“916”低聚糖抗卵磷脂氧化活性的研究

作者采用自由基引发氧化模型。通过测定卵磷脂氢过氧化物 ( PCOOH) ,研究了“916”低聚糖对卵磷脂 ( PC)氧化的抑制作用。实验结果表明 :( 1)“916”低聚糖具有良好的抗氧化活性 ;( 2 )各低聚糖在质量相同和含硫量大致相同的条件下 ,总体上分子量越小抗氧化活性越高。     

卵磷脂与双甘氨肽对碳酸钙变体和表面微结构的影响

许多生物矿化作用过程都与其不寻常的膜的组成和结构密切相关。作为双亲分子的磷脂,是生物膜的重要组成成分之一。运用以粉末X-射线衍射、扫描电子显微镜和动态光散射技术等实验手段,研究了卵磷脂(PC)和双甘氨肽参与下的碳酸钙矿化过程。结果表明,PC在溶液中形成的脂质体结构,导致了方解石(calcite)表面多孔结构的形成,且其含量的改变,可有效地调控方解石表面孔隙的孔径大小,并在一定程度上促进球霰石(vaterite)的生长和稳定;而PC在溶液表面形成的膜脂层,则通过静电力与双甘氨肽相互作用,有效调控膜脂层下矿物的形成。     

标准卵磷脂氢过氧化物(PC-OOH)与亚油酸甲酯氢过氧化物(ML-OOH)制备

报道了用自由基引发剂（ＡＡＰＨ）引发氧化,反相高效液相色谱法分离卵磷脂（Ｐｈｏｓ－ｐｈａｔｉｄｙｌｃｈｏｌｉｎｅ,ＰＣ）及其氢过氧化物（ＰＣ－ＯＯＨ）,获得纯品ＰＣ－ＯＯＨ,以及５０℃自动氧化后,用硅胶柱层析分离亚油酸甲酯（ＭｅｔｈｙｌＬｉｎｏｌｅａｔｅ,ＭＬ）及其氢过氧化物（ＭＬ－ＯＯＨ）,而获得标准ＭＬ－ＯＯＨ的方法。     

生物膜脂参与的非晶碳酸钙形成和稳定

非晶碳酸钙(amorphous calcium carbonate,ACC)是碳酸钙矿物体系中极不稳定的矿物相。但由海鞘类动物的研究表明,ACC可作为碳酸钙晶体矿物的前驱体在生物体内稳定存在,并且这些生物成因的ACC常常是由膜包裹着的。文中选用生物膜的主要成分卵磷脂(PC)为主要矿化调节剂,通过调控与碳酸钙矿化过程密切相关的无机离子Mg2+的浓度,模拟生物膜表面碳酸钙矿化作用过程。在空气/水界面处的膜脂调控下合成出可在溶液中稳定存在数天的非晶碳酸钙。该结果有力地证明了在生物矿化过程中,除了受生物体中可溶性有机大分子调控外,生物膜可能对ACC的形成和稳定也有显著的调控作用。     

海黍子提取物对不饱和脂质抗氧化作用

为了获得天然抗氧化物质,利用自由基引发氧化体系对青岛近海的24种海藻的抗氧化性能进行了筛选,获得了具有较强抗氧化活性的藻种-海黍子(Sagassum kjellmanianum),并从中分离得到两种混合组分(Fr1、Fr2),进一步研究了它们对鱼油和卵磷脂的抗氧化作用。研究结果表明(1)在37℃恒温自动氧化条件下,两种海黍子提取物(0.25%)在均相和乳化体系中,对鱼油都有较好抗氧化作用,抗氧化效果比维生素E(0.2%)好;(2)乳化和非乳化体系比较,海黍子提取物在乳化体系中对不饱和脂质的抗氧化作用更好;(3)在自由基引发剂引发氧化下,Fr2(0.6%)对卵磷脂抗氧化作用效果比BHT(0.02%)好。     

Formation and occurrence of organic hydroperoxides in the troposphere: Laboratory and field observations

The formation and occurrence of hydroperoxides in the troposphere have been studied by laboratory experiments and by preliminary field measurements. Nine alkenes were reacted individually with ozone in a reaction chamber in the presence of excess water, and the amounts of hydrogen peroxide and of nine organic hydroperoxides produced in the gas and aerosol phases and deposited on the chamber walls determined by HPLC. The reactions of ethene, propene, 1-butene and isoprene gave hydroxymethyl hydroperoxide as the major product with no hydrogen peroxide observed. In the case of - and -pinene, 2-carene and limonene the major product was hydrogen peroxide. Cis-2-butene produced hydrogen peroxide and methyl hydroperoxide. Preliminary measurements of hydrogen peroxide and five organic hydroperoxides in ambient air were made at Niwot Ridge, Colorado from 24 July–4 August 1989. The gas-phase species were preconcentrated by cryotrapping with subsequent HPLC separation. The gas-phase concentrations of H₂O₂ ranged from 0.5–2 ppbv with the lowest concentrations being measured at night and the highest under conditions of strong photochemical activity. The maximum concentrations of hydroxymethyl hydroperoxide approximated those of H₂O₂. Methyl hydroperoxide concentrations ranged from <50 to 800 pptv and three other organic hydroperoxides were detected at concentrations below 200 pptv. High volume aerosol samples yielded H₂O₂ and methyl hydroperoxide concentrations <10 ng m^-3 while H₂O₂ and six organic species were detected in rainwater at concentrations in the range <0.01–50 M.     

The effects of fucoidans from Laminaria japonica on AAPH mediated oxidation of human low-density lipoprotein

1Introduction Thegeneration,reactionandconsequenceof freeradicalsinbiologicalsystemshavereceived muchattentionrecentlyinconnectionwithavariety ofpathologicalevents(BarryandSusanna,1993;FangandLi,1999).LDLoxidizedbyexposureto tracemetalionsCu2 andFe3 (Hein…     

Prediction of wave pressures on smooth impermeable seawalls

Simple prediction methods are proposed to estimate the wave induced pressures on smooth impermeable seawalls. Based on the physics of the wave structure interaction, the sloped seawall is divided into a total of five zones (zones 1, 2 and 3 during run-up (corresponding pressures are called as positive pressures) and zones 4 and 5 during run-down (corresponding pressures are called negative pressures)) (Fig. 1). Zone 1 (0<z<d−H_i/2), where the wave pressure is governed by the partial reflection and phase shift; Zone 2 (d−H_i/2<z<d), where the effect of wave breaking and turbulence is significant; Zone 3 (d<z<Run-up height), where the pressure is induced by the run-up water; Zone 4 (Run-down<z<d), where the wave pressure is caused by the run-down effect and Zone 5 (0<z<d-Run down), where the negative wave pressures are due to partial reflection and phase shift effects. Here d is the water depth at the toe of the seawall, H_i is the incident wave height and z is the vertical elevation with toe of the seawall as origin and z is positive upward. For wave pressure prediction in zones 1 and 5, the empirical formula proposed by Ahrens et al. (1993) to estimate the wave reflection and Sutherland and Donoghue's recommendations (1998) for the estimation of phase shift of the waves caused by the sloped structures are used. Multiple regression analysis is carried out on the measured pressure data and empirical formulas are proposed for zones 2, 3 and 4. The recommendations of Van der Meer and Breteler (1990) and Schüttrumpf et al. (1994) for the prediction of wave run-down are used for pressure prediction at zone 4. Comparison of the proposed prediction formulas with the experimental results reveal that the prediction methods are good enough for practical purposes. The present study also shows a strong relation between wave reflection, wave run-up, wave run-down and phase shift of waves on wave pressures on the seawalls.