Evaluation of the inhibitory effect of docosahexaenoic acid and arachidonic acid on the initial stage of amyloid β1-42 polymerization by fluorescence correlation spectroscopy

Amyloid β(Aβ)1-42 fibrillation is a crucial step in the development of pathological hallmarks, such as neuritic plaques and neurofibrillary tangles, of Alzheimer’s disease (AD). In this study, we evaluated the effects of free docosahexaenoic acid (DHA), an essential brain polyunsaturated fatty acid (PUFA), on the inhibition of Aβ1-42 fibrillation by fluorescence correlation spectroscopy (FCS), a technique capable of detecting molecular movements and interactions in solution. We also examined whether free arachidonic acid (AA), eicosapentaenoic acid (EPA), and metabolites of DHA, including neuroprotectin D1 (NPD1, 10S, 17S-dihydroxy-DHA), resolvin D1 (RvD1, 7S, 8R, 17S-trihydroxy-DHA), and didocosahexaenoyl glycerol (diDHA), affect Aβ1-42 polymerization. The results of the FCS study reveal that DHA and AA significantly reduced the diffusion time of TAMRA (5-carboxytetramethylrhoda-mine)-Aβ1-42 by 28% and 31%, respectively, while EPA, NPD1, RvD1, and diDHA had no effects on diffusion time. These results indicate that DHA and AA inhibited Aβ1-42 polymerization and that their inhibitory effects occurred at the initial stage of Aβ1-42 polymerization. This study will advance the research on PUFAs in preventing AD progression.

Combination of Micro-fluidic Chip with Fluorescence Correlation Spectroscopy for Single Molecule Detection

A single molecule detection technique was developed by the combination of a single channel poly （dimethylsiloxane）/glass micro-fluidic chip and fluorescence correlation spectroscopy （FCS）. This method was successfully used to determine the proportion of two model components in the mixture containing fluorescein and the rhodamine-green succinimidyl ester.

Observation of Cell-Size Variation under Environmental Stress by Fluorescence Correlation Spectroscopy without Objective Image Magnification

Fluorescence correlation spectroscopy （FCS） without objective image magnification （without using con-focal microscope） was applied to observe the variation in cell size of Escherichia coli （E. coli） induced by the anti-cancer agent MitomycinC （MMC）. In the system without image magnification followed in this study, the suspension of E. coli cells was stirred, and the difference in movement due to the different cell sizes induced by the compulsive solution flow was detected. The addition of 0.1-0.4 pg/L of MMC elongated the E. coli cell length from about 3.6 to 7.8μm. The flow cell （i.d. = about 1 mm） also produced a size-dependent correlation curve, The present system is not based on single molecular FCS but is inexpensive and effective at observing the variation in cell size induced by environmental changes.

基于光谱特征的多重金属离子与DOM结合特性

通过淬灭滴定实验,文章采用同步荧光光谱和傅里叶红外光谱(FTIR)结合二维相关光谱分析,探究Cu^(2+)和Cd^(2+)多重离子与溶解态有机质(DOM)结合特性。研究结果表明,(1)DOM与Cu^(2+)和Cd^(2+)结合稳定常数(lg KM)分别为4.75~5.18和3.71~4.12,Cu^(2+)与DOM的结合能力要强于Cd^(2+)。(2)Cd^(2+)浓度为0和100μmol/L时,DOM点位与Cu^(2+)的结合顺序均为430~500 nm>330~420 nm,且Cd^(2+)存在时Cu^(2+)与DOM的lg KM为4.56~4.95。对比结果表明Cd^(2+)的存在并未影响DOM点位与Cu^(2+)的结合顺序,但减弱了DOM与Cu^(2+)的结合能力。(3)FTIR结果表明,Cd^(2+)浓度为0和100μmol/L时DOM官能团与Cu^(2+)结合顺序依次为酚类C-O>酰胺N-H>酰胺C=O>羧基C=O>芳香族C-H>多糖C-O和酰胺N-H>酰胺C=O>酚类C-O>芳香族C-H>多糖C-O。Cd^(2+)与酚类C-O结合后影响了Cu^(2+)与DOM中酚类C-O和羧基C=O官能团的结合。水环境中多重金属离子共存时的生物有效性和生态风险应受到关注。

不同有机肥对生菜生育期土壤剖面DOM分布的影响

施用有机肥是农作物生产过程中提质增效的有效途径,研究不同来源有机肥施加下土壤剖面溶解性有机质(DOM)的分布规律有助于优化有机肥利用及进一步了解DOM环境行为。采用二维相关光谱(2DCOS)等方法,研究施加不同来源有机肥(猪粪、鸡粪、羊粪、牛粪和沼渣)对土壤剖面DOM分布规律的影响。结果显示:有机肥还田主要影响土壤DOM的相对含量及组分构成。施加不同来源有机肥后,土壤中DOM相对含量始终大于对照(CK)处理,其中0~10cm土层DOM相对含量影响最大,平均增加14.67g·kg-1。不同类型有机肥对增加剖面DOM有一定差异,其中鸡粪有机肥对剖面DOM增加影响最大,增加了21.42%。有机肥的施加主要提高了类酪氨酸组分(C4)的相对含量,对10~20cm土层C4相对含量的影响最大,平均增加4.12%,其中羊粪和沼渣有机肥影响最大,分别增加了7.80%、7.89%。2D-COS分析显示,不同来源有机肥施用对溶解性微生物代谢产物、类蛋白质组分(295nm、315nm)影响最大,CK、鸡粪有机肥处理主要影响的是溶解性微生物代谢产物组分,其他处理最先响应的是类蛋白质组分;不同来源有机肥施用下,腐殖化指数HIX和Fn(330)、Fn(280)均随土层深度的增加而减小,但HIX和Fn(330)、Fn(280)的变化随有机肥种类不同而有所差异,其中牛粪有机肥对HIX和Fn(330)影响最大,羊粪有机肥对Fn(280)影响最大。生物指数BIX和新鲜度指数β∶α随着土层深度增加而增加,其中沼渣的影响最显著,但荧光指数FI并无显著变化。

荧光相关光谱(FCS)在生物活细胞中的应用

除了传统的分子浓度和扩散时间的测量荧光相关光谱(FCS),还可测量分子动力学或化学反应的动力参数.但是由于分子相互作用网络的复杂性,FCS在生物活细胞中的应用还有许多问题和困难需要解决.探讨了FCS在生物活体中分子相互作用网络、细胞膜、膜表面受体、细胞内结构分析以及胞内动力学研究等方面的应用.

基于光谱特征的pH对溶解态有机质与铜相互作用的影响研究

环境条件的变化能够影响和改变溶解态有机质(DOM)的组成结构及化学特征,进而影响其生物地球化学循环过程。采用同步荧光光谱、三维荧光光谱、傅里叶变换红外光谱(FTIR),结合二维相关光谱分析方法,研究了pH条件变化对DOM特性及其与Cu^(2+)相互作用的影响。结果表明,(1)随着pH值由5逐渐升高至10,DOM不同组分的荧光强度显著增强,其中类腐殖酸组分变化最显著,类富里酸组分变化最优先,这是由于pH的变化引起的醛酮、酚基、羧基等相关基团暴露导致的。(2)荧光光谱二维相关分析表明,pH的改变能够显著地影响DOM不同组分与Cu^(2+)的结合能力,但并不能影响其结合顺序。三维荧光光谱结合平行因子分析共解析出3个荧光组分,荧光组分的淬灭曲线非线性拟合结果更是定量验证了这一结果。(3)FTIR结果表明高pH条件下DOM与Cu^(2+)结合点位更多,结合强度更强。pH 5和pH 10条件下DOM官能团与Cu^(2+)的结合顺序分别依次为:多糖C—O>酚基>醛酮CO>芳香族C—H和多糖C—O>酰胺Ⅱ带C—N>酚基>脂肪族C—H>醛酮CO>羧基C—OH>芳香族C—H>羧基CO。荧光光谱和FTIR的异谱二维相关分析进一步表明Cu^(2+)与DOM类腐殖酸组分的相互作用滞后于酚基和芳基等基团。

溶解性有机质在盐田中的光谱学变化特征

二维相关光谱技术(2D-COS)、三维荧光光谱技术结合平行因子分析(EEM-PARAFAC)具有扩展识别重叠峰,判断不同组分动态变化规律的技术特点。因此,2D-COS和EEM-PARAFAC分析技术可以用来分析溶解性有机质(DOM)结构组成和光谱变化特征。采用溶解性有机碳(DOC)、紫外-可见吸收光谱(UV)和EEM分析技术,借助2D-COS和PARAFAC分析模型,对青藏高原具有代表性的察尔汗盐湖、西台吉乃尔盐湖和马海盐湖中DOM在盐田摊晒过程中的结构组成和光谱学变化特征进行了研究。结果表明,随着日照时间延长,盐田中DOM和有色DOM(CDOM)含量逐渐升高,且DOM的增长倍数明显高于CDOM。在整个盐田摊晒阶段,察尔汗、西台吉乃尔和马海盐田中DOM和CDOM分别增长了1.5 vs.1.0、8.2 vs.5.3和15.7 vs.11.0倍。此外,SUVA254、HIX值在盐田中总体上呈现出逐渐减小的变化趋势。2D UV-COS分析结果表明,在察尔汗、西台吉乃尔和马海盐田中,吸收峰分别在230、217和235 nm处的DOM变动较大,变化顺序分别为228>229>230>231>232 nm&235>234>233>232 nm、200>216>300 nm和201>203>231>232>237>238>281>217 nm。EEM-PARAFAC分析结果表明,盐湖卤水中有5种荧光组分,包括4种类腐殖质荧光组分,分别是类海洋腐殖质C1(Ex/Em:320/400 nm)、类腐殖酸C2(Ex/Em:250/400 nm)和C3(Ex/Em:260/400 nm)、疏水性腐殖酸C5(Ex/Em:280,360/430 nm)和1种类蛋白质组分C4(Ex/Em:280/350 nm)。其中,尤以类腐殖质为主,分别占总荧光组分的84.0%(察尔汗)、87.2%(西台吉乃尔)和93.1%(马海)。随着盐田日晒时间的延长,C1、C2和C5在盐田中逐渐减少直至稳定不变。其中,C2组分在盐田的尾卤阶段基本消失,表明C2组分更加容易降解。C3和C4在察尔汗和马海盐田的前期逐渐减少,后期却略有升高。相对来说,C3和C4性质相对顽固,在盐田中降解程度远小于其他三个组分:6.7%<C3/C4<75.2%vs.52.8%<C1/C2/C5<100%。

荧光三元相关光谱仪器中三元相关器的研制及应用

荧光三元相关光谱是原位研究多组分分子相互作用的一种新方法。三元相关器是荧光三元相关光谱仪器的核心计算单元。目前,我们尚未发现商品化三元相关器。本论文基于单光子计数器采集的光子信号序列的稀疏特性,提出了一种时间-光子模式相关算法,将其与传统多采样间隔时间相关算法相结合开发了改进的多采样间隔时间三元相关算法;进一步结合GPU并行加速,构建了三元相关器,显著加快了荧光三元相关光谱的运算速度;并将三元相关器成功地用于四色荧光微球和多色标记DNA荧光三元相关光谱分析。

Fluorescence correlation spectroscopy in laser gradient field

Fluorescence correlation spectroscopy (FCS) is capable of probing dynamic processes in living biological systems. From photon fluctuation of fluorescing particles which diffuse through a small detection volume, FCS reveals information on the concentration and the structure of the particles, as well as information on microscopic environment. In this note, we study the radiation forces experienced by Rayleigh particles in a laser field in details, and analyze the effects of gradient field on FCS measurements.

Quantification of Membrane Protein Dynamics and Interactions in Plant Cells by Fluorescence Correlation Spectroscopy

Deciphering the dynamics of protein and lipid molecules on appropriate spatial and temporal scales may shed light on protein function and membrane organization. However, traditional bulk approaches cannot unambiguously quantify the extremely diverse mobility and interactions of proteins in living cells. Fluores- cence correlation spectroscopy （FCS） is a powerful technique to describe events that occur at the singlemolecule level and on the nanosecond to second timescales; therefore, FCS can provide data on the heterogeneous organization of membrane systems. FCS can also be combined with other microscopy techniques, such as super-resolution techniques. More importantly, FCS is minimally invasive, which makes it an ideal approach to detect the heterogeneous distribution and dynamics of key proteins during development. In this review, we give a brief introduction about the development of FCS and summarize the significant contributions of FCS in understanding the organization of plant cell membranes and the dy- namics and interactions of membrane proteins .We also discuss the potential applications of this technique in plant biology.

Quantitative deconvolution of autocorrelations and cross correlations from two-dimensional lifetime decay maps in fluorescence lifetime correlation spectroscopy

Fluorescence correlation spectroscopy （FCS） is a widely used method for measuring molecular diffusion and chemical kinetics. However, when a mixture of fluorescent species is taken into account, the conven- tional FCS method has limitations in extracting autocorrelations for different species and cross correla- tions between different species. Recently developed fluorescence lifetime correlation spectroscopy （FLCS） based on time-tagged time-resolved （TITR） photon recording, which can record the global and micro arrival time for each individual photon, has been used to discriminate different species according to fluorescence lifetime. Here, based on two-dimensional lifetime decay maps constructed from TITR photon stream, we have developed a quantitative lifetime-deconvolution FCS model （LDFCS） to extract precise chemical rates for chemical conversions in multi-species systems. The key point of LDFCS model is separation of different species according to the global distribution of fluorescence lifetime and then deconvolution of autocorrelations and cross-correlations from the two-dimensional lifetime decay maps constructed bv the micro arrival times of photon pairs at each delay time.

Advantage of Fluorescence Correlation Spectroscopy for the Study of Polyelectrolytes

The advantage of fluorescence correlation spectroscopy to study single chain behavior of polyelectrolytes has been demonstrated by checking the coil-to-globule transition ofpoly 2-vinylpyridine with the change ofpH value in aqueous solution. The ultra-high sensitivity of FCS allows measurement at extreme dilution where the effect of electrostatic interaction between the chains is greatly suppressed. The results exposed first-order conformation tran- sition of P2VP as detected by FCS while inter-chain aggregation occurred in the experiments of dynamic light scat- tering.

荧光共振能量转移技术在生命科学中的应用及研究进展

荧光共振能量转移(FRET)是指两个荧光基团间能量通过偶极-偶极耦合作用以非辐射方式从供体传递给受体的现象,可被用于测定分子间的距离。FRET荧光探针主要有荧光蛋白、有机荧光染料、镧系染料和量子点,近年来有许多新的应用;测试方法上与时间分辨、单分子检测、荧光寿命和荧光相关光谱等技术联用取得了更好的成效。

土壤粒径大小对蒽荧光特性的影响及校正

为了准确检测土壤中的多环芳烃,以土壤中典型多环芳烃污染物蒽为检测对象,研究了土壤粒径大小对其荧光特性的影响,并提出了一种校正土壤粒径大小对多环芳烃标准曲线影响的方法。研究了蒽在土壤中的荧光特性,指出蒽在421nm、442nm和470nm处出现较强的荧光峰。接着,制备7种不同粒径大小的蒽土壤样品,并以土壤粒径大小为外扰,构建了同步和异步二维相关荧光谱,研究了蒽荧光强度和304nm处瑞利散射光强随土壤粒径大小的变化。结果显示,随着土壤粒径增大,蒽荧光强度和304nm处瑞利散射光强度都有增强。最后,分别建立了80目和160目土壤粒径下定量分析土壤蒽浓度的标准曲线,并通过304nm处瑞利散射光对蒽荧光进行校正。结果表明:该方法有效降低了土壤粒径大小对蒽标准曲线的影响。

二维相关荧光光谱鉴别4种食用植物油种类的研究

采用Cary Eclipse荧光分光光度计检测了4种食用植物油的同步荧光光谱,结合加热时间扰动下的二维相关荧光光谱技术,对一级大豆油、花生调和油、芝麻油和棕榈油,进行了快速无损的识别方法的研究。结果表明,在同步荧光光谱图上,不同植物油的特征吸收峰在出峰数目、出峰位置和峰强上均存在一定的差异;而在二维相关荧光谱图上,由于4种植物油的自动峰及交叉峰的位置、数量和强度不同,其差别体现得更为明显和直观。因此,二维相关图谱法可以作为鉴别不同植物油种类的一种有效方法。

荧光相关光谱及其在单分子检测中的应用进展

单分子检测在生命科学、化学、物理学等领域具有重要的意义。荧光相关光谱是单分子检测的新技术,在生命科学领域有巨大的应用潜力。综述了荧光相关光谱单分子检测的原理、实验技术以及在生物分子相互作用、活细胞、核酸、疾病诊断、高通量筛选以及与毛细管电泳联用等领域的研究,并展望了其发展前景。

通过DOM的光谱特性对长江源头典型高原深水湖泊进行评价

天然溶解有机质（dissolved organic matter,DOM）研究在水体生态环境系统的修复研究中扮演着重要的角色,是近年来水环境研究领域的一个热点和难点。目前,紫外？可见光谱和分子荧光光谱在天然溶解有机质是表征天然溶解有机质的重要有效的手段,也是研究天然溶解有机质的主要手段。红枫湖为贵阳市5个主要饮用水源地之一,对贵阳市社会发展具有重要作用。采用紫外？可见光谱和分子荧光光谱相结合的研究方法,对采自红枫湖中10个点的水样中天然溶解有机质的光谱特性研究。研究结果表明,红枫湖水体光谱特征主要表现为紫外？可见吸光值参数E3/E4的变化范围是1.70~8.77。除后五火电厂外,水下10 m比水下5 m的E3/E4值要高。此外,荧光指数f450/500的变化范围是1.38~1.52。初步认为红枫湖目前的主要有机物污染是陆源性的。后五火电厂,北湖湖心和张官三点水样的光谱特征与其他地方不同。同时还表明溶解有机质的腐殖化程度与水深具有一定的相关性。

同步荧光光谱技术研究胶原基表面活性剂溶液中分子的聚集行为

基于胶原基表面活性剂（collagen-based surfactant,CBS）中酪氨酸（Tyr）和苯丙氨酸（Phe）的荧光特性,应用恒波长差（Δλ）为15nm的同步荧光光谱技术研究CBS浓度、溶液pH值、NaCl浓度和温度对其在水溶液中分子的聚集行为的影响,并以温度为外扰,利用二维同步荧光相关分析研究CBS分子中Tyr残基和Phe残基随温度变化的响应顺序。结果表明,CBS分子在261和282nm处出现了分别归属于Phe和Tyr的特征吸收峰。随着CBS浓度的升高,CBS分子中Phe残基和Tyr残基数量逐渐增多使CBS分子聚集程度增加,并导致荧光强度增强;CBS溶液pH值（pH 5.0）在等电点附近时,由于CBS分子的疏水作用和氢键形成能力加强,导致CBS分子聚集程度增强;CBS溶液中NaCl浓度的升高,则使CBS分子间排斥力减弱,从而导致CBS分子的聚集;然而温度升高,CBS由聚集状态逐渐变为单分子状态,因猝灭、变性以及氢键形成能力降低,荧光强度逐渐降低。以温度为外扰的二维同步荧光相关光谱分析可知：低温下（10^40℃）,CBS聚集体随温度升高逐渐松散,位于聚集体内部的Phe残基比Tyr残基优先响应;而在45~70℃时,CBS由单分子状态逐步水解为无规卷曲构造,Tyr残基的间距变大,氢键形成能力大大降低,Tyr残基比Phe残基优先响应。

基于荧光光谱的茶汤中拟除虫菊酯类农药的智能识别

基于三维荧光光谱和二维荧光相关光谱,对茶汤中两种拟除虫菊酯农药进行了识别。利用图像局部极值算法,分别提取出三维荧光光谱图和二维相关光谱图中的峰、谷位置信息,然后进行峰位匹配实现茶汤中农药组分的智能识别。结果表明,三维荧光光谱图受到荧光峰重叠的影响,不能对氰戊菊酯进行有效匹配。而利用二维相关光谱不仅可以克服这一缺点,而且不受混合物中农药组分浓度的影响。基于二维荧光相关光谱,对实际茶汤中氰戊菊酯和顺式氯氰菊酯进行了识别,识别率分别为80%和83%。