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871.
872.
Lactococcus lactis CM1, an isolate from homemade “Dahi,” a traditional fermented milk from India, used maltose as carbon source to produce a
high level of bacteriocin. The bacterial cell mass and the bacteriocin production correlated with the initial pH of the medium
and were highest when the initial pH was 11.0. The level of bacteriocin reached its peak at the late log phase with concomitant
reduction of culture pH to 4.2, regardless of the initial pH of the medium. A combination of maltose and an initial medium
pH of 11 resulted in the highest bacteriocin production. The antibacterial spectrum of the bacteriocin was closely similar
to that of nisin and it inhibited a number of food spoilage and pathogenic bacteria. Upon sodium dodecyl sulfate polyacrylamide
gel electrophoresis, the compound migrated close to the position of nisin (3.5 kDa). However, it had higher stability than
nisin at a wide range of pH and temperature. PCR amplification using nisin gene-specific primers and sequencing of the amplified
DNA revealed the structural gene for the bacteriocin to be identical to that of nisZ. 相似文献
873.
Current studies of lariat RNA structure and function are hindered by the lack of access to synthetic lariats. A novel approach to the synthesis of both DNA and RNA lariats is presented here. Noteworthy features of the methodology are the regiospecific formation of the 2'-5'-phosphodiester linkage, the unusual parallel stranded DNA/RNA hybrid (or parallel RNA/RNA duplex) that forms between an RNA template and a folded 22-nt DNA (or RNA) substrate, and the efficiency of the chemical ligation step at an adenosine branchpoint (50-80%). The DNA and RNA lariats were purified by polyacrylamide gel electrophoresis, and their structure and nucleotide composition were confirmed by MALDI-TOF mass spectrometry. Thermal denaturation as well as enzymatic and chemical hydrolysis fully supported the proposed lariat structures. Characterization of control parallel duplexes was conducted by gel shift assays and enzymatic degradation with RNase H. The successful synthesis of the lariat molecules described here will allow structural and biochemical studies aimed at better understanding the splicing and debranching mechanisms in which these unusual nucleic acids are involved. 相似文献
874.
The reactions of 4‐amino‐5‐methyl‐2H‐1,2,4‐triazole‐3(4H)‐thione (AMTT, L1 ) with 2‐thiophen carbaldehyde, salicylaldehyde and 2‐nitrobenzaldehyde in methanol led to the corresponding Schiff‐bases ( L1a‐c ). The reaction of L1 with [(PPh3)2Cu]NO3 in ethanol gave the ionic complex [(PPh3)2Cu(L1)]NO3·EtOH ( 2 ) All compounds were characterized by infrared spectroscopy, elemental analyses as well as by X‐ray diffraction studies. Crystal data for L1a at 20 °C: space group P21/n with a = 439.6(2), b = 2074.0(9), c = 1112.8(4) pm, β = 93.51(3)°, Z = 4, R1 = 0.0406, L1b at ?80 °C: space group P21/n with a = 1268.9(2), b = 739.3(1), c = 1272.5(1) pm, β = 117.97(1)°, Z = 4, R1 = 0.0361, L1c at ?80 °C: space group P21/n with a = 847.8(1), b = 1502.9(2), c = 981.5(2) pm, β = 110.34(1)°, Z = 4, R1 = 0.0376 and for 2 at ?80 °C: space group with a = 1247.8(1), b = 1270.3(1), c = 1387.5(1) pm, α = 84.32(1)°, β = 84.71(1)°, γ = 63.12(1)°, Z = 2, R1 = 0.0539. 相似文献
875.
876.
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878.
Choice of binder and the electrode-making process play a pivotal role in the electrochemical performance of MoS2, when used as lithium-ion battery anode. In this work, MoS2 nanorods are prepared by gas phase synthesis method using molybdenum trioxide (MoO3) nanobelts and sulfur as starting materials. It has been observed that by tuning the reaction conditions, morphology and yield of the final product can be controlled. Carboxymethyl cellulose (CMC) is used as binder to fabricate the MoS2 electrode, and its electrochemical performance is tested against Li/Li+. The performance of electrode can be further improved by incorporating heat treatment to the active material and conductive carbon mixture prior to electrode fabrication. The electrochemical data shows that the optimum temperature for heat treatment is 700 °C. In the current report, we would like to elucidate a detailed study based on electrode fabrication process and their impact on the electrochemical performance. 相似文献
879.
Trisita Chatterjee Kaustav Bhattacharjee Mahua Ghosh Chaudhuri M. K. Mitra G. C. Das 《Journal of Sol-Gel Science and Technology》2014,72(1):189-196
Nanocrystalline tantalum carbide (TaC) particles of average size ~15 nm dispersed in silica matrix, have been synthesized by the carbothermal reduction of Ta2O5 over a range of temperature 1,100–1,360 °C in Ar atmosphere. Investigation of the stability diagram of carbon saturated Ta–O–N system suggests that the TaC phase can be successfully synthesized within the SiO2 matrix when the partial pressure of O2 and N2 are restricted to approximately lower than 1.25 and 0.0001 atm. respectively. Two different synthesis routes are investigated in the present study which differ fundamentally in the order of addition of the precursors, tetraethyl orthosilicate (TEOS) and tantalum isopropoxide (Ta-iso). Rietveld refinement analyses of the powder X-ray diffraction data are carried out for the quantitative estimation of the two phases in the samples. The yield of TaC increases from 18 to 52 % when both TEOS and Ta-iso are added simultaneously to the water compared to the process where TEOS is added first to the water followed by the delayed addition of Ta-iso. Samples are further characterized by field emission scanning electron microscopy and high resolution transmission electron microscopy. 相似文献
880.
Scanning SQUID Microscopy of Local Superconductivity in Inhomogeneous Combinatorial Ceramics
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Mitra Iranmanesh Dr. Manuela Stir Prof. Dr. John R. Kirtley Prof. Dr. Jürg Hulliger 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(48):15816-15823
Although combinatorial solid‐state chemistry promises to be an efficient way to search for new superconducting compounds, the problem of determining which compositions are strongly diamagnetic in a mixed‐phase sample is challenging. By means of reactions in a system of randomly mixed starting components (Ca, Sr, Ba, La, Y, Pb, Bi, Tl, and Cu oxides), samples were produced that showed an onset of diamagnetic response above 115 K in bulk measurements. Imaging of this diamagnetic response in ceramic samples by scanning SQUID microscopy (SSM) revealed local superconducting areas with sizes down to as small as the spatial resolution of a few micrometers. In addition, locally formed superconducting matter was extracted from mixed‐phase samples by magnetic separation. The analysis of single grains (d<80 μm) by X‐ray diffraction, elemental analysis, and bulk SQUID measurements allowed Tl2Ca3Ba2Cu4O12, TlCaBaSrCu2O7?δ, BaPb0.5Bi0.25Tl0.25O3?δ, TlBa2Ca2Cu3O9, Tl2Ba2CaCu2O8, and YBa2Cu3O7 phases to be identified. SSM, in combination with other diagnostic techniques, is therefore shown to be a useful instrument to analyze inhomogeneous reaction products in the solid‐state chemistry of materials showing magnetic properties. 相似文献