Supramolecular chiral host–guest nanoarchitecture induced by the selective assembly of barbituric acid derivative enantiomers

International audienceBarbituric acid derivatives are prochiral molecules, i.e. they are chiral upon adsorption on surfaces. Scanning tunneling microscopy reveals that barbituric acid derivatives self-assemble into a chiral guest-host supramolecular architecture at the solid-liquid interface on graphite. The host nanoarchitecture has a sophisticated wavy shape pattern and paired guest molecules are nested insides the cavities of the host structure. Each unit cell of the host structure is composed of both enantiomers with a ratio of 1:1. Furthermore, the wavy patterns of the nanoarchitecture are formed from alternative appearance of left- and right-handed chiral building blocks, which makes the network heterochiral. The functional guest-host nanoarchitecture is the result of two-dimensional chiral amplification from single enantiomers to organizational heterochiral supramolecular self-assembly

Two-Dimensional Hetero- to Homochiral Phase Transition from Dynamic Adsorption of Barbituric Acid Derivatives

International audienceBarbituric acid derivative (TDPT) is an achiral molecule, and its adsorption on a surface results in two opposite enantiomerically oriented motifs, namely TDPT-Sp and Rp. Two types of building blocks can be formed; block I is enantiomer-pure and is built up of the same motifs (format SpSp or RpRp) whereas block II is enantiomer-mixed and composes both motifs (format SpRp), respectively. The organization of the building blocks determines the formation of different nanoarchitectures which are investigated using scanning tunneling microscopy at a liquid/HOPG interface. Sophisticated, highly symmetric “nanowaves” are first formed from both building blocks I and II and are heterochiral. The “nanowaves” are metastable and evolve stepwisely into more close-packed “nanowires” which are formed from enantiomer-pure building block I and are homochiral. A dynamic hetero- to homochiral transformation and simultaneous multi-scale phase transitions are demonstrated at the single-molecule level. Our work provides novel insights into the control and the origin of chiral assemblies and chiral transitions, revealing the various roles of enantiomeric selection and chiral competition, driving forces, stability and molecular coverage

Estimation of Archie parameters by a novel hybrid optimization algorithm

© 2015 Elsevier B.V. Archie parameters play a critical role in accurately identifying water saturation for a given reservoir condition. Due to interdependence of these parameters, it is difficult to estimate them accurately. In order to achieve more accurate parameters, we model a non-convex optimization problem based on the core Archie parameters' estimate (CAPE). Then we present a new hybrid global optimization method to solve this non-convex problem. The hybrid technique has the features of both fast local convergence in interior point method and global convergence in Firefly algorithm (FA). Finally, our method was implemented to determine Archie parameters and some comparisons are done among two deterministic techniques and four population-based algorithms. Water saturation profiles were generated using the different Archie parameters determined by six techniques. These profiles have shown a significant difference in water saturation values between CAPE methods and population-based methods. These results highlight that our proposed algorithm performed better than conventional CAPE and three dimension (3D) method for reservoirs to calculate the water saturation values due to more accurate Archie parameters achieved by our method

Comprehensive Evaluation of Salt Tolerance in Asparagus Germplasm Accessions (Asparagus officinalis L.) at Different Growth Stages

The screening and cultivation of salt-tolerant crops are becoming more and more important owing to the constant increase in the saline soil area worldwide. Asparagus (A. officinalis L.) is a highly nutritious vegetable crop and widely consumed globally for a long time; however, little research has been done on asparagus. In this study, the salt tolerance of 95 asparagus germplasm accessions was evaluated at three growth stages (germination, seedling, and adult stages) under both salt-stressed and control conditions. Results showed that the growth parameters of most germplasm accessions were obviously inhibited by salt stress. The mean value of the seed germination rate at the germination stage decreased by half under salt-stressed conditions, the mean salt-injury index at the seedling stage reached 57.68%, and the fresh weight of the aboveground part (FWA) and the dry weight of the aboveground part (DWA) decreased the most among the traits determined at the adult stage by more than 60%. Our study screened out 30, 19, and 18 tolerant germplasm accessions (including highly salt-tolerant and salt-tolerant germplasm accessions) at the germination stage, seedling stage, and adult stage, respectively. Among them, two germplasm accessions (Ji08-2 and Jx1502) were simultaneously identified to be tolerant in all three growth stages, while other germplasm accessions were tolerant only at one or two stages. Thus, the salt tolerance of asparagus has periodic characteristics and changes throughout the lifecycle, and the identification of salt tolerance at all the main growth stages facilitates adequate assessment and application of tolerant germplasm accessions

Relationship between CYP2E1 Gene Polymorphism and Anti-tuberculosis Drug-induced Liver Injury

 Objective: To investigate the relationship between cytochrome P450 E1 (CYP2E1) gene polymorphisms and susceptibility to anti-tuberculosis drug-induced liver damage (ATDLI) in tuberculosis patients in the Chinese Han nationality. Methods: A retrospective analysis was performed on 360 patients with tuberculosis who had liver damage after tuberculosis treatment (case group) and 360 patients with tuberculosis who did not develop liver injury after treatment (control group). MassARRAY were used to detect CYP2E1 gene polymorphisms. Results: In a total of 8 tagged SNP loci selected, the rs8192773 locus failed to pass the test, and therefore, it is not included in subsequent analysis. At the remaining seven SNP sites, the difference in alleles was not statistically significant between the case group and the control group, suggesting that these sites may not be related to liver damage caused by anti-tuberculosis drugs. Three monomer domains were found in the seven tags SNP loci mentioned above. However, it was found that these haplotypes are not closely related to anti-tuberculosis drug-induced liver damage. Conclusion: The CYP2E1 gene polymorphism in the Chinese Han nationality is not related to the occurrence of anti-tuberculosis drug-induced liver injury

Physiological Basis of High Nighttime Temperature-Induced Chalkiness Formation during Early Grain-Filling Stage in Rice (<i>Oryza sativa</i> L.)

Heat stress during the grain-filling stage seriously affects grain quality in rice. However, very limited information is available regarding the effects of short-term high nighttime temperature (HNT) on grain chalkiness formation in rice. In this paper, the effects of HNT at the early grain-filling stage (7 days after ear emergence) on rice chalkiness formation and the potential causes were investigated by using two rice varieties that differed in susceptibility to high temperature. Although the HNT treatment at night dramatically increased the grain chalkiness in Jiuxiangzhan (JXZ) and Huanghuazhan (HHZ), the increase was greater in JXZ compared to HHZ. The net photosynthetic rate and SPAD value were significantly reduced by HNT treatment in the flag leaves of JXZ, while no significant differences were observed in HHZ. Furthermore, HNT treatment reduced the antioxidant enzyme activity in the flag leaves of JXZ, while the opposite was observed in HHZ, exhibiting increased antioxidant enzyme activity. Moreover, HNT treatment altered the endogenous hormone levels, enhanced the enzymatic activities related to starch biosynthesis, and accelerated the filling rate in grains of JXZ when compared to HHZ. Scanning electron microscopy (SEM) observation exhibited that the starch granules in the endosperm of JXZ were loosely packed together and more starch granules with small pits were produced after HNT treatment. Based on these data, we inferred that HNT stress during the early stage of rice grain filling accelerated the grain-filling rate but shortened the grain-filling duration by changing the endogenous hormone levels and enhancing the enzymatic activities responsible for starch biosynthesis, resulting in significant changes in the morphological structure and arrangement of starch granules and eventually causing the occurrence of grain chalkiness