preparation-hydrophobic-metal-organic-frameworks-via-plasma-enhanced

Preparation of Hydrophobic Metal-Organic Frameworks via Plasma Enhanced Chemical Vapor Deposition of Perfluoroalkanes for the Removal of Ammonia

Plasma enhanced chemical vapor deposition (PECVD) of perfluoroalkanes has long been studied for tuning the wetting properties of surfaces. For high ...

Research Development Engineering Command

Analysis of genetic diversity changes in existing gene pools of cultivated crops is important for understanding the impact of plant breeding on crop genetic diversity and developing effective indicators for genetic diversity of cultivated plants. The objective of this study was to assess genetic diversity changes in 75 Canadian hard red wheat (Triticum aestivum L.) cultivars released from 1845 to 2004 using 31 simple sequence repeats (SSRs) markers. A total of 267 SSR alleles were detected, and their allelic frequencies ranged from 0.01 to 0.97, with an average of 0.14. Significant allelic reduction was observed at only four SSR loci for the cultivars released from 1970 onwards. However, 51 alleles (about 19%) present in pre-1910 cultivars were undetected in cultivars released after 1990 and were spread over 27 SSR loci. The proportion of SSR variation accounted for by six breeding periods was 12.5%, by four ancestral families, 16.5%, and by eight breeding programs, 8.4%. The average genetic diversity measured by three different band-sharing methods did not change significantly among cultivars released from different breeding periods, breeding programs, and ancestral families. However, genetic shift was obvious in the cultivars released over the six breeding periods, reflecting well the various breeding efforts over years. These results clearly show the allelic reduction and genetic shift in the Canadian hard red spring wheat germplasm released over time. Consequently, more effort needs to be made to broaden the wheat breeding base and conserve wheat germplasm.

Allelic reduction and genetic shift in the Canadian hard red spring wheat germplasm released from 1845 to 2004.

Many core collections have been developed from large collections of crop germplasm, but most of these have not been characterized, particularly using molecular techniques, for germplasm management and utilization. We have attempted to characterize a structured sample representing a world collection of 11,622 cultivated hexaploid oat accessions in the hope of understanding the genetic structure of the world collection. The amplified fragment length polymorphism (AFLP) technique was applied to screen 670 accessions representing 79 countries and one group of uncertain origin. For each accession, 170 AFLP polymorphic bands detected by five AFLP primer pairs were scored. Analyses of the AFLP data showed the effectiveness of the stratified sampling applied in capturing country-wise AFLP variation. The frequencies of polymorphic bands ranged from 0.11 to 0.99, with an average of 0.72. The majority (89.9%) of the AFLP variation resided within accessions of each country, and only 6.2% of the AFLP differences existed among accessions of major geographic regions. Accessions from the Mediterranean region were the most distinct, while those from Russia and the USA were the most diverse. The two distinct groups that were observed were separated largely on the basis of common oat and red oat. Red oat was genetically more diverse than its common and hull-less counterparts, and hull-less oat was more related to common oat than red oat. Landrace and non-landrace accessions displayed similar AFLP variation patterns. These patterns are significant for understanding the domestication of cultivated oat and are useful in classifying the intraspecific diversity of oat germplasm, developing specific core subsets of the oat collection, and exploring new sources of genes for oat improvement.

Patterns of AFLP variation in a core subset of cultivated hexaploid oat germplasm.

A phylogenetic analysis was conducted on 34 alleles of 2.5 kb sized stearoyl-ACP desaturase II (sad2), obtained from 30 accessions of cultivated and pale flax (Linum spp.), to elucidate the history of flax domestication. The analysis supports a single domestication origin for extant cultivated flax. The phylogenetic evidence indicates that flax was first domesticated for oil, rather than fibre. The genetic diversity of the sad2 locus in cultivated flax is low when compared to that of the pale flax assayed. An absolute archaeological date could be applied to the synonymous substitution rate of sad2 in cultivated flax, yielding a high estimate of 1.60-1.71x10(-7) substitutions/site/year. The occurrence of nonsynonymous substitutions at conserved positions of the third exon in alleles from cultivated flax suggests that the locus may have been subjected to an artificial selection pressure. The elevated synonymous substitution rate is also compatible with a population expansion of flax since domestication, followed by a population decline in historic times. These findings provide new insight into flax domestication and are significant for the continuous exploration of the flax germplasm for utilization.

Evidence of the domestication history of flax (Linum usitatissimum L.) from genetic diversity of the sad2 locus.

Genetic diversity changes in wheat germplasm have been studied using different molecular markers, but little is known about the impact of plant breeding on the transcribed segments of the wheat genome. The objective of this study was to assess diversity changes in 75 Canadian hard red wheat cultivars released from 1845 to 2004 using 37 EST-derived microsatellite (eSSR) markers. These markers were derived from at least 19 transcribed sequences with putative functions assigned and sampled 17 wheat chromosomes. A total of 138 eSSR alleles was detected, and their allelic frequencies ranged from 0.01 to 0.99 with an average of 0.41. Allelic counts were significantly reduced at three loci for cultivars released after 1990. Sixteen alleles at 14 loci in pre-1910 cultivars were lost in cultivars released after 1990. The lost alleles had frequencies ranging from 0.03 to 0.17 and averaging 0.07. Partitioning the eSSR variation showed the four ancestral families accounted for 14.7% of the variation, followed by the six breeding periods with 12.8% and the eight breeding programs with 5.8%. A genetic shift was observed in the cultivars released over the six breeding periods, reflecting the various breeding efforts. These results illustrate the impact of the Canadian wheat breeding on the transcriptional segments of the wheat genome. These findings, along with those from genomic SSR markers, suggest the Canadian wheat breeding programs have reduced genetic diversity in the hard red spring wheat.

Impact of plant breeding on genetic diversity of the Canadian hard red spring wheat germplasm as revealed by EST-derived SSR markers.

Adsorption equilibria and NMR experiments were performed to study the adsorption and interactions of ammonia with metal-organic framework (MOF) HKUST-1, or Cu(3)(BTC)(2) (BTC = 1,3,5-benzenetricarboxylate). Ammonia capacities determined from chemical breakthrough measurements show significantly higher uptake capacities than from adsorption alone, suggesting a stronger interaction involving a potential reaction with the Cu(3)(BTC)(2) framework. Indeed, (1)H MAS NMR reveals that a major disruption of the relatively simple spectrum of Cu(3)(BTC)(2) occurs to generate a composite spectrum consistent with Cu(OH)(2) and (NH(4))(3)BTC species under humid conditions-the anticipated products of a copper(II) carboxylate reacted with limited ammonia. These species are not detected under dry conditions; however, reaction stoichiometry combined with XRD results suggests the partial formation of an indeterminate diammine copper (II) complex with some residual Cu(3)(BTC)(2) structure retained. Cu(II)-induced paramagnetic shifts exhibited by various species in (1)H and (13)C MAS NMR spectra are consistent with model compounds and previous literature. Although results show extensive ammonia capacity of Cu(3)(BTC)(2), much of the capacity is due to reaction with the structure itself, causing a permanent loss in porosity and structural integrity.

Ammonia Vapor Removal by Cu(3)(BTC)(2) and Its Characterization by MAS NMR.

Little is known about the genetic impacts of modern plant breeding on specific breeding target loci. Resequencing cloned genes can identify all mutations in single genes for population-based analyses of genetic changes in improved gene pools. Ninety-five wheat cultivars released in Canada from 1845 to 2004 were sequenced at the wheat leaf rust resistance locus Lr21. Characterization of the DNA fragment of length 4,071 bp, covering the Lr21 gene from -92 to +4,261, revealed 13 SNPs, four indels, 10 haplotypes, and 4 major haplotype groups. A new SCAR marker was developed to identify the resistant haplotype and haplotype groups. Non-synonymous polymorphic sites and haplotype numbers were increased over the 100 years of wheat breeding. Nucleotide diversity of the wheat cultivars was gradually reduced from 1845 to 1993 and increased after the release of the first Lr21 wheat cultivar AC Cora in 1994. Positive selection measured with Tajima's D was observed in the cultivars released before 1935. At least two recombination events were inferred in those cultivars released before 1993. Linkage disequilibrium at the locus was decreased over time. These findings demonstrate not only the effectiveness of the wheat breeding in the improvement of leaf rust resistance, but also are useful to understand the genetic influences of a long-term artificial selection on individual loci.

Population-based resequencing analysis of improved wheat germplasm at wheat leaf rust resistance locus Lr21.

A novel technique for determining the relative accessibility and reactivity of basic surface hydroxyl sites by reacting various zirconium(IV) hydroxide materials with 2,2,2-trifluoroethanol (TFE) and characterizing the resulting material using (19)F magic angle spinning (MAS) nuclear magnetic resonance (NMR) is presented here. Studied here are three zirconium hydroxide samples, two unperturbed commercial materials, and one commercial material that is crushed by a pellet press. Factors, such as the ratio of bridging/terminal hydroxyls, surface area, and pore size distribution, are examined and found to affect the ability of the zirconium(IV) hydroxide to react with TFE. X-ray diffraction, nitrogen isotherms, and (1)H MAS NMR were used to characterize the unperturbed materials, while thermogravitric analysis with gas chromatography and mass spectrometry along with the (19)F MAS NMR were used to characterize the materials that were reacted with TFE. Zirconium hydroxide materials with a high surface area and a low bridging/terminal hydroxyl ratio were found to react TFE in the greatest amounts.

Trifluoroethanol and 19F magic angle spinning nuclear magnetic resonance as a basic surface hydroxyl reactivity probe for zirconium(IV) hydroxide structures.

Recent advances in next-generation DNA sequencing (NGS) have enhanced the development of genomic resources such as contigs or single-nucleotide polymorphisms (SNPs) for evolutionary studies of a nonmodel species with a complex and unsequenced genome. This study presents an application of a NGS technique in combination with genomic reduction and advanced bioinformatics tools to identify contigs and SNPs from multiple samples of two Linum species. A full Roche 454 GS FLX run of 16 diverse Linum samples representing cultivated flax (Linum usitatissimum L.) and its wild progenitor (Linum bienne Mill.) generated approximately 1.6 million sequence reads with a total length of 498 Mbp. Application of the computational pipeline de novo identification of alleles identified 713 contigs and 1067 SNPs. A blast search revealed alignments of all 713 contigs with 491 existing Linum scaffolds and gene annotations associated with 512 contigs. Sanger sequencing confirmed 95% of 79 selected contigs and 94% of 272 SNPs and identified 211 new SNPs and 19 new indels. The scored 454 SNP data were highly imbalanced for assayed samples. These findings not only are useful for evolutionary studies of Linum species but also help to illustrate the utility of NGS technologies in SNP discovery for nonmodel organisms.

Developing genomic resources in two Linum species via 454 pyrosequencing and genomic reduction.

Metal organic frameworks (MOFs) are a leading class of porous materials for a wide variety of applications, but many of them have been shown to be unstable toward water. Cu-BTC (1,3,5 benzenetricarboxylic acid, BTC) was treated with a plasma-enhanced chemical vapor deposition (PECVD) of perfluorohexane creating a hydrophobic form of Cu-BTC. It was found that the treated Cu-BTC could withstand high humidity and even submersion in water much better than unperturbed Cu-BTC. Through Monte Carlo simulations it was found that perfluorohexane sites itself in such a way within Cu-BTC as to prevent the formation of water clusters, hence preventing the decomposition of Cu-BTC by water. This PECVD of perfluorohexane could be exploited to widen the scope of practical applications of Cu-BTC and other MOFs.

Enhanced stability of Cu-BTC MOF via perfluorohexane plasma-enhanced chemical vapor deposition.

The adsorption of ammonia on Zr(OH)(4), as well as Zr(OH)(4) treated with sulfuric acid, were examined. The results show that treating Zr(OH)(4) with sulfuric acid leads to the formation of a sulfate on the surface of the material, and that the sulfate contributes to the ammonia adsorption capacity through the formation of an ammonium sulfates species. Calcination of Zr(OH)(4) decreases the ammonia adsorption capacity of the material and limits the formation of sulfate species. NMR and FTIR spectroscopy results are presented that show the presence of two distinct ammonium species on the surface of the material. The adsorption capacity of the materials is shown to be a complex phenomenon that is impacted by the surface area, the sulfur content, and the pH of the material. The results illustrate that Zr(OH)(4), which is known to adsorb acidic gases, can be modified and used to adsorb basic gases.

Adsorption of ammonia by sulfuric acid treated zirconium hydroxide.

With the prevalence of air quality issues in our society, the ability to remove toxic gases from air is a necessity. This work addresses the development of biphasic, nanostructured, organoalkoxysilane-grafted, siliceous materials for use in single pass filters of various types for the removal of acidic and basic gases from humid air. Materials exhibit high single pass capacities for sulfur dioxide, a representative acid-forming gas, or ammonia, a representative basic gas. The nanostructured siliceous support provides initial ammonia capacity, and grafted amine and carbonyl groups provide desired functional chemistries for sulfur dioxide and enhanced ammonia capacities. Methacryloxypropyltrimethoxysilane (MAPS)-MCM-41 has the highest ammonia capacity at about 7 mol/kg at 1500 ppmv and 23 Â°C, and 3-aminopropyltriethoxysilane (APTES)-MCM-41 has the highest sulfur dioxide capacity at 0.85 mol/kg at 500 ppmv and 23 Â°C. These biphasic materials exhibit high adsorption capacity for two distinct gases and are promising candidates as adsorbents for protection from toxic industrial gases.

Organoalkoxysilane-grafted silica composites for acidic and basic gas adsorption.

The structure of a molecule and its concentration can strongly influence diffusional properties for transport in nanoporous materials. We study mass transfer of alkanes in BPL activated carbon using the concentration-swing frequency response method, which can easily discriminate among mass transfer mechanisms. We measure concentration-dependent diffusion rates for n-hexane, n-octane, n-decane, 2,7-dimethyloctane, and cyclodecane, which have different carbon numbers and geometries: straight chain, branched chain, and cyclic. Micropore diffusion is determined to be the controlling mass transfer resistance except at low relative saturation for n-decane, where an external mass transfer resistance also becomes important, showing that the controlling mass transfer mechanism can change with system concentration. Micropore diffusion coefficients are found to be strongly concentration dependent. Adsorption isotherm slopes obtained from measured isotherms, the concentration-swing frequency response method, and a predictive method show reasonably good agreement.

Mass transfer and adsorption equilibrium for low volatility alkanes in BPL activated carbon.

Porous organic polymers bearing metal-catecholate groups were evaluated for their ability to remove airborne ammonia, cyanogen chloride, sulphur dioxide, and octane by micro-breakthrough analysis. For ammonia, the metal-catecholate materials showed remarkable uptake under humid conditions.

Gregory W. Peterson

Edgewood Chemical Biological Center

Research Development Engineering Command

Preparation of Hydrophobic Metal-Organic Frameworks via Plasma Enhanced Chemical Vapor Deposition of Perfluoroalkanes for the Removal of Ammonia

Gregory W. Peterson

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Edgewood Chemical Biological Center

Research Development Engineering Command

Preparation of Hydrophobic Metal-Organic Frameworks via Plasma Enhanced Chemical Vapor Deposition of Perfluoroalkanes for the Removal of Ammonia

Edgewood Chemical Biological Center