Solid-State NMR 13C sensitivity at high magnetic field.

Sensitivity is the foundation of every NMR experiment, and the signal-to-noise ratio (SNR) should increase with static (B0) magnetic field, by a proportionality that primarily depends on the design of the NMR probe and receiver. In the low B0 field limit, where the coil geometry is much smaller than the wavelength of the NMR frequency, SNR can increase in proportion to B0 to the power 7/4. For modern magic-angle spinning (MAS) probes, this approximation holds for rotor sizes up to 3.2 mm at 14.1 Tesla (T), corresponding to 600 MHz 1H and 151 MHz 13C Larmor frequencies. To obtain the anticipated benefit of larger coils and/or higher B0 fields requires a quantitative understanding of the contributions to SNR, utilizing standard samples and protocols that reproduce SNR measurements with high accuracy and precision. Here, we present such a systematic and comprehensive study of 13C SNR under MAS over the range of 14.1 to 21.1 T. We evaluate a range of probe designs utilizing 1.6, 2.5 and 3.2 mm rotors, including 24 different sets of measurements on 17 probe configurations using five spectrometers. We utilize N-acetyl valine as the primary standard and compare and contrast with other commonly used standard samples (adamantane, glycine, hexamethylbenzene, and 3-methylglutaric acid). These robust approaches and standard operating procedures provide an improved understanding of the contributions from probe efficiency, receiver noise figure, and B0 dependence in a range of custom-designed and commercially available probes. We find that the optimal raw SNR is obtained with balanced 3.2 mm design at 17.6 T, that the best mass-limited SNR is achieved with a balanced 1.6 mm design at 21.1 T, and that the raw SNR at 21.1 T reaches diminishing returns with rotors larger than 2.5 mm.

Minimum Concentrations of Slow Pyrolysis Paper and Walnut Hull Cyclone Biochars Needed to Inactivate Escherichia coli O157:H7 in Soil.

Antimicrobial properties of biochar have been attributed to its ability to inactivate foodborne pathogens in soil, to varying degrees. High concentrations of biochar have reduced E. coli O157:H7 in soil and dairy manure compost, based on alkaline pH. Preliminary studies evaluating 31 different biochars determined that two slow pyrolysis biochars (paper biochar and walnut hull cyclone biochar) were the most effective at inactivating E. coli in soil. A study was conducted to determine the lowest percentages of paper and walnut hull cyclone biochars needed to reduce E. coli O157:H7 in soil. A model soil was adjusted to 17.75% moisture, and the two types of biochar were added at concentrations of 1.0, 1.5, 2.0, 2.5, 3.5, 4.5, 5.5, and 6.5%. Nontoxigenic E. coli O157:H7 were inoculated into soil at 6.84 log CFU/g and stored for up to 6 weeks at 21°C. Mean E. coli O157:H7 counts were 6.01-6.86 log CFU/g at all weeks between 1 and 6 in soil-only positive control samples. Populations in all soil amended with 1.0 and 1.5% of either type of biochar (as well as 2.0% of the walnut hull biochar) resulted in ≤0.68 log reductions at week 6, when compared with positive controls. All other concentrations (i.e., ≥2.0% paper and ≥2.5% walnut hull) inactivated ≥2.7 log at all weeks between 1 and 6 (p < 0.05). At the end of 6 weeks, E. coli O157:H7 declined by 2.84 log in 2.0% paper biochar samples, while concentrations of between 2.5 and 6.5% paper biochar completely inactivated E. coli O157:H7, as determined by spiral plating, at weeks 5 and 6. In contrast, 2.0% walnut hull biochar lowered populations by only 0.38 log at week 6, although 2.5-6.5% concentrations of walnut hull biochar resulted in complete inactivation at all weeks between 3 and 6, as assessed by spiral plating. In summary, ≥2.5% paper or walnut hull biochar reduced ≥5.0 log of E. coli O157:H7 during the 6-week storage period, which we attribute to high soil alkalinity. Amended at a 2.5% concentration, the pH of soil with paper or walnut hull biochar was 10.67 and 10.06, respectively. Results from this study may assist growers in the use of alkaline biochar for inactivating E. coli O157:H7 in soil.

Biocidal Activity of Fast Pyrolysis Biochar against Escherichia coli O157:H7 in Soil Varies Based on Production Temperature or Age of Biochar.

ABSTRACT: Soils in which fresh produce is grown can become contaminated with foodborne pathogens and are sometimes then abandoned or removed from production. The application of biochar has been proposed as a method of bioremediating such pathogen-contaminated soils. The objectives of the present study were to evaluate three fast-pyrolysis-generated biochars (FPBC; pyrolyzed in house at 450, 500, and 600°C in a newly designed pyrolysis reactor) and 10 United Kingdom Biochar Research Center (UKBRC) standard slow-pyrolysis biochars to determine their effects on the viability of four surrogate strains of Escherichia coli O157:H7 in soil. A previously validated biocidal FPBC that was aged for 2 years was also tested with E. coli to determine changes in antibacterial efficacy over time. Although neither the UKBRC slow-pyrolysis biochars or the 450 and 500°C FPBC from the new reactor were antimicrobial, the 600°C biochar was biocidal (P < 0.05); E. coli populations were significantly reduced at 3 and 3.5% biochar concentrations (reductions of 5.34 and 5.84 log CFU/g, respectively) compared with 0.0 to 2.0% biochar concentrations. The aged 500°C FPBC from the older reactor, which was previously validated as antimicrobial, lost efficacy after aging for 2 years. These results indicate that the biocidal activity of FPBC varies based on production temperature and/or age.

Guaiacol hydrodeoxygenation mechanism on Pt(111): insights from density functional theory and linear free energy relations.

Density functional theory is used to study the adsorption of guaiacol and its initial hydrodeoxygenation (HDO) reactions on Pt(111). Previous Brønsted-Evans-Polanyi (BEP) correlations for small open-chain molecules are inadequate in estimating the reaction barriers of phenolic compounds except for the side group (methoxy) carbon-dehydrogenation. New BEP relations are established using a select group of phenolic compounds. These relations are applied to construct a potential-energy surface of guaiacol-HDO to catechol. Analysis shows that catechol is mainly produced via dehydrogenation of the methoxy functional group followed by the CHx (x<3) removal of the functional group and hydrogenation of the ring carbon, in contrast to a hypothesis of a direct demethylation path. Dehydroxylation and demethoxylation are slow, implying that phenol is likely produced from catechol but not through its direct dehydroxylation followed by aromatic carbon-ring hydrogenation.

Bioenergy crops grown for hyperaccumulation of phosphorous in the Delmarva Peninsula and their biofuels potential.

Herbaceous bioenergy crops, including sorghum, switchgrass, and miscanthus, were evaluated for their potential as phytoremediators for the uptake of phosphorus in the Delmarva Peninsula and their subsequent conversion to biofuel intermediates (bio-oil) by fast pyrolysis using pyrolysis-gas chromatography/mass spectroscopy. Four cultivars of sorghum, five cultivars of switchgrass and one miscanthus (Miscanthus × giganteus) were grown in soils with two different levels of poultry manure (PM) applications. Little variation was seen in phosphorus uptake in the two different soils indicating that the levels of available phosphorus in the soil already saturated the uptake ability of the plants. However, all plants regardless of trial took up more phosphorus than that measured for the non- PM treated control. Sorghum accumulated greater levels of nutrients including phosphorus and potassium compared to switchgrass and miscanthus. The levels of these nutrients in the biomass did not have an effect on carbohydrate contents. However, the potential yield and composition of bio-oil from fast pyrolysis were affected by both agronomics and differences in mineral concentrations.

Aspen Plus® and economic modeling of equine waste utilization for localized hot water heating via fast pyrolysis.

Aspen Plus(®) based simulation models have been developed to design a pyrolysis process for on-site production and utilization of pyrolysis oil from equine waste at the Equine Rehabilitation Center at Morrisville State College (MSC). The results indicate that utilization of all the available waste from the site's 41 horses requires a 6 oven dry metric ton per day (ODMTPD) pyrolysis system but it will require a 15 ODMTPD system for waste generated by an additional 150 horses at the expanded area including the College and its vicinity. For this a dual fluidized bed combustion reduction integrated pyrolysis system (CRIPS) developed at USDA's Agricultural Research Service (ARS) was identified as the technology of choice for pyrolysis oil production. The Aspen Plus(®) model was further used to consider the combustion of the produced pyrolysis oil (bio-oil) in the existing boilers that generate hot water for space heating at the Equine Center. The model results show the potential for both the equine facility and the College to displace diesel fuel (fossil) with renewable pyrolysis oil and alleviate a costly waste disposal problem. We predict that all the heat required to operate the pyrolyzer could be supplied by non-condensable gas and about 40% of the biochar co-produced with bio-oil. Techno-economic Analysis shows neither design is economical at current market conditions; however the 15 ODMTPD CRIPS design would break even when diesel prices reach $11.40/gal. This can be further improved to $7.50/gal if the design capacity is maintained at 6 ODMTPD but operated at 4950 h per annum.

Reliable peak selection for multisample analysis with comprehensive two-dimensional chromatography.

Comprehensive two-dimensional chromatography is a powerful technology for analyzing the patterns of constituent compounds in complex samples, but matching chromatographic features for comparative analysis across large sample sets is difficult. Various methods have been described for pairwise peak matching between two chromatograms, but the peaks indicated by these pairwise matches commonly are incomplete or inconsistent across many chromatograms. This paper describes a new, automated method for postprocessing the results of pairwise peak matching to address incomplete and inconsistent peak matches and thereby select chromatographic peaks that reliably correspond across many chromatograms. Reliably corresponding peaks can be used both for directly comparing relative compositions across large numbers of samples and for aligning chromatographic data for comprehensive comparative analyses. To select reliable features for a set of chromatograms, the Consistent Cliques Method (CCM) represents all peaks from all chromatograms and all pairwise peak matches in a graph, finds the maximal cliques, and then combines cliques with shared peaks to extract reliable features. The parameters of CCM are the minimum number of chromatograms with complete pairwise peak matches and the desired number of reliable peaks. A particular threshold for the minimum number of chromatograms with complete pairwise matches ensures that there are no conflicts among the pairwise matches for reliable peaks. Experimental results with samples of complex bio-oils analyzed by comprehensive two-dimensional gas chromatography (GCxGC) coupled with mass spectrometry (GCxGC-MS) indicate that CCM provides a good foundation for comparative analysis of complex chemical mixtures.

Proton-detected solid-state NMR spectroscopy of natural-abundance peptide and protein pharmaceuticals.

The natural way: A sensitive NMR spectroscopic method is developed to obtain well-resolved two-dimensional spectra ((15)N-(1)H and (13)C-(1)H) for natural-abundance (that is, without the need for isotopic enrichment) large-molecule samples, such as biopharmaceuticals. This method gives structural insights on two lyophilized aprotinin samples and three insulin samples in lyophilized, microcrystalline suspension formulation (red; see picture) and fibril (green) forms.

Proton-detected solid-state NMR spectroscopy of fully protonated proteins at 40 kHz magic-angle spinning.

Remarkable progress in solid-state NMR has enabled complete structure determination of uniformly labeled proteins in the size range of 5-10 kDa. Expanding these applications to larger or mass-limited systems requires further improvements in spectral sensitivity, for which inverse detection of 13C and 15N signals with 1H is one promising approach. Proton detection has previously been demonstrated to offer sensitivity benefits in the limit of sparse protonation or with approximately 30 kHz magic-angle spinning (MAS). Here we focus on experimental schemes for proteins with approximately 100% protonation. Full protonation simplifies sample preparation and permits more complete chemical shift information to be obtained from a single sample. We demonstrate experimental schemes using the fully protonated, uniformly 13C,15N-labeled protein GB1 at 40 kHz MAS rate with 1.6-mm rotors. At 500 MHz proton frequency, 1-ppm proton line widths were observed (500 +/- 150 Hz), and the sensitivity was enhanced by 3 and 4 times, respectively, versus direct 13C and 15N detection. The enhanced sensitivity enabled a family of 3D experiments for spectral assignment to be performed in a time-efficient manner with less than a micromole of protein. CANH, CONH, and NCAH 3D spectra provided sufficient resolution and sensitivity to make full backbone and partial side-chain proton assignments. At 750 MHz proton frequency and 40 kHz MAS rate, proton line widths improve further in an absolute sense (360 +/- 115 Hz). Sensitivity and resolution increase in a better than linear manner with increasing magnetic field, resulting in 14 times greater sensitivity for 1H detection relative to that of 15N detection.

Catalytic asymmetric prins cyclizations: cation generation and trapping with (BINAP)Pt dications.

[reaction: see text] (R)-[(tolBINAP)Pt(NC(6)F(5))(2)][SbF(6)](2) (5) catalyzes the highly enantioselective Prins reaction between 2-allylphenols and glyoxylate esters. Other Lewis acid catalysts favor glyoxylate-ene products.

Reduction of RF-induced sample heating with a scroll coil resonator structure for solid-state NMR probes.

Heating due to high power 1H decoupling limits the experimental lifetime of protein samples for solid-state NMR (SSNMR). Sample deterioration can be minimized by lowering the experimental salt concentration, temperature or decoupling fields; however, these approaches may compromise biological relevance and/or spectroscopic resolution and sensitivity. The desire to apply sophisticated multiple pulse experiments to proteins therefore motivates the development of probes that utilize the RF power more efficiently to generate a high ratio of magnetic to electric field in the sample. Here a novel scroll coil resonator structure is presented and compared to a traditional solenoid. The scroll coil is demonstrated to be more tolerant of high sample salt concentrations and cause less RF-induced sample heating. With it, the viable experimental lifetime of a microcrystalline ubiquitin sample has been extended by more than an order of magnitude. The higher B1 homogeneity and permissible decoupling fields enhance polarization transfer efficiency in 15N-13C correlation experiments employed for protein chemical shift assignments and structure determination.