Search

Sorghum is a crop that is susceptible to low temperatures. However, due to the extreme global temperatures, new genotypes have been bred to adapt better to cold climates. Therefore, to better understand the metabolic and molecular differences that may contribute to the improved cold tolerance of these genotypes, it is essential to investigate whether specific molecules play a key role in determining the degree of sorghum tolerance. Furthermore, identifying genes associated with cold tolerance may assist in the development of more robust and productive sorghum cultivars. Here, we analysed the changes in selected elements of the antioxidant metabolism, genes, and miRNAs in two sorghum varieties with different degrees of tolerance to cold stress at different times of exposure to cold stress. The high expression of SbCBF6 in response to cold treatment in early time in the tolerant variety suggests its involvement in the cold response, thereby facilitating a better adaptation of the plant to cold conditions. MiR398 and miR394 showed contrasting behaviour in both varieties in low temperatures, resulting in interesting miRNAs in the degree of sorghum tolerance. MiR319, a marker for the selection of cold‐tolerant cultivars, presents a decrease, suggesting that the better capacity to repress the expression of several members of TCP family of transcription factor genes might be involved in better tolerance to cold stress. This study shows the changes of molecules of interest in response to cold stress in sorghum, marking the difference between cold‐susceptible and cold‐tolerant sorghum plants, which can contribute to selecting tolerant genotypes, allowing new strategies to enhance crop productivity and food security, in regions where low temperatures significantly constrain crop growth and yield. [ABSTRACT FROM AUTHOR]

Chia (Salvia hispanica L.) seeds contain antioxidants with great benefits for health and are widely used in the food industry. Antioxidants can be degraded by environmental factors, decreasing their biological activity. Their encapsulation in chitosan (CH) particles represents an alternative to protect them and increases their application. The encapsulation efficiency (%EE) of the antioxidants in the CH particles depends on the synthesis conditions. In this study, two methods for encapsulation of chia extract in chitosan particles were evaluated: method A, 0.05% CH in 1% acetic acid was mixed with 0.07% of tripolyphosphate (TPP) and method B, 0.3% CH in 2% acetic acid was mixed with 1% TPP. The results showed that the %EE decreased with the concentration of the extract, and the FTIR analysis suggested that the compounds of the extract were adsorbed on the surface of the particles. Dynamic light scattering and zeta potential analysis showed that the particles of method A are unstable and with a tendency to agglomerate, and the particles of method B are stable. The highest %EE was obtained with 0.2 mg·mL−1 (method A) and 1.0 mg·mL−1 (method B) of the extract. The higher loading capacity (%LC) (16–72%) was exhibited by the particles of method A. The best particle yield (62–69%) was observed for method B. The particles with the extract adsorbed showed antioxidant activity (5–60%) at 25°C; however, in the particles with the extract encapsulated, the activity increased after subjecting to acidic conditions at 40°C due to the breakdown of the particles. The results obtained will allow choosing the appropriate conditions for the synthesis of chitosan particles loaded with chia extracts with specific characteristics (%EE, %LC, size, and type) according to their future applications. The particles could be used in food and pharmaceutical industries and even in edible films for food packaging. [ABSTRACT FROM AUTHOR]

The preparation of long-term-stable giant unilamellar vesicles (GUVs, diameter ≥1000 nm) and large vesicles (diameter ≥500 nm) by self-assembly in THF of the crystalline- b-coil polyphosphazene block copolymers [N=P(OCH2CF3)2] n- b-[N=PMePh] m ( 4 a: n=30, m=20; 4 b: n=90, m=20; 4 c: n=200, m=85), which combine crystalline [N=P(OCH2CF3)2] and amorphous [N=PMePh] blocks, both of which are flexible, is reported. SEM, TEM, and wide-angle X-ray scattering experiments demonstrated that the stability of these GUVs is induced by crystallization of the [N=P(OCH2CF3)2] blocks at the capsule wall of the GUVS, with the [N=PMePh] blocks at the corona. Higher degrees of crystallinity of the capsule wall are found in the bigger vesicles, which suggests that the crystallinity of the [N=P(OCH2CF3)2] block facilitates the formation of large vesicles. The GUVs are responsive to strong acids (HOTf) and, after selective protonation of the [N=PMePh] block, they undergo a morphological evolution to smaller spherical micelles in which the core and corona roles have been inverted. This morphological evolution is totally reversible by neutralization with a base (NEt3), which regenerates the original GUVs. The monitoring of this process by dynamic light scattering allowed a mechanism to to be proposed for this reversible morphological evolution in which the block copolymer 4 a and its protonated form 4 a+ are intermediates. This opens a route to the design of reversibly responsive polymeric systems in organic solvents. This is the first reversibly responsive vesicle system to operate in organic media. [ABSTRACT FROM AUTHOR]

New advances into the chirality effect in the self-assembly of block copolymers (BCPs) have been achieved by tuning the helicity of the chiral-core-forming blocks. The chiral BCPs {[NP( R)-O2C20H12]200− x[NP(OC5H4N)2] x}- b- [NPMePh]50 (( R)-O2C20H12=( R)-1,1′-binaphthyl-2,2′-dioxy, OC5H4N=4-pyridinoxy (OPy); x=10, 30, 60, 100 for 3 a- d, respectively), in which the [NP(OPy)2] units are randomly distributed within the chiral block, have been synthesised. The chiroptical properties of the BCPs ([ α]D vs. T and CD) demonstrated that the helicity of the BCP chains may be simply controlled by the relative proportion of the chiral and achiral (i.e., [NP( R)-O2C20H12] and [NP(OPy)2], respectively) units. Thus, although 3 a only contained only 5 % [NP(OPy)2] units and exhibited a preferential helical sense, 3 d with 50 % of this unit adopted non-preferred helical conformations. This gradual variation of the helicity allowed us to examine the chirality effect on the self-assembly of chiral and helical BCPs (i.e., 3 a- c) and chiral but non-helical BCPs (i.e., 3 d). The very significant influence of the helicity on the self-assembly of these materials resulted in a variety of morphologies that extend from helical nanostructures to pearl-necklace aggregates and nanospheres (i.e., 3 b and 3 d, respectively). We also demonstrate that the presence of pyridine moieties in BCPs 3 a- d allows specific decoration with gold nanoparticles. [ABSTRACT FROM AUTHOR]

We describe a new and very versatile method to place chosen chemical functionalities at the edge of the pores of macroporous materials. The method is based on the synthesis and self-assembly of inorganic block copolymers (BCPs) having chiral rigid segments bearing controllable quantities of randomly distributed functional groups. The synthesis of a series of optically active block copolyphosphazenes (PP) with the general formula [NP( R-O2C20H12)0.9(FG)0.2] n- b-[NPMePh] m (FG=-OC5H4N ( 6), -NC4H8S ( 7), and -NC4H8O ( 8)), was accomplished by the sequential living cationic polycondensation of N-silylphosphoranimines, using the mono-end-capped initiator [Ph3PNPCl3][Cl] ( 3). The self-assembly of the phosphazene BCPs 6- 8 led to chiral porous films. The functionality present on those polymers affected their self-assembly behaviour resulting in the formation of pores of different diameters ( Dn=111 ( 6), 53 ( 7) and 77 nm ( 8)). The specific functionalisation of the pores was proven by decorating the films with gold nanoparticles (AuNPs). Thus, the BCPs 6 and 7, having pyridine and thiomorpholine groups, respectively, were treated with HAuCl4, followed by reduction with NaBH4, yielding a new type of block copolyphosphazenes, which self-assembled into chiral porous films specifically decorated with AuNPs at the edge of the pores. [ABSTRACT FROM AUTHOR]

A series of optically active helical polyphosphazene block copolymers of general formula R[NP(O2C20H12)] n- b-[NPMePh] m ( R- 7 a- c) was synthesized and characterized. The polymers were prepared by sequential living cationic polycondensation of N-silylphosphoranimines using the mono-end-capped initiator [Ph3PNPCl3][PCl6] ( 5) and exhibit a low polydispersity index (ca. 1.3). The temperature dependence of the specific optical activity ([ α]D) of R- 7 a, b relative to that for the homopolymers R-[NP(O2C20H12)] n ( R- 8 a) and the R/ S analogues ( R/ S- 7 a, b), revealed that the binaphthoxy-phosphazene segments induce a preferential helical conformation in the [NPMePh] blocks through a 'sergeant-and-soldiers' mechanism, an effect that is unprecedented in polyphosphazenes. The self-assembly of drop-cast thin films of the chiral block copolymer R- 7 b (bearing a long chiral and rigid R[NP(O2C20H12)] segment) evidenced a transfer of helicity mechanism, leading to the formation of twisted morphologies (twisted 'pearl necklace'), not observed in the nonchiral R/ S- 7 b. The chiral R- 7 a and the nonchiral R/ S- 7 a, self-assemble by a nondirected morphology reconstruction process into regular-shaped macroporous films with chiral-rich areas close to edge of the pore. This is the first nontemplate self-assembly route to chiral macroporous polymeric films with pore size larger than 50 nm. The solvent annealing (THF) of these films leads to the formation of regular spherical nanostructures (ca. 50 nm), a rare example of nanospheres exclusively formed by synthetic helical polymers. [ABSTRACT FROM AUTHOR]