Convertible and Constrained Nucleotides: The 2’-Deoxyribose 5’-C-Functionalization Approach, a French Touch

Many strategies have been developed to modulate the biological or biotechnical properties of oligonucleotides by introducing new chemical functionalities or by enhancing their affinity and specificity while restricting their conformational space. Among them, we review our approach consisting of modifications of the 5’-C-position of the nucleoside sugar. This allows the introduction of an additional chemical handle at any position on the nucleotide chain without disturbing the Watson–Crick base-pairing. We show that 5’-C bromo or propargyl convertible nucleotides (CvN) are accessible in pure diastereoisomeric form, either for nucleophilic displacement or for CuAAC conjugation. Alternatively, the 5’-carbon can be connected in a stereo-controlled manner to the phosphate moiety of the nucleotide chain to generate conformationally constrained nucleotides (CNA). These allow the precise control of the sugar/phosphate backbone torsional angles. The consequent modulation of the nucleic acid shape induces outstanding stabilization properties of duplex or hairpin structures in accordance with the preorganization concept. Some biological applications of these distorted oligonucleotides are also described. Effectively, the convertible and the constrained approaches have been merged to create constrained and convertible nucleotides (C2NA) providing unique tools to functionalize and stabilize nucleic acids.

Tensile strength and cellulose content of Persian ironwood (Parrotia persica) roots as bioengineering material

Unstable slopes create numerous problems for forest management and may destroy the road network and disturb access to forest. Soil bioengineering is a solution that can prevent these problems and reinforce the hillslope. Persian ironwood is considered as a good protective species for hillslope stability in Iran with an extensive lack of information about biotechnical properties. In this research the root strength of this species and also the relation between root diameter and cellulose content were investigated. The results showed that the mean tensile force and tensile strength were 99.70 ± 2.01 N and 173.23 ± 4.94 MPa, respectively, for the root diameter range between 0.22 and 3.78 mm. The results of ANOVA showed that the power models between root diameter and tensile force and tensile strength were statistically significant and the results of t-test showed that coefficients and constants of the models are also significant. The values of the parameters of the power law (α and β) obtained for Persian ironwood do not fall in the range that has already been suggested for hardwood roots, which may be due to a narrow diameter range. The mean cellulose content was 56.87 ± 5.79% and the relationship between root diameter and cellulose content was not statistically significant. The data presented in this study expand the knowledge of biotechnical properties of Persian ironwood and support the idea that there is still an extensive lack of information about plant roots as a bioengineering material.