ABSTRACT
Mixed-precision quantization mostly predetermines the model bit-width settings before actual training due to the non-differential bit-width sampling process, obtaining suboptimal performance. Worse still, the conventional static quality-consistent training setting, i.e., all data is assumed to be of the same quality across training and inference, overlooks data quality changes in real-world applications which may lead to poor robustness of the quantized models. In this article, we propose a novel data quality-aware mixed-precision quantization framework, dubbed DQMQ, to dynamically adapt quantization bit-widths to different data qualities. The adaption is based on a bit-width decision policy that can be learned jointly with the quantization training. Concretely, DQMQ is modeled as a hybrid reinforcement learning (RL) task that combines model-based policy optimization with supervised quantization training. By relaxing the discrete bit-width sampling to a continuous probability distribution that is encoded with few learnable parameters, DQMQ is differentiable and can be directly optimized end-to-end with a hybrid optimization target considering both task performance and quantization benefits. Trained on mixed-quality image datasets, DQMQ can implicitly select the most proper bit-width for each layer when facing uneven input qualities. Extensive experiments on various benchmark datasets and networks demonstrate the superiority of DQMQ against existing fixed/mixed-precision quantization methods.
ABSTRACT
Narrow bandwidths are a general bottleneck for applications relying on passive, linear, subwavelength resonators. In the past decades, several efforts have been devoted to overcoming this challenge, broadening the bandwidth of small resonators by the means of analog non-Foster matching networks for radiators, antennas and metamaterials. However, most non-Foster approaches present challenges in terms of tunability, stability and power limitations. Here, by tuning a subwavelength acoustic transducer with digital non-Foster-inspired electronics, we demonstrate five-fold bandwidth enhancement compared to conventional analog non-Foster matching. Long-distance transmission over airborne acoustic channels, with approximately three orders of magnitude increase in power level, validates the performance of the proposed approach. We also demonstrate convenient reconfigurability of our non-Foster-inspired electronics. This implementation provides a viable solution to enhance the bandwidth of sub-wavelength resonance-based systems, extendable to the electromagnetic domain, and enables the practical implementation of airborne and underwater acoustic radiators.
ABSTRACT
Succinate dehydrogenase inhibitors are essential fungicides used in agriculture. To explore new pyrazole-carboxamides with high fungicidal activity, a series of N-substitutedphenyl-3-di/trifluoromethyl-1-methyl-1H-pyrazole-4-carboxamides bearing a branched alkyl ether moiety were designed and synthesized. The in vitro bioassay indicated that some target compounds displayed appreciable fungicidal activity. For example, compounds 5d and 5e showed high efficacy against S. sclerotiorum with EC50 values of 3.26 and 1.52 µg/mL respectively, and also exhibited excellent efficacy against R. solani with EC50 values of 0.27 and 0.06 µg/mL respectively, which were comparable or superior to penflufen. The further in vivo bioassay on cucumber leaves demonstrated that 5e provided strong protective activity of 94.3 % against S. sclerotiorum at 100 µg/mL, comparable to penflufen (99.1 %). Cytotoxicity assessment against human renal cell lines (239A cell) revealed that 5e had low cytotoxicity within the median effective concentrations. Docking study of 5e with succinate dehydrogenase illustrated that R-5e formed one hydrogen bond and two π-π stacking interactions with amino acid residues of target enzyme, while S-5e formed only one π-π stacking interaction with amino acid residue. This study provides a valuable reference for the design of new succinate dehydrogenase inhibitor.
Subject(s)
Fungicides, Industrial , Molecular Docking Simulation , Pyrazoles , Succinate Dehydrogenase , Pyrazoles/chemistry , Pyrazoles/pharmacology , Pyrazoles/chemical synthesis , Humans , Structure-Activity Relationship , Fungicides, Industrial/pharmacology , Fungicides, Industrial/chemical synthesis , Fungicides, Industrial/chemistry , Succinate Dehydrogenase/antagonists & inhibitors , Succinate Dehydrogenase/metabolism , Microbial Sensitivity Tests , Molecular Structure , Ascomycota/drug effects , Amides/chemistry , Amides/pharmacology , Amides/chemical synthesis , Dose-Response Relationship, Drug , Ethers/chemistry , Ethers/pharmacology , Ethers/chemical synthesis , RhizoctoniaABSTRACT
Network pruning has attracted increasing attention recently for its capability of transferring large-scale neural networks (e.g., CNNs) into resource-constrained devices. Such a transfer is typically achieved by removing redundant network parameters while retaining its generalization performance in a static or dynamic manner. Concretely, static pruning usually maintains a larger and fit-to-all (samples) compressed network by removing the same channels for all samples, which cannot maximally excavate redundancy in the given network. In contrast, dynamic pruning can adaptively remove (more) different channels for different samples and obtain state-of-the-art performance along with a higher compression ratio. However, since the system has to preserve the complete network information for sample-specific pruning, the dynamic pruning methods are usually not memory-efficient. In this paper, our interest is to explore a static alternative, dubbed GlobalPru, from a different perspective by respecting the differences among data. Specifically, a novel channel attention-based learn-to-rank framework is proposed to learn a global ranking of channels with respect to network redundancy. In this method, each sample-wise (local) channel attention is forced to reach an agreement on the global ranking among different data. Hence, all samples can empirically share the same ranking of channels and make the pruning statically in practice. Extensive experiments on ImageNet, SVHN, and CIFAR-10/100 demonstrate that the proposed GlobalPru achieves superior performance than state-of-the-art static and dynamic pruning methods by significant margins.
Subject(s)
Data Compression , Generalization, Psychological , Learning , Neural Networks, ComputerABSTRACT
BACKGROUND: Maize productivity in semi-arid regions is increasingly at risk because of the sparse and uneven precipitation, and it is also restricted by excessive or insufficient fertilization management strategies. A 4-year (2016-2019) field experiment was therefore conducted to show the effects of fertilizer with five nitrogen levels (0, 75-90, 150-180, 270, and 360 kg ha-1 , represented as N0 , N75-90 , N150-180 , N270 , N360 , respectively) under two variable precipitation patterns (rainy at pre-anthesis in 2016 and 2018 versus dry at pre-anthesis in 2017 and 2019) on soil water storage (SWS), water use efficiency (WUE), nitrogen use efficiency (NUE), and maize yield in the Loess Plateau. RESULTS: Nitrogen inputs increased the amount of above-ground dry matter and the WUE for dry matter (WUEd). Dry years at pre-anthesis significantly reduced dry matter accumulation and kernel number per plant. However, soil water storage before sowing (SWSs) decreased from 440 mm in 2016 to 384 mm in 2019, and the increase in fertilization resulted in the water imbalance. Both the maximum grain yield and WUE for grain yield were found in N270 under rainy years at pre-anthesis, whereas in N150-180 under dry years at pre-anthesis. The average nitrogen recovery efficiency (NRE), nitrogen agronomy efficiency (NAE) and nitrogen partial factor productivity (NPFP) decreased with increases in N application, compared with N360 , the NRE,NAE and NPFP of N150-180 increased by 63.5%, 189.2% and 135.5%, respectively. CONCLUSIONS: Reducing basal N fertilizers could enhance maize yield and maintain moderate water and nitrogen productivity in years with less rainfall. © 2023 Society of Chemical Industry.
Subject(s)
Nitrogen , Zea mays , Nitrogen/analysis , Water , Agriculture/methods , Soil , Fertilizers , ChinaABSTRACT
Pickering emulsions prepared by food-grade particles have gained growing attention due to their promising application in functional food and pharmaceutical industries. In this study, we successfully fabricated soy peptide-based nanoparticles (SPN) through pH-driven process. Obtained particles with small particle size were surface active and shared intermediate wettability, and they could be well applied as an efficient particulate emulsifier for stabilizing oil-in-water Pickering emulsions at SPN concentration above 0.25 wt%. Furthermore, formed emulsions stabilized with SPN exhibited good protection towards Vitamin D3 against UV irradiation and oxidative deterioration, where controlled release of Vitamin D3in vitro could also be well achieved by modulating particle concentration. The whole process can contribute to a sustainable development of low-value peptide byproducts as functional food ingredients.
Subject(s)
Cholecalciferol , Nanoparticles , Emulsifying Agents , Emulsions , Hydrogen-Ion Concentration , Particle Size , Peptides , WaterABSTRACT
Increasing planting density is an effective strategy for improving maize productivity, but grain yield does not increase linearly with the increase in plant density, especially in semiarid environments. However, how planting density regulates the integrated utilization of key input resources (i.e., radiation, water, and nutrients) to affect maize production is not clear. To evaluate the effects of planting density and cultivar on maize canopy structure, photosynthetic characteristics, yield, and resource use efficiency, we conducted a successive field experiment from 2013 to 2018 in Heyang County (Shaanxi Province, China) using three different cultivars [i.e., Yuyu22 (C1), Zhengdan958 (C2), and Xianyu335 (C3)] at four planting densities [i.e., 52,500 (D1), 67,500 (D2), 82,500 (D3), and 97,500 (D4) plants ha-1]. Increasing planting density significantly increased the leaf area index (LAI) and the amount of intercepted photosynthetically active radiation (IPAR), thereby promoting plant growth and crop productivity. However, increased planting density reduced plant photosynthetic capacity [net photosynthetic rate (Pn)], stomatal conductance (Gc), and leaf chlorophyll content. These alterations constitute key mechanisms underlying the decline in crop productivity and yield stability at high planting density. Although improved planting density increased IPAR, it did not promote higher resource use efficiency. Compared with the D1 treatment, the grain yield, precipitation use efficiency (PUE), radiation use efficiency (RUE), and nitrogen use efficiency (NUE) increased by 5.6-12.5%, 2.8-7.1%, and -2.1 to 1.6% in D2, D3, and D4 treatments, respectively. These showed that pursuing too high planting density is not a desirable strategy in the rainfed farming system of semiarid environments. In addition, density-tolerant cultivars (C2 and C3) showed better canopy structure and photosynthetic capacity and recorded higher yield stability and resource use efficiency. Together, these results suggest that growing density-tolerant cultivars at moderate planting density could serve as a promising approach for stabilizing grain yield and realizing the sustainable development of agriculture in semiarid regions.
ABSTRACT
The insoluble soy peptide aggregates formed upon proteolysis are generally considered as "ready to be discarded", which placed additional burden on related industries. In this study, with the aim of promoting sustainable utilization of these large aggregates, novel soy peptide-based nanoparticles (SPN) were successfully fabricated from these aggregates via a controlled pH-shifting method, and the obtained SPN exhibited good storage stability and antioxidant activity. Furthermore, the pH-shifting process also provided a driven force for loading and delivering curcumin, which significantly improved its water solubility (up to 105 folds), storage and simulated gastric-intestinal digestive stability, as well as in vitro bioavailability and antioxidant activity. These results indicated that controlled pH-shifting could be an effective and facile method to trigger the assembly of insoluble aggregates into functional peptide nanoparticles for the delivery of bioactive cargoes, which provided a new strategy for the sustainable and high-value application of these low-value peptide byproducts.
Subject(s)
Drug Carriers/chemistry , Nanoparticles/chemistry , Peptides/chemistry , Protein Aggregates , Soybean Proteins/chemistry , Antioxidants/chemistry , Biological Availability , Curcumin/chemistry , Hydrogen-Ion Concentration , Hydrophobic and Hydrophilic Interactions , Particle Size , SolubilityABSTRACT
Straw mulching and subsoiling can protect soil and improve soil structure. However, long-term continuous subsoiling cannot continuously gain yield increasing and soil improvement. To realize continuous soil improvement and yield enhancement, a long-term experiment on subsoiling alternation patterns was carried out with spring maize continuous cropping in the Loess Plateau in 2007-2016. The subsoiling alternation patterns were no-tillage/conventional tillage/subsoiling (NT/CT/ST) and subsoiling/conventional tillage (ST/CT), with continuous subsoiling (ST) as control. We analyzed the effects of the different patterns on soil physical and chemical properties and maize yield. The results showed that, compared with the ST, the mechanical-stable aggregates (DR0.25) and water-stable aggregates (WR0.25) in NT/CT/ST were significantly increased by 9.2% and 21.9%, with the mean weight diameter (MWD) and geometrical mean diameter (GMD) being significantly increased. The WR0.25 in ST/CT was significantly increased by 11.9%. In 0-20 cm soil layer, soil bulk density in NT/CT/ST and ST/CT decreased by 7.0% and 11.5%, and soil porosity increased by 8.4% and 13.9%, respectively. In 20-40 cm soil layer, soil bulk density in ST/CT increased by 6.9%, and soil porosity decreased by 5.7%. In the NT/CT/ST, soil total nitrogen and organic matter contents significantly increased, but soil total phosphorus and total potassium contents reduced. The multi-year average grain yield of spring maize in NT/CT/ST was 10.2% higher than ST and 4.8% higher than ST/CT. The DR0.25, WR0.25, soil total nitrogen content and soil organic carbon content were all positively correlated with maize yield, indicating such changes faci-litated corn grain yield. Considering the effects on soil fertility and corn yield, the NT/CT/ST model was conducive to soil fertility, soil structural stability and higher maize yield.
Subject(s)
Soil , Zea mays , Agriculture , Carbon , ChinaABSTRACT
To get a scientific pattern for nitrogen-reducing and efficiency-increasing production of spring maize in Weibei dryland, we conducted an in-situ field experiment of spring maize (Zhengdan 958 and Shaandan 8806) under dryland farming from 2016 to 2019 in Heyang County, located in Weibei dryland of Shaanxi. There were five nitrogen (N) treatments, including 360 kg·hm-2(N360, a rate commonly adopted by local farm households), 270 kg·hm-2(N270), 150-180 kg·hm-2(N150-180), 75-90 kg·hm-2(N75-90) and 0 kg·hm-2(N0). We investigated the effects of reduced nitrogen application on maize yield, nitrogen uptake and utilization of spring maize and soil nitrate residue. The results showed that: 1) Maize yield of both varieties at N150-180 was increased by 0.9%-7.1% and nitrogen uptake was decreased by 4.1%-4.6%, while average reco-very efficiency, partial-factor productivity and agronomic efficiency of N at N150-180 were increased by 79.3%-83.6%, 105.9%-157.7%, and 101.9%-114.1% compared with those at N360, respectively. 2) The contents of residual nitrate increased significantly when nitrogen application rate was more than 180 kg·hm-2, while nitrogen uptake was significantly reduced under rainfall shortage, and thus resulted in increasing soil residual nitrogen. After four-year treatments, the residual nitrate was up to 504.7-620.8 kg·hm-2 in 0-200 cm soil layer, with a peak in 80-140 cm soil layer. There was a risk of nitrate leaching. According to the comprehensive evaluation for annual yield, nitrogen use efficiency and soil nitrate residue, the optimum N application rate was recommended to be 150-180 kg N·hm-2 for spring maize in Weibei dryland.
Subject(s)
Nitrogen , Soil , Fertilizers , Nitrates , Nitrogen/analysis , Zea maysABSTRACT
Methionine-restricted diets (MRD) have been shown to prevent high fat diet (HFD) induced complications including fat accumulation, insulin sensitivity decrease, oxidative stress and inflammation increase. We hypothesized that intestinal microbiota changes may mediate these effects, and this study aims to prove this hypothesis. Mice were fed a normal diet (ND, 0.86% methionine + 4% fat), a HF diet (HFD, 0.86% methionine + 20% fat), or a MRD (0.17% methionine + 20% fat) and euthanized at week 22. Our results showed that the HFD induced fat accumulation and gut microbiota dysbiosis; reduced short-chain fatty acid (SCFA) production; and increased intestinal permeability, inflammatory response, and oxidative stress. The MRD decreased the body weight, body fat rate, and blood glucose and plasma lipid levels; increased the abundance of putative SCFA-producing bacteria Bifidobacterium, Lactobacillus, Bacteroides, Roseburia, Coprococcus, and Ruminococcus and inflammation-inhibiting bacteria Oscillospira and Corynebacterium; and decreased the abundance of inflammation-producing bacteria Desulfovibrio in colonic contents. Moreover, the MRD improved intestinal barrier function, inflammatory response, and oxidative stress, and altered the metabolite levels of colonic contents (such as increasing SCFA and bile acid concentrations); the latter may have contributed to the prevention of HFD-induced obesity. In conclusion, the MRD can improve gut health by regulating the intestinal microbiota and its metabolite profiles in the HFD mice. Reducing methionine intake by simple dietary adjustment may be an effective method to improve intestinal health in animals and humans.
Subject(s)
Dysbiosis/diet therapy , Dysbiosis/immunology , Gastrointestinal Microbiome , Intestinal Mucosa/metabolism , Methionine/metabolism , Animals , Bacteria/classification , Bacteria/genetics , Bacteria/metabolism , Body Weight , Diet, High-Fat/adverse effects , Dysbiosis/metabolism , Dysbiosis/microbiology , Fatty Acids, Volatile/metabolism , Humans , Intestinal Mucosa/immunology , Intestinal Mucosa/microbiology , Male , Methionine/analysis , Mice , Mice, Inbred C57BL , PermeabilityABSTRACT
Soy proteins are prone to aggregate upon proteolysis, hindering their sustainable development in food processing. Here, a continuous work on the large insoluble peptide aggregates was carried out, aiming to develop a new type of soy peptide-based nanoparticle (SPN) for active cargo delivery. Sono-assembled SPN in spherical appearance and core-shell structure maintained by noncovalent interactions was successfully fabricated, exhibiting small particle size (103.95 nm) in a homogeneous distribution state (PDI = 0.18). Curcumin as a model cargo was efficiently encapsulated into SPN upon sonication, showing high water dispersity (129.6 mg/L, 104 higher than its water solubility) and storage stability. Additionally, the pepsin-resistant SPN contributed to the controlled release of curcumin at the intestinal phase and thus significantly improved the bioaccessibility. Encapsulated curcumin was effective in protecting glutamate-induced toxicity in PC12 cells, where the matrix SPN can simultaneously reduce lipid peroxidation and elevate antioxidant enzymes levels, innovatively demonstrating its bifunctionality during cellular delivery.
Subject(s)
Curcumin/chemistry , Drug Carriers/chemistry , Drug Delivery Systems/methods , Peptides/chemistry , Soybean Proteins/chemistry , Animals , Apoptosis/drug effects , Curcumin/pharmacology , Humans , Hydrophobic and Hydrophilic Interactions , Nanoparticles/chemistry , Oxidative Stress/drug effects , PC12 Cells , Particle Size , Rats , Reactive Oxygen Species/metabolism , SolubilityABSTRACT
Upon enzymatic hydrolysis, soy protein isolates showed a strong tendency to aggregate, presenting a significant loss of valuable proteins. This study mainly focused on the large insoluble aggregates formed during proteolysis, and the influence of heating was further explored for a better understanding of the mechanism involved. The results from SDS-PAGE and amino acid analysis clearly showed that the insoluble aggregates formed upon hydrolysis were aggregated peptides, mainly attributed to the hydrophobic interactions between peptides with hydrophobic amino acids (Val, Ala, Leu, Ile, Tyr, Phe, and Pro) and sulfur-containing (Met and Cys) residues. Heating of the hydrolysates further enhanced the peptide-protein interactions through hydrophobic forces and disulfide bonds, accelerating the aggregation, where fractions from the basic subunits of glycinin were particularly involved. Furthermore, taking into consideration the fact that aggregates had a high proportion of essential amino acids, the in vitro digestion properties of the aggregates were also investigated. Interestingly, the relatively pepsin-resistant aggregates showed a high degradability toward pancreatin, releasing low molecular weight peptides possessing a higher proportion of antioxidative amino acids, which therefore had a better antioxidant activity. These results indicated a potential use of the insoluble peptide aggregates as protein supplements or active delivery systems for human consumption.
Subject(s)
Soybean Proteins/chemistry , Antioxidants/chemistry , Antioxidants/isolation & purification , Electrophoresis, Polyacrylamide Gel , Hydrolysis , Hydrophobic and Hydrophilic Interactions , Molecular Weight , Nutritive Value , Pepsin A/chemistry , Peptides/chemistry , Peptides/isolation & purification , Protein Aggregates , Soybean Proteins/isolation & purificationABSTRACT
Systemic administration of chemotherapeutic agents can cause indiscriminate drug distribution and severe toxicity. Until now, encapsulation and targeting of drugs have typically relied on synthetic vehicles, which cannot minimize the clearance by the renal system and may also increase the risk of chemical side effects. Cell membrane capsules (CMCs) provide a generic and far more natural approach to the challenges of drug encapsulation and delivery in vivo. Here aptamer AS1411, which can recognize and bind overexpressed nucleolin on a cancer cell membrane, was chemically conjugated onto CMCs. As a result, AS1411 modified CMCs showed enhanced ingestion in certain cancer cells in vitro and accumulation in mouse cancer xenografts in vivo. Chemotherapeutics and contrast agents with therapeutically significant concentrations can be packaged into CMCs by reversible permeating their plasma membranes. The systematic administration of cancer targeting CMCs loaded with doxorubicin hydrochloride can significantly inhibit tumor growth in mouse xenografts, with significantly reduced toxicity compared to free drug. These findings suggest that cancer targeting CMCs may have considerable benefits in drug delivery and cancer treatment.
Subject(s)
Antineoplastic Agents/therapeutic use , Capsules/chemistry , Cell Membrane/chemistry , Doxorubicin/therapeutic use , Neoplasms/drug therapy , Animals , Antineoplastic Agents/chemistry , Antineoplastic Agents/toxicity , Aptamers, Nucleotide/chemistry , Aptamers, Nucleotide/metabolism , Cell Line , Cell Membrane/metabolism , Cell Survival/drug effects , Doxorubicin/chemistry , Doxorubicin/toxicity , Drug Carriers/chemistry , Humans , Male , Mice , Mice, Inbred BALB C , Mice, Nude , Microscopy, Confocal , Neoplasms/pathology , Phosphoproteins/chemistry , Phosphoproteins/metabolism , RNA-Binding Proteins/chemistry , RNA-Binding Proteins/metabolism , Tissue Distribution , Transplantation, Heterologous , NucleolinABSTRACT
Effects of limited enzymatic hydrolysis with pepsin on the functional properties and structure characteristics of soybean proteins were investigated. Hydrolysates with different incubation time (10 to 900 min) were prepared. Results showed that SPI hydrolyzed for 60 min exhibited the best emulsibility and the ability of resisting freezing/thawing. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis proved that pepsin can degrade glycinin but had little effect on the α' subunit of ß-conglycinin. The structure unfolding reached the largest extent after incubation for 60 min and the soluble and flexible aggregates were formed. After 120 min, glycinin was degraded totally and ß-conglycinin formed insoluble aggregates. Moreover, 2 methods were applied for the deactivation of pepsin to obtain final hydrolysates at pH 2.0 and 7.0, respectively. The structure analysis revealed that the unfolding extent and structure characteristic were different in these 2 conditions. When adjusting the pH value from 2.0 to 7.0, the unfolding protein molecular would reaggregate again at pH 7.0 due to the charge neutralization, and the hydrodynamic diameter and λmax absorbance decreased compared to pH 2.0. Moreover, some of the insoluble aggregates formed at pH 2.0 became soluble at pH 7.0, because of the salt-in phenomenon.
Subject(s)
Antigens, Plant/chemistry , Globulins/chemistry , Pepsin A/chemistry , Protein Hydrolysates/chemistry , Seed Storage Proteins/chemistry , Soybean Proteins/chemistry , Electrophoresis, Polyacrylamide Gel , Food Handling , Hydrogen-Ion Concentration , Hydrophobic and Hydrophilic Interactions , Particle Size , Glycine max/chemistryABSTRACT
Two highly selective two-photon fluorescent probes for cysteine over homocysteine, N-acetyl-L-cysteine, dithiothreitol, glutathione and other amino acids, and their fluorescent imaging in living cells have been shown.
Subject(s)
Cysteine/analysis , Fluorescent Dyes/chemistry , Cysteine/chemistry , Cysteine/metabolism , Fluorescent Dyes/chemical synthesis , Fluorescent Dyes/metabolism , HeLa Cells , Humans , Microscopy, Fluorescence, MultiphotonABSTRACT
A new carbazole-derived dicationic compound, namely 2,7-bis(1-hydroxyethyl-4-vinylpyridinium iodine)-N-ethylcarbazole (2,7-9E-BHVC), with a large two-photon action absorption cross section in nucleic acids has been obtained. Moreover, it possesses the potential of imaging RNA in nucleoli and cytoplasm in two-photon fluorescence microscopy and exhibits good counterstain compatibility with the commercial fluorescent nucleic dye DAPI.
Subject(s)
Carbazoles/chemistry , Cell Nucleolus/metabolism , Cytoplasm/metabolism , Microscopy, Fluorescence/methods , Photons , Pyridinium Compounds/chemistry , RNA/metabolism , Spectrometry, Fluorescence/methods , Carbazoles/chemical synthesis , Fluorescent Dyes/chemical synthesis , Fluorescent Dyes/chemistry , HeLa Cells , Humans , Pyridinium Compounds/chemical synthesis , RNA/chemistryABSTRACT
A series of carbazole cationic compounds based on donor- Π-acceptor (D-Π-A) structure were synthesized and characterized. They exhibit large two-photon absorption cross sections when excited by a 810 nm a laser beam, and their photophysical properties show that the intramolecular charge transfer (ICT) character is predominant. Moreover these compounds can easily pass though the intact cell membrane of living cells, amongst, 3-(1-hydroxyethyl-4-vinylpyridium iodine)-N-butyl carbazole (9B-HVC) has been proven to be capable of accumulating within the mitochondria possessing large membrane potential and imaging this organelle in living cells by means of two-photon fluorescence microscopy. At the same time usable fluorescent photos can be obtained at lower incident excitation power (5 mW) and low-micromolar concentrations (2 µM), which does not result in significant reduction in cell viability over a period of at least 24 h.
Subject(s)
Carbazoles/chemistry , Microscopy, Fluorescence/methods , Mitochondria/metabolism , Molecular Imaging/methods , Photons , Absorption , Carbazoles/metabolism , Carbazoles/toxicity , Cell Line, Tumor , Cell Survival/drug effects , HumansABSTRACT
Three carbazole dicationic salts, namely 3,6-bis(1-methyl-4-vinylpyridinium) carbazole diiodide (BMVC), 9-ethyl-3,6-bis(1-methyl-4-vinylpyridinium) carbazole diiodide (9E-BMVC) and 9-ethyl-3,6-bis(1-hydroxyethyl-4-vinylpyridinium)carbazole diiodide (9E-BHVC), were synthesized successfully. Their photophysical properties were evaluated by absorption, one- and two-photon fluorescence spectra, and their higher fluorescence intensity and larger two-photon excited fluorescence action cross-sections (Φ×δ) in the presence of DNA than those in the absence of DNA give them good DNA two-photon light-switch properties. Furthermore, their ability to image nuclei in living plant cells and turbid tissues by using two-photon excited fluorescence was carefully studied, and the experimental results indicate that these dicationic salts can exclusively label nuclei in intact living plant cells and tissues. In particular, 9E-BHVC exhibits optimized DNA labeling performance. Very importantly, compared to DAPI, 9E-BHVC can be used to carry out deeper observation using the same incident power, or can be used to obtain usable fluorescent images by using a lower incident power.