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Linking optical and chemical signatures of dissolved organic matter in the southern Argentine shelf: Distribution and bioavailability
摘要： Fluorescence spectroscopy is commonly used to investigate the distribution and dynamics of dissolved organic matter (DOM) in marine systems. However, the direct comparison with chemical signatures is essential to substantiate the molecular composition of specific fluorescent components. Here we report the relation between optical and chemical signatures of DOM in waters of the Beagle Channel (BCW) (south-east of Tierra del Fuego, in the southern Argentine shelf) at the Pacific-Atlantic connection and neighboring coastal (CW) and oceanic (OW) waters (54.75-55.75°S, 64-68°W). The relationships among concentrations of total dissolved carbohydrates (TDCHO) and amino acids (TDAA), and fluorescent DOM (FDOM), including terrestrial “humic-like” (FDOMC) and “protein-like” compounds (FDOMT), and bioavailability of DOM components were assessed from field measurements acquired in the austral summer 2012. The maximal concentrations of TDCHO, dissolved organic carbon (DOC) and FDOMc intensities were found in BCW, while the minima in OW, displaying a negative correlation with salinity. This spatial distribution of biogeochemical signals suggests that humic compounds contributed by continental runoff contain refractory carbohydrates, and FDOMC resulted as a reliable tracer of carbon pathways in the Pacific-Atlantic connection. Conversely, TDAA and FDOMT showed the opposite distributional trend, with minimal concentrations in BCW and the maxima in CW and OW. The significant positive correlation of TDAA with salinity suggests open water sources of these components, however, phytoplankton biomass (Chla) in CW and OW was significantly lower than in BCW, ruling out the assumption of autochthonous source in open waters. TDAA were negatively correlated with the abundance of heterotrophic bacteria (HB), which displayed a consistent decrease from BCW towards OW, suggesting high bacterial uptake of TDAA in the BCW. This bacterial uptake is supported by the observed variation in carbon contribution of TDAA to DOC (amino acids carbon yield, in %), which is an indicator of DOM lability. The negative correlation found between amino acids carbon yield and HB abundance reflects intense bacterial activity in BCW, where phytoplankton biomass was maximum. Hence, higher DOM “freshness” occurs in the BCW, suggesting a tight coupling between microbial production and consumption.
关键词： Pacific-Atlantic connection.,amino acids,fluorescent dissolved organic matter,carbohydrates
更新于2025-11-14 15:26:12
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Synthesis and photochromic properties of azobenzene-derived glycomacrolactones Chaoqi Lin,[a] Stéphane Maisonneuve,[a] Cyril Theulier,[a] and Juan Xie*[a]
摘要： Reversible photocontrol of glycosides and glycoconjugates structures is a very attractive approach to modulate, in a spatiotemporal way, the various properties and biological activities of carbohydrates. We have synthesized three new azobenzene-derived glycomacrolactones from thioglycopyranosides. The synthesized cyclic glycoazobenzenes can be reversibly photoisomerized between E and Z isomers with high fatigue resistance. 1H NMR study shows that E→Z isomerization of glycomacrocycles induces large conformational change of the macrocyclic structures, without changing sugar 4C1 chair conformation. The Z-glycoazobenzenes can be thermally converted back to the E-isomers. Interestingly, these 16 to 17-membered Z-glycomacrolactones display higher thermal stability than the reported macrocyclic azobenzenes, with the half-life varied from 37 to 72 days. The excellent photoswitching property and bi-stability of the synthesized glycoazobenenes open a new opportunity for the convergent synthesis of diastereomers of glycomacrocycles. Furthermore, chiroptical properties have been observed for both E and Z glycomacrolactones. The geometry of different isomers of macrocycles has been optimized with DFT calculations. Theoretical CD spectra obtained by TD-DFT suggest that the E and Z glycomacrocycles adopt preferentially (P) helical structure for the azobenzene moiety.
关键词： photochromism,azo compounds,carbohydrates,macrolactones,chirality
更新于2025-09-23 15:22:29
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Triple Orthogonal Labeling of Glycans Applying Photoclick Chemistry
摘要： Bioorthogonal labeling of multiple biomolecules is of current interest in chemical biology. For the visualization of carbohydrates, metabolic glycoengineering (MGE) has been shown to be an appropriate approach. Here, we report that the nitrile imine–alkene cycloaddition (photoclick reaction) is a suitable ligation reaction in MGE. Using a mannosamine derivative with an acrylamide reporter group, that is efficiently metabolized by cells and that quickly reacts in the photoclick reaction, we achieved the labeling of sialic acids on the surface of living cells. Screening of several alkenes unraveled that a previously reported carbamate-linked methylcyclopropene reporter, that is well suited for the inverse-electron-demand Diels-Alder (DAinv) reaction, has a surprisingly low reactivity in the photoclick reaction. This enabled us to achieve for the first time a triple labeling of glycans by the combination of DAinv, photoclick, and copper-free click chemistry.
关键词： carbohydrates,tetrazines,bioorthogonal reactions,click chemistry,metabolic engineering
更新于2025-09-23 15:21:21
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Nutrient Levels in Brassicaceae Microgreens Increase Under Tailored Light-Emitting Diode Spectra
摘要： To increase the nutritional value and levels of essential minerals in vegetable food, microgreens are promising targets. The metabolic processes of microgreens can be managed with different cultivation techniques, which include manipulating the properties of light derived by light-emitting diodes (LEDs). In this study Brassicaceae microgreens (kohlrabi Brassica oleracea var. gongylodes, broccoli Brassica oleracea, and mizuna Brassica rapa var. Japonica) were cultivated under different light spectral quality, and the metabolic changes insoluble sugars (hexoses and sucrose), ascorbic acid, β-carotene, and contents of non-heme iron (Fe) and its connection with magnesium (Mg) or calcium (Ca) levels were monitored. Plants grew under the primary LED light spectrum (the combination of blue light at 447 nm, red at 638 and 665 nm, and far-red at 731 nm) or supplemented with LED green light at 520 nm, yellow at 595 nm, or orange at 622 nm. The photoperiod was 16 h, and a total PPFD of 300 μmol m-2 s-1 was maintained. Under supplemental yellow light at 595 nm, the content of soluble carbohydrates increased significantly in mizuna and broccoli. Under all supplemental light components, β-carotene accumulated in mizuna, and ascorbic acid accumulated significantly in kohlrabi. Under supplemental orange light at 622 nm, Fe, Mg, and Ca contents increased significantly in all microgreens. The accumulation of Fe was highly dependent on promoters and inhibitors of Fe absorption, as demonstrated by the very strong positive correlations between Fe and Ca and between Fe and Mg in kohlrabi and broccoli, and the strong negative correlations between Fe and β-carotene and between Fe and soluble carbohydrates in kohlrabi. Thus, the metabolic changes that occurred in treated microgreens led to increases in the contents of essential nutrients. Therefore, selected supplemental LED wavelengths can be used in the cultivation of Brassicaceae microgreens to preserve and increase the contents of specific nutritionally valuable metabolites.
关键词： microgreens,Brassicaceae,carbohydrates,β-carotene,ascorbic acid,mineral elements,light-emitting diodes
更新于2025-09-11 14:15:04
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X-ray irradiation effects on nuclear and membrane regions of single SH-SY5Y human neuroblastoma cells investigated by Raman micro-spectroscopy
摘要： Raman micro-spectroscopy was performed in vitro on nuclear and membrane regions of single SH-SY5Y human neuroblastoma cells after irradiation by graded X-ray doses (2, 4, 6, 8 Gy). The acquired spectra were analyzed by principal component analysis (PCA) and interval-PCA (i-PCA) methods. Biochemical changes occurring in the different regions of single cells as a consequence of the radiation exposure were observed in cells fixed immediately after the irradiation. The most relevant effects arose from the analysis of the spectra from the cell nucleus region. The observed changes were discussed in terms of the modifications in the cell cycle, resulting in an increase in the DNA-related signal, a protein rearrangement and changes in lipid and carbohydrates profiles within the nucleus. Potential markers of an apoptotic process in cell population irradiated with 6 and 8-Gy X-ray doses could have been singled out. No significant effects were found in spectra from cells fixed 24 h after the irradiation, thus suggesting the occurrence of repairing processes of the X-ray induced damage.
关键词： X-ray effects on DNA, lipids, proteins and carbohydrates,Single SH-SY5Y human cancer cells,Raman micro-spectroscopy,Cellular nucleus and membrane,Multivariate analysis
更新于2025-09-11 14:15:04
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Chiral Analysis || Raman Optical Activity
摘要： Raman optical activity (ROA) has many advantages over conventional Raman spectroscopy for investigation of chiral molecules, in general, and biological molecules, in particular, on account of their homochirality. Since it is a manifestation of vibrational optical activity [1], being complementary to vibrational circular dichroism (VCD), ROA is more sensitive to the 3D structures of chiral molecules through its dependence on their absolute handedness, which has led to its development as an incisive probe of the structure and behavior of biomolecules in aqueous solution. For example, ROA spectra obtained from proteins can provide detailed information on the secondary and tertiary structures adopted by polypeptide backbones. Additionally, ROA can probe the tautomers of side chains. In common with other vibrational spectroscopies, there is no restriction on the size of molecules, or in their type, that can be investigated by ROA, broadening its application to unfolded proteins, viruses, and carbohydrates.
关键词： vibrational circular dichroism,proteins,Raman optical activity,aqueous solution,carbohydrates,vibrational optical activity,biological molecules,biomolecules,viruses,chiral molecules
更新于2025-09-09 09:28:46