New light-sensitive cofactor required for oxidation of succinate by Mycobacterium phlei

Irradiation of the electron transport particles of Mycobacterium phlei with light at a wavelength of 360 manometers resulted in a loss of oxidase activities of succinate and the reduced form of nicotinamide adenine dinucleotide. The lesion in the two pathways caused by irradiation of the particles differs. The succinoxidase pathway was more labile to irradiation than the pathway linked to nicotinamide adenine dinucleotide. Restoration of succinoxidase activity (up to 50 to 60 percent) occurred on addition of a thermostable, water-soluble material obtained from Mycobacterium phlei cells or with an extract of mitochondria from boiled rat liver. Other known cofactors, such as flavine adenine dinucleotide, flavine mononucleotide, benzo- and naphthoquinones, as well as sulfhydryl agents, failed to restore succinoxidase activity after irradiation. Water-soluble material from Mycobacterium phlei appears to function between the flavoprotein and cytochrome b on the succinoxidase pathway. In contrast to the requirements for restoration of the pathway linked to nicotinamide adenine dinucleotide, restoration of succinoxidase does not occur with quinones or other cofactors such as flavine adenine dinucleotide.     

Inhibition of growth of leukemia cells by enzymic folate depletion

A new bacterial enzyme, designated as carboxypeptidase G(1), inhibited growth of the L5178Y and L1210 murine leukemias, as well as the Walker carcinoma and the human lymphoblastoid line (RPMI 4265), propogated in vitro. This enzyme hydrolyzes the glutamate moiety from both oxidized and reduced folate forms, and thus it may prove to be of value in creating rapid folate depletion in vivo.     

Suppressing wall turbulence by means of a transverse traveling wave

Direct numerical simulations of wall-bounded flow reveal that turbulence production can be suppressed by a transverse traveling wave. Flow visualizations show that the near-wall streaks are eliminated, in contrast to other turbulence-control techniques, leading to a large shear stress reduction. The traveling wave can be induced by a spanwise force that is confined within the viscous sublayer; it has its maximum at the wall and decays exponentially away from it. We demonstrate the application of this approach in salt water, using arrays of electromagnetic tiles that produce the required traveling wave excitation at a high efficiency.     

酶解法提高葡萄皮中白藜芦醇含量的研究

为了提高葡萄皮中白藜芦醇的含量,采用酶解法使葡萄皮中自藜芦醇苷等衍生物转化为白藜芦醇.对影响酶解的pH值、温度、时间3个因素进行考察,得出了最佳的酶解工艺:在pH值为5时,于37℃下条件酶解36 h.酶解后葡萄皮中白藜芦醇的含量提高为原来的2.89倍.     

Pancreatic ribonuclease: enzymic and physiological properties of a cross-linked dimer

Monomeric ribonuclease A has very low activity toward typically double-stranded RNA's; the dimeric form of ribonuclease A obtained by cross linking the enzyme by dimethyl suberimidate has more than 78 times the activity of the monomer toward polyadenylate . polyuridylate and 440 times the activity of the monomer toward the double-stranded RNA of a virus from Penicillium chrysogenum. The half-life of the dimer in the bloodstream of the rat is 12 times that of the mononmer.     

Specific enzymic methylation of an arginine in the experimental allergic encephalomyelitis protein from human myelin

A cytoplasmic enzyme from guinea pig brain was shown to transfer methyl groups from S-adenosylmethionine to only one of 19 arginine residues in the basic protein from human brain. The products were omega-N-monomethylarginine and omega-N,N'-dimethylarginine. These methylated arginines are adjacent to the main encephalitogenic determinant in the protein. Methylation may aid in the transfer of this region of the protein into the nonpolar environment within myelin and in maintaining the integrity of myelin.     

基于高副低代方法的平面凸轮设计

基于高副低代原理，将平面凸轮机构代换为平面连杆机构，运用圆向量函数建立代换机构的位移、速度、加速度矢量方程式，通过计算虚拟连杆的杆长和方向，求得凸轮实际廓线、曲率半径和压力角的表达式。并给出用圆形刀具加工凸轮时刀具中心的轨迹方程。运用该方法详细分析了滚子直动和滚子摆动从动件盘形凸轮机构中的凸轮设计问题，并对平面凸轮进行了设计，结果表明，该方法正确可行。     

Chloride methylation by plant pectin: an efficient environmentally significant process

Atmospheric chloromethane (CH3Cl) plays an important role in stratospheric ozone destruction, but many uncertainties exist regarding the strengths of its sources and sinks and particularly regarding the processes generating this naturally occurring gas. Evidence is presented here that CH3Cl is produced in many terrestrial environments by a common mechanism. Abiotic conversion of chloride to CH3Cl occurs readily in plant material, with the widespread plant component pectin acting as a methyl donor. Significant CH3Cl emissions from senescent and dead leaves were observed at ambient temperatures; those emissions rose dramatically when temperatures increased. This ubiquitous process acting in terrestrial ecosystems and during biomass burning could contribute the bulk of atmospheric CH3Cl.     

Separation of IL-4 production from Th cell proliferation by an altered T cell receptor ligand.

In the presence of antigen presenting cells, a murine T helper (Th) cell specific for murine hemoglobin (Hb) responded to its immunogenic peptide by both cytokine (interleukin-4) secretion and proliferation. An altered Hb peptide with a single amino acid substitution induced only cytokine secretion and did not induce proliferation. Interleukin-1 costimulated and restored the Th proliferative response to normal levels. The altered peptide also supported cognate T cell-B cell interactions indicative of T cell helper function. Thus, this result suggests that the T cell receptor has the capacity of differential signaling.     

Relaxation of isolated ventricular cardiomyocytes by a voltage-dependent process

Cell contraction and relaxation were measured in single voltage-clamped guinea pig cardiomyocytes to investigate the contribution of sarcolemmal Na+-Ca2+ exchange to mechanical relaxation. Cells clamped from -80 to 0 millivolts displayed initial phasic and subsequent tonic contractions; caffeine reduced or abolished the phasic and enlarged the tonic contraction. The rate of relaxation from tonic contractions was steeply voltage-dependent and was significantly slowed in the absence of a sarcolemmal Na+ gradient. Tonic contractions elicited in the absence of a Na+ gradient promptly relaxed when external Na+ was applied, reflecting activation of Na+-Ca2+ exchange. It appears that a voltage-dependent Na+-Ca2+ exchange can rapidly mechanically relax mammalian heart muscle.     

Experimental therapy of human glioma by means of a genetically engineered virus mutant.

Malignant gliomas are the most common malignant brain tumors and are almost always fatal. A thymidine kinase-negative mutant of herpes simplex virus-1 (dlsptk) that is attenuated for neurovirulence was tested as a possible treatment for gliomas. In cell culture, dlsptk killed two long-term human glioma lines and three short-term human glioma cell populations. In nude mice with implanted subcutaneous and subrenal U87 human gliomas, intraneoplastic inoculation of dlsptk caused growth inhibition. In nude mice with intracranial U87 gliomas, intraneoplastic inoculation of dlsptk prolonged survival. Genetically engineered viruses such as dlsptk merit further evaluation as novel antineoplastic agents.     

Mercury detection by means of thin gold films

The adsorption of elemental mercury vapor on a thin (several hundred angstroms) gold film produces resistance changes in the film. An instrument for the detection of mercury based on this phenomenon is simple and rapid and requires no chemical separations other than passage of the vapor sample through a few standard dry filters. The instrument is portable, and the technique is directly applicable to environmental problems and geochemical prospecting. The limit of detection of the prototype instrument is 0.05 nanogram of mercury.     

Inhibitory oxidation products of indole-3-acetic acid: enzymic formation and detoxification by pea seedlings

Extracts of etiolated pea seedlings oxidize indole-3-acetic acid, a plant auxin, to 3-hydroxymethyloxindole. At physiological pH this compound is dehydrated to 3-methyleneoxindole, a highly reactive sulfhydryl reagent and inhibitor of cell growth. 3-Methlyeneoxindole is in turn detoxified by an enzymatic, triphosphopyridine nucleotide-linked reduction to 3-methyloxindole, a nontoxic compound. These enzymatic conversions may be responsible for some of the responses to auxin, particularly sensitivity to its inhibitory effects on growth.     

Predicting drift from field spraying by means of a 3D computational fluid dynamics model

In order to investigate and understand drift from field sprayers, a steady state computational fluid dynamics (CFD) model was developed. The model was developed in 3D in order to increase the understanding of the causes of drift: a deviation in the wind direction cannot be captured by a 2D approach, the wake behind a wind screen is not symmetrical, the effects of a changed nozzle orientation may not be symmetrical. The model's accuracy was validated with field experiments carried out according to the international standard ISO 22866. A field sprayer with a spray boom width of 27 m and 54 nozzles (Hardi ISO F110-03 at 3 bar) was driving at 2.22 m/s over a flat pasture. During the experiments the wind direction was perpendicular to the tractor track. The model explained the variation in drift replicates during each single field experiment through varying boom height (0.3–0.7 m), wind velocity (1.3–2.5 m/s), wind deviation (−18° to +18°) from the direction perpendicular to the tractor track and injection velocity of the droplets (17–27 m/s). Boom movements had the highest impact on the variations in drift values (deviations in drift deposits of 25%), followed by variation in wind velocity (deviations in drift deposits of 3%) and injection velocity of the droplets (deviations in drift deposits of 2.5%). Wind deviation from the direction perpendicular to the tractor track had a reducing effect on the drift values (deviations in drift deposits of 2%). Small variations in driving speed had little influence on drift values. Near drift (<5 m) is predicted well by the model but the increased complexity compromised the predictions at greater distances. The model will be further developed in order to improve far drift prediction. Dynamic simulations will be performed and the model for turbulent dispersion will be optimized. The model did not require calibration.     

Enhanced c2 yields from methane oxidative coupling by means of a separative chemical reactor

Of the processes for converting natural gas into a more useful chemical feedstock, the oxidative coupling of methane to form ethane and ethylene (C(2)) has perhaps been the most intensively investigated in recent years, but it has proved extremely difficult to obtain C(2) yields in excess of 20 to 25%. Methane oxidative coupling was carried out in a separative chemical reactor that simulated a countercurrent chromatographic moving-bed. This reaction gives 65% methane conversion, 80% C(2) selectivity, and a C(2) yield slightly better than 50% with Sm(2)O(3) catalyst at approximately 1000 K.     

境外促销是农产品贸易促进的重要手段

农产品贸易促进是世界上发达国家农业和农产品政策的重要组成部分.境外促销这一方法广泛被有关国家利用来推动地区农产品贸易的发展.本文借鉴发达国家和地区农产品贸易促进的主要政策,分析江苏省开展农产品促销的积极作用和意义,提出境外促销是江苏省当前乃至长期的农产品贸易促进的重要手段,并从政策、实践和操作的角度探讨了最大限度发挥境外促销效果的三项措施:宏观上政策引导、企业参与和社会支持;实践上要拓宽领域、长远规划和统筹协调;操作上要明确市场定位,组织有效实施.