392 research outputs found

    Reactivity and Chemical Characterization of Dissolved Organic Matter in an Estuary

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    This dissertation used Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (13C-NMR) data to quantify the changes of major chemical compound classes in high molecular weight (HMW, \u3e1kDa) DOM isolated along a transect from Great Dismal Swamp through the Elizabeth River/Chesapeake Bay system to the coastal Atlantic Ocean off Virginia, USA. Results show that both carboxylic acids and aromatic compounds are lost along the transect, while amide, and carbohydrate moieties could have a mid-transect source. Addressing the seasonal and spatial changes in the chemical composition of high molecular weight DOM using C/N ratio and δ13C signatures indicates a dramatic shift in the relative importance of the processes affecting the HMW-DOM as it moves from fresh water to the marine end member. Sorption and flocculation and reworking by heterotrophic bacteria seem to be the major players in the lower salinity region, but at the higher salinity regions the introduction of new carbon sources by primary production seems to be the major process. Applying principal component analysis (PCA) and two dimensional correlation spectroscopy to the 13C-NMR spectra of the HMW-DOM shows that HMW-DOM consists of three major components that have different biogeochemical reactivity. The first component appears to be composed of a heteropolysaccharide (HPS) component and it increases as I move to the marine end member, while the second component appears to be composed of carboxyl-rich compounds (CRC) and its carbon percentage decreases as we move away from the fresh water end member. The third component contains the major functional group of amide/amino sugar (AMS) and its carbon percentage stays almost constant regardless of the seasonal and spatial changes along the salinity transect. It seems that the HPS and CRC components are present in many aquatic environments at different relative ratios. Across aquatic environments the components contain compounds that share similar backbone structures although there is significant variation in some of their functional groups as a function of aquatic system. The 13C-label method presented here for determining the enhanced aqueous solubility of organic compounds by natural aqueous DOM is a promising new tool for investigating the reactivity of DOM. Applying the method to Dismal Swamp DOM shows that the reactivity differences between high molecular weight, low molecular weight, and total DOM samples are consistent with potential variations in their higher order structures. However, coupling the method with FTIR analysis indicates that ultrafiltration is not merely a pure physical separation but involves a chemical separation as well

    Abiotic Formation of Dissolved Organic Sulfur in Anoxic Sediments of Santa Barbara Basin

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    Sulfurization has been found to enhance organic matter preservation and petroleum formation in marine sediments. However, we do not yet have a comprehensive understanding of sulfurization mechanisms. In this study, we investigated several possible mechanisms of dissolved organic sulfur (DOS) formation in the top 4.5 m of anoxic sediments of Santa Barbara Basin (SBB), California Borderland. Using Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FTICR-MS), we identified chemical formulas of potential dissolved organic matter (DOM) precursors to these DOS compounds. We also examined how the formulas of abiotically formed DOS changed as a function of depth across a major redox gradient. Results show that abiotic nucleophilic addition reactions involving bisulfide (HS-) and polysulfide (HSx) are the major sulfurization pathways that form DOS in anoxic pore waters of SBB sediments. We identified 2124 unique DOS formulas that could be generated from the addition of HS- and HSx to 2203 DOM formulas, and this accounted for ~70% of all DOS formulas detected in these pore waters. Examining the DOM formulas that served as reactants in the abiotic sulfurization reactions, we found that 64% contained only carbon, hydrogen, and oxygen (CHO formulas) while the remainder (34%) included nitrogen (DON formulas). Our results revealed high reactivity toward sulfurization among many of the CHO and DON formulas that have H/C and O/C elemental ratios that overlap with those of carboxylrich alicyclic molecules (CRAM). This specific class of formulas could play an important role in the formation of organic sulfur compounds in sulfidic marine ecosystems, and in the formation of sulfur-containing protokerogen in marine sediments. Our results further suggest that anoxic sediments are a source of DOS compounds to the oceans

    Estimating Hydroxyl Radical Photochemical Formation Rates in Natural Waters During Long-Term Laboratory Irradiation Experiments

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    In this study it was observed that, during long-term irradiations (\u3e1 day) of natural waters, the methods for measuring hydroxyl radical (˙OH) formation rates based upon sequentially determined cumulative concentrations of photoproducts from probes significantly underestimate actual ˙OH formation rates. Performing a correction using the photodegradation rates of the probe products improves the ˙OH estimation for short term irradiations (\u3c1 day), but not long term irradiations. Only the ‘instantaneous’ formation rates, which were obtained by adding probes to aliquots at each time point and irradiating these sub-samples for a short time (≤2 h), were found appropriate for accurately estimating ˙OH photochemical formation rates during long-term laboratory irradiation experiments. Our results also showed that in iron- and dissolved organic matter (DOM)-rich water samples, ˙OH appears to be mainly produced from the Fenton reaction initially, but subsequently from other sources possibly from DOM photoreactions. Pathways of ˙OH formation in long-term irradiations in relation to H2O2 and iron concentrations are discussed

    A coupled geochemical and biogeochemical approach to characterize the bioreactivity of dissolved organic matter from a headwater stream

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    The bioreactivity or susceptibility of dissolved organic matter (DOM) to microbial degradation in streams and rivers is of critical importance to global change studies, but a comprehensive understanding of DOM bioreactivity has been elusive due, in part, to the stunningly diverse assemblages of organic molecules within DOM. We approach this problem by employing a range of techniques to characterize DOM as it flows through biofilm reactors: dissolved organic carbon (DOC) concentrations, excitation emission matrix spectroscopy (EEMs), and ultrahigh resolution mass spectrometry. The EEMs and mass spectral data were analyzed using a combination of multivariate statistical approaches. We found that 45% of stream water DOC was biodegraded by microorganisms, including 31–45% of the humic DOC. This bioreactive DOM separated into two different groups: (1) H/C centered at 1.5 with O/C 0.1–0.5 or (2) low H/C of 0.5–1.0 spanning O/C 0.2–0.7 that were positively correlated (Spearman ranking) with chromophoric and fluorescent DOM (CDOM and FDOM, respectively). DOM that was more recalcitrant and resistant to microbial degradation aligned tightly in the center of the van Krevelen space (H/C 1.0–1.5, O/C 0.25–0.6) and negatively correlated (Spearman ranking) with CDOM and FDOM. These findings were supported further by principal component analysis and 2‐D correlation analysis of the relative magnitudes of the mass spectral peaks assigned to molecular formulas. This study demonstrates that our approach of processing stream water through bioreactors followed by EEMs and FTICR‐MS analyses, in combination with multivariate statistical analysis, allows for precise, robust characterization of compound bioreactivity and associated molecular level composition. Key Points Humic DOM is susceptible to microbial degradation along with peptide‐like DOM Labile DOM can be distinguished from recalcitrant DOM in van Krevelen space EEMs and FTICR‐MS chemically characterize bioreactive and recalcitrant DOMPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/108612/1/jgrg20256.pd

    A Coupled Geochemical and Biogeochemical Approach to Characterize the Bioreactivity of Dissolved Organic Matter From a Headwater Stream

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    The bioreactivity or susceptibility of dissolved organic matter (DOM) to microbial degradation in streams and rivers is of critical importance to global change studies, but a comprehensive understanding of DOM bioreactivity has been elusive due, in part, to the stunningly diverse assemblages of organic molecules within DOM. We approach this problem by employing a range of techniques to characterize DOM as it flows through biofilm reactors: dissolved organic carbon (DOC) concentrations, excitation emission matrix spectroscopy (EEMs), and ultrahigh resolution mass spectrometry. The EEMs and mass spectral data were analyzed using a combination of multivariate statistical approaches. We found that 45% of stream water DOC was biodegraded by microorganisms, including 31-45% of the humic DOC. This bioreactive DOM separated into two different groups: (1) H/C centered at 1.5 with O/C 0.1-0.5 or (2) low H/C of 0.5-1.0 spanning O/C 0.2-0.7 that were positively correlated (Spearman ranking) with chromophoric and fluorescent DOM (CDOM and FDOM, respectively). DOM that was more recalcitrant and resistant to microbial degradation aligned tightly in the center of the van Krevelen space (H/C 1.0-1.5, O/C 0.25-0.6) and negatively correlated (Spearman ranking) with CDOM and FDOM. These findings were supported further by principal component analysis and 2-D correlation analysis of the relative magnitudes of the mass spectral peaks assigned to molecular formulas. This study demonstrates that our approach of processing stream water through bioreactors followed by EEMs and FTICR-MS analyses, in combination with multivariate statistical analysis, allows for precise, robust characterization of compound bioreactivity and associated molecular level composition

    PENGEMBANGAN BISKUIT MP-ASI DENGAN PENAMBAHAN PUREE LABU KUNING (Cucurbita moschata) DAN TEPUNG BERAS MERAH (Oryza nivara)

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    Makanan pendamping air susu ibu (MP-ASI) merupakan makanan pendamping dari air susu ibu yang disiapkan untuk membantu memenuhi kebutuhan gizi bayi. MP-ASI diberikan kepada bayi ketika air susu ibu sudah tidak cukup dalam memenuhi kebutuhan gizi anak. Pada bayi usia 12-24 bulan mulai diperkenalkan dengan jenis makanan padat seperti biskuit sebagai MP-ASI. Biskuit MP-ASI dapat dikembangkan melalui pemanfaatan bahan pangan lokal seperti labu kuning yang memiliki kandungan beta karoten dan tepung beras merah yang memiliki kandungan protein. Puree labu kuning merupakan bentuk produk olahan dari buah labu kuning dengan pemberian proses pengukusan. Tepung beras merah merupakan bentuk produk olahan dari beras merah. Penelitian ini bertujuan untuk mendapatkan biskuit MP-ASI yang mampu memberikan kandungan gizi terbaik seperti vitamin A dan protein, untuk mengetahui pengaruh penambahan puree labu kuning dan tepung beras merah pada biskuit MP-ASI, selain itu juga mengetahui tingkat kesukaan pada masing-masing formulasi biskuit. Pada penelitian ini menggunakan 4 formulasi biskuit MP-ASI, yaitu biskuit kontrol tanpa penambahan puree labu kuning dan tepung beras merah, biskuit formulasi 1 dengan penambahan 5% tepung beras merah dan 10% puree labu kuning, biskuit formulasi 2 dengan penambahan 7,5% tepung beras merah dan 7,5% puree labu kuning, serta biskuit formulasi 3 dengan penambahan 10% tepung beras merah dan 5% puree labu kuning. Analisa yang dilakukan dalam penelitian ini adalah analisa fisik, analisa kimiawi, dan analisa organoleptik. Pada analisa fisik warna yang terbaik dimiliki biskuit kontrol dan analisa tekstur terkeras dimiliki biskuit formulasi 3 dan formulasi terlunak dimiliki biskuit formulasi 1 dengan penambahan puree labu kuning terbanyak. Analisa kimiawi yang dilakukan menghasilkan biskuit formulasi 3 memiliki kadar abu tertinggi yaitu 1,63%, kadar protein tertinggi yaitu 6,16%. Kadar air tertinggi dimiliki biskuit formulasi 1 yaitu 4,80%, kadar lemak teringgi dimiliki biskuit kontrol sebesar 37,59%, dan kadar karbohidrat tertinggi dimiliki biskuit formulasi 2 yaitu sebesar 56,61%. Kadar beta karoten tertinggi dimiliki biskuit formulasi 1 yaitu sebesar 4,32 mg/100 gram produk. Hasil analisa organoleptik biskuit MP-ASI kontrol memiliki tingkat kesukaan overall tertinggi dengan rata-rata 2,88. Selain itu biskuit formulasi 1 merupakan formulasi yang agak disukai disukai panelis dengan rata-rata 2,65 dengan penambahan 10% puree labu kuning dan 5% tepung beras merah

    Novel derivative of aminobenzenesulfonamide (3c) induces apoptosis in colorectal cancer cells through ROS generation and inhibits cell migration

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    Background: Colorectal cancer (CRC) is the 3rd most common type of cancer worldwide. New anti-cancer agents are needed for treating late stage colorectal cancer as most of the deaths occur due to cancer metastasis. A recently developed compound, 3c has shown to have potent antitumor effect; however the mechanism underlying the antitumor effect remains unknown. Methods: 3c-induced inhibition of proliferation was measured in the absence and presence NAC using MTT in HT-29 and SW620 cells and xCELLigence RTCA DP instrument. 3c-induced apoptotic studies were performed using flow cytometry. 3c-induced redox alterations were measured by ROS production using fluorescence plate reader and flow cytometry and mitochondrial membrane potential by flow cytometry; NADPH and GSH levels were determined by colorimetric assays. Bcl2 family protein expression and cytochrome c release and PARP activation was done by western blotting. Caspase activation was measured by ELISA. Cell migration assay was done using the real time xCELLigence RTCA DP system in SW620 cells and wound healing assay in HT-29. Results: Many anticancer therapeutics exert their effects by inducing reactive oxygen species (ROS). In this study, we demonstrate that 3c-induced inhibition of cell proliferation is reversed by the antioxidant, N-acetylcysteine, suggesting that 3c acts via increased production of ROS in HT-29 cells. This was confirmed by the direct measurement of ROS in 3c-treated colorectal cancer cells. Additionally, treatment with 3c resulted in decreased NADPH and glutathione levels in HT-29 cells. Further, investigation of the apoptotic pathway showed increased release of cytochrome c resulting in the activation of caspase-9, which in turn activated caspase-3 and −6. 3c also (i) increased p53 and Bax expression, (ii) decreased Bcl2 and BclxL expression and (iii) induced PARP cleavage in human colorectal cancer cells. Confirming our observations, NAC significantly inhibited induction of apoptosis, ROS production, cytochrome c release and PARP cleavage. The results further demonstrate that 3c inhibits cell migration by modulating EMT markers and inhibiting TGFβ-induced phosphorylation of Smad2 and Samd3. Conclusions: Our findings thus demonstrate that 3c disrupts redox balance in colorectal cancer cells and support the notion that this agent may be effective for the treatment of colorectal cancer

    Analytical and computational advances, opportunities, and challenges in marine organic biogeochemistry in an era of "Omics"

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    © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Steen, A. D., Kusch, S., Abdulla, H. A., Cakic, N., Coffinet, S., Dittmar, T., Fulton, J. M., Galy, V., Hinrichs, K., Ingalls, A. E., Koch, B. P., Kujawinski, E., Liu, Z., Osterholz, H., Rush, D., Seidel, M., Sepulveda, J., & Wakeham, S. G. Analytical and computational advances, opportunities, and challenges in marine organic biogeochemistry in an era of "Omics". Frontiers in Marine Science, 7, (2020): 718, doi:10.3389/fmars.2020.00718.Advances in sampling tools, analytical methods, and data handling capabilities have been fundamental to the growth of marine organic biogeochemistry over the past four decades. There has always been a strong feedback between analytical advances and scientific advances. However, whereas advances in analytical technology were often the driving force that made possible progress in elucidating the sources and fate of organic matter in the ocean in the first decades of marine organic biogeochemistry, today process-based scientific questions should drive analytical developments. Several paradigm shifts and challenges for the future are related to the intersection between analytical progress and scientific evolution. Untargeted “molecular headhunting” for its own sake is now being subsumed into process-driven targeted investigations that ask new questions and thus require new analytical capabilities. However, there are still major gaps in characterizing the chemical composition and biochemical behavior of macromolecules, as well as in generating reference standards for relevant types of organic matter. Field-based measurements are now routinely complemented by controlled laboratory experiments and in situ rate measurements of key biogeochemical processes. And finally, the multidisciplinary investigations that are becoming more common generate large and diverse datasets, requiring innovative computational tools to integrate often disparate data sets, including better global coverage and mapping. Here, we compile examples of developments in analytical methods that have enabled transformative scientific advances since 2004, and we project some challenges and opportunities in the near future. We believe that addressing these challenges and capitalizing on these opportunities will ensure continued progress in understanding the cycling of organic carbon in the ocean.The Hanse-Wissenschaftskolleg Delmenhorst, Germany, sponsored the “Marine Organic Biogeochemistry” workshop in April 2019, of which this working group report was a part. The workshop was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – project number: 422798570. The Geochemical Society provided additional funding for the conference. AS was supported by DOE grant DE-SC0020369
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