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Metal-enrichment in microbial carbonates: the role of carboxylated biomacromoleculesPetrash, Daniel Alejandro 11 1900 (has links)
Carboxylated macromolecules such as alginate and glycoproteins are abundant components of modern shallow marine sediments where they are secreted by bacteria and marine infauna. Both organic compounds are proton and metal reactive; hence, they have the potential to facilitate metal sorption and biomineralization reactions. In this study, lab experiments were coupled to field-based sampling to assess the role that these compounds play in microbial mats, with particular emphasis on the hypersaline lagoons of Los Roques, Venezuela.
Here I applied a surface complexation approach to model proton and Cd adsorption behaviour of both uronic acid-rich alginate and mucin. Measured total site concentrations, available for metal adsorption, demonstrate that these compounds have the potential to induce metal partitioning in early diagenetic microenvironments. Field results from Venezuela are consistent with Mg- and trace metal- enrichment that follows a likely correlation with the degradation states of microbial biomass trapped during accretion of modern microbialites.
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Alkaline hydrolysis of sodium methyl alpha-D-glucopyranosiduronate and methyl alpha-D-glucopyranosideRobins, J. Hamilton 01 June 1968 (has links)
No description available.
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Biochemical Characterization of Plant Small CTD Phosphatases and Application of CTD Phosphatase Mutant in Hyperaccumulation of Flavonoids in ArabidopsisFeng, Yue 2010 August 1900 (has links)
In addition to AtCPL1-4, the genome of Arabidopsis thaliana encodes a large number of putative acid phosphatases. The predicted Arabidopsis SCP1-like small phosphatases (SSP) are highly homologous to the catalytic domain of eukaryotic RNA polymerase II carboxyl terminal domain (pol II CTD) phosphatases. Among the family members, SSP4, SSP4b and SSP5 form a unique group characterized by long N-terminal extensions. These three SSPs showed similar and ubiquitous gene expression. SSP4 and SSP4b were localized exclusively in the nuclei, while SSP5 accumulated both in the nucleus and cytoplasm. In vitro observation revealed that SSP4 and SSP4b dephosphorylated the pol II CTD-PO4 at both Ser2 and Ser5 in the conserved heptad repeats; however, SSP5 dephosphorylated only Ser5 of CTD-PO4. These results indicate that Arabidopsis SSP family encodes active CTD phosphatases similarly to animal SCP1 family proteins and plant CPLs family proteins, but with distinct substrate specificities.
ssp mutants did not exhibit phenotypic abnormalities under normal growth conditions. However, ssp5 single mutants and ssp4 ssp4b ssp5 triple mutants showed enhanced sensitivity to ABA and glucose during seed germination. Yet, increased ABA-inducible gene expressions were not distinguishable in triple mutants compared to wild type plants upon ABA treatment. Unlike the ssp mutations, the cpl1 mutation strongly induced RD29A expression in response to cold, ABA and NaCl treatments. Thus, the cpl1 mutant is an ideal genetic background for an inducible gene expression system, in which the detrimental effect to host plants caused by a conventional constitutive expression could be avoided.
Production of flavonoid such as anthocyanins in Arabidopsis is relatively easy to monitor and is regulated by transcription factors such as PAP1. PAP1 activates the expression of multiple enzymes in the anthocyanin biosynthesis pathway; however, high level of flavonoid production could cause vegetative growth retardation. To optimize flavonoid accumulation, a three-component system was designed consisting of a cold inducible RD29A-PAP1 expression cassette, a feedforward effector RD29A-CBF3, and a mutation in host repressor CPL1. Transgenic cpl1 plants containing both homozygous PAP1 and CBF3 transgenes produced 30-fold higher level of total anthocyanins than control plants upon cold treatment. LC/MS/MS analysis showed the flavonoid profile in cold-induced transgenic plants resembled that of previously reported pap1-D plants but were enriched for kaempferol derivatives. Furthermore, PAP1 and environmental signals synergistically regulate flavonoid pathway to produce a flavonoid blend that has not been produced by PAP1 overexpression or cold treatment alone. These results delineate the usability of the three-component inducible system in plant metabolic engineering.
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Metal-enrichment in microbial carbonates: the role of carboxylated biomacromoleculesPetrash, Daniel Alejandro Unknown Date
No description available.
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An Infrared Study of some Ω-Phenyl and Ω-Benzoyl Alkanoic AcidsChanslor, Robert Janes 08 1900 (has links)
There is no available information in the literature on interaction between carboxyl hydrogen and ω-phenyl groups. Consequently, it was of interest to seek such interactions. Some form of interaction is evident from the study of the spectra of some phenylalkanoic acids and benzoyalkanoic acids.
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Studies on N-(Purin-6-Ylcarbamoyl) ThreonineLaloue, Michel André 11 1900 (has links)
<p> N-[(9-β-D-ribofuranosyl-9H-purin-6-yl)carbamoyl]- threonine, a hypermodified nucleoside found in transfer RNA represents the archetype structure of a group of synthetic ureidopurines which promote cell division in plants. L-threonine was shown to be incorporated into this nucleoside in Tobacco tissue and Rhizopogon roseolus transfer RNA. Also, this nucleoside was isolated as a free molecule in Rhizopogon roseolus growth medium.</p> <p> Chromatographic analysis of an enzymic hydrolysate of 3 g of yeast transfer RNA failed to indicate the presence of a lipophilic derivative of PCT riboside. It is concluded that PCT riboside occurs in transfer RNA with a free carboxyl group.</p> / Thesis / Master of Science (MSc)
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The Characterization of Baxb, a Splice Variant of the Pro-Apoptotic Bax and ProteinPound, Kathleen 12 1900 (has links)
Baxa is a pro-apoptotic member of the Bcl-2 protein family that regulates a
key point in the control of apoptosis. The bax RNA undergoes a complex pattern
of RNA splicing, with eight splice isoforms known to date. The next most
abundant isoform to Baxa is Baxp, which has a unique carboxyl-terminal
sequence and consequently lacks the transmembrane domain of Baxa. This
study characterized Baxp as part of a larger project aimed at deducing the role of
cellular localization in Bax protein function.
A transient transfection assay was designed to determine the cell death
activity of a protein in adherent cells. Baxp induced cell death to a greater extent
than Baxa when transiently expressed in NIH 3T3 cells. The levels of Baxp
expression were always low, regardless of the cell type or transfection method
used. Additionally, Baxp adopted a conformation in which amino acids 13 to 19
are accessible to the monoclonal antibody 6A7. In Baxa this epitope is only
exposed in the membrane-bound activated conformation that is associated with
accessibility of the BH3 domain of Baxa that mediates protein-protein
interactions among Bcl-2 family members. Although the mechanism remains
elusive, Baxp was identified as a potent inducer of cell death. / Thesis / Master of Science (MSc)
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Sorption of selected heavy metal ions from aqueous solutions by mango seed shell derived sorbentsMoyo, Malvin 11 March 2017 (has links)
Vaal University of Technology / ii
Abstract
The use of biosorption to complement conventional water treatment techniques has gained
widespread appeal partly due to the abundance of waste materials that can be used as low
cost biosorbents. However, some materials have not yet been exploited in this regard. This
research was aimed at evaluating the biosorption potential of Mangifera indica (mango) seed
shells that are readily available in several farming areas of the Limpopo and Mpumalanga
Provinces of South Africa.
In this work, powdered ethylenediaminetetraacetic acid (EDTA) functionalized biosorbent was
prepared from alkali treated biomass of waste mango seed shells. The influence of alkali
treatment and EDTA functionalization on the physicochemical properties of the biomass was
characterized using Fourier transform infra-red spectroscopy, X-ray diffraction and
thermogravimetric analysis. Results confirmed removal of hemicelluloses, conversion of
crystalline to amorphous cellulose and the introduction of carboxyl, ester and tertiary amine
groups from EDTA. Furthermore, the powdered biosorbent was immobilized using calcium
alginate for adaptation to column sorption.
The powdered biosorbents were tested for sorption of lead(II) ions using batch sorption
experiment. Through EDTA functionalization, improvement in sorption capacity for lead(II)
ions from 59.25 mg.g-1 to 306.33 mg.g-1 was realized. The Langmuir and Pseudo-nth order
models most suitably simulated the equilibrium and kinetics of sorption by both functionalized
and non-functionalized biomaterials. The calcium alginate immobilized biosorbent was
evaluated for non-specific sorption of ionic species of copper, chromium, nickel and iron from
electroplating wastewater through discontinuous column sorption experiments. Highest
copper, chromium, nickel and iron removal was 12.3%, 14.8%, 4.4% and 13.8% from nonacidified
samples at an initial pH of 3.4, and 15.5%, 18.7%, 13.7% and 17.3% from samples
acidified to an initial pH of 1.8. Repeated sorption-desorption cycles involving acidified
wastewater resulted in successive improvement in metal uptake against declining recovery
indicating irreversible binding on –COOH groups formed from –CH2OH groups through a
redox reaction involving reduction of chromium(VI) to chromium(III).
Keywords: Mangifera indica; biosorption; alkali treatment; carboxyl functionalization; calcium
alginate
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Lewis base organocatalysts for carboxyl and acyl transfer reactionsWoods, Philip A. January 2011 (has links)
This thesis is concerned with the use of Lewis base organocatalysts for carboxyl and acyl transfer reactions. Chapter 1 introduces the ability of organic Lewis bases other than DMAP-type to promote a range of asymmetric O-, N- and C-acyl transfer processes. This chapter summarizes the developments in catalyst architectures and approaches to these processes that have been disclosed to date in this dynamic area of asymmetric organocatalysis. Chapter 2 introduces studies into the synthesis of pyrrolyl carbonates via cyclization of gamma-amino esters and ring closing metathesis (RCM) of N-allylamides. The ability of a range of Lewis bases to promote the regioselective O- to C-carboxyl transfer of pyrrolyl carbonates is also presented. Chapter 3 introduces isothiourea DHPB as an efficient Lewis base catalyst for the diastereoselective C-acylation of silyl ketene acetals with anhydrides or benzoyl fluoride, giving 3-acyl-3-aryl or 3-acyl-3-alkylfuranones in excellent yields and stereoselectivities (up to 99:1 dr). Chapter 4 introduces C(2)-aryl substituted DHPB derived-isothioureas as efficient Lewis base catalysts for the enantioselective C-acylation of silyl ketene acetals with propionic anhydride, giving 3-acyl-3-aryl or 3-acyl-3-alkylfuranones in good isolated yields and enantioselectivities (up to 98% ee). This chapter also demonstrates that these chiral isothioureas are required for high reactivity and asymmetry in related acylation manifolds. Chapter 5 presents and overall conclusion for chapters 2,3 and 4. Chapter 6 contains full experimental procedures and characterization data for all compounds synthesized in Chapters 2, 3 and 4.
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Hydroxyl-Containing Aromatic Polyimides for Carbon Dioxide Removal from Natural GasAlaslai, Nasser Y. 10 1900 (has links)
Natural gas is among the most dominant resources to provide energy supplies and Saudi
Arabia ranks among the top 5 producers worldwide. However, prior to use of methane, natural
gas has to be treated to remove other feed gas components, such as H2O, CO2, H2S, N2 and C2+
hydrocarbons. Most NG fields in KSA contain about 10 mol% carbon dioxide that has to be
reduced to less than 2 mol% for pipeline delivery.
The conventional unit operations for natural gas separations, that is, molecular sieves, amine
absorption, cryogenic distillation, and turbo expansion exhibit some disadvantages in terms of
economics, operational flexibility or system footprint. One of the most attractive alternative is
membrane technology in either standalone- or hybrid system configuration. Currently, the only
two membrane materials used in industrial natural gas applications are cellulose acetate and
polyimide, which have moderate permeability and fairly low selectivity when tested under
realistic industrial conditions. The goal for future research is to develop unique polymeric
membranes, which can at least partially replace conventional gas processing in future natural gas
projects. This will support global economics and specifically the economy of Saudi Arabia.
Newly developed polymeric materials must meet certain criteria to be used on a commercial
scale. These criteria include: (i) high permeability and selectivity, (ii) processability into thin
films, (iii) mechanical and thermal stability, and (iv) chemical stability against feed gas
components.
This project focused on the removal of carbon dioxide from natural gas by
developing and characterizing functionalized aromatic polyimide membrane materials that
exhibit very high selectivity under aggressive mixed-gas conditions. 6FDA-DAR demonstrated a
mixed-gas CO2/CH4 selectivity of 78 at a CO2 partial pressure of 10 bar with no pronounced
indication of plasticization. Combining hydroxyl- and carboxyl groups in a miscible polyimide
blend led to mixed-gas CO2/CH4 selectivity of 100 with no aging and no plasticization effects.
This burgeoning membrane material has very high potential in large-scale natural gas separations
with the best overall performance of any type developed to date.
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