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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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Novel BODIPY-conjugated amino acids: Synthesis and spectral properties
摘要： Three BODIPY-based conjugates with lysine, methionine, and tryptophan bound via amino group were synthesized and characterized. Spectral properties of the compounds were studied and a number of photophysical characteristics were obtained. Bioconjugates investigated are water soluble, which makes them promising markers for various bioobjects.
关键词： conjugation,fluorescence,BODIPY,amino acids,markers
更新于2025-11-14 15:14:40
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Modulation the electronic property of 2D monolayer MoS2 by amino acid
摘要： 2D molybdenum disulfide (MoS2) has a strong potential for the detection of biomolecules, however, the specific interactions between individual amino acids and MoS2 surface are still unclear. Herein, the adsorption properties and electronic structures of amino acid/MoS2 systems were investigated systematically for the 20 standard amino acids based on density functional theory. The adsorption strength of amino acids on MoS2 monolayer decreases in the following order: TRP > ARG > PHE > TYR > LYS > HIS > PRO > ASN > MET > LEU > ILE > VAL > GLU > GLN > THR > ASP > CYS > SER > ALA > GLY. The band gap of amino acid/MoS2 system is determined by the energy level of HOMO orbit of the adsorbed amino acid, in which the higher energy level of HOMO orbit will result in a smaller band gap. As proof of concept, optical and electrical detection of the MoS2 based transistors with and without amino acid molecules (TRP and CYS) were studied. Adsorption of amino acids on a MoS2 surface allows their chemical information to be transformed into distinct analytically optical and electronic signals, which opens up new possibilities for fabricating novel MoS2 based highly selective biosensors.
关键词： Amino acid,MoS2,Density functional theory,Field effect transistors
更新于2025-09-23 15:23:52
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Photooxidase-mimicking nanovesicles with superior photocatalytic activity and stability based on amphiphilic amino acid and phthalocyanine co-assembly
摘要： Enzyme mimics have broad applications in catalysis and can assist elucidation of the catalytic mechanism of natural enzymes. However, challenges arise from the design of catalytic sites, the selection of host molecules and their integration into active three-dimensional structures. Herein, we develop a mimic photooxidase by synergetic molecular self-assembly. 9-Fluorenylmethyloxycarbonyl-L-histidine in combination with phthalocyanine shows efficient co-assembly into nanovesicles with flexibly tunable particle size and membrane thickness. The obtained nanovesicles are capable of reactive oxygen-mediated photosensitive oxidation with improved efficiency and stability. This work highlights the co-assembly of simple building blocks into a supramolecular photocatalyst, which might give insight into possible evolutionary paths of photocatalytic membraneous systems and will allow the facile transfer into photosensitive nanoreactors or artificial organelles.
关键词： self-assembly,photooxidase,amino acids,nanovesicles,phthalocyanines
更新于2025-09-23 15:23:52
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Observation of Site-Resolved Vibrational Energy Transfer Using a Genetically Encoded Ultrafast Heater
摘要： Allosteric information transfer in proteins has been linked to distinct vibrational energy transfer (VET) pathways in a number of theoretical studies. Experimental evidence for such pathways, however, is sparse because site-selective injection of vibrational energy into a protein, i.e. localized heating, is required for their investigation. Here, we solve this problem by the site-specific incorporation of the non-canonical amino acid β-(1-azulenyl)-L-alanine (AzAla) via genetic code expansion. Being an exception to Kasha′s rule, AzAla undergoes ultrafast internal conversion and heating after S1 excitation while upon S2 excitation it serves as a fluorescent label. We endowed PDZ3, a protein interaction domain of postsynaptic density protein 95, with this ultrafast heater at two distinct positions. Using ultrafast IR spectroscopy, we could indeed observe VET from the incorporation sites in the protein to a bound peptide ligand on a picosecond timescale. This approach based on genetically encoded AzAla paves the way for detailed studies of VET and its role for function in a wide range of proteins.
关键词： protein modification,energy transfer,non-canonical amino acid,time-resolved spectroscopy,mutagenesis
更新于2025-09-23 15:23:52
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Antimicrobial photodynamic inactivation of fungal biofilm using amino functionalized mesoporus silica-rose bengal nanoconjugate against Candida albicans
摘要： Candida albicans is an opportunistic fungal pathogen that causes both superficial and systemic infection and an important candidate that contribute to high morbidity and mortality rates in immunocompromised patients. The ability of C. albicans to switch from yeast to filamentous form and thereby forming biofilms make them resistant to most of the antifungal drugs available today. Thus the development of more effective antifungal drugs are essential and crucial at this point of time. Antimicrobial photodynamic therapy is an alternative modality to treat such biofilm forming resistant strains. This study aims to investigate the enhanced efficiency of newly synthesized MSN-RB conjugate as an antimicrobial photosensitizer for antimicrobial photodynamic therapy against C. albicans. Functionalization of MSN with amino groups was performed to increase the dye loading capacity. Conjugation process of MSN-RB was confirmed using different techniques including UV–Vis spectroscopy, Fluorescent spectroscopy and FTIR analysis. A low power green laser 50 mW irradiation was applied (5 min) for activation of MSN-RB conjugate and RB against C. albicans biofilm and planktonic cell. The comparative study of MSN-RB conjugate and free RB on aPDT was evaluated using standard experimental procedures. Antibiofilm efficacy was determined using biofilm inhibition assay, cell viability, EPS quantification and CLSM studies. The results revealed that MSN-RB conjugate has a significant antimicrobial activity (88.62 ± 3.4%) and antibiofilm effect on C. albicans when compared to free dye after light irradiation. The MSN-RB conjugate based aPDT can be employed effectively in treatment of C. albicans infections.
关键词： Antimicrobial photodynamic therapy,Conjugation,Amino functionalization,Mesoporus silica nanoparticles,Lipid peroxidation,Anti-biofilm activity
更新于2025-09-23 15:23:52
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ROS dependent antitumour activity of photo-activated iron(III) complexes of amino acids
摘要： Several amino acid-based photo-active monomeric iron(III) complexes of the general formula, [Fe(L)2]?, where L = Schiff base ligands (salisalidene arginine, salicylidenetryptophan, 3,5-di-tert-butyl benzalidine arginine and salicylidene tryptophan) were synthesized, characterized and explored for photo-activated anticancer activity to Chang Liver Cells, HeLa and MCF-7 cells. Complexes exhibited remarkable photo-cytotoxicity with IC50 value to the extent of 0.7 μM to Chang Liver Cells in visible light and there was a 40-fold enhancement in cytotoxicity in comparison to the cytotoxicity in dark. Complexes were non-toxic to MCF-10A (normal cells) in dark and visible light (IC50 > 100 μM in dark; IC50 > 80 μM in visible light) signifying target-speci?c nature of the anti-tumour activity of the complexes. Increased ROS concentration, as probed by DCFDA assay, in the cancer cells was responsible for apoptotic cell death. Decarboxylation or phenolate-Fe(III) charge transfer of photo-activated iron(III) complexes generating ?OH radicals (ROS) were responsible for the apoptosis. Overall, the tumour-selective photo-activated anticancer activity of the amino acid-based iron(III) complexes have shown a promising aspect in developing iron-based photo-chemotherapeutics as the next generation PDT agents.
关键词： ROS generation,photo-activation,Iron(III) complexes,amino acid,photocytotoxicity
更新于2025-09-23 15:23:52
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Amino-Functionalized Al-MOF for Fluorescent Detection of Tetracyclines in Milk
摘要： A fluorescent method for detection of tetracyclines (TCs) in milk was developed by using the NH2-MIL-53(Al) nanosensor synthesized via a one-pot hydrothermal method. The nanosensor had a crystalline nanoplates structure with rich groups of -NH2 and -COOH. The -NH2/-COOH of NH2-MIL-53(Al) reacted with the -CO-/-OH of TCs to form a complex. The electron of -NH2/-COOH from the NH2-BDC ligand transferred to the -CO-/-OH of TCs. -NH2 of the NH2-MIL-53(Al) interacted with the -CO-/-OH of TCs by hydrogen bonding. Quenching efficiency of inner filter effect (IFE) was calculated to contribute 57-89%. The synergistic effect of photoinduced electron transfer (PET) and IFE account for fluorescence quenching. TCs were quantitatively detected in milk samples with recoveries of 85.15 ~ 112.13%, the results were in great accordance with high performance liquid chromatography (HPLC) (P > 0.05), confirming the NH2-MIL-53(Al) nanosensor has potential applicability for the detection of TCs in food matrix.
关键词： Nanosensor,inner filter effect (IFE),Amino-functionalized organic Metal Framework,Tetracyclines,Fluorescence detection,Milk
更新于2025-09-23 15:23:52
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Rapid Identification of Functional Pyrrolysyl-tRNA Synthetases via Fluorescence-Activated Cell Sorting
摘要： The orthogonal pyrrolysyl-tRNA synthetase/tRNACUA pair and their variants have provided powerful tools for expanding the genetic code to allow for engineering of proteins with augmented structure and function not present in Nature. To expedite the discovery of novel pyrrolysyl-tRNA synthetase (PylRS) variants that can charge non-natural amino acids into proteins site-specifically, herein we report a streamlined protocol for rapid construction of the pyrrolysyl-tRNA synthetase library, selection of the functional PylRS mutants using fluorescence-activated cell sorting, and subsequent validation of the selected PylRS mutants through direct expression of the fluorescent protein reporter using a single bacterial strain. We expect that this protocol should be generally applicable to rapid identification of the functional PylRS mutants for charging a wide range of non-natural amino acids into proteins.
关键词： non-natural amino acids,flow cytometry,mutagenesis,amber codon suppression,genetic code expansion
更新于2025-09-23 15:23:52
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Unprecedented Multicolor Photoluminescence from Hyperbranched Poly(amino ester)s
摘要： A novel kind of water-soluble fluorescent hyperbranched poly(amino ester) (PAE) is prepared through a one-pot polycondensation reaction of citric acid (CA) and N-methyldiethanolamine (NMDEA). The PAE exhibits enhanced and red-shift fluorescence with increasing solution concentration, showing distinct aggregation-induced emission character. Interestingly, the resulting PAE exhibits tunable photoluminescence from blue, cyan, and green to red irradiated by altering the excitation wavelengths. Such unique emission of non-conjugated PAE is attributed to the clustering of ester and tertiary amine groups derived from PAE self-assembly aggregates. Moreover, the fluorescence of PAE is very sensitive to Fe3+ ions. The facile preparation and unique optical features make PAE potentially useful in numerous applications such as multicolor cellular imaging, Fe3+ ions probe, and light-emitting diodes.
关键词： aggregation-induced emission,poly(amino ester)s,water-soluble polymers,hyperbranched,fluorescence
更新于2025-09-23 15:23:52