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981.
氮离子注入棉花花粉诱发农艺性状变异的研究 总被引:6,自引:0,他引:6
N+注入陆地棉和海岛棉的成熟花粉用于自交和远缘杂交,结果表明:离子注入花粉,在M1代就可表出现较高频率的有益突变,在M1相对成苗率和花粉育性为50%时,花粉辐照M2突变率是种子辐照的1.6倍,用N+离子注入陆地棉和海岛棉花粉进行正反远缘杂交,F2M2农艺性状表现出偏母遗传且后代遗传稳定加快,并观察到父本某些性状的转移。离子注入花粉适宜的剂量范围为2×1015—10×1015N+/cm2。 相似文献
982.
钙稳态失衡与癌细胞抑制 总被引:3,自引:0,他引:3
细胞胞浆钙离子浓度必须处于严格的调控之中,钙稳态失调必将导致细胞严重损伤或死亡(凋亡或坏死).综述了钙稳态失调在外界因素引起细胞死亡中的作用、直接钙稳态失调的细胞死亡效应、以及钙离子在细胞凋亡中的作用,并讨论了上述作用的机制,最后在总结基础上提出了一种抑癌新途径——选择性引发癌细胞钙稳态失衡. 相似文献
983.
A colorimetric and turn‐on fluorescent probe for fluoride ions, tert‐butyldimethylsilane 6‐acetyl‐2‐naphtholate, was readily synthesized from 6‐acetyl‐2‐naphthol and tert‐butyldimethylchlorosilane (TBSCl). The probe exhibits high sensitivity and good selectivity for fluoride ions in acetonitrile. The inherent mechanism involves the cleavage of the Si–O bond in the probe, which induced yellow color formation and prominent fluorescence enhancement. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
984.
A Novel Graphene Oxide Wrapped Na2Fe2(SO4)3/C Cathode Composite for Long Life and High Energy Density Sodium‐Ion Batteries 下载免费PDF全文
Mingzhe Chen David Cortie Zhe Hu Huile Jin Shun Wang Qinfen Gu Weibo Hua Enhui Wang Weihong Lai Lingna Chen Shu‐Lei Chou Xiao‐Lin Wang Shi‐Xue Dou 《Liver Transplantation》2018,8(27)
The cathode materials in the Na‐ion battery system are always the key issue obstructing wider application because of their relatively low specific capacity and low energy density. A graphene oxide (GO) wrapped composite, Na2Fe2(SO4)3@C@GO, is fabricated via a simple freeze‐drying method. The as‐prepared material can deliver a 3.8 V platform with discharge capacity of 107.9 mAh g?1 at 0.1 C (1 C = 120 mA g?1) as well as offering capacity retention above 90% at a discharge rate of 0.2 C after 300 cycles. The well‐constructed carbon network provides fast electron transfer rates, and thus, higher power density also can be achieved (75.1 mAh g?1 at 10 C). The interface contribution of GO and Na2Fe2(SO4)3 is recognized and studied via density function theory calculation. The Na storage mechanism is also investigated through in situ synchrotron X‐ray diffraction, and pseudocapacitance contributions are also demonstrated. The diffusion coefficient of Na+ ions is around 10?12–10?10.8 cm2 s?1 during cycling. The higher working voltage of this composite is mainly ascribed to the larger electronegativity of the element S. The research indicates that this well‐constructed composite would be a competitive candidate as a cathode material for Na‐ion batteries. 相似文献
985.
Studying the tight activity regulation of platelet-specific integrin αIIbβ3 is foundational and paramount to our understanding of integrin structure and activation. αIIbβ3 is essential for the aggregation and adhesion function of platelets in hemostasis and thrombosis. Structural and mutagenesis studies have previously revealed the critical role of αIIbβ3 transmembrane (TM) association in maintaining the inactive state. Gain-of-function TM mutations were identified and shown to destabilize the TM association leading to integrin activation. Studies using isolated TM peptides have suggested an altered membrane embedding of the β3 TM α-helix coupled with αIIbβ3 activation. However, controversies remain as to whether and how the TM α-helices change their topologies in the context of full-length integrin in native cell membrane. In this study, we utilized proline scanning mutagenesis and cysteine scanning accessibility assays to analyze the structure and function correlation of the αIIbβ3 TM domain. Our identification of loss-of-function proline mutations in the TM domain suggests the requirement of a continuous TM α-helical structure in transmitting activation signals bidirectionally across the cell membrane, characterized by the inside-out activation for ligand binding and the outside-in signaling for cell spreading. Similar results were found for αLβ2 and α5β1 TM domains, suggesting a generalizable mechanism. We also detected a topology change of β3 TM α-helix within the cell membrane, but only under conditions of cell adhesion and the absence of αIIb association. Our data demonstrate the importance of studying the structure and function of the integrin TM domain in the native cell membrane. 相似文献
986.
S.K. Das M. Masuda M. Hatashita A. Sakurai M. Sakakibara 《Letters in applied microbiology》2008,47(6):534-538
Aims: To obtain a higher cordycepin production using Cordyceps militaris mutant obtained by a new mutagenesis technique called ‘ion beam’. Methods and Results: Successful irradiation of C. militaris NBRC 9787 by a proton beam with high energy was performed, and 30 classes of 8‐azaadenine‐ and 28 classes of 8‐azaaguanine‐resistant mutants were obtained on mutant screening, of which seven classes were selected as promising preliminary mutants having an antibacterial ability as an index of cordycepin production. In a surface liquid culture technique, some of the 8‐azaadenine‐resistant mutants gave a better performance for the cordycepin productivity; in contrast, among the 8‐azaaguanine‐resistant mutants, it was shown that mutant no. G81‐3 was much better than the control in the metabolic rate of glucose and the cordycepin productivity. In primary optimization using the enriched medium, the cordycepin production was 3·1 and 1·8 g l?1 on 21‐day culture for mutant no. G81‐3 and the control, respectively. The cordycepin production obtained by the mutant was 72% more than the control. Conclusions: The mutant obtained by proton beam irradiation had higher productivity of cordycepin than that of the control. Significance and Impact of the Study: The mutant obtained by irradiation had a superior production performance of cordycepin, and therefore, it could be used in the realm of applied industrial biotechnology for the large‐scale production of cordycepin. 相似文献
987.
Using a patch-clamp technique, we studied the biophysical properties of large-conductance channels in the nuclear envelope
of rat cerebellar Purkinje neurons. Our experiments showed that channels with identical conductance, selectivity, and kinetics
are expressed in the external and internal nuclear membranes of these cells. These channels connect the perinuclear space
with the cyto-and nucleoplasm; they are not channels of the complex of the nuclear pores for passive diffusion of ions and
small molecules, as was believed earlier [17]. We hypothesize that large-conductance cationic channels in the membranes of
the nuclear envelope are identical to ion channels of the endoplasmic reticulum and are necessary for functioning of the intermembrane
space of the envelope as a calcium store.
Neirofiziologiya/Neurophysiology, Vol. 39, No. 2, pp. 113–118, March–April, 2007. 相似文献
988.
Inhibitory effects of gold(III) ions (Au(III)) on ribonuclease A (RNase A) and deoxyribonuclease I (DNase I) were investigated at neutral pH. RNase A was completely inhibited by 3 molar equivalents of Au(III) ions. DNase I was inhibited by 10 molar equivalents of Au(III) ions. Stoichiometric analyses suggest that Au(III) ions were coordinated to RNase A molecules. The Au(III)-inhibited RNase A and DNase I were renatured to exhibit 80% and 60% of their intrinsic activity, when the bound Au(III) ions were eliminated from the nucleases by addition of thiourea, which forms a strong complex with gold ions. This suggests that RNase A and DNase I were not oxidized to lose their activity, but reversibly complexed with Au(III) ions to lose their activity. Au(III) ions were probably considered to be bound to histidine and methionine residues in the nucleases, resulting in the inhibition of their activity. CD spectra revealed that the Au(III)-induced inhibition caused a conformational change in RNase A molecules and that the addition of thiourea induced refolding of the Au(III)-inhibited RNase A. 相似文献
989.
Van Biervliet S Van Biervliet JP Vande Velde S Robberecht E 《Biological trace element research》2007,119(1):19-26
Aim Assess the risk of zinc (Zn) deficiency in the older cystic fibrosis (CF) population.
Method Cross-sectional investigation of all CF patients above the age of 4 followed at the Ghent University center between 2002 and
2003. Data on age, weight, height z-score, pancreatic and pulmonary functions, chronic Pseudomonas infection, and CF transmembrane conductance regulator (CFTR) mutations were collected. Serum Zn, vitamins (vit) A and E,
retinol-binding protein (RBP), albumin, sedimentation rate, total IgG, and cholesterol were determined. Serum Zn was compared
with a local healthy control group (Van Biervliet et al., Biol Trace Elem Res 94:33–40, 2003) and with literature data (Hotz
C, et al. Am J Clin Nutr 78:756–764, 2003).
Results 101 patients (median age 16 years) were included. There was no difference in serum Zn concentration between CF patients and
controls. In CF patients no difference in serum Zn concentration between pancreatic-sufficient or pancreatic-insufficient
patients was seen. Serum Zn was not associated to nutritional status or height z-score. A significant association serum Zn to serum albumin (p < 0.0005) and to vit A (p < 0.01) was seen. No associations of serum Zn to serum vit E, RBP, cholesterol, or CFTR were present, but there is a significant
association serum Zn to forced vital capacity (p < 0.01). Serum Zn was not associated to inflammatory parameters or chronic Pseudomonas infection.
Conclusion Comparison of CF patients with local controls revealed no significant differences. However, because persisting steatorrhea
increases Zn loss (Easley et al., J Pediatr Gastroenterol Nutr 26:136–139, 1998) and 12.6% of our population has a serum Zn
below the p value of 2.5 of the NHANES II study (Hotz C, et al. Am J Clin Nutr 78:756–764, 2003), there could remain an increased risk
of Zn deficiency in some CF patients. Furthermore, the association with pulmonary function needs more investigation. 相似文献
990.
As a model of Brownian motor we consider the jump diffusion motion of a particle in the presence of an asymmetric periodic potential with a unique minimum and subject to half-period space shifts at the instants of occurrence of two Poisson processes. The relevant quantities, i.e., probability current, effective driving force, stall force, power and efficiency of the motor are explicitly calculated as averages of certain functions of the random variable representing the particle position. 相似文献