Aptamers as a kind of biological recognition element have shown great potential in monitoring and the rapid quantification of organophosphorus pesticides(OPPs). However, molecules of OPPs are structurally similar and ...Aptamers as a kind of biological recognition element have shown great potential in monitoring and the rapid quantification of organophosphorus pesticides(OPPs). However, molecules of OPPs are structurally similar and original aptamers selected by systematic evolution of ligands by exponential enrichment are usually long-chain bases, which hamper the further application under OPPs-aptamer recognition. The aim of the research was to develop a new strategy to design oligonucleotide sequences for binding OPPs by combination of experimental and molecular modeling methods. 3D models of aptamers binding OPPs were constructed, and binding energy and the most probable binding site for the OPPs were then determined by molecular docking, and the binding sites were further confirmed by the results of 2-AP replaced experiments. Based on the docking results, a new aptamer for detection 4 representative OPPs with only 29 bases was designed by reasonable truncation and mutation of the reported aptamer(named S4-29). The interaction between this new aptamer and OPPs were analyzed by molecular docking, microscale thermophoresis, circular dichroism and fluorometric analysis. The results revealed that the new aptamer exhibit more superior recognition performance to OPPs, which can be promote the monitoring ability of OPPs contaminations in food.展开更多
This study aimed to characterize and identify calcium-chelating peptides from rabbit bone collagen and explore the underlying chelating mechanism.Collagen peptides and calcium were extracted from rabbit bone by instan...This study aimed to characterize and identify calcium-chelating peptides from rabbit bone collagen and explore the underlying chelating mechanism.Collagen peptides and calcium were extracted from rabbit bone by instant ejection steam explosion(ICSE)combined with enzymatic hydrolysis,followed by chelation reaction to prepare rabbit bone peptide-calcium chelate(RBCP-Ca).The chelating sites were further analyzed by liquid chromatography-tandem mass(LC-MS/MS)spectrometry while the chelating mechanism and binding modes were investigated.The structural characterization revealed that RBCP successfully chelated with calcium ions.Furthermore,LC-MS/MS analysis indicated that the binding sites included both acidic amino acids(Asp and Glu)and basic amino acids(Lys and Arg),Interestingly,three binding modes,namely Inter-Linking,Loop-Linking and Mono-Linking were for the first time found,while Inter-Linking mode accounted for the highest proportion(75.1%),suggesting that chelation of calcium ions frequently occurred between two peptides.Overall,this study provides a theoretical basis for the elucidation of chelation mechanism of calcium-chelating peptides.展开更多
To provide new insights into the development and utilization of Douchi artificial starters,three common strains(Aspergillus oryzae,Mucor racemosus,and Rhizopus oligosporus)were used to study their influence on the fer...To provide new insights into the development and utilization of Douchi artificial starters,three common strains(Aspergillus oryzae,Mucor racemosus,and Rhizopus oligosporus)were used to study their influence on the fermentation of Douchi.The results showed that the biogenic amine contents of the three types of Douchi were all within the safe range and far lower than those of traditional fermented Douchi.Aspergillus-type Douchi produced more free amino acids than the other two types of Douchi,and its umami taste was more prominent in sensory evaluation(P<0.01),while Mucor-type and Rhizopus-type Douchi produced more esters and pyrazines,making the aroma,sauce,and Douchi flavor more abundant.According to the Pearson and PLS analyses results,sweetness was significantly negatively correlated with phenylalanine,cysteine,and acetic acid(P<0.05),bitterness was significantly negatively correlated with malic acid(P<0.05),the sour taste was significantly positively correlated with citric acid and most free amino acids(P<0.05),while astringency was significantly negatively correlated with glucose(P<0.001).Thirteen volatile compounds such as furfuryl alcohol,phenethyl alcohol,and benzaldehyde caused the flavor difference of three types of Douchi.This study provides theoretical basis for the selection of starting strains for commercial Douchi production.展开更多
Three materials(agar,konjac glucomannan(KGM)andκ-carrageenan)were used to prepare ternary systems,i.e.,sol-gels and their dried composites conditioned at varied relative humidity(RH)(33%,54%and 75%).Combined methods,...Three materials(agar,konjac glucomannan(KGM)andκ-carrageenan)were used to prepare ternary systems,i.e.,sol-gels and their dried composites conditioned at varied relative humidity(RH)(33%,54%and 75%).Combined methods,e.g.,scanning electron microscopy,small-angle X-ray scattering,infrared spectroscopy(IR)and X-ray diffraction(XRD),were used to disclose howκ-carrageenan addition tailors the features of agar/KGM/κ-carrageenan ternary system.As affirmed by IR and XRD,the ternary systems withκ-carrageenan below 25%(agar/KGM/carrageenan,50:25:25,m/m)displayed proper component interactions,which increased the sol-gel transition temperature and the hardness of obtained gels.For instance,the ternary composites could show hardness about 3 to 4 times higher than that for binary counterpart.These gels were dehydrated to acquire ternary composites.Compared to agar/KGM composite,the ternary composites showed fewer crystallites and nanoscale orders,and newly-formed nanoscale structures from chain assembly.Such multi-scale structures,for composites withκ-carrageenan below 25%,showed weaker changes with RH,as revealed by especially morphologic and crystalline features.Consequently,the ternary composites with lessκ-carrageenan(below 25%)exhibited stabilized elongation at break and hydrophilicity at different RHs.This hints to us that agar/KGM/κ-carrageenan composite systems can display series applications with improved features,e.g.,increased sol-gel transition point.展开更多
Tea plant(Camellia sinensis)is an important cash crop with extensive adaptability in the world.However,complex environmental factors force a large variation of tea quality-related components.Caffeine is essential for ...Tea plant(Camellia sinensis)is an important cash crop with extensive adaptability in the world.However,complex environmental factors force a large variation of tea quality-related components.Caffeine is essential for the formation of bitter and fresh flavors in tea,and is the main compound of tea that improves human alertness.Continuous strong light stimulation was observed to cause caffeine reduction in tea leaves,but the mechanism is not clear.In this study,the response of tea plant to light intensity was analysed mainly by multi-omics association,antisense oligodeoxynucleotide(asODN)silencing technique,and in vitro enzyme activity assay.The results revealed multiple strategies for light intensity adaptation in tea plant,among which the regulation of chloroplasts,photosynthesis,porphyrin metabolism,and resistance to oxidative stress were prominent.Caffeine catabolism was enhanced in continuous strong light,which may be a light-adapted strategy due to strict regulation by xanthine dehydrogenase(XDH).asODN silencing and enzymatic activity assays confirmed that CsXDH1 is a protein induced by light intensity to catalyze the substrate xanthine.CsXDH1 asODN silencing resulted in significant up-regulation of both caffeine and theobromine in in vitro enzyme activity assay,but not in vivo.CsXDH1 may act as a coordinator in light intensity adaptation,thus disrupting this balance of caffeine catabolism.展开更多
As a famous fruit worldwide,citrus is susceptible to green mold caused by Penicillium digitatum,which causes large economic losses every year.e-Poly-L-lysine(e-PL)is a novel preservative with strong inhibitory effects...As a famous fruit worldwide,citrus is susceptible to green mold caused by Penicillium digitatum,which causes large economic losses every year.e-Poly-L-lysine(e-PL)is a novel preservative with strong inhibitory effects on fungi,and has the capacity to induce disease resistance in fruit,but the mechanism has been reported rarely,especially in citrus.In the present study,8ooμg/mL e-PL and P digitatum spores were inoculated in two different wounds on the citrus pericarp at an interval of 24 h.The results revealed that e-PL inhibited that the development of green mold without direct contact with P digitatum,indicating that the disease resistance of citrus was activated.Transcriptome analysis revealed that e-PL activated amino acid metabolism and phenylpropanoid biosynthesis.Besides,the accumulation of glutamic acid,proline,arginine,serine,lysine,phenylalanine,and tyrosine were changed during storage.In phenylpropanoid biosynthesis,-PL increased phenylalanine ammonia-lyase(PAL),cinnamate 4-hydroxylase(C4H),and 4-coumarate:coenzyme A ligase(4CL)activities and total phenolic and flavonoid contents.Importantly.among these phenolic compounds,e-PL promoted the accumulation of individual phenolic compounds including ferulic acid,chlorogenic acid,p-coumaric acid,caffeic acid,gallic acid,catechins,epicatechin,and narirutin.In conclusion,e-PL enhanced the resistance of citrus through amino acid metabolism and accumulation of phenolic compounds.These results improved the knowledge of the mechanism of-PL-induced disease resistance and provided a fresh theoretical basis for the use of e-PL in postharvest citrus preservation.展开更多
Segment drying is a severe physiological disorder of citrus fruit,and vesicles become granulated or collapsed.Aside from the hypothesis that alteration of cell wall metabolism is the main factor of citrus granulation,...Segment drying is a severe physiological disorder of citrus fruit,and vesicles become granulated or collapsed.Aside from the hypothesis that alteration of cell wall metabolism is the main factor of citrus granulation,little is known about vesicle collapse.This study aimed to elucidate the changes in pectin metabolism during vesicle collapse in blood orange.Vesicle collapse was characterized by decreased nutrients and increased chelate-and sodium carbonate-soluble pectin and calcium content.The nanostructure of chelate-soluble pectin became complex and developed multi-branching upon collapse.The activity of pectin methylesterase increased,while that of polygalacturonase and pectate lyase decreased upon collapse.Genome-wide transcriptional analysis revealed an increasing pattern of genes encoding pectin methylesterase and other enzymes involved in pectin synthesis and demethylesterification upon collapse.Drying vesicles were characterized by increased abscisic acid content and relevant gene expression.In conclusion,we discovered alteration in pectin metabolism underlying citrus vesicle collapse,mainly promoting pectin demethylesterification,remodeling pectin structures,and further inhibiting pectin degradation,which was hypothesized to be a main factor for citrus collapse.This is the first study to disclose the potential intrinsic mechanism underlying vesicle collapse in orange fruit.展开更多
基金supported by the National Natural Science Foundation of China (31801647)Sichuan Science and Technology Program (2018JY0194,2020YFN0153,2020YFN0151)。
文摘Aptamers as a kind of biological recognition element have shown great potential in monitoring and the rapid quantification of organophosphorus pesticides(OPPs). However, molecules of OPPs are structurally similar and original aptamers selected by systematic evolution of ligands by exponential enrichment are usually long-chain bases, which hamper the further application under OPPs-aptamer recognition. The aim of the research was to develop a new strategy to design oligonucleotide sequences for binding OPPs by combination of experimental and molecular modeling methods. 3D models of aptamers binding OPPs were constructed, and binding energy and the most probable binding site for the OPPs were then determined by molecular docking, and the binding sites were further confirmed by the results of 2-AP replaced experiments. Based on the docking results, a new aptamer for detection 4 representative OPPs with only 29 bases was designed by reasonable truncation and mutation of the reported aptamer(named S4-29). The interaction between this new aptamer and OPPs were analyzed by molecular docking, microscale thermophoresis, circular dichroism and fluorometric analysis. The results revealed that the new aptamer exhibit more superior recognition performance to OPPs, which can be promote the monitoring ability of OPPs contaminations in food.
基金granted by the National Key R&D Program of China (2021YFD21001005)National Natural Science Foundation of China (31972102,32101980)+1 种基金Special key project of Chongqing technology innovation and application development (cstc2021jscx-cylhX0014)Chongqing Technology Innovation and Application Development Special Project (cstc2021jscx-tpyzxX0014)。
文摘This study aimed to characterize and identify calcium-chelating peptides from rabbit bone collagen and explore the underlying chelating mechanism.Collagen peptides and calcium were extracted from rabbit bone by instant ejection steam explosion(ICSE)combined with enzymatic hydrolysis,followed by chelation reaction to prepare rabbit bone peptide-calcium chelate(RBCP-Ca).The chelating sites were further analyzed by liquid chromatography-tandem mass(LC-MS/MS)spectrometry while the chelating mechanism and binding modes were investigated.The structural characterization revealed that RBCP successfully chelated with calcium ions.Furthermore,LC-MS/MS analysis indicated that the binding sites included both acidic amino acids(Asp and Glu)and basic amino acids(Lys and Arg),Interestingly,three binding modes,namely Inter-Linking,Loop-Linking and Mono-Linking were for the first time found,while Inter-Linking mode accounted for the highest proportion(75.1%),suggesting that chelation of calcium ions frequently occurred between two peptides.Overall,this study provides a theoretical basis for the elucidation of chelation mechanism of calcium-chelating peptides.
基金supported by Special key project of technological innovation and application development in Yongchuan District,Chongqing(2021yc-cxfz20002)the special funds of central government for guiding local science and technology developmentthe funds for the platform projects of professional technology innovation(CSTC2018ZYCXPT0006).
文摘To provide new insights into the development and utilization of Douchi artificial starters,three common strains(Aspergillus oryzae,Mucor racemosus,and Rhizopus oligosporus)were used to study their influence on the fermentation of Douchi.The results showed that the biogenic amine contents of the three types of Douchi were all within the safe range and far lower than those of traditional fermented Douchi.Aspergillus-type Douchi produced more free amino acids than the other two types of Douchi,and its umami taste was more prominent in sensory evaluation(P<0.01),while Mucor-type and Rhizopus-type Douchi produced more esters and pyrazines,making the aroma,sauce,and Douchi flavor more abundant.According to the Pearson and PLS analyses results,sweetness was significantly negatively correlated with phenylalanine,cysteine,and acetic acid(P<0.05),bitterness was significantly negatively correlated with malic acid(P<0.05),the sour taste was significantly positively correlated with citric acid and most free amino acids(P<0.05),while astringency was significantly negatively correlated with glucose(P<0.001).Thirteen volatile compounds such as furfuryl alcohol,phenethyl alcohol,and benzaldehyde caused the flavor difference of three types of Douchi.This study provides theoretical basis for the selection of starting strains for commercial Douchi production.
基金the National Natural Science Foundation of China(32172240)BL19U2 beamline of National Facility for Protein Science in Shanghai(NFPS)at Shanghai Synchrotron Radiation Facility,for their assistance during data collection。
文摘Three materials(agar,konjac glucomannan(KGM)andκ-carrageenan)were used to prepare ternary systems,i.e.,sol-gels and their dried composites conditioned at varied relative humidity(RH)(33%,54%and 75%).Combined methods,e.g.,scanning electron microscopy,small-angle X-ray scattering,infrared spectroscopy(IR)and X-ray diffraction(XRD),were used to disclose howκ-carrageenan addition tailors the features of agar/KGM/κ-carrageenan ternary system.As affirmed by IR and XRD,the ternary systems withκ-carrageenan below 25%(agar/KGM/carrageenan,50:25:25,m/m)displayed proper component interactions,which increased the sol-gel transition temperature and the hardness of obtained gels.For instance,the ternary composites could show hardness about 3 to 4 times higher than that for binary counterpart.These gels were dehydrated to acquire ternary composites.Compared to agar/KGM composite,the ternary composites showed fewer crystallites and nanoscale orders,and newly-formed nanoscale structures from chain assembly.Such multi-scale structures,for composites withκ-carrageenan below 25%,showed weaker changes with RH,as revealed by especially morphologic and crystalline features.Consequently,the ternary composites with lessκ-carrageenan(below 25%)exhibited stabilized elongation at break and hydrophilicity at different RHs.This hints to us that agar/KGM/κ-carrageenan composite systems can display series applications with improved features,e.g.,increased sol-gel transition point.
基金This work was supported by the Chongqing Technology Innovation and Application Demonstration Project(cstc2021jscxgksbX0016)the Germplasm Creation Research Program of Southwest University.
文摘Tea plant(Camellia sinensis)is an important cash crop with extensive adaptability in the world.However,complex environmental factors force a large variation of tea quality-related components.Caffeine is essential for the formation of bitter and fresh flavors in tea,and is the main compound of tea that improves human alertness.Continuous strong light stimulation was observed to cause caffeine reduction in tea leaves,but the mechanism is not clear.In this study,the response of tea plant to light intensity was analysed mainly by multi-omics association,antisense oligodeoxynucleotide(asODN)silencing technique,and in vitro enzyme activity assay.The results revealed multiple strategies for light intensity adaptation in tea plant,among which the regulation of chloroplasts,photosynthesis,porphyrin metabolism,and resistance to oxidative stress were prominent.Caffeine catabolism was enhanced in continuous strong light,which may be a light-adapted strategy due to strict regulation by xanthine dehydrogenase(XDH).asODN silencing and enzymatic activity assays confirmed that CsXDH1 is a protein induced by light intensity to catalyze the substrate xanthine.CsXDH1 asODN silencing resulted in significant up-regulation of both caffeine and theobromine in in vitro enzyme activity assay,but not in vivo.CsXDH1 may act as a coordinator in light intensity adaptation,thus disrupting this balance of caffeine catabolism.
基金supported by the National Key Research and Development Program of China(No.2021YFD2100505)the Project of Chongqing Science and Technology Bureau,China(cstc2021jscx-cylhX0015)the Project of Sichuan Science and Technology Plan,China(No.2021YFQ0071).
文摘As a famous fruit worldwide,citrus is susceptible to green mold caused by Penicillium digitatum,which causes large economic losses every year.e-Poly-L-lysine(e-PL)is a novel preservative with strong inhibitory effects on fungi,and has the capacity to induce disease resistance in fruit,but the mechanism has been reported rarely,especially in citrus.In the present study,8ooμg/mL e-PL and P digitatum spores were inoculated in two different wounds on the citrus pericarp at an interval of 24 h.The results revealed that e-PL inhibited that the development of green mold without direct contact with P digitatum,indicating that the disease resistance of citrus was activated.Transcriptome analysis revealed that e-PL activated amino acid metabolism and phenylpropanoid biosynthesis.Besides,the accumulation of glutamic acid,proline,arginine,serine,lysine,phenylalanine,and tyrosine were changed during storage.In phenylpropanoid biosynthesis,-PL increased phenylalanine ammonia-lyase(PAL),cinnamate 4-hydroxylase(C4H),and 4-coumarate:coenzyme A ligase(4CL)activities and total phenolic and flavonoid contents.Importantly.among these phenolic compounds,e-PL promoted the accumulation of individual phenolic compounds including ferulic acid,chlorogenic acid,p-coumaric acid,caffeic acid,gallic acid,catechins,epicatechin,and narirutin.In conclusion,e-PL enhanced the resistance of citrus through amino acid metabolism and accumulation of phenolic compounds.These results improved the knowledge of the mechanism of-PL-induced disease resistance and provided a fresh theoretical basis for the use of e-PL in postharvest citrus preservation.
基金funded by the National Natural Science Foundation of China(No.32172262)the Fundamental Research Funds for the Central Universities(No.XDJK2021F008)Chongqing Graduate Student Research Innovation Project(No.CYS21118),China.
文摘Segment drying is a severe physiological disorder of citrus fruit,and vesicles become granulated or collapsed.Aside from the hypothesis that alteration of cell wall metabolism is the main factor of citrus granulation,little is known about vesicle collapse.This study aimed to elucidate the changes in pectin metabolism during vesicle collapse in blood orange.Vesicle collapse was characterized by decreased nutrients and increased chelate-and sodium carbonate-soluble pectin and calcium content.The nanostructure of chelate-soluble pectin became complex and developed multi-branching upon collapse.The activity of pectin methylesterase increased,while that of polygalacturonase and pectate lyase decreased upon collapse.Genome-wide transcriptional analysis revealed an increasing pattern of genes encoding pectin methylesterase and other enzymes involved in pectin synthesis and demethylesterification upon collapse.Drying vesicles were characterized by increased abscisic acid content and relevant gene expression.In conclusion,we discovered alteration in pectin metabolism underlying citrus vesicle collapse,mainly promoting pectin demethylesterification,remodeling pectin structures,and further inhibiting pectin degradation,which was hypothesized to be a main factor for citrus collapse.This is the first study to disclose the potential intrinsic mechanism underlying vesicle collapse in orange fruit.
