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1.
The resonance scattering spectral probe for Pb 2+ was obtained using aptamer-modified AuPd Nanoalloy. In the pH 7.0 Na 2HPO 4–NaH 2PO 4 buffer solution, the aptamer interacted with AuPd nanoalloy particles to form stable aptamer-AuPd nanoalloy probe for Pb 2+ that is stable in high concentration of salt. The probe combined with Pb 2+ ions to form a G-quadruplex and to release AuPd nanoalloy particles that aggregate to form big particles which led the resonance
scattering (RS) intensity enhancing. The reaction solution was filtered by 0.15 μm membrane to obtain the filtration containing
aptamer-AuPd nanoalloy probe that has strong catalytic effect on the electrodeless nickel particle plating reaction between
Ni(II) and PO 23− that exhibited a strong RS peak at 508 nm. The RS intensity at 508 nm decreased when the Pb 2+ concentration increased. The decreased intensity (Δ I
508nm) is linear to the concentration of 0.08–42 nM Pb 2+, with regress equation of D I508nm = 16.3 c + 1.5 \Delta {I_{{5}0{\rm{8nm}}}} = {16}.{3}\,c + {1}.{5} , correlation coefficient of 0.9965, and detection limit of 0.04 nM Pb 2+. The RS assay was applied to the analysis of Pb 2+ in wastewater, with satisfactory results. 相似文献
2.
In the pH 6.6 Na 2HPO 4–NaH 2PO 4 buffer solutions and in the presence of urease catalyst, urea can be decomposed to form NH 4
+. The NH 4
+ reacted with sodium tetraphenyl boron (NaTPB) to form the association particles that exhibited a resonance scattering (RS)
peak at 474 nm. When the urea concentration increased, NH 4
+ increased, and RS intensity at 474 nm enhanced linearly. Under the chosen conditions, the increased RS intensity (Δ I
474 nm) had a linear response to the urea concentration in the range of 0.125–15 μM, with a detection limit of 0.058 μM urea, and
a regression equation of Δ I
474 nm = 31.6 C + 2.1, a correlation coefficient of 0.9986. This catalytic RS method was applied for the detection of urea in human serum
sample, with good selectivity and sensitivity, and the results were consistent with the reference method. 相似文献
3.
The biohydration of acrylonitrile, propionitrile and benzonitrile catalysed by the NHase activity contained in resting cells
of Microbacterium imperiale CBS 498-74 was operated at 5, 10 and 20°C in laboratory-scale batch and membrane bioreactors. The bioreactions were conducted
in buffered medium (50 mM Na 2HPO 4/NaH 2PO 4, pH 7.0) in the presence of distilled water or tap-water, to simulate a possible end-pipe biotreatment process. The integral
bioreactor performances were studied with a cell loading (dry cell weight; DCW) varying from 0.1 mg DCW per reactor to 16 mg DCW per reactor, in order to realize near 100% bioconversion of acrylonitrile, propionitrile and benzonitrile without consistent
loss of NHase activity. 相似文献
4.
α-Chymotrypsin and lysozyme were solubilized in a water/ O-[(2-tridecyl, 2-ethyl-1,3-dioxolan-4-yl)methoxy]– O′-methoxy poly(ethylene glycol) (CK-2,13 surfactant)/isooctane water-in-oil microemulsion solution at 1.5–2 and 10 g l −1 for 0.15 and 1.2 M CK-2,13, respectively. Upon contact with an equal volume of 0.1 M NaH 2PO 4/Na 2HPO 4 buffer, pH 5, a three-phase system (Winsor-III system) was formed, consisting of a surfactant-rich middle phase and aqueous
and isooctane-rich “excess” phases. Both enzymes were rapidly released into the aqueous excess phase, with 70% recovery of
each in 30 and 60 min for microemulsion solutions containing 0.15 and 1.2 M surfactant, respectively. The recovered enzymes retained >90% of their original specific activity. 相似文献
5.
Summary Present studies indicate that all the three species of Alternaria possessed both intra- and extracellular PME activity but only the latter was significant. The role of the enzyme in pathogenicity of the strains has been discussed. The various optima determined for the extracellular enzyme activity were pH 4.5–7.0, temperature 50° C, time 24 hrs, and substrate concentration 1% pectin; the activity was proportional to enzyme concentration. Of the chemicals used to characterise the properties of the enzyme Na 2HPO 4, NaH 2PO 4, Mg ++, Ca ++ produced marked activation. 相似文献
6.
Gold nanoparticle particles in size of 10 nm were used to label the thiol-modified single-stranded DNA aptamer (SH-ssDNA)
to obtain an aptamer-modified gold nanoparticle probe (AussDNA) for target DNA (tDNA). In pH 7.4 NaH 2PO 4–Na 2HPO 4 buffer solution, the hybridization reaction between AussDNA and tDNA took place to form larger aptamer-modified gold nanoparticle
cluster complex. The excess aptamer-modified gold nanoparticle probe in the supernatant solutions was obtained by centrifuging
and can be used as nanocatalyst for the 0.276 mmol/L CuSO 4-65.4 mmol/L potassium-sodium tartrate-0.37 mmol/L glucose system at 70 °C. The cubic Cu 2O particles generated by the nanocatalytic reducing exhibit a strong resonance scattering (RS) peak at 620 nm. In the selected
conditions, the RS intensity at 620 nm decreased with addition of tDNA, and the decreased intensity Δ I
620 nm is proportional to tDNA concentration ( C
tDNA) from 0.12 to 72 pM, with regress equation of Δ I
620 nm = 1.29 C
tDNA + 4.05, correlation coefficient of 0.9917, and detection limit of 0.084 pM tDNA. 相似文献
7.
Based upon analyses of the composition of electric eel blood serum we suggest a new physiological saline solution as follows: 188 mM NaCl, 5 mM KCl, 2 mM MgCl 2, 2 mM CaCl 2, 0.15 mM NaH 2PO 4, 1.45 mM Na 2HPO 4 and 5 mM glucose; pH 7.4. The major difference between this saline and that used in most of the previous investigations using eel electroplaques is that the total Na + concentration is increased from between 162.7 and 171.7 mequiv/l to 191 mequiv./l. This increase does not appear to affect the electrophysiological properties of the electroplaque. 相似文献
8.
A large amount of adenosine triphosphate with high energy phosphate bonds is required for uridine triphosphate regeneration
during curdlan biosynthesis by Agrobacterium sp. ATCC 31749. To supply high energy for curdlan synthesis, three low-polyphosphates (Na 4P 2O 7, Na 5P 3O 10, and (NaPO 3) 6) with higher energy phosphate bonds were employed to substitute for KH 2PO 4-K 2HPO 4 in fermentation medium. Two genes encoding the polyphosphate metabolizing enzymes, polyphosphate kinase and exopolyphosphatase,
were amplified and showed 95% homology to those in Agrobacterium sp. C58 by sequence analysis. The curdlan yields were enhanced by 23 and 134% when phosphate concentrations 0.024 mol/L of
Na 5P 3O 10 and 0.048 mol/L of (NaPO 3) 6 respectively, were added in the medium. The maximum curdlan yield of 30 ± 1.02 g/L was obtained with the addition of 0.048
mol/L of (NaPO 3) 6 with 5 g/L CaCO 3 in the medium. When CaCO 3 was removed from the culture and the three lowpolyphosphates were added, the pH and biomass yield dropped remarkably and
little or no curdlan was produced. The culture containing 0.048 mol/L of (NaPO 3) 6 was mixed with KH 2PO 4-K 2HPO 4 and CaCO 3 in the medium, but showed no effect on curdlan production. However, curdlan yield was improved by 49 ∼ 60% when CaCO 3 was removed from the medium and KH 2PO 4-K 2HPO 4 acted as a buffer. It appears that the positive effect of (NaPO 3) 6 on curdlan production required the buffering capacity of CaCO 3 and the absence of KH 2PO 4-K 2HPO 4 competing as a phosphate supplier. 相似文献
9.
Nanosilver of 10-nm size was prepared by the NaBH 4–sodium citrate procedure, and it was modified by a single-strand DNA (ssDNA) aptamer to fabricate an AgssDNA probe for melamine.
The probe was stabile at pH 7.0 Na 2HPO 4–NaH 2PO 4 buffer solutions and in the presence of 25.0 mmol/L NaCl. Upon the addition of melamine, it interacted with the probe to
aggregate big clusters, which led to the resonance scattering (RS) intensity at 470 nm increasing greatly. Under the selected
conditions, the increased RS intensity (Δ I
470 nm) is linear to melamine concentration in the range of 6.31–378.4 μg/L, with a regression equation of D I470 nm = 1.124 c + 10.8 \Delta {I_{{47}0{\rm{ nm}}}} = {1}.{124}c + { 10}.{8} and a detection limit of 3.1 μg/L. The aptamer-modified nanosilver RS assay has been applied for the determination of melamine
in milk, with satisfactory results. 相似文献
10.
Nanogold of 10 nm was used to label carcinoembryonic antigen antibody (CEAAb) to prepare a probe (Au-CEAAb) for carcinoembryonic
antigen (CEA). In a Na 2HPO 4–NaH 2PO 4 buffer solution of pH 6.8, CEA reacted with Au-CEAAb to form a big Au-CEAAb–CEA immunocomplex that can be removed by centrifugation.
The unreacted Au-CEAAb in the centrifugal supernatant exhibited catalytic effect on the Cu 2O particle reaction, and the Cu 2O particles displayed a resonance scattering (RS) peak at 602 nm. When CEA increased, the RS intensity at 602 nm decreased,
and the decreased RS intensity (Δ I
602 nm) was linear to CEA concentration ( C
CEA) in the range of 0.02–12 ng mL −1, with the regression equation of Δ I
602 nm = 27.1 C
CEA + 3.3, correlation coefficient of 0.9978 and detection limit of 3 pg mL −1 CEA. The proposed method was applied to detect CEA in real samples, with satisfactory results. 相似文献
11.
Thirty-five strains capable of secreting extracellular alkaline proteases were isolated from the soil and waste water near
the milk processing plant, slaughterhouse. Strain APP1 with the highest-yield alkaline proteases was identified as Bacillus sp. The cultural conditions were optimized for maximum enzyme production. When the initial pH of the medium was 9.0, the
culture maintained maximum proteolytic activity for 2,560 U ml −1 at 50°C for 48 h under the optimized conditions containing (g −1): soyabean meal, 15; wheat flour, 30; K 2HPO 4, 4; Na 2HPO 4, 1; MgSO 4·7H 2O, 0.1; Na 2CO 3, 6. The alkaline protease showed extreme stability toward SDS and oxidizing agents, which retained its activity above 73
and 110% on treatment for 72 h with 5% SDS and 5% H 2O 2, respectively. 相似文献
12.
Heart cells from the clam Ruditapes decussatus were routinely cultured with a high level of reproducibility in sea water based medium. Three cell types attached to the
plastic after 2 days and could be maintained in vitro for at least 1 month: epithelial-like cells, round cells and fibroblastic
cells. Fibroblastic cells were identified as functional cardiomyocytes due to their spontaneous beating, their ultrastructural
characteristics and their reactivity with antibodies against sarcomeric α-actinin, sarcomeric tropomyosin, myosin and troponin
T-C. Patch clamp measurements allowed the identification of ionic currents characteristic of cardiomyocytes: a delayed potassium
current ( I
K slow) strongly suppressed (95%) by tetraethylammonium (1 mM), a fast inactivating potassium current ( I
K fast) inhibited (50%) by 4 amino-pyridine at 1 mM and, at a lower level (34%) by TEA, a calcium dependent potassium current ( I
KCa) activated by strong depolarization. Three inward voltage activated currents were also characterized in some cardiomyocytes:
L-type calcium current ( I
Ca) inhibited by verapamil at 5 × 10 −4 M, T-type Ca 2+ current, rapidly activated and inactivated, and sodium current ( I
Na) observed in only a few cells after strong hyperpolarization. These two currents did not seem to be physiologically essential
in the initiation of the beatings of cardiomyocytes. Potassium currents were partially inhibited by tributyltin (TBT) (1 μM)
but not by okadaic acid (two marine pollutants). DNA synthesis was also demonstrated in few cultured cells using BrdU (bromo-2′-deoxyuridine).
Observed effects of okadaic acid and TBT demonstrated that cultured heart cells from clam Ruditapes decussatus can be used as an experimental model in marine toxicology. 相似文献
13.
Penicillium roqueforti is used for the production of blue-veined cheeses but is a spoilage fungus as well. It reproduces asexually by forming conidia. Germination of these spores can start the spoilage process of food. Germination is typically characterized by the processes of activation, swelling and germ tube formation. Here, we studied nutrient requirements for germination of P. roqueforti conidia. To this end,?>?300 conidia per condition were monitored in time using an oCelloScope imager and an asymmetric model was used to describe the germination process. Spores were incubated for 72 h in NaNO3, Na2HPO4/NaH2PO4, MgSO4 and KCl with 10 mM glucose or 10 mM of 1 out of the 20 proteogenic amino acids. In the case of glucose, the maximum number of spores (Pmax) that had formed germ tubes was 12.7%, while time needed to reach 0.5 Pmax (τ) was about 14 h. Arginine and alanine were the most inducing amino acids with a Pmax of germ tube formation of 21% and 13%, respectively, and a τ of up to 33.5 h. Contrary to the typical stages of germination of fungal conidia, data show that P. roqueforti conidia can start forming germ tubes without a detectable swelling stage. 相似文献
14.
In this study, we isolated and characterized a novel feather-degrading bacterium that shows keratinolytic, antifungal and
plant growth-promoting activities. A bacterium S8 was isolated from forest soil and confirmed to belong to Bacillus subtilis by BIOLOG system and 16S rRNA gene analysis. The improved culture conditions for the production of keratinolytic protease
were 0.1% (w/v) sorbitol, 0.3% (w/v) KNO 3, 0.1% (w/v) K 2HPO 4, 0.06% (w/v) KH 2PO 4 and 0.04% (w/v) MgCl 2·6H 2O (pH 8.0 and 30°C), respectively. In the improved medium containing 0.1% (w/v) feather, keratinolytic protease production
was around 53.3 ± 0.3 U/ml at 4 day; this value was 10-fold higher than the yield in the basal feather medium (5.3 ± 0.1 U/ml).
After cultivation for 5 days in the improved medium, intact feather was completely degraded. Feather degradation resulted
in free –SH group, soluble protein and amino acids production. The concentration of free –SH group in the culture medium was
15.5 ± 0.2 μM at 4 days. Nineteen amino acids including all essential amino acids were produced in the culture medium; the
concentration of total amino acid produced was 3360.4 μM. Proline (2809.9 μM), histidine (371.3 μM) and phenylalanine (172.0 μM)
were the major amino acids released in the culture medium. B. subtilis S8 showed the properties related to plant growth promotion: hydrolytic enzymes, ammonification, indoleacetic acid (IAA),
phosphate solubilization, and broad-spectrum antimicrobial activity. Interestingly, the strain S8 grown in the improved medium
produced IAA and antifungal activity, indicating simultaneous production of keratinolytic and antifungal activities and IAA
by B. subtilis S8. These results suggest that B. subtilis S8 could be not only used to improve the nutritional value of feather wastes but also is useful in situ biodegradation of
feather wastes. Furthermore, it could also be a potential biofertilizer or biocontrol agent applicable to crop plant soil. 相似文献
15.
HAuCl 4 was reduced by sodium citrate to prepare 10 nm gold nanoparticles (AuNPs) that were modified by the bisphenol A aptamer (Apt) to obtain an aptamer–nanogold probe (Apt‐AuNP) for bisphenol A (BPA). The probes were aggregated nonspecifically to form large clusters, which showed a strong resonance light scattering (RLS) peak at 520 nm, under preparation conditions (pH 7.6 Na 2HPO 4‐NaH 2PO 4 buffer and ultrasonication). Upon addition of BPA, the probe reacted specifically to form dispersed BPA‐Apt‐AuNP conjugates that exhibited strong catalysis of the two particle reactions of glucose‐Cu(II) and hydrazine hydrochloride‐Cu(II) with a strong RLS peak at 360 nm and 510 nm respectively. When the BPA concentration increased, the RLS intensity at 360 nm and 510 nm increased respectively. Accordingly, two new and highly‐sensitive RLS methods were established for the detection of BPA, using the Apt‐AuNP catalytic amplification. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
16.
A whole-cell biocatalytic process for uridine 5′-monophosphate (UMP) production from orotic acid by Saccharomyces cerevisiae was developed. To rationally redistribute the metabolic flux between glycolysis and pentose phosphate pathway, statistical
methods were employed first to find out the critical factors in the process. NaH 2PO 4, MgCl 2 and pH were found to be the important factors affecting UMP production significantly. The levels of these three factors required
for the maximum production of UMP were determined: NaH 2PO 4 22.1 g/L; MgCl 2 2.55 g/L; pH 8.15. An enhancement of UMP production from 6.12 to 8.13 g/L was achieved. A significant redistribution of metabolic
fluxes was observed and the underlying mechanism was discussed. 相似文献
17.
Aeromonas hydrophila SBK1 (GenBank accession no. HM802878.1), a potent chitinolytic bacterium, was isolated from a pool of 30 chitinolytic isolates.
The isolate showed higher chitinolytic activity in respect to clear zone to colony size ratio of 2.15. Maximum production
of chitinolytic enzymes, viz., β- N-acetyl-glucosaminidase and chitinase (specific activity 655.3 and 71.6 U mg −1, respectively) by A. hydrophila SBK1 was observed in the synthetic media, containing (w/v)-colloidal chitin, 4.0%; peptone, 0.3%; phosphate, 0.3% (0.15%
of each KH 2PO 4 and K 2HPO 4); NaCl, 0.25%; MgSO 4, 0.05%; KCl, 0.05%; pH 7.0 and at 35°C after 72 h of incubation. Both carbon-to-nitrogen (C/N) and carbon-to-phosphate (C/P)
ratio of 13.33 were found optimum for chitinase production. Enzyme productivity increased about twofold in optimized culture
condition in respect to its un-optimized state. The crude enzyme showed optimum activity against Culex
quinquefasciatus larvae in native water at pH 7.0 and 35°C (LD 50 0.60 U ml −1 at 48 h). Therefore, the studied chitinases can be used as an effective mosquitocidal agent. 相似文献
18.
The selective action of the antibiotics chloramphenicol and cycloheximide on the synthesis of ferredoxin in liquid cultures of Chlamydomonas reinhardii was studied. Highly specific antibodies raised against Chlamydomonas ferredoxin were used to determine the in vivo synthesis of apoferredoxin and conversion into native protein. The results indicate that 80S ribosomes are involved in the synthesis. Chlamydomonas cells growing in the absence of iron did not synthesize immunologically detectable amounts of ferredoxin. We suggest that this is based upon feed-back inhibition of apoferredoxin synthesis at the translational level.Abbreviations CAP
chloramphenicol
- CHI
cycloheximide
- IgG
Immunoglobulin G
- PBS
140.4 mM NaCl. 9 mM Na 2HPO 4, 1.3 mM NaH 2PO 4 (pH 74)
- SDS
sodium dodecvl sulphate
- Fd
Ferredoxin
- apoFd
Apoferredoxin
- CM-Fd
Scarboxymethylated Fd
- TCA-Fd
Fd treated with trichloroacetic acid 相似文献
19.
Negatively charged bacteria combined with positively charged alkaline dye rhodamine 6G (Rh6G) in NaH 2PO 4–Na 2HPO 4 buffer solution pH 7.4, by electrostatic interaction. The dyed bacteria exhibited a strong fluorescence peak at 552 nm and fluorescence intensity was directly linear to Escherichia coli ( E. coli), Bacillus subtilis ( B. subtilis) and Staphylococcus aureus ( S. aureus) concentrations in the range of 7.06 × 10 4 to 3.53 × 10 7, 4.95 × 10 5 to 2.475 × 10 8 and 32.5 to 16250 colony forming unit/mL (cfu/mL) respectively, with detection limits of 3.2 × 10 4 cfu/mL E. coli, 2.3 × 10 5 cfu/mL B. subtilis and 16 cfu/mL S. aureus, respectively. Samples were cultured for 12 h, after which the linear detection range for E. coli was 2 to 88 cfu/mL. This simple, rapid and sensitive method was used for the analysis of water and drinking samples. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
20.
Polyhydroxyalkanotes (PHAs), the eco-friendly biopolymers produced by many bacteria, are gaining importance in curtailing
the environmental pollution by replacing the non-biodegradable plastics derived from petroleum. The present study was carried
out to economize the polyhydroxybutyrate (PHB) production by optimizing the fermentation medium using corn steep liquor (CSL),
a by-product of starch processing industry, as a cheap nitrogen source, by Bacillus sp. CFR 256. Response surface methodology (RSM) was used to optimize the fermentation medium using the variables such as
corn steep liquor (5–25 g l −1), Na 2HPO 4 2H 2O (2.2–6.2 g l −1), KH 2PO 4 (0.5–2.5 g l −1), sucrose (5–55 g l −1) and inoculum concentration (1–25 ml l −1). Central composite rotatable design (CCRD) experiments were carried out to study the complex interactions of the variables.
The optimum conditions for maximum PHB production were (g l −1): CSL-25, Na 2HPO 4 2H 2O-2.2, KH 2PO 4 − 0.5, sucrose − 55 and inoculum − 10 (ml l −1). After 72 h of fermentation, the amount of PHA produced was 8.20 g l −1 (51.20% of dry cell biomass). It is the first report on optimization of fermentation medium using CSL as a nitrogen source,
for PHB production by Bacillus sp. 相似文献
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