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排序方式: 共有164条查询结果,搜索用时 15 毫秒
1.
Changes in pigment contents and ultrastructure have followed in cotyledons of mustard (Sinapis alba L.) seedlings during dark-mediated senescence. The seedlings were kept in white light for 7 d, treated with 5 min long wavelength far-red light and then kept in darkness up to 14 d after sowing. Under these conditions the chloroplasts remain stable for 2 d before a sequential plastidal disintegration commences. The data indicate a selective breakdown of the light-harvesting chlorophyll a/b protein. Phytochrome retards the differential loss of chlorophyll a, b and carotenoids and preserves the fine structure of chloroplasts. 相似文献
2.
A comparison of changes in absorption properties and electron transport activities of chloroplasts ageing in vivo and in vitro is made. Chloroplasts from sunflower leaves senescing in vivo during 7 days in dark do not show a blue shift of the red absorption band; in contrast, the shift becomes apparent within 24 h of in vitro ageing of isolated organelles. Photosynthetic activity by chloroplasts is lost much faster during in vitro than in vivo ageing. During in vitro ageing, the rate of degradation of thylakoid membranes as characterised by the shift in the red absorption band and loss in Hill reaction is further accelerated in chloroplasts isolated from dark-induced senescing leaves, suggesting the influence of the in vivo status of the chloroplasts on their in vitro stability.Abbreviations DCPIP
2,6-dichlorophenol indophenol
- PSI
Photosystem I
- Chl+
Chlorophyll 相似文献
3.
P. N. Joshi B. Biswal G. Kulandaivelu U. C. Biswal 《Radiation and environmental biophysics》1994,33(2):167-176
Response of senescing leaves of wheat seedlings to ultraviolet A (UVA) radiation (365 nm) has been examined. The results indicate that senescence-induced disorganization of thylakoid membrane, decline in carotenoid-to-chlorophyll energy transfer, and enhancement of lipid peroxidation are furthered by radiation. The senescence-induced decline in photochemical activity of photosystem II further declines on irradiation. UVA does not specifically alter any site other than those damaged by senescence. 相似文献
4.
Photodynamic treatment of herpes simplex virus type 1-infected hamster embryo fibroblasts (LSH strain) with a low concentration of proflavine (0.08 mug/10(5) cells per ml), a 3-9-diamine acridine dye, inhibited production not only of infectious progeny but also of virion particles. However, there was no appreciable inhibition of viral or cellular DNA synthesis, even when the infected cells were repeatedly exposed to this low concentration of dye and light during the replication cycle of the virus. It thus appears that photodynamic treatment of infected cells interferes with the processes involved in virus maturation. 相似文献
5.
Summary Phytohormones like IAA and kinetin inhibit chlorophyll loss during aging of wheat chloroplasts duringin vivo andin vitro. GA, on the other hand, stimulates the pigment degradation during aging of attached leaves in contrast to its senescence inhibiting action in detached leaves and isolated chloroplasts. A shift in optimum concentration of hormone in inhibiting chlorophyll degradation suggests a differential pool size of endogenous hormone regulating aging of chloroplastsin vivo andin vitro. The retardation of chlorophyll loss by kinetin, IAA and GA during aging of chloroplastsin vitro would indicate that the effect of hormones in preventing yellowing of senescing leaves may be mediated through their direct action on chloroplasts. 相似文献
6.
Aging induced changes in photosynthetic electron transport of detached barley leaves 总被引:2,自引:0,他引:2
Primary leaf segments of 11-day-old seedlings of barley (Hordtumvulgare L. cv IB 65) were floated on distilled water in darknessat 25°C to induce senescence. This stress induced agingbrings significant loss in the total content of pigments, proteinsand nucleic acids (DNA, RNA) of the leaves and of chloroplastsisolated from the senescing leaves. Of the three macromolecularcomponents, RNA content of theisolated chloroplasts was foundmost susceptible to stress-induced aging. Loss of DCPIP Hill activity of the isolated chloroplasts couldbe correlated, in a general way, with the loss of pigments,proteins and nucleic acids of the leaves and chloroplasts isolatedfrom them. However, during the stress period, the ability ofdifferent exogenous electron donors like MnCl2 and diphenylcarbazide(DPC) to feed electrons to Photo System II (PS II) was foundto be different. MnCl2 supported photoreduction of DCPIP onlyup to the fourth day, whereas DPC sustained its ability to donateelectrons up to the seventh day of incubation of the leavesin darkness. These results suggest a sequential alteration ofthe sites in the electron-transport chain between H2O and PSII reaction centers of chloroplasts during dark-induced senescence.Kinetin not only prevented the loss of pigments and proteinsduring senescence, but also preserved the integrity of the electron-transportchain. (Received November 15, 1975; ) 相似文献
7.
Jayashree Biswal Prajisha Jayaprakash Rayala Suresh Kumar Ganesh Venkatraman Saritha Poopandi Raghu Rangasamy 《Journal of biomolecular structure & dynamics》2020,38(1):13-31
Abstractp21-activated kinases (Paks) play an integral component in various cellular diverse processes. The full activation of Pak is dependent upon several serine residues present in the N-terminal region, a threonine present at the activation loop, and finally the phosphorylation of these residues ensure the complete activation of Pak1. The present study deals with the identification of novel potent candidates of Pak1 using computational methods as anti-cancer compounds. A diverse energy based pharmacophore (e-pharmacophore) was developed using four co-crystal inhibitors of Pak1 having pharmacophore features of 5 (DRDRR), 6 (DRHADR), and 7 (RRARDRP and DRRDADH) hypotheses. These models were used for rigorous screening against e-molecule database. The obtained hits were filtered using ADME/T and molecular docking to identify the high affinity binders. These hits were subjected to hierarchical clustering using dendritic fingerprint inorder to identify structurally diverse molecules. The diverse hits were scored against generated water maps to obtain WM/MM ΔG binding energy. Furthermore, molecular dynamics simulation and density functional theory calculations were performed on the final hits to understand the stability of the complexes. Five structurally diverse novel Pak1 inhibitors (4835785, 32198676, 32407813, 76038049, and 32945545) were obtained from virtual screening, water thermodynamics and WM/MM ΔG binding energy. All hits revealed similar mode of binding pattern with the hinge region residues replacing the unstable water molecules in the binding site. The obtained novel hits could be used as a platform to design potent drugs that could be experimentally tested against cancer patients having increased Pak1 expression. 相似文献
8.
Dominic Frigon Basanta Kumar Biswal Alberto Mazza Luke Masson Ronald Gehr 《Applied and environmental microbiology》2013,79(3):835-844
Effluents discharged from wastewater treatment plants are possible sources of pathogenic bacteria, including Escherichia coli, in the freshwater environment, and determining the possible selection of pathogens is important. This study evaluated the impact of activated sludge and physicochemical wastewater treatment processes on the prevalence of potentially virulent E. coli. A total of 719 E. coli isolates collected from four municipal plants in Québec before and after treatment were characterized by using a customized DNA microarray to determine the impact of treatment processes on the frequency of specific pathotypes and virulence genes. The percentages of potentially pathogenic E. coli isolates in the plant influents varied between 26 and 51%, and in the effluents, the percentages were 14 to 31%, for a reduction observed at all plants ranging between 14 and 45%. Pathotypes associated with extraintestinal pathogenic E. coli (ExPEC) were the most abundant at three of the four plants and represented 24% of all isolates, while intestinal pathogenic E. coli pathotypes (IPEC) represented 10% of the isolates. At the plant where ExPEC isolates were not the most abundant, a large number of isolates were classified as both ExPEC and IPEC; overall, 6% of the isolates were classified in both groups, with the majority being from the same plant. The reduction of the proportion of pathogenic E. coli could not be explained by the preferential loss of one virulence gene or one type of virulence factor; however, the quinolone resistance gene (qnrS) appears to enhance the loss of virulence genes, suggesting a mechanism involving the loss of pathogenicity islands. 相似文献
9.
Proteolytic enzymes of the caspase family, which reside as latent precursors in most nucleated metazoan cells, are core effectors of
apoptosis. Of them, the executioner caspases- 3 and -7 exist within the cytosol as inactive dimers and are activated by a process
called dimerization. Caspase inhibition is looked upon as a promising approach for treating multiple diseases. Though caspases
have been extensively studied in the human system, their role in eukaryotic pathogens and parasites of human hosts has not drawn
enough attention. In protein sequence analysis, caspases of blood flukes (Schistosoma spp) were revealed to have a low sequence
identity with their counterparts in human and other mammalian hosts, which encouraged us to analyse interacting domains that
participate in dimerization of caspases in the parasite and to reveal differences, if any, between the host-parasite systems.
Significant differences in the molecular surface arrangement of the dimer interfaces reveal that in schistosomal caspases only eight
out of forty dimer conformations are similar to human caspase structures. Thus, the parasite-specific dimer conformations (that are
different from caspases of the host) may emerge as potential drug targets of therapeutic value against schistosomal infections.
Three important factors namely, the size of amino acids, secondary structures and geometrical arrangement of interacting domains
influence the pattern of caspase dimer formation, which, in turn, is manifested in varied structural conformations of caspases in the
parasite and its human hosts. 相似文献
10.
Variations in enzyme activity in stomach and pancreatic tissue and digesta in piglets around weaning
A study was performed to investigate the effect of weaning at 4 weeks of age on the activity of digestive enzymes in the stomach and pancreatic tissue and in digesta from 3 days prior to weaning to 9 days postweaning in 64 piglets. In stomach tissue the activity of pepsin and gastric lipase was determined. Pepsin activity declined abruptly after weaning but 5 days postweaning the weaning level was regained and in the gastric contents no change in pepsin activity was observed. Weaning did not influence the activity of gastric lipase. The activity of eight enzymes and a cofactor was measured in pancreatic tissue. The effect of weaning on the enzyme activity was highly significant for all enzymes except elastase. The activity of all enzymes remained at the weaning level during day 1–2 postweaning followed by a reduction of the activity. The activity of trypsin, carboxypeptidase A, amylase and lipase exhibited minimum activity 5 days postweaning. Trypsin activity increased to the preweaning level on day 7–9 whereas the activity of the others increased but did not reach the preweaning level. The activity of chymotrypsin, carboxypeptidase B and carboxyl ester hydrolase decreased during the entire experimental period. In digesta no effect of weaning was observed on the activity of amylase and trypsin. The activity of chymotrypsin was reduced after weaning in the proximal third of the small intestine and lipase and carboxyl ester hydrolase activity was reduced in the middle and distal parts of the small intestine after weaning. The present study shows that the activities of the digestive enzymes in the pancreatic tissue are affected by weaning. Even though the pancreatic secretion cannot be judged from these results they show that the enzymes respond differently to weaning. In general the activity of the digestive enzymes in pancreatic tissue is low on day 5 postweaning which in interaction with other factors may increase the risk of developing postweaning diarrhoea. 相似文献