Visualizing biochemical activities in living cells through chemistry

The development of molecular probes to visualize cellular processes is an important challenge in chemical biology. One possibility to create such cellular indicators is based on the selective labeling of proteins with synthetic probes in living cells. Over the last years, our laboratory has developed different labeling approaches for monitoring protein activity and for localizing synthetic probes inside living cells. In this article, we review two of these labeling approaches, the SNAP-tag and CLIP-tag technologies, and their use for studying cellular processes.     

Nutritional knowledge and consumption frequency of foods--a case study

The relationship between nutritional knowledge and the consumption frequency of preferred food-types was studied among one sample of Uruguayan consumers. A locally-adapted version of Parmenter & Wardle's General Nutrition Knowledge Questionnaire and a food consumption survey based on 39 food groups were completed by a total of 270 participants. Cluster Analysis enabled the identification of two clusters showing different levels of nutritional knowledge--cluster 1 (n = 177) and cluster 2 (n = 93), providing an average of 73.6% and 52.9% of correct answers, respectively. These clusters differed significantly (p < or = 0.05) in age and educational distribution--cluster 1 was composed mainly by older adults and persons with a higher educational level. A number of areas were identified where nutritional knowledge was extremely poor, as was the case with the recommended daily fruit and vegetable intake and the caloric content of the nutrients. Overall, nutritional knowledge was found to have a positive influence on food preferences and consumption frequency, those participants with a higher nutritional knowledge reporting a higher consumption of fruits, vegetables and low-fat products, in addition to a lower consumption of high-fat and high-sugar foods.     

Urolithin as a converging scaffold linking ellagic acid and coumarin analogues: design of potent protein kinase CK2 inhibitors

Casein kinase 2 (CK2) is a ubiquitous, essential, and highly pleiotropic protein kinase; its abnormally high constitutive activity is suspected to underlie its pathogenic potential in neoplasia and other relevant diseases. Previously, using different in silico screening approaches, two potent and selective CK2 inhibitors were identified by our group: ellagic acid, a naturally occurring tannic acid derivative (K(i)=20 nM) and 3,8-dibromo-7-hydroxy-4-methylchromen-2-one (DBC, K(i)=60 nM). Comparing the crystallographic binding modes of both ellagic acid and DBC, an X-ray structure-driven merging approach was taken to design novel CK2 inhibitors with improved target affinity. A urolithin moiety is proposed as a possible bridging scaffold between the two known CK2 inhibitors, ellagic acid and DBC. Optimization of urolithin A as the bridging moiety led to the identification of 4-bromo-3,8-dihydroxy-benzo[c]chromen-6-one as a novel, potent and selective CK2 inhibitor, which shows a K(i) value of 7 nM against the protein kinase, representing a significant improvement in affinity for the target compared with the two parent fragments.     

A facile spin-cast route for cation exchange of multilayer perpendicularly-aligned nanorod assemblies

A facile spin cast route was developed to convert perpendicularly aligned nanorod assemblies of cadmium chalcogenides into their silver and copper analogues. The assemblies are rapidly cation exchanged without affecting either the individual rod dimensions or collective superlattice order extending over several multilayers.     

Mapping local microstructure and mechanical performance around carbon nanotube grafted silica fibres: methodologies for hierarchical composites

The introduction of carbon nanotubes (CNTs) modifies bulk polymer properties, depending on intrinsic quality, dispersion, alignment, interfacial chemistry and mechanical properties of the nanofiller. These effects can be exploited to enhance the matrices of conventional microscale fibre-reinforced polymer composites, by using primary reinforcing fibres grafted with CNTs. This paper presents a methodology that combines atomic force microscopy, polarised Raman spectroscopy, and nanoindentation techniques, to study the distribution, alignment and orientation of CNTs in the vicinity of epoxy-embedded micrometre-scale silica fibres, as well as, the resulting local mechanical properties of the matrix. Raman maps of key features in the CNT spectra clearly show the CNT distribution and orientation, including a 'parted' morphology associated with long grafted CNTs. The hardness and indentation modulus of the epoxy matrix were improved locally by 28% and 24%, respectively, due to the reinforcing effects of CNTs. Moreover, a slower stress relaxation was observed in the epoxy region containing CNTs, which may be due to restricted molecular mobility of the matrix. The proposed methodology is likely to be relevant to further studies of nanocomposites and hierarchical composites.     

Assorted analytical and spectroscopic techniques for the optimization of the defect-related properties in size-controlled ZnO nanowires

In this article, the important role of the intrinsic defects in size-controlled ZnO nanowires (NWs) which play a critical role in the properties of the NWs, was studied with a combined innovative experimental analysis. The NWs prepared by both the aqueous solution method and chemical vapour deposition process were of increasing length and decreasing size-to-volume (S/V) ratio. The combined approach involved different analytical and spectroscopic techniques and from the correlation between the different measurements, the concentration of the oxygen vacancies jointly with the zinc interstitials defects and the zinc vacancy defects was observed to be positively or negatively correlated, respectively, with the magnitude of the photoluminescence intensity and radiative lifetimes. Furthermore, the experimental results also suggest that the oxygen vacancy defects are not only spatially located on the surface of the NW but an increasing fraction of the total oxygen vacancy defects connected with the green emission is also located in an annulus region beneath the surface as the ZnO NWs elongate. On the other hand, as the donor concentration plays a critical function in the properties of the ZnO NWs, an analytical model was derived for the calculation of the donor concentration of the NWs directly from its reverse-biased current-voltage characteristics obtained from the conductive atomic force microscopy measurements.     

A multiplexed separation of iron oxide nanocrystals using variable magnetic fields

The size-dependent magnetic properties of nanocrystals are exploited in a separation process that distinguishes particles based on their diameter. By varying the magnetic field strength, four populations of magnetic materials were isolated from a mixture. This separation is most effective for nanocrystals with diameters between 4 and 16 nm.     

Organic-based molecular switches for molecular electronics

In a general sense, molecular electronics (ME) is the branch of nanotechnology which studies the application of molecular building blocks for the fabrication of electronic components. Among the different types of molecules, organic compounds have been revealed as promising candidates for ME, due to the easy access, great structural diversity and suitable electronic and mechanical properties. Thanks to these useful capabilities, organic molecules have been used to emulate electronic devices at the nanoscopic scale. In this feature article, we present the diverse strategies used to develop organic switches towards ME with special attention to non-volatile systems.     

Increasing the thermostability of sucrose phosphorylase by a combination of sequence- and structure-based mutagenesis

Sucrose phosphorylase is a promising biocatalyst for the glycosylation of a wide variety of acceptor molecules, but its low thermostability is a serious drawback for industrial applications. In this work, the stability of the enzyme from Bifidobacterium adolescentis has been significantly improved by a combination of smart and rational mutagenesis. The former consists of substituting the most flexible residues with amino acids that occur more frequently at the corresponding positions in related sequences, while the latter is based on a careful inspection of the enzyme's crystal structure to promote electrostatic interactions. In this way, a variant enzyme could be created that contains six mutations and whose half-life at the industrially relevant temperature of 60 °C has more than doubled compared with the wild-type enzyme. An increased stability in the presence of organic co-solvents could also be observed, although these effects were most noticeable at low temperatures.     

Fullerene C₆₀ as a multifunctional system for drug and gene delivery

The fullerene family, and especially C(60), has delighted the scientific community during the last 25 years with perspective applications in a wide variety of fields, including the biological and the biomedical domains. Several biomedical uses have been explored using water-soluble C(60)-derivatives. However, the employment of fullerenes for drug delivery is still at an early stage of development. The design and synthesis of multifunctionalized and multimodal C(60) systems able to cross the cell membranes and efficiently deliver active molecules is an attracting challenge that involves multidisciplinary strategies. Promising results have emerged in the last years, bringing fullerenes again to the front of interest. Herein, the state of the art of this emerging field is presented and illustrated with some of the most representative examples.