG involve transition dipole moments in different orientations. While TPEF is detectable in all directions around the sample, SHG is detected in the forward direction of the incident light meaning there is an overall cancelling of the SHG signal from anti-parallel dyes. In order to improve these systems, control over orientation within cell membranes is crucial however, chromophores based on these PPa-OMe derivatives are promising prototypes for future cell imaging studies.

To find out more see:

Push-pull pyropheophorbides for nonlinear optical imaging
Anjul Khadria, Yovan de Coene, Przemyslaw Gawel, Cécile Roche, Koen Clays and Harry L. Anderson
DOI: 10.1039/C6OB02319C


Victoria Corless is currently completing her Ph.D. in organic chemistry with Prof. Andrei Yudin at The University of Toronto. Her research is centred on the synthesis of kinetically amphoteric molecules, which offer a versatile platform for the development of chemoselective transformations with particular emphasis on creating novel biologically active molecules.

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Editor’s Choice – Meet our Associate Editors

Professor Jin-Quan Yu’s (Scripps Research Institute, La Jolla, California, USA) research centres around the discovery of novel reactions based on C-H activation.

Jin’s recommended articles:

C–H activation enables a rapid structure–activity relationship study of arylcyclopropyl amines for potent and selective LSD1 inhibitors
Shin Miyamura, Misaho Araki, Yosuke Ota, Yukihiro Itoh, Shusuke Yasuda, Mitsuharu Masuda, Tomoyuki Taniguchi, Yoshihiro Sowa, Toshiyuki Sakai, Takayoshi Suzuki, Kenichiro Itami, Junichiro Yamaguchi

Asymmetric synthesis of (−)-renieramycin T
Junhao Jia, Ruijiao Chen, Hao Liu, Xiong Li, Yuanliang Jia, Xiaochuan Chen


Professor Margaret Brimble (University of Auckland, New Zealand) is the Director of Medicinal Chemistry and a distinguished Professor at the University of Auckland. Her research program focuses on the synthesis of bioactive natural products, antimicrobial peptides and peptidomimetics.

Margaret’s recommended articles:

Concise diastereoselective synthesis of calcaripeptide C via asymmetric transfer hydrogenation/Pd-induced chiral allenylzinc as a key reaction
Gullapalli Kumaraswamy, Vykunthapu Narayanarao, Ragam Raju

Concise synthesis of calystegines B and B< intramolecular Nozaki–Hiyama–Kishi reaction
Hong-Yao Wang, Atsushi Kato, Kyoko Kinami, Yi-Xian Li, George W. J. Fleet, Chu-Yi Yu


Professor Christian Hackenberger’s (Leibniz-Institut für Molekulare Pharmakologie and Humboldt Universität zu Berlin, Germany) research focuses on the development of new bioorthogonal reactions to study protein function and in particular posttranslational modifications, addressing issues such as the study of the Alzheimer-relevant tau protein, antibody-drug conjugates and new methods for the delivery of functional proteins into cells.

Christian’s recommended articles:

Site-selective incorporation and ligation of protein aldehydes
Richard J. Spears, Martin A. Fascione

Protein ubiquitination via dehydroalanine: development and insights into the diastereoselective 1,4-addition step
Roman Meledin, Sachitanand M. Mali, Sumeet K. Singh, Ashraf Brik


Professor Lei Liu’s (Tsinghua University, China) research group is interested in all aspects of chemical protein synthesis.

Lei’s recommended articles:

Hybrid phase ligation for efficient synthesis of histone proteins
Ruixuan R. Yu, Santosh K. Mahto, Kurt Justus, Mallory M. Alexander, Cecil J. Howard, Jennifer J. Ottesen

Enediyne-based protein capture agents: demonstration of an enediyne moiety acting as a photoaffinity label
Joyee Das, Sayantani Roy, Swapnil Halnor, Amit Kumar Das and Amit Basak


We invite you to submit your urgent research to their editorial offices. With a reputation for quality and fast times to publication, OBC is the home of highly significant original research and reviews in all areas of organic chemistry, including organic synthesis, physical organic chemistry, supramolecular chemistry and bioorganic chemistry.

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*Access is free until 31/12/2016 through a registered RSC account.

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Improving liposomal boron carriers for effective boron neutron capture therapy

For years, radiotherapy has been an essential mode of noninvasive cancer therapy and advancements have led to life saving treatments for patients. In contrast to other conventional radiotherapies, boron neutron capture therapy (BNCT) is unique in its selective destruction of cancerous cells. BNCT is based on nuclear capture and fission reactions when nonradioactive 10B is irradiated with neutrons to yield excited 11B* which decays into high energy alpha particles and 7Li nuclei. Boron is preferentially accumulated into tumour cells though non-toxic carriers and the short length of the generated neutron beams (5-9 µm) destroys nearby cells leaving the surrounding healthy tissue intact.

The development of carrier systems that deliver sufficient amounts of boron to carry out effective destruction of all vicinal tumour cells has been a significant area of BNCT research for many years. A recent breakthrough made by Professors Atsushi Ikeda of Hiroshima University, Takeshi Nagasaki of Osaka City University and Kazuya Koumoto of Konan University has led to the development of a novel method for incorporating boron-containing moieties within hydrophobic lipid membranes.

Liposomes have been studied extensively as boron carriers and are promising candidates for BNCT as lipids display low toxicity. In the past, boron-containing liposomes have been prepared by dissolution of boron compounds in an internal water phase (Figure, A) or by using amphiphilic boron compounds embedded in the liposomal bilayer such that boron coats the outer surface of the lipid membrane (Figure, B). Unfortunately, even when these two methods are used in conjunction, the concentration of boron within the liposome is insufficient for effective BNCT and increasing liposomal dosing is problematic as high concentrations of lipids interfere with uptake mechanisms in the liver.

A novel method for boron transport is therefore of high value and in their recent OBC publication, the first example of boron incoporation into liposomal lipid membranes was successfully demonstrated. Key was the preparation of aryl pinacolato boronate esters bearing methyl groups at both ortho positions (Figure, R1 positions) of the phenyl rings which helped in stabilizing the boronate esters against hydrolysis.

While the concentration of boron within the lipid membrane was not particularly high, this study has unlocked yet another avenue through which non-toxic liposomal boron carrier concentrations can be improved and when used with previous boron loading methods, produces liposomes with sufficient boron concentrations to carry out BCNT. This result will no doubt enhance BNCT and lead to critical, life saving therapies for cancer patients.

To find out more see:

Lipid-membrane-incorporated arylboronate esters as agents for boron neutron capture therapy
Masafumi Ueda, Kengo Ashizawa, Kouta Sugikawa, Kazuya Koumoto, Takeshi Nagasaki and Atsushi Ikeda
DOI:10.1039/C6OB02142E


Victoria Corless is currently completing her Ph.D. in organic chemistry with Prof. Andrei Yudin at The University of Toronto. Her research is centred on the synthesis of kinetically amphoteric molecules, which offer a versatile platform for the development of chemoselective transformations with particular emphasis on creating novel biologically active molecules.

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An efficient second-generation total synthesis of Aplyronine A

The importance of natural products in health and medicine is enormous owing to their diverse biological activities and their role as a basis for drug development. Endeavours in total synthesis have attracted some of the most talented organic chemists–providing intellectual and creative outlets–and have been central to the evolution and technical development of organic synthesis.

In the early 1990’s, Professor Hideo Kigoshi of the University of Tsukuba reported the first total synthesis of the marine macrolide Aplyronine A which is still a highly desirable synthetic target due to its potent and unique biological properties.

In collaboration with Professor Ichiro Hayakawa of Okayama University, the group has recently published a highly efficient second-generation total synthesis of Aplyronine A which requires fewer synthetic steps and boasts an improved overall yield. Issues with poor stereoselectivity, regioselectivity and isomerization were overcome through the optimization of a Ni/Cr-mediated coupling.

As shown in the retrosynthetic pathway below, Aplyronine A was obtained from 10, the same intermediate used in the first generation synthesis however, instead of the Julia coupling between ketone and sulfone-containing fragments, the macrolactone 11 was cyclized via an intramolecular Ni/Cr-mediated coupling. This modification drastically reduced the number of unwanted byproducts obtained from the Julia coupling and eliminated the need to employ a modified Yamaguchi lactonization which had resulted in the formation of an undesired 26-membered lactone that required an additional isomerization to yield the desired product. Precursor 11 was constructed through an intermolecular esterification between carboxylic acid 12 and alcohol 13 which were each prepared through asymmetric Ni/Cr-mediated couplings. In the case of the carboxylic acid, route efficiency was further enhanced as this strategy resulted in the simultaneous formation of the C14–C15 (E)-trisubstituted double bond and the C13 stereogenic center through the use of a chiral ligand.

In addition to establishing an efficient synthetic pathway to Aplyronine A, the Ni/Cr-mediated coupling has significant potential in the preparation of structurally diverse derivatives which may result in enhanced biological activity and the discovery of a novel lead.

The popularity of natural products as synthetic targets will continue as they provide unparalleled inspiration for drug leads and the synthesis of non-natural compounds. Strategies to develop concise and efficient synthetic routes are significantly important not only in terms of their utility in medicine but in the downstream application of novel synthetic methodologies developed during the process of their total synthesis.

To find out more see:

Second generation total synthesis of aplyronine A featuring Ni/Cr-mediated coupling reactions
Ichiro Hayakawa, Keita Saito, Sachiko Matsumoto, Shinichi Kobayashi, Ayaka Taniguchi, Kenichi Kobayashi, Yusuke Fujii, Takahiro Kanekob and Hideo Kigoshi
DOI: 10.1039/C6OB02241C


Victoria Corless is currently completing her Ph.D. in organic chemistry with Prof. Andrei Yudin at The University of Toronto. Her research is centred on the synthesis of kinetically amphoteric molecules, which offer a versatile platform for the development of chemoselective transformations with particular emphasis on creating novel biologically active molecules.

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Halogen bonding in anion recognition and sensing

As part of an ongoing research programme in host-guest supramolecular chemistry, Professor Paul Beer of Oxford University has been developing methods for the synthesis of interlocking molecular architectures based on halogen bond donor motifs.

Halogen bonding interactions—the noncovalent, attractive interaction between an electron deficient halogen (X) and a Lewis base (B)—are slowly becoming more prevalent as a complimentary alternative to more commonly used binding interactions. Since its discovery in the late 1960’s, anion recognition chemistry has developed from an interesting area of academic research to a pillar of supramolecular chemistry. In recent years, there has been dramatic advancements within the field that have resulted in a number of practical applications such as organocatalysis involving ion complexation, ion extraction from mixtures and the development of sensory devices and molecular switches.

Anions play fundamental roles in a large number of biological, chemical, medicinal and environmental processes and nature’s binders typically complex anions through intricate networks of electrostatic interactions. The ability to mimic the selectivity of biological systems in artificial settings has been a longstanding challenge in this field.

In a recent OBC publication, the Beer group successfully synthesized two mono-cationic and two dicationic halogen and hydrogen bonding rotaxane anion recognition systems (see figure) and successfully demonstrated the enhanced binding affinity and selectivity of the dicationic halogen bonding analogue relative to its hydrogen bond-containing counterpart. In addition, the dicationic halogen bonding system displayed an enhanced preference for binding to bromine anions over other halides, nitrate and dihydrogen phosphate oxoanions. NMR binding studies reveal that the enhanced strength and selectivity of halide recognition is the result of chelated charge assisted halogen bonding interactions in the dicationic system. This study elegantly demonstrates efforts in exploiting the XB chelate effect to improve anion binding affinity and selectivity. Halogen bonding is still an emerging area of research however, examples such as this highlight its utility as a complementary mode of binding when compared to other more established interactions and will no doubt lead to an evolution in anion receptor design.


To find out more see:

Chelated charge assisted halogen bonding enhanced halide recognition by a pyridinium-iodotriazolium axle containing [2]rotaxane
Alexander E. Hess and Paul D. Beer
DOI: 10.1039/C6OB01851C


Victoria Corless is currently completing her Ph.D. in organic chemistry with Prof. Andrei Yudin at The University of Toronto. Her research is centred on the synthesis of kinetically amphoteric molecules, which offer a versatile platform for the development of chemoselective transformations with particular emphasis on creating novel biologically active molecules.

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Congratulations to Ben Feringa

The prestigious Nobel Prize in Chemistry 2016 was awarded jointly to Jean-Pierre Sauvage, Sir J. Fraser Stoddart and Bernard L. Feringa for their outstanding contributions to the design and synthesis of molecular machines. Many congratulations to all of them!


Ben Feringa has not only significantly influenced our journal as the  inaugural Chair of Organic & Biomolecular Chemistry from 2003 to 2007, but he has also so far published an impressive 40 manuscripts in OBC since it’s launch. We would like to mark this special occasion by highlighting only a few of them here:


Bacterial patterning controlled by light exposure
Willem A. Velema, Jan Pieter van der Berg, Wiktor Szymanski, Arnold J. M. Driessen and Ben L. Feringa

Mild Ti-mediated transformation of t-butyl thio-ethers into thio-acetates
Thomas C. Pijper, Jort Robertus, Wesley R. Browne and Ben L. Feringa

Silanization of quartz, silicon and mica surfaces with light-driven molecular motors: construction of surface-bound photo-active nanolayers
Gábor London, Gregory T. Carroll and Ben L. Feringa

Chiral separation by enantioselective liquid-liquid extraction
Boelo Schuur, Bastiaan J. V. Verkuijl, Adriaan J. Minnaard, Johannes G. de Vries, Hero J. Heeres and Ben L. Feringa

Catalytic asymmetric conjugate addition of dialkylzinc reagents to α,β-unsaturated sulfones
Pieter H. Bos, Beatriz Maciá, M. Ángeles Fernández-Ibáñez, Adriaan J. Minnaard and Ben L. Feringa

Copper-free ‘click’: 1,3-dipolar cycloaddition of azides and arynes
Lachlan Campbell-Verduyn, Philip H. Elsinga, Leila Mirfeizi, Rudi A. Dierckx and Ben L. Feringa

A redesign of light-driven rotary molecular motors
Michael M. Pollard, Auke Meetsma and Ben L. Feringa

Photoresponsive dithienylethene-urea-based organogels with “reversed” behavior
Masako Akazawa, Kingo Uchida, Jaap J. D. de Jong, Jetsuda Areephong, Marc Stuart, Giuseppe Caroli, Wesley R. Browne and Ben L. Feringa

Rhodium/phosphoramidite-catalyzed asymmetric arylation of aldehydes with arylboronic acids
Richard B. C. Jagt, Patrick Y. Toullec, Johannes G. de Vries, Ben L. Feringa and Adriaan J. Minnaard

Enantioselective synthesis of β2-amino acids using rhodium-catalyzed hydrogenation
Rob Hoen, Theodora Tiemersma-Wegman, Barbara Procuranti, Laurent Lefort, Johannes G. de Vries, Adriaan J. Minnaard and Ben L. Feringa


If you are interested please find a full list of his OBC articles here.

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The development of novel diagnostic tools in the treatment of infectious diseases

Antibiotic resistance has become a major clinical issue in recent decades and is one of the greatest health problems of our time. Tuberculosis (TB) has been present for thousands of years and according to WHO is globally, one of the leading causes of death from a curable infectious disease. The advent of the antibiotic era represented a major breakthrough for those suffering from TB however the spread of multi-drug resistant strains, which have propagated due to incorrect drug use, prescription errors or low patient compliance has become a major threat to disease control. In order to mitigate this, new drugs and diagnostic tools are desperately needed.

A collaborative study between Peter Woodruff of the University of Southern Maine and Benjamin Swarts of Central Michigan University has looked at in vivo nuclear imaging as a non-invasive means of diagnosing TB as well as disease monitoring and treatment response in real time. This means that vital information regarding disease progression that is complimentary to other forms of diagnosis can be quickly attained.

Current imaging methods rely on radiotracers to provide information on host inflammatory response to the infection however there can be some inaccuracy due to a lack of specificity in cellular uptake. An attractive alternative are radiolabeled analogues of antimycobacterial compounds which specifically label the desired bacteria and can provide in vivo imaging.

In the past, the disaccharide trehalose and its analogues have been applied to study metabolic mechanisms of mycobacteria and provide a means to design specifc probes for the mycobacteria induced infections. In this current publication, the researchers successfully developed a robust and concise synthetic route to access a number of fluorinated trehalose (FDTre) analogues using a rapid chemoenzymatic process followed by a simple purification by ion exchange chromatography. This drastic improvement compared to previously reported synthetic routes, which require lengthy reaction times and often result in low recovery, makes this new route highly desirable as well as compatible with timescale required for radiolabel synthesis. In addition, the authors demonstrated the ability of their FDTre analogues to be successfully recognized and taken up through trehalose transporter pathways in M. smegmatis and pathogenic mycobacteria, allowing for FDTre accumulation within cells.

Further investigations are still required to overcome remaining hurdles such as the cost associated with synthesis, assessment of uptake efficiencies at concentrations closer to in vivo radiotracer concentrations as well as evaluation of the speficity of the FDTre radioprobes. Regardless, the methodology established in this study provides an exceptional platform for the development of a new class of nuclear imaging probes to help treat multi-drug resistant TB and other mycobacterial infections.



To find out more see:

Deoxyfluoro-D-trehalose (FDTre) analogues as potential PET probes for imaging mycobacterial infection
Sarah R. Rundell, Zachary L. Wagar, Lisa M. Meints, Claire D. Olson, Mara K. O’Neill, Brent F. Piligian, Anne W. Poston, Robin J. Hood, Peter J. Woodruff and Benjamin M. Swarts
DOI: 10.1039/C6OB01734G


Victoria Corless is currently completing her Ph.D. in organic chemistry with Prof. Andrei Yudin at The University of Toronto. Her research is centred on the synthesis of kinetically amphoteric molecules, which offer a versatile platform for the development of chemoselective transformations with particular emphasis on creating novel biologically active molecules.

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Application of the paranemic crossover motif in 2D self-assembly

Nature uses a cooperative interplay of noncovalent interactions to control complex self-assembly of organized nanostructures with extreme precision. Taking this as inspiration, the field of structural DNA nanotechnology has been working toward the development of programmable, self-assembling nanomaterials and motion control at the nanoscale level by exploiting the remarkable molecular recognition properties of DNA. A number of basic structural motifs using branched DNA have been designed and are key elements for the construction of supramolecular arrays, molecular scaffolds and mechanical and logical nanodevices.

The paranemic crossover (PX) motif, as described in a recent OBC publication, has been of particular interest due to its unique ability to behave as both a self-assembling building block or tile and cohesive linker. Its application, until now, has been limited to 1D arrays as the level of flexibility within PX tiles needed to be controlled in order to access well-defined 2D and 3D DNA structures.

PX DNA arises from the fusion of two parallel double helices through strand cross-overs wherever the two strands come in contact. The component double strands are not linked and can hypothetically pair with each other indefinitely in a manner similar to the pairing of a buldged double helix. Advantageously, the PX structural motif reduces the need for sticky end cohesion, traditionally used in DNA-based self-assembly, which leads to an overall increase in nanostructure stability as sticky ends are susceptible to enzymatic degradation. In addition, complex DNA nanostructures made solely from PX motifs reduce topological problems during self-assembly thus minimizing error.

Researchers from the National Centre for NanoScience and Technology in Beijing, Anhui Normal University in China and Purdue University in the United States have collaboratively studied various structural parameters in order to optimize PX DNA’s ability to participate in the assembly of highly desirable 2D nanostructures. By varying the number of base pairs that make up the major (wide, W) and minor (narrow, N) grooves of the bulged double helix, several versions of PX tiles were prepared. Optimal parameters were observed when T65 (according to the formula TWN), which assembled into an extended, flat and regular 2D array (see image). Any deviation from this number of base pairs resulted in the tile becomes stressed and twisted leading to random aggregates.

This discovery has made possible the application of the highly desirable PX motif in 2D nanoconstruction which will no doubt lead to the synthesis of more stable and structurally and functionally intricate DNA self-assembling nanostructures.

To find out more see:

The study of the paranemic crossover (PX) motif in the context of self-assembly of DNA 2D crystals
Weili Shen, Qing Liu, Baoquan Ding, Zhiyong Shen, Changqing Zhu and Chendge Mao
DOI: 10.1039/c6ob01146b


Victoria Corless is currently completing her Ph.D. in organic chemistry with Prof. Andrei Yudin at The University of Toronto. Her research is centred on the synthesis of kinetically amphoteric molecules, which offer a versatile platform for the development of chemoselective transformations with particular emphasis on creating novel biologically active molecules.
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Engineering artificial metalloenzymes for applications in photoredox catalysis

Synthetic methodologies to control the selectivity and specificity of catalytic reactions remain the subject of intense research due to the importance of chiral compounds in pharmaceuticals, agrochemicals and functional materials. Homogenous catalysis takes advantage of weak interactions between the substrate, catalyst and groups distal to the active site to impart selectivity. Such features are ubiquitous in enzymes which display exceptionally high levels of stereochemical control and activity. In order to exploit the advanced capabilities of such enzymes for selective catalytic transformations, researchers have linked transition metal catalysts with different biological scaffolds–proteins, peptides, DNA–to create artificial metalloenzymes.

Since their inception in the late 1970’s, artificial metalloenzymes have emerged as a vibrant area of research with numerous examples of a variety of catalytic transformations reported alongside creative methods for incorporating the transition metal complex into the biomolecular scaffold. Key to their design is the ‘second coordination sphere’ provided by the biological scaffold where supramolecular interactions within the active site contribute to the rate and enantioselectivity of the system.

Prof. Thomas Ward and Prof. Oliver Wenger of the University of Basel have recently reported a novel biotin-streptavidin system equipped with an anchored photosensitizer capable of undergoing electron transfers between the biotinylated electron donor and ruthenium(II)-labeled streptavidin.

In the past, studies of the luminescent properties of biotinylated d6 metal complexes, common in photoredox catalysis, have been carried out for the purposes of cell imaging and ruthenium and rhenium complexes have been employed in the elucidation of electron tunneling pathways of various proteins. The application of phototriggered electron transfers to ruthenium photosensitizers, up until this point, had not yet been realized and this recent discovery demonstrates a significant advancement within this field.

This new biotin-streptavidin artificial metalloenzyme contains a ruthenium catalyst and photosensitizers embedded within the biotin binding pocket of streptavidin through covalent interactions with non-native cysteine residues. Their performance in various electron transfer studies demonstrates their potential to behave as advanced photoredox catalysts and given the diversity of reactions amenable to photoredox processes, these novel artificial metalloenzymes will provide unique opportunities within selective catalysis.

To find out more see:

Light-driven electron injection from a biotinylated triarylamine donor to [Ru(diimine)3]2+-labeled streptavidin
Sascha G. Keller, Andrea Pannwitz, Fabian Schwizer, Juliane Klehr, Oliver S. Wenger and Thomas R. Ward
DOI: 10.1039/C6OB01273F


Victoria Corless is currently completing her Ph.D. in organic chemistry with Prof. Andrei Yudin at The University of Toronto. Her research is centred on the synthesis of kinetically amphoteric molecules, which offer a versatile platform for the development of chemoselective transformations with particular emphasis on creating novel biologically active molecules.

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