Nanostructured Micelle Nanotubes Self-Assembled from Dinucleobase Monomers in Water.

Despite the central importance of aqueous amphiphile assemblies in science and industry, the size and shape of these nano-objects is often difficult to control with accuracy owing to the non-directional nature of the hydrophobic interactions that sustain them. Here, using a bioinspired strategy that consists of programming an amphiphile with shielded directional Watson-Crick hydrogen-bonding functions, its self-assembly in water was guided toward a novel family of chiral micelle nanotubes with partially filled lipophilic pores of about 2 nm in diameter. Moreover, these tailored nanotubes are successfully demonstrated to extract and host molecules that are complementary in size and chemical affinity.

Elucidating Noncovalent Reaction Mechanisms: G-Quartet as an Intermediate in G-Quadruplex Assembly.

In analogy to covalent reactions, the understanding of noncovalent association pathways is fundamental to influence and control any supramolecular process. Following an approach that is reminiscent of covalent methodologies, we study here, for the first time, the mechanism of G-quadruplex formation in organic solvents. Our results support a reaction pathway in which the cation shifts the equilibrium towards a G-quartet transient intermediate, which then acts as a template in the formation of the G-quadruplex product.

Noncovalent Synthesis of Self-Assembled Nanotubes through Decoupled Hierarchical Cooperative Processes.

Because of their wide number of biological functions and potential applications, self-assembled nanotubes constitute highly relevant targets in noncovalent synthesis. Herein, we introduce a novel approach to produce supramolecular nanotubes with defined inner and outer diameters from rigid rod-like monomers programmed with complementary nucleobases through two distinct, decoupled cooperative processes of different hierarchy and acting in orthogonal directions: chelate cooperativity, responsible for the formation of robust Watson-Crick H-bonded cyclic tetramers, and nucleation-growth cooperative polymerization.

Reversible dispersion and release of carbon nanotubes via cooperative clamping interactions with hydrogen-bonded nanorings.

Due to their outstanding electronic and mechanical properties, single-walled carbon nanotubes (SWCNTs) are promising nanomaterials for the future generation of optoelectronic devices and composites. However, their scarce solubility limits their application in many technologies that demand solution-processing of high-purity SWCNT samples. Although some non-covalent functionalization approaches have demonstrated their utility in extracting SWCNTs into different media, many of them produce short-lived dispersions or ultimately suffer from contamination by the dispersing agent. Here, we introduce an unprecedented strategy that relies on a cooperative clamping process. When mixing (6,5)SWCNTs with a dinucleoside monomer that is able to self-assemble in nanorings via Watson-Crick base-pairing, a synergistic relationship is established. On one hand, the H-bonded rings are able to associate intimately with SWCNTs by embracing the tube sidewalls, which allows for an efficient SWCNT debundling and for the production of long-lasting SWCNT dispersions of high optical quality along a broad concentration range. On the other, nanoring stability is enhanced in the presence of SWCNTs, which are suitable guests for the ring cavity and contribute to the establishment of multiple cooperative noncovalent interactions. The inhibition of these reversible interactions, by just adding, for instance, a competing solvent for hydrogen-bonding, proved to be a simple and effective method to recover the pristine nanomaterial with no trace of the dispersing agent.

How Large Can We Build a Cyclic Assembly? Impact of Ring Size on Chelate Cooperativity in Noncovalent Macrocyclizations.

Self-assembled systems rely on intramolecular cooperative effects to control their growth and regulate their shape, thus yielding discrete, well-defined structures. However, as the size of the system increases, cooperative effects tend to dissipate. We analyze here this situation by studying a set of oligomers of different lengths capped with guanosine and cytidine nucleosides, which associate in cyclic tetramers by complementary Watson-Crick H-bonding interactions. As the monomer length increases, and thus the number of C(sp)-C(sp2 ) σ-bonds in the π-conjugated skeleton, the macrocycle stability decreases due to a notable reduction in effective molarity (EM), which has a clear entropic origin. We determined the relationship between EM or ΔS and the number of σ-bonds, which allowed us to predict the maximum monomer lengths at which cyclic species would still assemble quantitatively, or whether the cyclic species would not able to compete at all with linear oligomers over the whole concentration range.

Mitochondrial haplogroups associated with end-stage heart failure and coronary allograft vasculopathy in heart transplant patients.

AIMS: Mitochondrial haplogroups are known to influence individual predisposition to a wide spectrum of metabolic and degenerative diseases, including ischaemic cardiovascular diseases. We have examined the influence of the mitochondrial DNA (mtDNA) background on the development of human end-stage heart failure (HF) in patients undergoing heart transplantation. The influence of mtDNA haplogroups on the incidence of transplant-related complications, mainly cardiac allograft vasculopathy (CAV), and on post-transplant survival was also studied. METHODS AND RESULTS: The most common mitochondrial haplogroups in European populations were genotyped in 450 heart transplant recipients, 248 heart transplant donors, and 206 healthy controls. Mitochondrial haplogroups were determined by PCR amplification of short mtDNA fragments, followed by restriction fragment length polymorphism analysis. After adjustment for age and sex the frequency of haplogroup H was significantly higher in heart transplant recipients than in controls [OR: 1.86 (95% confidence intervals, CI: 1.27-2.74), P= 0.014], and in heart donors [OR: 1.47 (95% CI: 0.99-2.19), P= 0.032]. Likewise, haplogroup Uk was found significantly more frequently among CAV patients than in non-CAV heart allograft recipients [OR: 4.1 (95% CI: 1.51-11.42), P= 0.042]. Finally, heart donor haplogroups had no influence on the morbidity or mortality after heart transplantation. CONCLUSIONS: Mitochondrial haplogroups behave like risk factors for the progress to end-stage HF in a Spanish cardiac transplant population. Mitochondrial DNA variants may have some influence on the appearance of cardiac transplant complications.