Browsing by Subject "structure"

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    Bulletin No. 38. The Stratigraphy and Structure of the Mesabi Range, Minnesota
    (Minnesota Geological Survey, 1954) White, David A.
    The later Precambrian Animikie group in northeastern Minnesota consists of three sedimentary units: the Pokegama (quartzite), Biwabik (iron-rich rock), and Virginia (argillite) formations. "Mesabi range" designates the preglacial outcrop belt, 1/4 to 3 miles wide and 120 miles long, of the Biwabik formation. Varieties of iron-rich rock ("taconite") are either granular or slaty and consist dominantly of chert, iron silicates, magnetite, and siderite. The Lower Cherty, Lower Slaty, Upper Cherty, and Upper Slaty members of the Biwabik formation, which averages 600 feet in thickness, can be further subdivided as shown on a detailed longitudinal stratigraphic section. These members are fairly uniform along most of the range, but only one cherty and one slaty member exist on the Westernmost Mesabi, where the lithic units are intertongued. The areal distribution of rock units on the Westernmost Mesabi is shown on a geologic map. The Biwabik, Pokegama, and Virginia formations are considered conformable. Mesabi rocks probably correlate with those of the Emily district 30 miles away. Chert, greenalite, minnesotaite, stilpnomelane, magnetite, some hematite, and siderite probably formed either during deposition or diagenesis. The rocks are essentially unmetamorphosed. The Pokegama and Biwabik formations were probably produced by the migration of a series of coexisting environments of deposition during an advance, a retreat, and a second advance of the Animikie sea. The deposits formed, during the retreat, in successive environments seaward from shore, were clastic material, carbonaceous-pyritic mud, chert-siderite, chert-magnetite, and iron silicate. Fine clastics of the Virginia formation, perhaps furnished by an outburst of volcanic activity, spread across the former environments of chemical sedimentation. Possible conditions of iron sedimentation were as follows: derivation of iron and silica by weathering of a low-lying land mass, perhaps under an atmosphere rich in carbon dioxide, and a seasonal climate; tectonic stability; and deposition in a shallow, quiescent epicontinental sea. The Animikie beds strike about N. 75 degrees E. and commonly dip 6-12 degrees SE. A structure contour map on the base. of the Biwabik formation shows numerous small anticlines, synclines, monoclines, and faults. Three major joint sets are present. The few rocks intrusive into the Biwabik formation include diabase sills, the Duluth gabbro, and the Aurora syenite sill. Contact metamorphism by the soda-rich Aurora sill has produced crocidolite in adjacent taconite. Minor internal folding of Animikie beds seems to be more prevalent where the underlying rocks are volcanic or sedimentary rather than granitic. The Mesabi range is covered by glacial drift which thickens southward, commonly from 20 to 200 feet, away from a ridge known as the Giants Range. Drift is as much as 500 feet thick over the Westernmost Mesabi. A map of the thickness of drift shows many drift-buried preglacial bedrock valleys that extend from notches in the Giants Range southward across the Mesabi range. Cretaceous iron-ore conglomerates, which at places overlie the Biwabik formation, occur as erosional remnants on bedrock ridges. The scattered soft iron-ore bodies in the Biwabik formation are residual concentrates of oxidized iron minerals formed by the leaching of silica from the chert and iron silicates in taconite. Conditions favoring ore concentration are thought to be as follows: accentuated fracturing at folds and faults allowing ready circulation of leaching solutions; a high iron content in taconite; reducing rather than oxidizing conditions of deposition of the original taconite; the fine size of the grains in taconite and the intimate intermixing of different minerals; a lack of metamorphism, which coarsens the grain; and the availability of large amounts of solutions. The soft ores may have been concentrated by downward-circulating ground waters.
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    The extraction, characterization, modification, and texturization of novel pennycress (Thlaspi arvense) protein for food applications
    (2023-11) Mitacek, Rachel
    The food industry is actively seeking functional, nutritious, and sustainably produced crops as novel sources of plant protein ingredients to aid in feeding the growing population and address consumer demands. Pennycress (Thlaspi arvense) protein is an attractive alternative to market leading proteins, soy and wheat, as it is currently non-allergenic, non-GMO, and has vast environmental benefits. As a winter cover crop, pennycress provides soil stabilization, nutrient sequestration, and reduced nitrate leaching. Furthermore, pennycress oilseeds are high in protein and oil contents, which are attractive to valorize as two potential food ingredients. The oil from pennycress is currently utilized for industrial biofuels, leaving behind a proteinaceous meal as a by-product. Extracting protein from the meal will increase crop value, creating incentive for farmers to grow this sustainable crop, and will aid in addressing the growing consumer demands for alternative sources of plant proteins. Research on the utilization of pennycress oilseeds for food applications is limited due to antinutritional compounds, namely erucic acid and glucosinolates. Recent agricultural advancements have identified accessions of pennycress with no erucic acid, which are suitable for human consumption. In addition, glucosinolates, which are typically abundant in pennycress meal, are lost during protein isolation steps. Determining optimal, scalable protein extraction conditions that have a high yield of functional, nutritious protein isolates is crucial when evaluating novel crops for food applications. Furthermore, identifying differences in protein structural and functional characteristics among genetically diverse lines is an instrumental knowledge in the advancement of breeding efforts for pennycress. Many plant proteins are known to have inferior functionality compared to whey and soy protein, limiting their use in a variety of applications. Accordingly, this research was divided into two studies to evaluate protein extraction conditions and their impact on structural, functional, and nutritional characteristics of pennycress protein, and then to enhance inferior functional properties through targeted structural modification techniques. Therefore, the objectives of the first study were to 1) optimize protein extraction conditions to maximize yield and purity following two extraction methods, alkaline solubilization coupled with isoelectric precipitation and salt solubilization coupled with ultrafiltration and 2) characterize structural, functional, and nutritional properties of pennycress protein isolates as impacted by the extraction method, scaling up, and difference in genetic variety. Wild-type (W), and zero erucic acid (0EA) pennycress seeds harvested in 2017 were screw-pressed to expel the oil, milled to 60-mesh, and then residual oil was extracted using hexane to produce defatted pennycress meal (DPM). W-DPM was utilized for protein extraction following alkaline solubilization coupled with isoelectric precipitation and salt solubilization coupled with ultrafiltration. Pennycress protein isolate (PcPI) from alkaline extraction (W-PcPI-pH) had a dark, undesirable color, therefore, sodium sulfite was utilized during alkaline solubilization as a reducing agent to mitigate browning. Salt extracted pennycress protein isolate (W-PcPI-Salt) had superior color and functionality. Therefore, salt extraction was used for pilot plant scale up production of PcPI and for protein extraction from 0EA-DPM. Structural and functional characterization was performed on PcPI produced following selected alkaline (with and without sodium sulfite, W-PcPI-pH and W-PcPI-pH-S, respectively) and salt extraction conditions, scaled up salt extraction, and from 0EA seeds. Structural and functional properties of the PcPI samples were compared to native (nSPI) and commercial (cSPI) soy protein isolates. Furthermore, PcPI-salt and W-DPM were evaluated for in-vitro and in-vivo protein digestibility corrected amino acid score (PDCAAS). PcPI-pH, produced with and without the use of sodium sulfite, had relatively poor functionality overall as a consequence of excessive protein denaturation and aggregation and high surface hydrophobicity. On the other hand, W-PcPI-Salt had similar gel strength, three times higher solubility under acidic conditions, and 1.5 times higher emulsification capacity compared to cSPI. 0EA-PcPI-Salt had comparable functionality to that of W-PcPI-Salt. The scaling up process of W-PcPI-Salt resulted in partial denaturation and mild polymerization that contributed to enhanced surface hydrophilic/hydrophobic balance, water holding capacity (WHC), and gel strength compared to its bench scale counterpart. Protein profiling showed that PcPI contains primarily small molecular weight proteins compared to nSPI, contributing to inferior gelation and WHC. Finally, the in-vitro (0.87) and in-vivo (0.72) PDCAAS of PcPI-Salt was superior or comparable to other commercially available plant protein sources. Protein crosslinking and formation of soluble aggregates are required for the development of a strong 3-dimensional gel network that entraps water. Proteins of relatively large molecular weight are correlated with a high potential to form cohesive, strong gel networks. Crosslinking proteins in PcPI will increase gel strength and WHC for enhanced texturization potential, and incorporation into high-value meat analogue applications. Protein crosslinking can be induced by either transglutaminase (TG) or physical treatment with cold atmospheric plasma (CAP). Therefore, the objectives of the second study were to 1) evaluate the effect of CAP and TG modifications on the structural and functional characteristics of PcPI, and 2) to determine the texturization potential of the modified PcPI. CAP treatment with dielectric barrier discharge (DBD) was utilized to polymerize PcPI (PcPI-CP). The production of TG modified PcPI (PcPI-TG) was optimized for enzyme dose, the use of pre-treatment denaturation, and time based on lysine crosslinking and protein profile. PcPI-CP and PcPI-TG were evaluated for structural and functional properties compared to unmodified PcPI. Micro-compounding was utilized for bench scale texturization of unmodified, PcPI-CP, and PcPI-TG at 50% water content. The texturization potential was assessed through mechanical responses during micro-compounding, structural properties, and texture profile analysis. CAP treatment induced polymerization primarily through intermolecular disulfide interchange, whereas TG resulted in a relatively higher extent of polymerization that was induced through a combination of inter- and intramolecular disulfide linkages and other covalent interactions involving acidic subunits of cruciferin. Compared to unmodified PcPI, PcPI-CP and PcPI-TG had double and triple the gel strength, respectively. Furthermore, PcPI-TG had the highest WHC (almost 100%). Upon micro-compounding, unmodified PcPI did not form fibrous structures and instead was a soft mass with low resilience and cohesiveness. Micro-compounding of PcPI-CP resulted in hard, dense fibrous structures due to the low WHC. However, the high gel strength and WHC of PcPI-TG resulted in fibrous structures with more air incorporation upon micro-compounding. Results confirmed that polymerization, especially with TG, can enhance gelation properties and texturization potential of PcPI. This work was the first to optimize protein extraction conditions from pennycress and provide a comprehensive structural, functional, and nutritional comparison among the resulting isolates. Overall, this work demonstrated that PcPI can be successfully extracted from DPM with high protein purity and yield, and acceptable color. Furthermore, the characterization of PcPI from genetically diverse lines provided a benchmark of knowledge to progress pennycress breeding efforts. Results confirmed that salt extraction is scalable and can result in PcPI with favorable functional properties that are comparable, or in some cases superior to cSPI. The low gel strength of PcPI was overcome by inducing polymerization through CAP and TG treatment, ultimately enhancing texturization potential. In particular, TG modification increased the WHC of PcPI, which resulted in textural properties that are desirable for meat analogue applications. This research provided foundational knowledge for the processing, modification, and utilization of PcPI. The introduction of PcPI into the protein ingredients market provides a sustainable, nutritious, and highly functional protein source for use in a wide range of food applications.
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    Guidebook 9. Field Trip Guidebook for Stratigraphy, Structure and Mineral Resources of East-Central Minnesota
    (Minnesota Geological Survey, 1979) Morey, G.B.; Davidson, D.M. Jr
    Early in the 20th century, east-central Minnesota became the source of appreciable quantities of iron and ferromanganese, and even earlier, the source of a variety of granite products (Morey, 1977). Because of the obvious economic importance of the commodities to the state, most of the geologic work in east-central Minnesota focused on the Cuyuna iron-mining district or on the St. Cloud area where there are numerous granite quarries. Less attention was given to the geology of other parts of east-central Minnesota and to the possible presence of other mineral resources. This was true mainly because a fairly ubiquitous mantle of Quaternary materials made it difficult, time consuming and expensive for a company to establish the basic geologic information necessary to a successful exploration program. However, recent geologic work (Morey, 1978) has led to the recognition of several geologic environments that are similar to mineral-producing districts elsewhere in the world (Morey, 1977). Although these studies have shown that a variety of mineral occurrences may exist, most attention to date has focused on environments that may contain uranium. This road log starts at the Minnesota-Wisconsin border along the st. Louis River near Fond du Lac, the westernmost suburb of Duluth, Minnesota, and terminates near Sturgeon Lake on U.S. Interstate Highway 35 some 50 miles southwest of Duluth. Note that the mileages in this road log are approximate.
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    Structural- and Spectroscopic-Reactivity Relationships of Nonheme Oxoiron(IV) Complexes
    (2019-05) Rasheed, Waqas
    Non-heme oxoiron(IV) motifs have been identified as key intermediates that activate strong C—H bonds. Unlike the enzymatic intermediates however, most oxoiron(IV) complexes in synthetic chemistry have a triplet ground spin state and thus differ in their functional and electronic properties from the S = 2 units characterized in the enzymes. One striking exception is the complex [FeIV(O)(TQA)(L)]2+, where TQA = tris(2-quinolylmethyl)amine, which has Mössbauer parameters that closely resemble those of TauD-J, an enzymatic intermediate that has been relatively well-characterized. This oxoiron(IV) complex contains quinoline donors, and its thermal instability precludes its structural characterization (half-life = 15 minutes at 233 K). In this dissertation, several oxoiron(IV) complexes supported by pentadentate and tetradentate ligands are characterized, and examined for their reactivity and spectroscopic features. Crystallographic characterization of a few of these molecules is also reported. The structurally characterized oxoiron(IV) complexes along with some previously reported oxoiron(IV) complexes are used to set up structure-reactivity and spectroscopic-reactivity relationships, and show linear correlations with increasing isomer shifts, λmax values as well as metal-ligand distances. In addition, this thesis also uses 1H-NMR spectroscopy as an effective tool to identify solution-state structure as well the spin state of oxoiron(IV) complexes. We also characterize the first example of a spin crossover oxoiron(IV) complex, examples of which are only seen in iron(II) and iron(III) complexes.
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    Structure determination of zeolite nanosheets
    (2012) Zhang, Xueyi; Tsapatsis, Michael
    MFI and MWW zeolite nanosheets are building units for state-of-the-art zeolite thin films for gas separation. In this study, the structures of exfoliated MFI and MWW zeolite nanosheets were determined using a combination of experimental and simulation methods. Based on characterization results from atomic force microscopy and transmission electron microscopy, the structures and thicknesses of the exfoliated zeolite nanosheets were proposed. After optimization with Car-Parrinello molecular dynamics, X-ray diffraction patterns and electron diffraction patterns are simulated from these structures. The agreement between experimental and simulated characterization data suggested that the proposed structures should represent the actual structures of the exfoliated zeolite nanosheets. The methods used in this study can be extended to determining structures of other zeolite nanostructures.