To explore the quality variation and genetic diversity of Desmodium styracifolium from different provenances, and lay a foundation for rational exploitation on germplasm resources and fine variety breeding of D. styracifolium.Amplified fragment length polymorphism (AFLP) markers were developed to analyze genetic diversity in D. styracifolium from 18 resources. NTSYSpc-2. 11F software was used to analyze the similarity among the D. styracifolium germplasms and construct the genetic phylogenetic tree. The schaftoside content in D. styracifolium from different provenances was determined by HPLC.A total of 844 fragments were amplified with 8 primers, in which 717 were polymorphic bands, accounting for 84. 27% of the total detected variation. All the specimens from 18 resources could be grouped into 3 clusters by cluster analysis. The schaftoside contents of D. styracifolium germplasms differed significantly, with the highest content in the germplasm from Sanya, Hainan.Significant quality variation and genetic diversity can be observed among D. styracifolium germplasms. The diverse germplasm resources should be explored and the fine variety should be selected to breed.
The “dual-cycle” pathway (i.e., olefin-based cycle and aromatic-based cycle) of methanol-to-olefin (MTO) has been generally accepted as hydrocarbon pool mechanism. Understanding the role of diffusion of reactant, intermediate, and product in the MTO process is essential in revealing its reaction mechanism. By using molecular dynamics (MD) simulations for two one-dimensional zeolites (ZSM-12 and ZSM-22) with a channel difference being only 0.3 Å in pore size, the diffusion behaviors of some representative species following “dual-cycle” mechanism (e.g., methanol, polymethylbenzenes, and olefins molecules) have been theoretically investigated in this work. It was found that the diffusion coefficients of methanol and olefins along ZSM-12 were ca. 2–3 times faster than that along ZSM-22 at 673 K. In the aromatic-based cycle, the polymethylbenzenes are crucial intermediates during the MTO reaction. 1,2,3,5-Tetramethylbenzene is almost imprisoned inside ZSM-12; such slower diffusion of tetramethylbenzene offers more opportunities for the geminal methylation reaction to form MTO activated pentamethylbenzenium cation, which would split into olefins through “paring” or “side-chain” pathways. However, in the ZSM-22 zeolite, since 1,2,4-trimethylbenzene is stacked, the following methylation reaction solely results in the formation of tetramethylbenzene, which is not an MTO activated species in ZSM-22 and more bulky polymethylbenzene further blocks the channel more seriously. When it comes to the olefin-based cycle, olefins can diffuse freely inside these two zeolites with methoxide intermediates bound to the zeolite frameworks, which thus facilitates formation of longer-chain olefin through olefin methylation reaction in these two zeolite catalysts. The combination of the higher reaction activity (from DFT calculation) and the longer contact time (from MD simulation) between the olefin and methoxide is apparently illustrated as the olefin-based cycle does more preferentially occur inside ZSM-22 than inside ZSM-12. Apparently, the MTO reaction mechanism is strongly determined by the diffusion behaviors of reaction species inside the zeolite confined pores.
Abstract Zeolites have been widely used for the processes of adsorption, separation, and catalysis, which are strongly correlated with molecular diffusion. However, the correlation between pore dimension and diffusion properties has not been systematically investigated so far. In this work, the diffusion properties of alkanes in six zeolites with similar pore sizes but different pore dimension have been examined. It is found that the diffusion coefficients of alkanes in zeolites are 2–5 orders of magnitude smaller than that in gas phase. Moreover, the diffusion of alkanes inside zeolites is sensitive to the pore dimension, and can be differentiated by 1‐D straight, 1‐D tortuous, and 3‐D intersecting channels, based on the derived quantitative correlation between the diffusion behavior and pore dimension. Our work may not only provide deep insights into the effects of pore dimension on diffusion, but also benefits for the future design and practical applications of zeolite catalysts.
Abstract Carbonium ions are an important class of reaction intermediates, but their dynamic evolution is difficult to be monitored by in situ techniques under experimental conditions because of their extremely short lifetime. Probably the most famous case is 2‐norbornyl cation (2NB + ): its existing form (classical or non‐classical) had been debated for decades, until the concrete proof of non‐classical geometry was achieved by X‐ray crystallographic characterization at ultra‐low temperature (40 K) and super acidic environment. However, we lack the understanding about 2NB + at ambient conditions. Herein, by taking advantage of the confinement effect and delocalized acidic environment of zeolites, we successfully stabilized 2NB + and unequivocally confirmed its “non‐classical” structure inside the ZSM‐5 zeolite by ab initio molecular dynamics simulations and 13 C solid‐state nuclear magnetic resonance experiments. It is the first time to in situ observe the non‐classical 2NB + without the super acidic environment at ambient temperature, which provides a new strategy to expand the carbocation chemistry.
A cytogenetic map has been developed for diploid potato (Solanum tuberosum), in which the arms of the 12 potato bivalents can be identified in pachytene complements using multicolor fluorescence in situ hybridization (FISH) with a set of 60 genetically anchored bacterial artificial chromosome (BAC) clones from the RHPOTKEY BAC library. This diagnostic set of selected BACs (five per chromosome) hybridizes to euchromatic regions and corresponds to well-defined loci in the ultradense genetic map, and with these probes a new detailed and reliable pachytene karyotype could be established. Chromosome size has been estimated both from microscopic length measurements and from 4',6-diamidino-2-phenylindole fluorescence-based DNA content measurements. In both approaches, chromosome 1 is the largest (100-115 Mb) and chromosome 11 the smallest (49-53 Mb). Detailed measurements of mega-base-pair to micrometer ratios have been obtained for chromosome 5, with average values of 1.07 Mb/mum for euchromatin and 3.67 Mb/mum for heterochromatin. In addition, our FISH results helped to solve two discrepancies in the potato genetic map related to chromosomes 8 and 12. Finally, we discuss the significance of the potato cytogenetic map for extended FISH studies in potato and related Solanaceae, which will be especially beneficial for the potato genome-sequencing project.
Summary The microstructures and characteristics (water holding capacity (WHC) and rheological properties) of pea protein isolate (PPI) emulsion gels produced via transglutaminase (TGase) with different oil‐weight fractions (φ, 20%~50%) were studied in the present work. The results showed that the WHC and gel strength (storage modulus) of PPI emulsion gel were raised with increasing of φ. Simultaneously, the proteins entrapped within the network gradually increase due to the enzymatic treatment, which resulted in a tighter internal structure of emulsion gel. At high oil‐weight fractions (e.g. 50%), the network of the emulsion was essentially a coarse chain of particulate, mainly forming a ‘close‐knit’ oil droplet. Therefore, the gelation mechanism is related to the state of proteins in the system, which are divided into proteins adsorbed and unadsorbed on the interface. The results will be of significant assistance in comprehending the theories of the gelation process and the protein emulsion gels immobilisation by the enzyme.
Significance In many eukaryotes, two types of meiotic crossovers (COs) coexist: class I COs that show CO interference and class II COs that do not show interference. Little is known about the separate properties of these two CO pathways or their interaction in wild-type organisms because individual COs cannot be assigned by class using marker segregation. We present an improved cytogenetic approach to identify COs from each class simultaneously on tomato meiotic chromosomes to reveal that the two CO classes have different distributions, with class II COs enriched in short arms and heterochromatin. Although class II CO distributions are consistent with no interference, interference between the two pathways was detected, with suppression of close class I and class II COs.
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