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991.
Georgi Z. Genchev Morten Källberg Gamze Gürsoy Anuradha Mittal Lalit Dubey Ognjen Perisic Gang Feng Robert Langlois Hui Lu 《Cell biochemistry and biophysics》2009,55(3):141-152
Efficient communication between the cell and its external environment is of the utmost importance to the function of multicellular
organisms. While signaling events can be generally characterized as information exchange by means of controlled energy conversion,
research efforts have hitherto mainly been concerned with mechanisms involving chemical and electrical energy transfer. Here,
we review recent computational efforts addressing the function of mechanical force in signal transduction. Specifically, we
focus on the role of steered molecular dynamics (SMD) simulations in providing details at the atomic level on a group of protein
domains, which play a fundamental role in signal exchange by responding properly to mechanical strain. We start by giving
a brief introduction to the SMD technique and general properties of mechanically stable protein folds, followed by specific
examples illustrating three general regimes of signal transfer utilizing mechanical energy: purely mechanical, mechanical
to chemical, and chemical to mechanical. Whenever possible the physiological importance of the example at hand is stressed
to highlight the diversity of the processes in which mechanical signaling plays a key role. We also provide an overview of
future challenges and perspectives for this rapidly developing field. 相似文献
992.
Although nitrate is a macronutrient and can serve as good nitrogen source for many species of phytoplankton, high nitrate
concentrations do not benefit the growth of phytoplankton. We hypothesise that algae cultured under high nitrate concentrations
can accumulate intracellular nitrite, which is produced by nitrate reductase (NR) and can inhibit the growth of algae. To
assess the validity of this hypothesis, Microcystis aeruginosa was grown under different nitrate concentrations from 3.57 to 21.43 mM in low CO2 and high CO2 conditions for 15 days. We observed that, with increasing nitrate concentrations, the intracellular nitrite concentrations
of the alga increased and the growth rates and photosynthesis declined. When grown under high CO2 conditions, M. aeruginosa showed lower intracellular nitrite concentrations and higher growth rates and
\textP\textm\textchla {\text{P}}_{\text{m}}^{{\text{chl}}a} ,
\textR\textd\textchla {\text{R}}_{\text{d}}^{{\text{chl}}a} , αchla
than under low CO2 conditions. These results suggest that the accumulation of intracellular nitrite could be the cause of inhibition of algal
growth under high nitrate concentrations. 相似文献
993.
The chitosan with three-dimensional porous structure greatly increased the effective electrode surface for loading of platinum nanoparticles and promoted efficient electron transfer. The resulting biosensor had a response time (within 5 s) and a linear response from 6 μM to 4.2 mM glucose with a detection limit of 2 μM (S/N = 3). Moreover, the methodology can be applied for the immobilization of other enzymes. 相似文献
994.
995.
Laurence Dutot Pascaline Lécorché Fabienne Burlina Rodrigue Marquant Vanessa Point Sandrine Sagan Gérard Chassaing Jean-Maurice Mallet Solange Lavielle 《Journal of chemical biology》2010,3(2):51-65
Cell-penetrating peptides (CPPs), which are usually short basic peptides, are able to cross cell membranes and convey bioactive
cargoes inside cells. CPPs have been widely used to deliver inside cells peptides, proteins, and oligonucleotides; however,
their entry mechanisms still remain controversial. A major problem concerning CPPs remains their lack of selectivity to target
a specific type of cell and/or an intracellular component. We have previously shown that myristoylation of one of these CPPs
affected the intracellular distribution of the cargo. We report here on the synthesis of glycosylated analogs of the cell-penetrating
peptide (R6/W3): Ac-RRWWRRWRR-NH2. One, two, or three galactose(s), with or without a spacer, were introduced into the sequence of this nonapeptide via a triazole link, the Huisgen reaction being achieved on a solid support. Four of these glycosylated CPPs were coupled via a disulfide bridge to the proapoptotic KLAK peptide, (KLAKLAKKLAKLAK), which alone does not enter into cells. The effect
on cell viability and the uptake efficiency of different glycosylated conjugates were studied on CHO cells and were compared
to those of the nonglycosylated conjugates: (R6/W3)S-S-KLAK and penetratinS-S-KLAK. We show that glycosylation significantly
increases the cell viability of CHO cells compared to the nonglycosylated conjugates and concomitantly decreases the internalization
of the KLAK cargo. These results suggest that glycosylation of CPP may be a key point in targeting specific cells. 相似文献
996.
Niels Tørring Susan Ball Dave Wright Gaïané Sarkissian Marie Guitton Bruno Darbouret 《Reproductive biology and endocrinology : RB&E》2010,8(1):129
Background
A disintegrin and metalloprotease 12 (ADAM12-S) has previously been reported to be significantly reduced in maternal serum from women with fetal aneuploidy early in the first trimester and to significantly improve the quality of risk assessment for fetal trisomy 21 in prenatal screening. The aim of this study was to determine whether ADAM12-S is a useful serum marker for fetal trisomy 21 using the mixture model. 相似文献997.
Study of the factors affecting the extraction of soybean protein by reverse micelles 总被引:3,自引:0,他引:3
Xihong Zhao Yanmei Li Xiaowei He Nanjing Zhong Zhenbo Xu Liansheng Yang 《Molecular biology reports》2010,37(2):669-675
In this work, the forward and back extraction of soybean protein by reverse micelles was studied. The reverse micellar systems
were formed by anionic surfactant sodium bis(2-ethyl hexyl) sulfosuccinate (AOT), isooctane and KCl solution. The effects
of AOT concentration, aqueous pH, KCl concentration and phase volume ratio on the extraction efficiency of soybean protein
were tested. Suitability of reverse micelles of AOT and Triton-X-100/AOT mixture in organic solvent toluene for soybean protein
extraction was also investigated. The experimental results lead to complete forward extraction at the AOT concentration 120 mmol l−1, aqueous pH 5.5 and KCl concentration 0.8 mol l−1. The backward extraction with aqueous phase (pH 5.5) resulted in 100% extraction of soybean protein from the organic phase. 相似文献
998.
The alternative pathway in cucumber seedlings under low temperature stress was enhanced by salicylic acid 总被引:1,自引:0,他引:1
Tao Lei Hong Feng Xin Sun Qi-Lin Dai Fan Zhang Hou-Guo Liang Hong-Hui Lin 《Plant Growth Regulation》2010,60(1):35-42
The alternative pathway is a cyanide-resistant and non-phosphorylatory electron transport pathway in mitochondria of higher
plants. Alternative oxidase (AOX) is the terminal oxidase of this pathway. Our present study investigated the effect of exogenous
salicylic acid (SA) on alternative pathway in cucumber (Cucumis sativus L.) seedlings under low temperature stress. Results showed that during the process of low temperature stress, the alternative
pathway capacity was enhanced as AOX expression increased in SA pretreated seedlings. Compared with seedlings without SA pretreatment,
slower decrease of relative water content and lower levels of electrolyte leakage, H2O2 and malonyldialdehyde content were detected in SA pretreated seedlings. These results indicated that SA could alleviate the
injury caused by low temperature on cucumber seedlings. Since the special protective functions of alternative pathway and
AOX in plants, we suggested that the alternative pathway was related to SA-mediated plant resistance to environmental stresses
such as low temperature. 相似文献
999.
We assessed diurnal variation of Chironomidae exuviae in two small upland streams in temperate Australia, during summer. Understanding
the diel periodicity of exuviae can be an important consideration for biomonitoring purposes or to investigate adult emergence
patterns. We collected 1,813 floating exuviae, comprising 54 taxa from four subfamilies, from flowing water using a drift
net. Unlike many northern hemisphere temperate studies, we observed that peak exuviae abundance (7.3 exuviae per m3) and taxon
richness (1.7 taxa per m3) occurred in the dusk and night hours, with the lowest numbers (0.9 exuviae per m3) and taxon richness
(0.6 taxa per m3) recorded in the late morning to early afternoon. We suggest that this could be an adaptation to avoid stressful
weather during the heat of summer days, or it could be to avoid visual predators. The numerically dominant taxa exhibited
peak abundance in the dusk/night samples which indicates predominant crepuscular/nocturnal patterns of adult emergence. This
pattern was consistent across both streams surveyed. Our taxon inventory rose steeply during the first 24-h occasion, then
at a reduced rate during the second and third days of sampling. For flowing water collections of exuviae that utilise drift-netting,
we suggest that sampling at all sites includes at least three 24-h cycles and avoids periods of heavy rainfall and increased
stream flow. 相似文献
1000.
Chien-Chih Chen Li-Wen Hsu Li-Tung Huang Tiao-Lai Huang 《Neurochemical research》2010,35(7):1098-1104
Neurotrophins, including the brain-derived neurotrophic factor (BDNF), are essential for regulating neuronal differentiation
in developing brains. BDNF and its receptor tyrosine kinase receptor B (TrkB) are involved in neuronal signaling, survival
and plasticity. Cyclosporine A (CsA) is a potent immunosuppressive agent which prevents allograft rejection in organ transplantation
and various immunological diseases. We investigated whether chronic administration of CsA decreases BDNF gene expression in
rats, and the influence of CsA on mRNA levels of TrkB receptors was also examined. For 30 days of CsA (10 mg/kg/day) administration,
the expression of BDNF and TrkB mRNA was significantly decreased in the hippocampus and midbrain, but there was no significant
difference in the cortex. CsA (0, 1, 5 10, 15 ug/ml) down-regulated BDNF and TrkB gene expression through cultured SH-SY5Y
cells, as did all-trans retinoic acid (ATRA), and there was no effect on cell viability. These experimental results indicate
that suppression of the BDNF and TrkB mRNA, protein level of BDNF expression in the hippocampus and midbrain may be related
to altered behavior observed following chronic administration of CsA. A common mechanism of adverse effects of CsA induced
depressive symptoms may involve neurotoxicity mediated by down-regulation of brain BDNF and TrkB. 相似文献