Excellent performance of aromatic polyguanamines induced by multiple hydrogen bondable tetraazacalix[2]arene[2]-triazine ring in their main chain

A series of poly(guanamine) (c-PG)s containing tetraazacalix[2]arene[2]-triazine (mPDA₂CyC₂) were successfully prepared by solution polycondensation of mPDA₂CyC₂ with various aromatic diamines in an aprotic organic solvent with a lithium chloride additive (5 wt%) at 150 °C for 6 hours. The number-average molecular weights (M_n)s of these c-PG polymers reached up to 31 500, with a relatively broad molecular weight distribution (M_w/M_n) of 5.3. They showed good solubility in aprotic organic solvents, such as N-methylpyrrolidone and N,N-dimethylacetamide at a concentration of 2 mg mL⁻¹. The glass transition temperatures (T_g) of the c-PG polymers were in the range 359 °C–392 °C, approximately 160 °C higher than those of counterpart polymers (i.e., with no aza-calixarene-based PG (l-PG)). The coefficients of thermal expansion (CTEs) of the c-PG polymers were 29.7–48.1 ppm K⁻¹ (at 100 °C–150 °C), much lower than those of l-PG samples, i.e., 59.1–85.1 ppm K⁻¹. Transparent and almost colorless c-PG films were successfully prepared by a solution casting method, showing maximum tensile strength (σ_S), modulus (E_γ), and elongation at break (E_b) values of 151 MPa, 6.3 GPa, and 4.4%, respectively, for the c-PG polymer from mPDA₂CyC₂ and 4,4′-oxydianiline monomers. The corresponding l-PG film exhibited σ_S, E_γ, and E_b values of just 76 MPa, 5.4 GPa, and 1.6%, respectively. These outstanding thermal and mechanical properties of the c-PG polymers can be attributed to their multiple hydrogen bonding interaction between mPDA₂CyC₂ residues in the polymer backbone. This interaction was identified by infrared spectroscopy measurements at the broad absorption band around 3000–3400 cm⁻¹.

Poly(guanamine)s containing tetraazacalix[2]arene[2]triazine ring within the polymer main-chain show outstanding thermal and mechanical properties arisen from the multiple-hydrogen bond.

Synthesis of highly refractive and highly fluorescent rigid cyanuryl polyimines with polycyclic aromatic hydrocarbon pendants

A series of rigid cyanuryl polyimines, polyguanamines (PGs) bearing polycyclic aromatic hydrocarbon pendants were successfully synthesized from 2-substituted 4,6-dichloro-1,3,5-triazine and aromatic diamine monomers.

Design of boronic acid-attributed carbon dots on inhibits HIV-1 entry

The development of gp120 targeted human immunodeficiency virus (HIV) drug has improved antiretroviral therapies owing to its effects on attachment to target cells.

Rapid identification of 1-aminocyclopropane-1-carboxylate (ACC) synthase genotypes in cultivars of Japanese pear (Pyrus pyrifolia Nakai) using CAPS markers

In Japanese pear (Pyrus pyrifolia Nakai), fruit storage potential is closely related to the amount of ethylene produced. We have developed a rapid and accurate method for analyzing genes involved in high ethylene production during fruit ripening in Japanese pear. This involves cleaved-amplified polymorphic sequences (CAPS) of two 1-aminocyclopropane-1-carboxylate (ACC) synthase genes (PPACS1 and PPACS2). Two CAPS markers (A for PPACS1 and B for PPACS2), associated with the amount of ethylene produced, were identified. Marker A was associated with high ethylene producers and marker B with moderate ethylene producers. The absence of these two markers enabled the identification of low ethylene producers. Using these markers, we have identified ethylene genotypes for 40 Japanese pear cultivars and two Chinese pear (P. bretschneideri) cultivars that are commercially important and used in breeding programs. Furthermore, we performed linkage analysis of these two genes in the F(2) population, which revealed that the recombination frequency between the two markers was 20.8 +/- 3.6%. This information is critical to the selection of parents and in breeding strategies to improve storage ability of Japanese pears.

Oosorption in the stink bug, Plautia crossota stali: induction and vitellogenin dynamics

Oosorption, resorption of developing oocytes in the ovary, in P. c. stali is characterized by changes in appearance of oocytes from opaque greyish green or orange to transparent, degeneration of yolk granules and disappearance of oocyte contents. Starvation and virginity were indicated to be factors that induce oosorption. SDS PAGE/Western blotting analysis using anti-vitellogenin antiserum detected two major and many minor bands in haemolymph samples. Egg extracts showed a more complicated set of positive bands in the same analysis. Yolk protein, vitellin, therefore, seemed to be formed after complicated processing of vitellogenin following its uptake by the oocytes. In starved, oosorption-induced females, vitellogenin concentration in the haemolymph was lower than that of fed females, and Western blotting failed to detect either oosorption-specific or ovary-specific peptide fragments in haemolymph samples collected from those females. These results suggest that once oosorption was induced vitellogenin/vitellin in oocytes was degraded rapidly and released into the haemolymph in the form of amino acids or small peptides too small to be recognized by the anti-vitellogenin antiserum.

Design, synthesis and peroxidase-like activity of 3alpha-helix proteins covalently bound to heme

As a model of artificial peroxidase, de novo designed three-alpha-helix proteins, 3alpha-H9 and 3alpha-H12, covalently bound to Fe(III)-mesoporphyrin IX were synthesized and examined for a peroxidase-like activity. The activity was regulated according to the positions of His residues in the proteins, and the His residues played a role in an acid-base catalytic function.