Over the past 25 years, organic field-effect transistors (OFETs) have witnessed impressive improvements in materials performance by 3–4 orders of magnitude, and many of the key materials discoveries have been published in Advanced Materials. This includes some of the most recent demonstrations of organic field-effect transistors with performance that clearly exceeds that of benchmark amorphous silicon-based devices. In this article, state-of-the-art in OFETs are reviewed in light of requirements for demanding future applications, in particular active-matrix addressing for flexible organic light-emitting diode (OLED) displays. An overview is provided over both small molecule and conjugated polymer materials for which field-effect mobilities exceeding > 1 cm2 V–1 s–1 have been reported. Current understanding is also reviewed of their charge transport physics that allows reaching such unexpectedly high mobilities in these weakly van der Waals bonded and structurally comparatively disordered materials with a view towards understanding the potential for further improvement in performance in the future.

/pdf/25th-anniversary-article-organic-field-effect-transistors-56cmlfirhg.pdf

25th anniversary article: organic field-effect transistors: the path beyond amorphous silicon.

One of the advantages of organic over inorganic semiconductors is they can be grown from solution, but their electrical mobility is often poor. Yuan et al. report a technique for fabricating organic transistors with mobilities far beyond that of amorphous silicon and close to that of polycrystalline silicon.

/pdf/ultra-high-mobility-transparent-organic-thin-film-4csee58y23.pdf

Ultra-high mobility transparent organic thin film transistors grown by an off-centre spin-coating method

https://www.scripps.edu/cravatt/pdf/SpeersCravattCB2004.pdf

Profiling Enzyme Activities In Vivo Using Click Chemistry Methods

Glucose detection is of great significance in biomedical applications. Principles, methods and recent developments in electrochemical glucose sensors are reviewed here. Special attention is given to the discussion on some problems and bottlenecks in areas of nonenzymatic and enzymatic (glucose oxidase-based) amperometric glucose sensing.

/pdf/recent-advances-in-electrochemical-glucose-biosensors-a-4zf5h9p6ys.pdf

Recent advances in electrochemical glucose biosensors: a review

Spatially addressable DNA nanostructures facilitate the self-assembly of heterogeneous elements with precisely controlled patterns. Here we organized discrete glucose oxidase (GOx)/horseradish peroxidase (HRP) enzyme pairs on specific DNA origami tiles with controlled interenzyme spacing and position. The distance between enzymes was systematically varied from 10 to 65 nm, and the corresponding activities were evaluated. The study revealed two different distance-dependent kinetic processes associated with the assembled enzyme pairs. Strongly enhanced activity was observed for those assemblies in which the enzymes were closely spaced, while the activity dropped dramatically for enzymes as little as 20 nm apart. Increasing the spacing further resulted in a much weaker distance dependence. Combined with diffusion modeling, the results suggest that Brownian diffusion of intermediates in solution governed the variations in activity for more distant enzyme pairs, while dimensionally limited diffusion of interme...

Interenzyme Substrate Diffusion for an Enzyme Cascade Organized on Spatially Addressable DNA Nanostructures

Many enzymes contain a nondiffusible organic cofactor, often termed a prosthetic group, which is located in the active site and essential for the catalytic activity of the enzyme. These cofactors can often be extracted from the protein to yield the respective apoenzyme, which can subsequently be reconstituted with an artificial analogue of the native cofactor. Nowadays a large variety of synthetic cofactors can be used for the reconstitution of apoenzymes and, thus, generate novel semisynthetic enzymes. This approach has been refined over the past decades to become a versatile tool of structural enzymology to elucidate structure-function relationships of enzymes. Moreover, the reconstitution of apoenzymes can also be used to generate enzymes possessing enhanced or even entirely new functionality. This Review gives an overview on historical developments and the current state-of-the-art on apoenzyme reconstitution.

Apoenzyme Reconstitution as a Chemical Tool for Structural Enzymology and Biotechnology

Two mechanism-based activity probes, adopting a cassette-like design, for protein tyrosine phosphatases (PTPs) were synthesized. Both probes carry a phosphate group that serves as the recognition head for the target PTPs but differ in their reporter groups; probe LCL-1 uses a dansyl fluorophore, while LCL-2 has a biotin reporter group. LCL-1 and LCL-2 are specifically activated by phosphatase, leading to its covalent labeling, as exemplified with PTP-1B. However, they show no activation with other classes of hydrolases, including trypsin and ‚-galactosidase. LCL-1 and LCL-2 thus represent the first example of class-selective probes for phosphatases.

Design and Synthesis of Class-Selective Activity Probes for Protein Tyrosine Phosphatases

Cytochrome P450 BM3 is a versatile enzyme, which holds great promise for applications in biocatalysis and biomedicine. We here report on the generation of a hybrid DNA-protein device based on the two subdomains of BM3, the reductase domain BMR and the porphyrin domain BMP. Both subdomains were fused genetically to the HaloTag protein, a self-labeling enzyme, allowing for the bioconjugation with chloroalkane-modified oligonucleotides. The subdomain-DNA-chimeras could be reassembled by complementary oligonucleotides, thus leading to reconstitution of the monooxygenase activity of BM3 holoenzyme, as demonstrated by conversion of the reporter substrate 12-pNCA. Arrangement of the two chimeras on a switchable DNA scaffold allowed one to control the distance between both subdomains, as indicated by the DNA-dependent activity of the holoenzyme. Furthermore, a switchable chimeric device was constructed, in which monooxygenase activity could be turned off by DNA strand displacement. This study demonstrates that P450 BM3 engineering and strategies of DNA nanotechnology can be merged to open up novel ways for the development of novel screening systems or responsive catalysts with potential applications in drug delivery.

DNA-Mediated Assembly of Cytochrome P450 BM3 Subdomains

A series of contorted tetrabenzo[a,d,j,m]coronenes (TBCs) substituted with four fluoro-, chloro-, or methyl groups at 2,7,12,17-positions were synthesized and characterized. Except for the one with methyl substituents, which exhibits a shifted π–π stacking, the rest all show cofacial π–π stacking with small parallel displacements. One-dimensional growth along the stacking direction was observed in the single crystals for all derivatives. A systematic comparison of the crystal packing and the calculated electronic coupling/mobility with the measured field-effect mobility for single-crystal field-effect transistors shows a good correlation.

Contorted Tetrabenzocoronene Derivatives for Single Crystal Field Effect Transistors: Correlation between Packing and Mobility

Enhanced and anisotropic field-effect mobility of thin-film transistors based on pentacene was obtained on a substrate covered with a prerubbed, self-assembled monolayer (SAM) of n-alkyltrichlorosilane. The field-effect mobility along the rubbing direction increased by a factor of ∼15 on rubbed n-nonyltrichlorosilane-modified surface, whereas on n-octadecyltrichlorosilane-modified surface, an increase by a factor of 2–4 was observed. The structures of pentacene films deposited on the SAM/rubbed SAM were characterized by powder x-ray diffraction, atomic force microscopy, and carbon K-edge near edge x-ray fine structure spectroscopy. An in-plane alignment effect on the pentacene packing and film morphology is proposed.

Chi-Hsien Kuo

Papers

Apoenzyme Reconstitution as a Chemical Tool for Structural Enzymology and Biotechnology

Design and Synthesis of Class-Selective Activity Probes for Protein Tyrosine Phosphatases

DNA-Mediated Assembly of Cytochrome P450 BM3 Subdomains

Contorted Tetrabenzocoronene Derivatives for Single Crystal Field Effect Transistors: Correlation between Packing and Mobility

Anisotropic field-effect mobility of pentacene thin-film transistor: Effect of rubbed self-assembled monolayer