不同来源和粒径的胶体对光合细菌生长的效应

天然胶体是近岸海域细菌和浮游植物可利用氮的一个重要来源 ,其含量的增加可促进藻类的繁殖和生长 ,有时甚至引发赤潮。研究显示 ,细菌在高分子量胶体存在下的生长和代谢速率比在低分子量中的提高 3～ 6倍 ,暴露在阳光下的胶体有机物可释放生物可利用的富氮组分 ,进而提高细菌对胶体的分解。利用错流超滤技术从河流、河口、海洋水体和微藻培养液中提取胶体 ,研究了胶体来源和粒径对光合细菌 (PSB,沼泽红假单胞菌 Rhodopseudomonaspalustris)生长的影响。结果表明 ,在一定的胶体有机碳浓度范围 ,河流胶体 (0～ 2 81.0μmol/ L )、河口胶体 (0～ 12 1.2μmol/ L )、海洋胶体 (0～ 88.8μmol/ L )和生源胶体 (7.7～5 4 8.6μmol/ L )都能促进 PSB的生长 ,分别使其相对增长率平均提高了 4 7.3%～ 196 .2 % ,3.6 %～ 9.3% ,8.1%～ 10 .4 %和2 .4 %～ 6 .9%。其中 ,PSB在河流胶体中的相对增长率的平均值 (Y)与有机碳浓度 (CDOC)呈对数相关 (Y (% ) =- 193.7 70 .7ln CDOC) ,表明高浓度的河流胶体 ,对 PSB生长的促进效果更显著。两种生源胶体中 ,海水小球藻胶体 (0～ 5 4 8.6μmol/ L )对PSB生长的促进作用大于球等鞭金藻胶体 (7.7～ 384 .4 μmol/ L) ;PSB在粒径为 10 k D～ 0 .2 2 μm的海洋胶体中的生长大于     

One- and two-photon induced fluorescence of Pacific Blue-labeled human serum albumin deposited on different core size silver colloids

We studied one- and two-photon induced fluorescence of Pacific Blue (PB)-labeled human serum albumin (HSA) in the presence of different size silver colloids. The PB fluorescence emission intensity was observed with small (30-40 nm) and large (about 120 nm) colloids and compared with PB emission in absence of colloids. For the system with a small core size colloids we did not detect any fluorescence enhancement with one-photon excitation and the enhancement observed with two-photon excitation was about 2.5-fold. In contrast, for large silver colloids we observed about a 2-fold increase in PB fluorescence brightness for one-photon excitation, and the enhancement with two-photon excitation excided 13-folds. Much stronger increases in brightness observed with two-photon excitation, compared to one-photon excitation, indicate a dominant role of enhanced local field in fluorescence enhancement on silver colloids in solutions.     

现场模拟添加磷、铁及胶体对北部湾2007年春季生物固氮的影响

生物固氮是海洋氮循环的重要过程。固氮作用能够促进海洋初级生产力的提高,增强海洋吸收CO₂能力,对于降低大气CO₂浓度,减缓温室效应具有重要意义。2007年春季对北部湾海区进行了现场模拟添加P,Fe和胶体实验,并应用乙炔还原法（ARA,Acetylene Reducing Activity）分析其固氮速率,研究其主要影响因素。结果表明,温盐与固氮速率相关性不显著（P > 0.05）。对固氮速率来说,外加P其变化范围为-97%-545%,外加Fe其变化范围为-86%-146%,外加胶体其变化范围为-96%-1456%。对叶绿素含量而言,外加P其变化范围为-24%-50%,外加Fe其变化范围为-32%-36%,外加胶体其变化范围为-53%-41%。N可能是春季北部湾海区浮游植物生长的限制因子,固氮作用主要受到P限制,而外加胶体对固氮生物和固氮速率表现出较大的促进作用。     

Ethnobotany of seaweeds: clues to uses of seaweeds

Extensive uses of fresh and dried seaweeds by coastal populations over the world can furnish clues to potential food and other uses of seaweeds, just as the first extraction of a seaweed gelatin now used for bacteriological purposes was discovered by a housewife in search of a pudding. Ethnic uses as food depend heavily on closely related species suitable for making cool, gelatinous dishes or concoctions, or on species suitable for adding to soups or stews. Rarely, single species like cochajugo (Durvillea antarctica) in Chile and rimu (Durvillea antarctica) in New Zealand point to different kinds of food preparation. Oriental cuisine incorporates many different species of seaweeds in a wide variety of ways, whereas commercial western uses depend upon extracts of wall materials to suspend, emulsify or stabilize a broad variety of foods and products.     

Sequential adsorption of F(ab')(2) and BSA on negatively and positively charged polystyrene latexes

The aim of the present work is to study the sequential adsorption of F(ab')(2) and bovine serum albumin (BSA) molecules adsorbed onto positively and negatively charged polystyrene latexes. Cationic and anionic latexes were prepared by emulsifier-free emulsion polymerization. Adsorptions of F(ab')(2) on both latexes at a low ionic strength and different pHs were performed. The cationic latex showed a higher adsorption of F (ab')(2) molecules over a range of pH, which could be due to the formation of multilayers. Sequential adsorption of anti-CRP F(ab')(2) and monomeric BSA were performed at two different pre-adsorbed F(ab')(2) amounts on both types of latex. Displacement of F(ab')(2) occurred only when the preadsorbed amounts were larger than a certain critical value, which depends on the adsorption pH. A greater displacement of larger preadsorbed amounts might be the result of a weaker contact between the protein molecules and the polystyrene surface. The displacement of F(ab')(2) previously adsorbed onto both latexes occurred due to pH changes, an increase of ionic strength and the presence of BSA molecules. The effect caused by these three factors was studied independently. The main factors in the desorption of F(ab')(2) on the anionic latex are the changes in pH and ionic strength, whereas on the cationic latex the desorption is mainly caused by the increase of the ionic strength and the presence of BSA. The colloidal stability of the immunotatex was improved by BSA adsorption, especially on cationic latex. (c) 1995 John Wiley & Sons, Inc.     

Examination of trafficking of phagocytosed colloid particles in neutrophils using synchrotron-based X-ray fluorescence microscopy (XFM)

Synchrotron-based X-ray fluorescence microscopy (XFM) can localise chemical elements at a subcellular level. 99mTechnetium stannous (TcSn) colloid is taken up by phagocytes via a Complement Receptor 3 mediated phagocytic process. In the current study, XFM was used to examine the intracellular trafficking of TcSn colloid in neutrophils. XFM was performed on TcSn colloid, and neutrophils labelled with TcSn colloid, in whole blood. We developed a set of pixel by pixel analysis and mapping techniques incorporating cluster analysis that allowed us to differentiate neutrophils and artefactual contaminants, and we examined the changes in element distribution that accompany neutrophil phagocytosis of TcSn colloid. Sn became associated with half the neutrophils. Within cells, Sn colocalised with iron (Fe) and sulphur (S), and was negatively associated with calcium (Ca). Despite the high sensitivity of XFM, Tc was not detected. XFM can help clarify the intracellular processes that accompany neutrophil phagocytosis. The subcellular colocalisation of Sn with Fe is consistent with fusion of the colloid-containing phagosome with neutrophil granules. The association of Sn with S suggests that proteins rich in S-containing amino acids are present in the phagosome. The negative colocalisation with Ca indicates that ongoing maturation of the TcSn colloid phagosome is no longer calcium dependent one hour after phagocytosis.     

Measurement of the size and structure of natural aquatic colloids in an urbanised watershed by atomic force microscopy

Atomic force microscopy (AFM) in tapping mode was used to determine the conformation of humic substances and aquatic colloids from rivers in an urban catchment in the West Midlands, U.K. Humic macromolecules were shown to have a size of about 1–3 nm in agreement with the literature, indicating that the preparation methods and the AFM were both performing satisfactorily. Three types of natural aquatic colloids were observed by AFM. Firstly, a surface coating about 1–5 nm thick, likely composed of organic and oxide material flattened by drying and interaction with the AFM tip. Secondly, small irregular, globular material between 1 and 70 nm in size, again most likely made of oxide and organic material. Lastly, fibrillar material was present which was 1–10 nm in diameter and 10–1000 nm in length. Most likely this material was microbially produced (muco-) polysaccharides. Size distributions of colloids from all samples, regardless of sample site and sample preparation, indicated colloids with a fairly low polydispersity and with particle numbers dominated by material <10 nm.