Sucrose-associated SnRK1a1-mediated phosphorylation of Opaque2 modulates endosperm filling in maize.

During maize endosperm filling, sucrose not only serves as a source of carbon skeletons for storage-reserve synthesis but also acts as a stimulus to promote this process. However, the molecular mechanisms underlying sucrose and endosperm filling are poorly understood. In this study, we found that sucrose promotes the expression of endosperm-filling hub gene Opaque2 (O2), coordinating with storage-reserve accumulation. We showed that the protein kinase SnRK1a1 can attenuate O2-mediated transactivation, but sucrose can release this suppression. Biochemical assays revealed that SnRK1a1 phosphorylates O2 at serine 41 (S41), negatively affecting its protein stability and transactivation ability. We observed that mutation of SnRK1a1 results in larger seeds with increased kernel weight and storage reserves, while overexpression of SnRK1a1 causes the opposite effect. Overexpression of the native O2 (O2-OE), phospho-dead (O2-SA), and phospho-mimetic (O2-SD) variants all increased 100-kernel weight. Although O2-SA seeds exhibit smaller kernel size, they have higher accumulation of starch and proteins, resulting in larger vitreous endosperm and increased test weight. O2-SD seeds display larger kernel size but unchanged levels of storage reserves and test weight. O2-OE seeds show elevated kernel dimensions and nutrient storage, like a mixture of O2-SA and O2-SD seeds. Collectively, our study discovers a novel regulatory mechanism of maize endosperm filling. Identification of S41 as a SnRK1-mediated phosphorylation site in O2 offers a potential engineering target for enhancing storage-reserve accumulation and yield in maize.

A mechanism for two-step thermal decomposition of 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105).

2,6-Diamino-3,5-dinitropyrazine-1-oxide (LLM-105) is a representative of the new generation of low-sensitivity energetic materials and has been applied extensively in formulations as an insensitive high-energetic ingredient. Although the initial thermal decomposition mechanism of LLM-105 has been studied based on quantum chemical calculations, the internal mechanism of the two-step thermal decomposition still lacks experimental research. Thus, this study involves a detailed experimental study to reveal the mechanism of the two-step thermal decomposition of LLM-105. The results showed that LLM-105 decay was a consecutive reaction. The first-step reaction dominated the early stage of the LLM-105 decomposition, and its products participated in the reaction of the second step. The cleavage of NO2 and NH2 groups of LLM-105 mainly occurred in the first step, while gaseous products NO and C2N2 were released during the second reaction step. The first-step reaction had a higher oxygen consumption rate and a lower carbon consumption rate, producing more heat due to more extensive oxidation of the carbon backbone. The difference in the oxidative ability and reaction rate between the two steps resulted in a two-step exothermic and mass loss behavior. This study provides further insights into the entire reaction process of LLM-105 and would be helpful for its better application and for the design of new explosives.

Kinetics and mechanism of decomposition induced by solvent evolution in ICM-101 solvates: solvent-evolution-induced low-temperature decomposition.

[2,2'-Bi(1,3,4-oxadiazole)]-5,5'-dinitramide (ICM-101), a high-energy-density material, was reported in recent years. ICM-101 is the first energetic material with the 2,2'-bi(1,3,4-oxadiazole) structure as the main ring structure. The molecular structure of ICM-101 shows excellent planar characteristics, providing a new option for the design of high-energy-density materials. However, during crystal preparation, ICM-101 easily interacts with solvents and forms the corresponding solvates. Interestingly, during thermal decomposition, when the solvent escapes from ICM-101 solvates, it induces the decomposition of ICM-101. In this study, the decomposition of ICM-101 induced by solvent evolution was evaluated in detail, and the decomposition kinetic equation was established. The mechanism of solvent-evolution-induced decomposition in ICM-101 solvates was further studied, and it was found that solvent evolution might produce defects in the crystals of ICM-101 solvates, and induce the decomposition of ICM-101 on the defects.

5-Amino-1H-1,2,4-triazole-3-carbohydrazide and its applications in the synthesis of energetic salts: a new strategy for constructing the nitrogen-rich cation based on the energetic moiety combination.

Nitrogen-rich cation 5-amino-1H-1,2,4-triazole-3-carbohydrazide and its derivatives were synthesized by a new molecular design strategy based on the energetic moiety combination. All derivatives were fully characterized by vibrational spectroscopy (IR), multinuclear (1H, 13C) NMR spectroscopy, elemental analysis, differential scanning calorimetry (DSC), and impact and friction-sensitivity tests. The structures of compounds 1-4, 7 and 8 were further confirmed by single-crystal X-ray diffraction and six different types of crystal packing were surprisingly discovered. The results show that the extensive hydrogen bonding interactions between the cations and anions lead to a complex 3D network, which contribute greatly to the high density, insensitivity and thermal stability of the 5-amino-1H-1,2,4-triazole-3-carbohydrazide salts. It is also found that the cationic form of 5-amino-1H-1,2,4-triazole-3-carbohydrazide can decrease the sensitivity and elevate the nitrogen content of the target salts effectively. Some of these salts exhibit reasonable physical properties, such as good thermal stability (up to 407 °C) and reasonable impact sensitivities (IS = 5-80 J). In addition, theoretical detonation properties of the energetic salts obtained with EXPLO 5 (version 6.02) confirm them as competitively energetic compounds comparable to those of RDX or HMX.

Synthesis, and single crystal structure of fully-substituted polynitrobenzene derivatives for high-energy materials.

New energetic fully-substituted polynitrobenzene derivatives were synthesized via the reaction of 1,3,5-trichloro-2,4,6-trinitrobenzene (TCTNB) with 1,2,4-triazole followed by the nucleophilic substitution of the halo groups by aqueous ammonia or sodium azide. These compounds were charactered by 1H NMR, 13C NMR and HRMS. Additionally, the structures of amino derivatives 6, 8 and azido derivative 7 were further confirmed by single crystal X-ray diffraction analysis. Their decomposition temperatures and impact sensitivities were also determined. The derivative 1,2-di-1H-triazol-4,6-diamino-3,5-dinitrobenzene (8) exhibits good thermal stability (T d = 314 °C) and low impact sensitivity (IS = 30 J), which are both superior to that of TNT (T d = 295 °C, IS = 15 J). These synthesized compounds showed high heat of formation ranging from 31.77 to 1014.68 kJ mol-1, and reasonable detonation velocities and pressures.

Correction: Synthesis, and single crystal structure of fully-substituted polynitrobenzene derivatives for high-energy materials.

[This corrects the article DOI: 10.1039/C7RA13346D.].

Energetic π-conjugated vinyl bridged triazoles: a thermally stable and insensitive heterocyclic cation.

A new family of vinyl bridge 1,1'-(ethane-5-yl)-bis(3,4-diamino-1,2,4-triazolium) salts were explored as novel structural energetic materials. These new salts were further characterized by elemental analysis, infrared and multinuclear NMR spectra. Structural confirmation of nine salts such as 4-11 and 14 was supported by single-crystal X-ray diffraction. Theoretical investigations associated with heats of formation and detonation performance were carried out by employing the Gaussian 09 program and the EXPLO5 V6.02 code, respectively. The sensitivities towards impact and friction were studied using BAM standards. According to the experimental and computational data, these salts show densities ranging from 1.61 to 1.82 g cm-3 at 298 K, good thermal stabilities (Td: 217 °C-322 °C), excellent detonation performance (P: 7809 m s-1 to 9640 m s-1, D: 24.6 GPa-33.9 GPa) and rational impact and friction sensitivities (IS: 4 J to 60 J, FS: 120 N to 360 N).

Thermally Stable Energetic Salts Composed of Heterocyclic Anions and Cations Based on 3,6,7-Triamino-7 H-s-triazolo[5,1-c]-s-triazole: Synthesis and Intermolecular Interaction Study.

To create intermolecular N-H⋅⋅⋅O and N-H⋅⋅⋅N hydrogen-bond (HB) interactions, a series of energetic N-heterocyclic anions including polynitro- and multi-nitrogen anions were introduced into the 3,6,7-triamino-7 H-s-triazolo[5,1-c]-s-triazole (TATT) cation to get numerous novel energetic salts. Single-crystal X-ray diffraction was employed to confirm the crystal structure and crystal packing properties of compounds 2⋅H2 O, 6, and 9. Additionally, Hirshfeld surface analysis and atoms-in-molecules topology analysis provided insights into the intermolecular hydrogen-bond interaction of these new salts. With the assistance of the EXPLO5 program, the detonation velocities, detonation pressures, and specific impulses of the salts were found to fall in the ranges 8113-9477 m s-1 , 24.1-31.4 GPa, and 203.2-224.2 s, respectively. The predicted detonation performance indicate that all the energetic salts based on TATT are similar to those of 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) or even overtake octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), which reveal that they can be candidates for the future insensitive high-performance energetic materials (IHPEMs).