Klaus Krickeberg und Vietnam. Erinnerungen

Ohne Zusammenfassung

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Original Russian Text ? X.X.Nguyen, 2009, published in Izvestiya NAN Armenii. Matematika, 2009, No. 1, pp. 26–31.     

Catalytic reduction of NO to N2O by a designed heme copper center in myoglobin: implications for the role of metal ions

The effects of metal ions on the reduction of nitric oxide (NO) with a designed heme copper center in myoglobin (F43H/L29H sperm whale Mb, CuBMb) were investigated under reducing anaerobic conditions using UV-vis and EPR spectroscopic techniques as well as GC/MS. In the presence of Cu(I), catalytic reduction of NO to N2O by CuBMb was observed with turnover number of 2 mol NO.mol CuBMb-1.min-1, close to 3 mol NO.mol enzyme-1.min-1 reported for the ba3 oxidases from T. thermophilus. Formation of a His-heme-NO species was detected by UV-vis and EPR spectroscopy. In comparison to the EPR spectra of ferrous-CuBMb-NO in the absence of metal ions, the EPR spectra of ferrous-CuBMb-NO in the presence of Cu(I) showed less-resolved hyperfine splitting from the proximal histidine, probably due to weakening of the proximal His-heme bond. In the presence of Zn(II), formation of a five-coordinate ferrous-CuBMb-NO species, resulting from cleavage of the proximal heme Fe-His bond, was shown by UV-vis and EPR spectroscopic studies. The reduction of NO to N2O was not observed in the presence of Zn(II). Control experiments using wild-type myoglobin indicated no reduction of NO in the presence of either Cu(I) or Zn(II). These results suggest that both the identity and the oxidation state of the metal ion in the CuB center are important for NO reduction. A redox-active metal ion is required to deliver electrons, and a higher oxidation state is preferred to weaken the heme iron-proximal histidine toward a five-coordinate key intermediate in NO reduction.     

Apparent 'electrocatalytic' activity of multiwalled carbon nanotubes in the detection of the anaesthetic halothane: occluded copper nanoparticles

The electrocatalytic detection of the anaesthetic halothane on a multiwalled carbon nanotube modified glassy carbon electrode is reported with a low limit of detection of 4.6 microM. A thorough investigation of the underlying cause of this apparent catalytic effect is undertaken by comparing the response of various carbon electrodes including glassy carbon, basal- and edge-plane pyrolytic graphite electrodes (bppg and eppg respectively) to increasing additions of halothane. The reduction of halothane is shifted by 250-300 mV to more negative potentials at an eppg electrode than that observed at the GC-CNT electrode. Therefore the results of this investigation show that, surprisingly, the electrocatalysis is not solely due to the introduction of edge-plane-like defect sites on the carbon nanotubes as is commonly found for many other substrates showing favourable voltammetry at nanotube modified electrodes. Instead, we reveal that in this unusual case the electroactive sites for the reduction of halothane are due to the presence of copper nanoparticles occluded within the carbon nanotubes during their production, which are never completely removed by standard purification techniques such as acid washing. This is only the third known case where apparent electrocatalysis by carbon nanotube modified electrodes is due to occluded metal-related nanoparticles within the nanotube structure, rather than the active sites being the edge-plane-like defect sites on the nanotubes. Furthermore this is the first case where the active sites are nanoparticles of copper metal, rather than metal oxide nanoparticles (namely oxides of iron(II)/(III)) as was found to be the case in the previous examples.     

Highly diastereoselective enolate addition of O-protected alpha-hydroxyacetate to (S(R))-tert-butanesulfinylimines: synthesis of taxol side chain

The taxol side chain (S(R),2R,3S)-N-tert-butanesulfinyl-O-Boc-3-phenylisoserine benzyl ester 4c was synthesized through a lithium enolate addition of O-Boc-alpha-hydroxyacetate benzyl ester 5c to benzylidene (S(R))-tert-butanesulfinamide 6a in excellent yield and diastereoselectivity. By similar approach, a series of enantiopure 3-substituted isoserine benzyl esters 4 useful for the semi-syntheses of taxol derivatives were also prepared in high to excellent yields and diastereoselectivities. The diastereoselective addition mechanism was discussed on the basis of the experimental observation.     

Continuous separation of microparticles by size with direct current-dielectrophoresis

Direct current-dielectrophoresis (DC-DEP), the induced motion of the dielectric particles in a spatially nonuniform DC electric field, is demonstrated to be a highly efficient method to separate the microparticles by size. The locally nonuniform electric field is generated by an insulating block fabricated inside a polydimethylsiloxane microchannel. The particle experiences a negative DEP (accordingly a repulsive force) at the corners of the block, where the local electric-field strength is the strongest. Thus, the particle deviates from the streamline and the degree of deviation is dependent on the DEP force (i.e., the particle size). Combined with the electrokinetic flow, mixed polystyrene particles of a few micrometers difference in diameter can be continuously separated into distinct reservoirs. For separating target particles of a specific size, it is required to simply adjust the voltage outputs of the electrodes. A numerical model based on the Lagrangian tracking method is developed to simulate the particle motion and the results showed a reasonable agreement with the experimental data.     

Cryopreservation of the late stage embryos of Spodoptera exigua (Lepidoptera: Noctuidae)

Genetic devolution, genetic drift and contamination are all threats to maintain germplasm stability during mass rearing of many insects. Cryopreservation of beet armworm (Spodoptera exigua) embryos was studied to provide information to improve mass rearing. A series of experiments was conducted on late-stage embryos (45-48 h at 27 degree C) of the beet armyworm, which included evaluation of cryoprotectants (CPAs), their toxicity and glass-forming tendency and optimization of experimental procedures. The results showed that ethylene glycol (EG) was the best CPA with comparatively low toxicity compared to the other six CPAs tested (methanol, 1,3-propanediol, glycerol, 2-amino-1-ethanol, 3-amino-1-propanol 3-methoxy-1 and 2-propanediol). The highest hatching rate of 8.8 degree was attained after freezing with a 3-step loading procedure and a 1-step unloading procedure, but the hatched larvae from frozen-thawed embryos did not actively feed and could not develop to a later stage. This was attributed to injuries from freezing in late stage embryos of S. exigua which had formed midguts.     

Ultrasonic treatment on activated sewage sludge from petro-plant for reduction

In this essay, the influences of low frequency ultrasound (20 kHz) on dewater ability and anaerobic digestion behaviors of activated sewage sludge, obtained from Yangzi Water Treatment Plant, Yangzi Petrochemical Corporation, were discussed. Ultrasound pretreatment could enhance the filtration progress and decrease the moisture content of the sludge from 99% to 80%. Together with flocculant, the ultrasound pretreatment decreased the specific filtration resistance (SFR) of the sludge from 3.59 x 10(12) m/kg to 1.18 x 10(12) m/kg and saved about 25-50% of the flocculant dosage. Bound water of the sludge was measured by dilatometer. After 2-4 min treatment of ultrasound under intensity of 400 W/m(2), the bound water of sludge decreased from 16.7 g/g (dry base) to above 2.0 g/g (dry base). Ultrasound pretreatment could also enhance digestion and reduce digestion time. To the same resolution ratio, such as 49%, the digestion time of sludge with ultrasound pretreatment was 7 days less than that without ultrasound. Proper ultrasound pretreatment could also improve the dewater ability of the digested sludge, the final moisture of which was 73.7%.     

一维钴(Ⅱ)/镍(Ⅱ)配位聚合物的合成、结构、磁性及荧光传感性质

采用水热法合成了2个新的配位聚合物[Co(L)_0.5(1,4-bib)(H₂O)₃]_n(1)和[Ni(L)_0.5(1,4-bib)(H₂O)₃]_n(2)(H₄L=1,4-二(2,6-二甲基-3,5-二羧基吡啶基)苯,1,4-bib=1,4-双(1-咪唑基)苯),通过X射线单晶及粉末衍射、元素分析、红外光谱分析和热重分析对其结构进行表征。结构分析表明配合物1和2为异质同构,均为一维结构。通过变温磁化率测量发现,配合物1和2中的Co(Ⅱ)/Ni(Ⅱ)离子之间存在反铁磁相互作用。此外,配合物1可通过荧光猝灭法检测头孢克肟(CEF),配合物2可用来检测四环素(TET),该方法灵敏度高、选择性好,其检出限分别为0.86 μmol·L^-1(CEF)和0.49 μmol·L^-1(TET)。     

花状NaLa(MoO4)2∶Eu3+,M(M=Gd3+,Ti4+)红色荧光粉的水热合成及发光性能

以乙二醇和水的混合溶液为溶剂,采用水热法合成了花状的NaLa(MoO4)2∶Eu3+红色荧光粉.通过X射线衍射仪、扫描电子显微镜、荧光分光光度计等手段对产物进行了分析和表征.结果表明:产物NaLa(MoO4)2∶Eu3+属于四方晶系白钨矿结构.样品分散性好,粒度均匀,呈花状结构.样品的激发光谱分为两部分:位于250～350 nm的宽激发带归属于Eu-O,Mo-O之间的电荷迁移;350～500 nm的系列尖锐峰归属于Eu3+的f-f跃迁.样品的发射光谱中主发射峰位于615 nm处,归属于Eu3的5 Do→7R电偶极跃迁.此外,共掺杂适量的Gd3+或Ti4能够有效敏化Eu3+的发光,明显增强了615 nm的红光发射.     

超高效液相色谱-荧光法测定大鼠尿液中的黄蝶呤、异黄蝶呤、酪氨酸和色氨酸

建立了一种大鼠尿液中黄蝶呤、异黄蝶呤、酪氨酸和色氨酸的超高效液相色谱-荧光分析方法(UPLCFLD),大鼠尿液利用甲醇和乙腈除蛋白后,采取C18固相萃取小柱进行净化,然后用UPLC-FLD法进行测定。黄蝶呤、异黄蝶呤、酪氨酸和色氨酸分别在0.01~10.0,0.005~10.0,0.5~100,0.5~200mg·L-1范围内与色谱峰面积呈线性关系,4种物质的仪器检测限分别为0.005,0.000 3,0.004和0.002mg·L-1,加标回收率除黄蝶呤在61.1%~78.0%之间,其余各物质回收率均在86.0%~110.0%之间,RSD小于10.5%。