Application of Two-Dimensional Correlation UV-Vis Spectroscopy in Chinese Liquor Moutai Discrimination

Chinese liquor Moutai is the “National alcoholic drink” in China and plays a very important role of social activities in Chinese people’s life. In pursuit of high profits, some illegal counterfeit Moutai liquors have begun to appear in the market. Therefore, it is an urgent need for new techniques to discriminate the genuine and counterfeit Moutai liquor. In this work, the conventional Ultraviolet-Visible (UV-Vis) spectroscopy and two-dimensional correlation UV-Vis spectroscopy are applied to obtain the UV-Vis characteristic of Moutai liquor and counterfeit one, respectively. The experimental results reveal that the conventional UV-Vis spectra of the genuine and counterfeit Moutai liquor are similar. However, the two-dimensional correlation UV-Vis spectra of them are different and this method would be applied to differentiate the counterfeit Moutai liquor from the genuine Moutai liquor. Compared with conventional methods, this novel method has the advantages of easy operation, simple instrumentation and direct recognition, which make it a potential tool in the fields of food safety.

Structure and Two-dimensional Correlation Infrared Spectroscopy Study of a New One-dimensional Chain Compound: (4,4’-Hbpy)_3[NaMo_8O_(26)](4,4’- bpy)_2(H_2O)_4 (bpy = Bipydine)

A novel compound, （4,4＇-Hbpy）3[NaMo8O26]（4,4＇-bpy）2（H2O）4 1 （bpy=bipydine）, was synthesized by the hydrothermal method. Single-crystal X-ray diffraction shows that compound 1 belongs to the monoclinic system, space group C2/m with a=19.1921（5）, b=18.6931（6）, c=9.3821（3） A° β=104.8020（11）°, V=3254.22（17）A°^3 C50H51Mo8N10NaO30, Mr=2062.52, Z=2, F（000）=2016, μ=1.591 mm^-1 and Dc=2.105 g/cm^3. The final R=0.0283 and wR=0.0912 for 3118 observed reflections （I〉20（I））. Compound 1 contains the β-[Mo8O26]^4-anion, sodium ion, 4,4＇-bpy and lattice crystalline water molecules. The β-[MosO26] units link the sodium ion to form a chain structure. The infinitechains of [Na（Mo8O26）]^3- blocks are surrounded by protonized 4,4＇-bpy cations, 4,4＇-bpy and lattice crystalline water molecules. The 2D-IR correlation spectroscopy study indicates that the stretching vibrations of Mo=O occur more preferentially due to the thermal effect. The TGA analysis shows that compound 1 has high thermal stability.

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.

Evolution of Two-Dimensional Correlation Spectroscopy

A number of useful techniques associated with two-dimensional correlation spectroscopy(2DCOS)to improve its performance and utility have been developed in the last 30years.Evolution of these 2DCOS techniques,including some of the very recent developments,is reviewed with examples.Topics include merged or modified asynchronous 2Dcorrelation spectrum,two-dimensional codistribution spectroscopy(2DCDS),Pareto scaling,and null-space projection treatment of spectral dataset.

Study on the Hydrogen Bond Interaction Between Soy Protein Isolate and Glycerol Using Two-Dimensional Correlation Fourier-Transform Infrared Spectroscopy

A series of soy protein isolate(SPI)films plasticized by glycerol(Gly)were studied using attenuated total reflectance-Fourier transform infrared spectroscopy(ATR/FTIR).Perturbation-correlation movingwindow two-dimensional(PCMW2D)and two-dimensional correlation(2DCOS)analyses were applied to the amideⅠband and thus the hydrogen bond interaction between SPI and Gly was systematically investigated.When Gly concentrations were in the range 0~35%,the hydrogen bond amongβ-sheets was replaced by the one between SPI chain and Gly molecule,which caused these protein chains being changed toα-helix.However,the transformation ofβ-sheet toα-helix was saturated and both of them tend to change to random coil when Gly concentrations were in the range 35%~60%.

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.

Laser-induced Fluorescence Spectroscopy of Uranium Monofluoride

The laser-induced fluorescence excitation spectra of uranium monofluoride have been recorded in the range of17000-19000 cm^(-1) using twodimensional spectroscopy.High resolution dispersed fluorescence spectra and time-resolved fluorescence spectroscopy were also recorded.Three rotationally resolved bands were intensively analyzed,and all bands were found to be derived from the ground state X(1)4.5 with a rotational constant of 0.23421 cm^(-1).The low-lying electronic states were observed near 435 and 651 cm^(-1) in the dispersed fluorescence spectra,which were assigned as?′=3.5 and 2.5,respectively.The vibrational constants for the X(1)4.5 and X(1)3.5 states were calculated.The branching ratios of the dispersed fluorescence spectra for the[18.62]3.5,[17.72]4.5,and[17.65]4.5 states were reported.Radiative lifetime of332(9)ns,825(49)ns,and 433(15)ns for the[18.62]3.5,[17.72]4.5,and[17.65]4.5 states were obtained by fitting the time-resolved fluorescence spectroscopy,respectively.Transition dipole moments were performed using the branching ratios and the radiative lifetimes.

Laser-induced fluorescence experimental spectroscopy and theoretical calculations of uranium monoxide

As a model molecule of actinide chemistry,UO molecule plays an important role in understanding the electronic structure and chemical bonding of actinide-containing species.We report a study of the laser-induced fluorescence spectra of the U^(16)O and U^(18)O using two-dimensional spectroscopy.Several rotationally resolved excitation spectra were investigated.Accurate molecular rotational constants and equilibrium internuclear distances were reported.Low-lying electronic states information was extracted from high resolution dispersed fluorescence spectra and analyzed by the ligand field theory model.The configuration of the ground state was determined as U^(2+)(5 f^(3)7 s)O^(2-).The branching ratios,and the vibrational harmonic and anharmonic parameters were also obtained.Radiative lifetimes were determined by recording the timeresolved fluorescence spectroscopy.Transition dipole moments were calculated using the branching ratios and the radiative lifetimes.These findings were elucidated by using quantum-chemical calculations,and the chemical bonding was also analyzed.The findings presented in this work will enrich our understanding of actinide-containing molecules.

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.

Two-dimension fluorescence correlation spectroscopy to characterize the binding of organic ligands with zinc in eutrophic lake

Metal binding of organic ligands can definitely affect its environmental behavior in waters,while information on the binding heterogeneity with different organic ligands is still lacked till now.In this study,the binding of zinc with organic matters associated with cyanobacterial blooms,including dissolved organic matters（DOM） and attached organic matters（AOM）,were studied by using fluorescence quenching titration combined with two-dimensional correlation spectroscopy（2D-COS）.Metal-induced fluorescent quenching was obviously observed both for DOM and AOM,indicating the formation of metal-ligand complexes.Compared with the one-dimensional spectra,2D-COS revealed the sequences of metal-ligand interaction with the following orders：276 nm 〉 232 ran for DOM and232 nm 〉 276 nm for AOM.Furthermore,the modified Stern-Volmer model showed that the binding constant（logKM） of 276 nm in DOM was higher than that of 232 nm（4.93 vs.4.51）,while AOM was characterized with a high binding affinity for 232 nm（log KM：4.83）.The ranks of log KM values were consistent with the sequential orders derived from 2D-COS results both for the two samples.Fluorescence quenching titration combined with 2D-COS was an effective method to characterize the metal-ligand interaction.

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。

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.

Generalized two-dimensional correlation near-infrared spectroscopy and principal component analysis of the structures of methanol and ethanol

Liquid state methanol and ethanol under different temperatures have been investigated by FT-NIR(Fourier transform nearinfrared) spectroscopy,generalized two-dimensional(2D) correlation spectroscopy,and PCA(principal component analysis) . First,the FT-NIR spectra were measured over a temperature range of 30-64(or 30-71) °C,and then the 2D correlation spectra were computed.Combining near-infrared spectroscopy,generalized 2D correlation spectroscopy,and references,we analyzed the molecular structures(especially the hydrogen bond) of methanol and ethanol,and performed the NIR band assignments. The PCA method was employed to verify the results of the 2D analysis.This study will be helpful to the understanding of these reagents.

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.

Generalized two-dimensional correlation spectroscopy——Theory and applications in analytical field

Since the theory of generalized two-dimensional (2-D) correlation spectroscopy was proposed, it has been keenly concerned in scientific research and its analytical method has been widely applied in various analytical fields. The mathematical process to construct generalized 2-D correlation spectroscopy and the physical meaning of 2-D correlation spectral map are described, and three examples in the fields of chemical analysis and molecular biology are provided, such as the component analysis of organic solvent, the analysis of biological molecules in the solvent with different pH values and structural analysis of protein. The theory and analytical method of generalized 2-D correlation spectroscopy are also detailedly commented.

Spectral Insights into Microdynamics of Thermoresponsive Polymers from the Perspective of Two-dimensional Correlation Spectroscopy

Generalized two-dimensional correlation spectroscopy （2DCOS） and its derivate technique, perturbation correlation moving window （PCMW）, have found great potential in studying a series of physico-chemical phenomena in stimuli-responsive polymeric systems. By spreading peaks along a second dimension, 2DCOS can significantly enhance spectral resolution and discern the sequence of group dynamics applicable to various external perturbation-induced spectroscopic changes, especially in infrared （IR）, near-infrared （NIR） and Raman spectroscopy. On the basis of 2DCOS synchronous power spectra changing, PCMW proves to be a powerful tool to monitor complicated spectral variations and to find transition points and ranges. This article reviews the recent work of our research group in the application of 2DCOS and PCMW in thermoresponsive polymers, mainly focused on liquid crystalline polymers and lower critical solution temperature （LCST）-type polymers. Details of group motions and chain conformational changes upon temperature perturbation can thus be elucidated at the molecular level, which contribute to the understanding of their phase transition nature.

Recent developments in two-dimensional (2D) correlation spectroscopy

Recent noteworthy developments in the field of two-dimensional（2D） correlation spectroscopy are reviewed.2D correlation spectroscopy has become a very popular tool due to its versatility and relative ease of use.The technique utilizes a spectroscopic or other analytical probe from a number of selections for a broad range of sample systems by employing different types of external perturbations to induce systematic variations in intensities of spectra.Such spectral intensity variations are then converted into2 D spectra by a form of correlation analysis for subsequent interpretation.Many different types of 2D correlation approaches have been proposed.In particular,2D hetero-correlation and multiple perturbation correlation analyses,including orthogonal sample design scheme,are discussed in this review.Additional references to other important developments in the field of 2D correlation spectroscopy,such as projection correlation and codistribution analysis,were also provided.

Two-dimensional correlation spectroscopic analysis on the interaction between humic acids and aluminum coagulant

In this study, two-dimensional correlation spectroscopy integrated with synchronous fluorescence and infrared absorption spectroscopy was employed to investigate the interaction between humic acids and aluminum coagulant at slightly acidic and neutral p H. Higher fluorescence quenching was produced for fulvic-like and humic-like fractions at p H 5. At p H 5, the humic-like fractions originating from the carboxylic acid, carboxyl and polysaccharide compounds were bound to aluminum first, followed by the fulvic-like fractions originating from the carboxyl and polysaccharide compounds. This finding also demonstrated that the activated functional groups of HA were involved in forming the Al-HA complex, which was accompanied by the removal of other groups by co-precipitation.Meanwhile, at p H 7, almost no fluorescence quenching occurred, and surface complexation was observed to occur, in which the activated functional groups were absorbed on the amorphous Al（OH）3. Two-dimensional FT-IR correlation spectroscopy indicated the sequence of HA structural change during coagulation with aluminum, with IR bands affected in the order of COOH〉 COO-〉NH deformation of amide Ⅱ〉 aliphatic hydroxyl C／OH at p H 5, and COO-〉aliphatic hydroxyl C／OH at p H 7. This study provides a promising pathway for analysis and insight into the priority of functional groups in the interaction between organic matters and metal coagulants.

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.