联合荧光光谱与寿命法检测多次高温加热油

三维荧光光谱法检测多次高温加热植物油,该方法能快速、准确的获得待测样品的三维荧光光谱特征图,但只是定性的分析。当荧光强度变化较小的时候,容易出现误检、漏检的情况。先用三维荧光光谱技术分析植物油样品的光谱信息,然后再通过荧光寿命法,计算多次高温加热植物油中荧光光子的寿命,通过与未加热油荧光寿命的对比,检测多次高温加热植物油。二者联合,进一步提高了检测的准确度,有利于解决误检、漏检的问题,从而为高温加热油的检测提供有力的参考。     

植物油的荧光光谱法研究

荧光光谱技术具有灵敏度高,选择性好等优点。植物油中含有各种荧光成分,对食用油中菜籽油、玉米油、芝麻油、葵花仁油、花生油的同步荧光光谱和三维荧光光图谱进行了分析研究,结果表明：利用同步荧光光谱和三维荧光图谱的特征,可以区分植物油的品种,可用于植物油的鉴别和质量监控,该法提供了一种油定性分析的方法,同时也扩展了荧光法在食用油鉴别中的应用。     

稳态和时间分辨荧光光谱法检测pBR322质粒中十字形结构

在目的DNA不被酶切成不同片段的情况下,应用光谱方法探测pBR322质粒中十字形结构DNA的形成。吡咯脱氧胞苷(Pyrrolo deoxycytidine,PdC)取代dC掺入到pBR322质粒的特定位点(3195,3222或3281位点)。应用稳态和时间分辨荧光法研究十字形结构DNA的形成。结果显示:(1)稳态荧光特性表明,当PdC掺入到pBR322质粒的3222位点,PdC-pBR322超螺旋荧光强度大约是松弛型PdC-pBR322的4倍;与此同时,其时间分辨荧光寿命大约比松弛型PdC-pBR322长约0.3ns。当PdC掺入到3195或3281位点时,稳态荧光光谱和荧光寿命(两位点处约1.42ns)并没有显著变化。(2)随着盐浓度的增大,荧光寿命略微有变化,但不是很明显。通过检测和分析pBR322质粒的荧光光谱和荧光寿命,表明能够形成在非配对环状部分3222位点含有dC的十字形结构。在一定的盐浓度(0-100mmol/L)条件下,十字形结构能够保持其稳定性。     

辨别山苍子油掺假方法的研究

通过采用挥发油提取器和气质联用仪两种方法,可以辨别山苍子油是否掺假。采用挥发油提取器方法可以判定山苍子油中是否掺入不挥发性成分;采用气质联用仪,以及用对照品对照的方法,可以直接测定山苍子油中柠檬醛的含量,从而判定山苍子油中是否掺入其他成分。     

权重依赖荧光寿命成像检测甘油-水混合物黏度

目的 基于荧光寿命成像技术,提出一种黏度检测的新方法,并评估不同权重荧光寿命在区分甘油-水混合物黏度的能力,从而提供对黏度区分的准确度和可靠性。方法 采用电子学中的权重依赖原理,分别引入了振幅加权平均荧光寿命(τ_m)和强度加权平均荧光寿命(τ_i)。通过τ_m和τ_i检测甘油-水混合物黏度变化。振幅加权平均荧光寿命反映了荧光信号振幅与时间的关系,而强度加权平均荧光寿命则关注荧光信号强度的时变特性。结果 τ_m和τ_i两种结果相互佐证,这不仅提高了对甘油-水混合物黏度变化的可靠性,同时也揭示了τ_m和τ_i在检测过程中的独特作用。尽管τ_m在捕捉荧光信号振幅变化方面发挥了关键作用,然而,τ_i在考虑荧光信号强度的时变特性时表现出更高的黏度检测准确度。特别值得注意的是,由于τ_i更为敏感,微环境黏度检测可以直接利用τ_i进行分析。这为实时、高灵敏...     

黑龙江省1995～1998年大豆植物油检测结果分析

黑龙江省作为全国食用油脂标准修订协作组成员单位 ,对 1 995～ 1 998年地产大豆植物油的检测结果做了较全面、系统的分析。1　材料与方法1 1　材料来源 :随机采取黑龙江省浸出法生产大豆油厂成品库产品 1 49件。1 2　检验项目 :按ＧＢ2 71 6 - 88《食用植物油卫生标准》规定的检验项目 :酸价、过氧化值、羰基价、浸出油溶剂残留。1 3　检验方法 :按ＧＢ/Ｔ5 0 0 9《食用植物油卫生标准的检验方法》操作。2　结果与分析2 1　 1 995～ 1 998年大豆植物油检测结果 (见表 1 )表 11995～ 1998年 149件食用植物油检测结果项　目 酸　价ｍ…     

荧光光谱分析法在地沟油鉴别中的应用研究

由于地沟油的成分含量复杂性和不定量性,导致了现有的单一检测方法不能同时满足快速和准确的辨认。荧光光谱具有高灵敏度和分辨率的特性,由此提出了一种利用荧光光谱快速检测食用油中是否掺有地沟油的新方法。将花生油分成7组,每组油所含的地沟油的比例不同,用220 nm到800 nm的激发和发射光检测各组样品油,收集其荧光数据后做归一化处理进行分析。在荧光实验中,特别是在365 nm和720 nm激发波长波段和434 nm发射波长波段,样品油的荧光强度与所含地沟油的体积分数大小明显成反比,当地沟油的体积分数大于5%时,荧光强度的衰减更为明显。结果证明了荧光光谱法检测地沟油的可行性,而且步骤更为简单。利用荧光光谱的非接触和高灵敏度的优势,能够更为简便地检测到加入了5%以上地沟油的花生油。     

利用荧光寿命变化定量分子内和分子间相互作用的方法

荧光寿命是指荧光分子在回到基态前在激发态停留的平均时间.本文发展了基于荧光寿命测量来定量分子内和分子间相互作用的方法:通过G碱基猝灭对于荧光寿命的影响定量DNA二级结构的形成;通过荧光共振能量传递(FRET)中荧光寿命的变化来定量分子间的相互作用.第一种方法巧妙利用了G碱基会猝灭临近的染料分子的性质,结合荧光寿命的变化...     

双色荧光多重PCR技术及在禽流感病毒检测中的应用

为快速检测7种亚型禽流感病毒,对引物进行双色荧光标记,建立双色荧光多重PCR(DFM-PCR)方法,通过运用DFM-PCR可一次检测出7种禽流感病毒亚型。此方法为应用于病毒或病原等一些要求快速、高通量的检测领域打下基础,而且为禽流感病毒检测以及其他种类病毒等病原检测提供了一种新型方法。     

羊肉掺假鉴别快速荧光定量PCR芯片制备及应用研究

为了建立一种基于芯片的快速鉴别羊肉掺假成分的方法,将不同动物源性成分的引物及反应所需试剂预先冻干固定到空白芯片反应池内,以制备羊肉掺假鉴别快速荧光定量PCR芯片。同时,通过模拟掺假样品（在羊肉中掺入猪肉、鸡肉、鸭肉、鼠肉成分）检测实验,对所得芯片的性能进行了评价。从与ABI7500荧光定量PCR结果对比可知,基于芯片的快速荧光定量PCR检测方法可以准确检测5种动物源性成分,具有较高的准确性及可用性,且其PCR扩增时间较短,操作简单,满足了羊肉掺假快速鉴别的要求。该芯片的研制及快速检测方法的建立将有效的简化羊肉制品掺假检测的步骤、缩短检测时间,且成本较低,仪器便于携带,使现场检测成为可能。研究结果为我国肉类食品安全监管提供了有力保障。     

The time resolved emission spectra of peptide conformers measured by pulsed laser excitation

The fluorescence decays of a number of peptides were measured using pulsed laser excitation and time correlated single photon counting techniques. In all cases double exponential kinetics were observed with the short lifetime component (0.5 – 0.85 ns) predominating over the long lifetime componet (1.62 – 2.21 ns). The lifetimes varied with the peptides measured. The time resolved emission spectra of LysTrpLys shows both components have similar spectral maxima at 345 nm. It is suggested that the dual exponential kinetics originate from different conformers of the peptides.     

Electron donor properties of the antitumour drug amsacrine as studied by fluorescence quenching of DNA-bound ethidium

The effect of the antitumour acridine derivative amsacrine [4'-(9-acridinylamino)methanesulphon-m-anisidide] on the fluorescence lifetime of DNA-bound ethidium has been investigated using a synchronously pumped cavity dumped dye laser producing picosecond pulses for sample excitation and a time-correlated single photon counting detection system. As the proportion of DNA-bound amsacrine on the synthetic DNA polymer poly[deoxyadenylic-thymidylic acid] is increased, the fluorescence decay curve of ethidium can be accurately resolved into two exponential components. The short lifetime component, whose proportion increases with increasing proportions of DNA-bound amsacrine, has a lifetime of between 3 and 4 ns, significantly longer than that of ethidium in aqueous solution (1.63 ns). The magnitude of the long lifetime component decreases from 25.4 to 14 ns with increasing proportions of bound amsacrine. It is concluded that a new fluorescence state of ethidium (lifetime 3-4 ns) is present, probably resulting from reversible electron transfer between ethidium and amsacrine. The ability of various 9-anilinoacridine derivatives to quench the fluorescence of DNA-bound ethidium appears to be related to the electron donor properties of the substituents on the anilino ring, as well as to experimental antitumour activity. The electron donor properties of DNA-bound amsacrine may therefore be relevant to its antitumour action.     

Wide-field photon counting fluorescence lifetime imaging microscopy: application to photosynthesizing systems

Fluorescence lifetime imaging microscopy (FLIM) is a technique that visualizes the excited state kinetics of fluorescence molecules with the spatial resolution of a fluorescence microscope. We present a scanningless implementation of FLIM based on a time- and space-correlated single photon counting (TSCSPC) method employing a position-sensitive quadrant anode detector and wide-field illumination. The standard time-correlated photon counting approach leads to picosecond temporal resolution, making it possible to resolve complex fluorescence decays. This allows parallel acquisition of time-resolved images of biological samples under minimally invasive low-excitation conditions (<10mW/cm²). In this way unwanted photochemical reactions induced by high excitation intensities and distorting the decay kinetics are avoided. Comparably low excitation intensities are practically impossible to achieve with a conventional laser scanning microscope, where focusing of the excitation beam into a tight spot is required. Therefore, wide-field FLIM permits to study Photosystem II (PS II) in a way so far not possible with a laser scanning microscope. The potential of the wide-field TSCSPC method is demonstrated by presenting FLIM measurements of the fluorescence dynamics of photosynthetic systems in living cells of the chlorophyll d-containing cyanobacterium Acaryochloris marina.     

Time-resolved spectroscopy of the blue fluorescence of spinach leaves

When excited by ultraviolet radiation, leaves of a great number of species of higher plants exhibit emission of blue fluorescence, comparable in intensity to the red emission of chlorophyll. The fluorescence decay of the blue emission of spinach leaves recorded by single photon counting techniques is decomposed into exponential components and it is shown that at least three different components are present. The lifetime of the three components does not show significant variations with the excitation or emission wavelengths. The excitation and emission spectra of each component were determined. The nature of the chemical compounds which cause this emission is discussed in relation to these spectra.     

Two‐photon excited fluorescence lifetime measurements through a double‐clad photonic crystal fiber for tissue micro‐endoscopy

This paper presents an endoscopic configuration for measurements of tissue autofluorescence using two–photon excitation and time‐correlated single photon counting detection through a double‐clad photonic crystal fiber (DC‐PCF) without pre‐chirping of laser pulses. The instrument performance was evaluated by measurements of fluorescent standard dyes, biological fluorophores (collagen and elastin), and tissue specimens (muscle, cartilage, tendon). Current results demonstrate the ability of this system to accurately retrieve the fluorescence decay profile and lifetime of these samples. This simple setup, which offers larger penetration depth than one‐photon‐based techniques, may be combined with morphology‐yielding techniques such as photoacoustic and ultrasound imaging. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Measurements of fluorescence lifetimes by use of a hybrid time-correlated and multifrequency phase fluorometer

Measurements of homogeneous and heterogeneous fluorescence intensity decays using a hybrid time-correlated single photon counting/multifrequency phase fluorometer are reported. A trio of fluorophores exhibiting a range of decay profiles was selected. p-Terphenyl, 1,4-bis[2-(4-methyl-5-phenyloxazolyl)]benzene [(Me)2POPOP], and p-bis[2-(5-phenyloxazolyl)]benzene (POPOP), commonly used reference fluorophores, were analyzed initially; their emissions were characterized by monoexponential decay functions. Additionally, emissions from two single tryptophan proteins with different decay profiles were measured. Scorpion neurotoxin variant 3 required three exponentials to fit the emission decay properly (average lifetime approximately 500 ps). At pH 5.5, the fluorescence emission of ribonuclease T1 showed a monoexponential decay with a measured lifetime of approximately 4.0 ns. Thus, in each case, the results from both measurements were consistent between the two detection systems, confirming the view that the two approaches for measuring fluorescence lifetimes are equivalent.     

Time-resolved fluorescence microscopy.

In fluorescence microscopy, the fluorescence emission can be characterised not only by intensity and position, but also by lifetime, polarization and wavelength. Fluorescence lifetime imaging (FLIM) can report on photophysical events that are difficult or impossible to observe by fluorescence intensity imaging, and time-resolved fluorescence anisotropy imaging (TR-FAIM) can measure the rotational mobility of a fluorophore in its environment. We compare different FLIM methods: a chief advantage of wide-field time-gating and phase modulation methods is the speed of acquisition whereas for time-correlated single photon counting (TCSPC) based confocal scanning it is accuracy in the fluorescence decay. FLIM has been used to image interactions between proteins such as receptor oligomerisation and to reveal protein phosphorylation by detecting fluorescence resonance energy transfer (FRET). In addition, FLIM can also probe the local environment of fluorophores, reporting, for example, on the local pH, refractive index, ion or oxygen concentration without the need for ratiometric measurements.     

Spectrally and spatially resolved fluorescence lifetime imaging in living cells: TRPV4-microfilament interactions

Time- and space-correlated single photon counting method has been used to demonstrate the interactions of cation channel "transient receptor potential vanilloid 4" (TRPV4) and microfilaments. Living cells co-expressing TRPV4-CFP and actin-YFP, when excited for the donor molecules (CFP) exhibited an emission peak at 527 nm and decrease of the lifetime in the wavelength band 460-490 nm; corresponding to resonance energy transfer to YFP. CFP fluorescence decay was fitted best by a dual mode decay model. Considering the average lifetime of the donor, both in the presence and absence of acceptor yielded an apparent FRET efficiency of approximately 20%. This is rather high placing the minimum distance of chromophores in the two fluorescent proteins in the range of 4 nm. Thus, this study shows for the first time that TRPV4 and actin intimately associate within living cells. The significance of this finding for cell volume regulation is highlighted.