叶酸的低温磷光分析

叶酸有光、酸中强、碱中弱、HCl浓度高,光强,但不稳定。叶酸经紫外光照射后光增强,增强量与叶酸含量成比例,建立了叶酸的低温光分析法,并用作小鼠,豚鼠肝中叶酸含量分析     

Comparison of different alcohols in a caged lumophore for measuring supersaturated dissolved oxygen

Intense phosphorescence is observed when an alcohol is introduced to an aqueous solution containing 1-bromonaphthalene and a cyclodextrin complex. The enhancement of the phosphorescence intensity of 1-bromonaphalene is related closely with the alcohol’s effectiveness in shielding the photo-excited lumophore from dissolved oxygen. The phosphorescence intensity decreases and the phosphorescence decay rate increases as the dissolved oxygen concentration increases. In this paper, we measure the phosphorescence intensity and decay rate of the complex using different alcohols and explain their respective advantages. By relating the concentration of oxygen to the intensity and the lifetime of the phosphorescence, the dissolved oxygen concentration can be measured. The sensitivities and measurement ranges with the complexes containing different alcohols are compared. Currently, this technique can measure dissolved oxygen concentrations from 0 to 40.2 mM (31,400% saturation). The range of the measurement is 40 times larger than previous studies.     

Characterization of room temperature phosphorescence of propranolol and the chiral discrimination between R- and S-isomers

Upon addition of a small amount of bromocyclohexane, propranolol displays room temperature phosphorescence in γ-cyclodextrin solution without deoxygenation. Several factors including the pH, and the concentration of γ-cyclodextrin and bromocyclohexane, which affect the room temperature phosphorescence (RTP) intensity and room temperature phosphorescence lifetime of propranolol are studied in detail. Under optimal conditions, the room temperature phosphorescence lifetimes of propranolol enantiomers are measured. The experimental results show that the associated phosphorescence decay curves can be best fitted to mono-exponential patterns and room temperature phosphorescence lifetimes of R- and S-propranolol are 4.60 ms and 5.74 ms, respectively. The difference of the room temperature phosphorescence lifetimes of R- and S-propranolol is 22.05%. Based on that, chiral discrimination of propranolol enantiomers is carried out successfully by time-resolved phosphorescence.     

Metal-enhanced phosphorescence: interpretation in terms of triplet-coupled radiating plasmons

We report our detailed metal-enhanced phosphorescence (MEP) findings using Rose Bengal at low temperature. Silver Island Films (SiFs) in close proximity to Rose Bengal significantly enhance the phosphorescence emission intensity. In this regard, a 5-fold brighter phosphorescence intensity of Rose Bengal was observed from SiFs as compared to a glass control sample at 77 K. In addition, several factors affecting MEP, such as distance dependence and silver film morphology, were also investigated. Our findings suggest that both singlet and triplet states can couple to surface plasmons and enhance both fluorescence and phosphorescence yields. This finding suggests that MEP can be used to promote triplet-based assays, such as those used in photodynamic therapy.     

Measurement of the rate of decay of DNA phosphorescence in the temperature range from 4.2 to 160°K

The kinetics of the phosphorescence decay of DNA, poly dAT and the constituent mononucleotides have been found complex (non single-exponential). The decays can generally be interpreted in terms of sums of two exponentials. The temperature dependence of the phosphorescence intensity and decay of DNA film has been investigated.     

Metal nanoparticle-enhanced room temperature phosphorescence of diiodofluorescein on the filter paper substrate

<正>Metal-enhanced room temperature phosphorescence of diiodofluorescein was first observed on filter paper surface.The phosphorescence intensity is 2.5-fold brighter from diiodofluorescein on silver nanoparticles-deposited filter paper as compared with an identical control sample without silver nanoparticles.Furthermore,enhanced absorption was also observed for the same system.Our findings suggest that both singlet and triplet states can couple to surface plasmons and enhance phosphorescence quantum yields at room temperature,as well as to increase the excitation rate of lumophores at room temperature.     

β-环糊精存在下直链脂肪醇诱导1-溴萘室温磷光光谱研究

研究了β-环糊精（β-CD）溶液中直链脂肪醇（A）诱导1-溴萘（1-BrN）的室温磷光光谱性质．结果表明，三元包络物中1-BrN分子的磷光起初随醇中碳原子数的增加而增强，正戊醇对磷光呈现最大的敏化作用，随后从正己醇至正辛醇，磷光强度逐渐下降．测定了包络物组成和稳定常数，发现1-BfN和A：β-CD包络物的结合强度是三元包络物磷光强弱的决定性因素，并从三元包络物可能的结构解释了醇分子大小对室温磷光的影响．     

5,10,15,20-tetrakis(N-methyl-4-pyridyl)-21H,23H-porphine (TMPyP) as a sensitizer for singlet oxygen imaging in cells: characterizing the irradiation-dependent behavior of TMPyP in a single cell

Singlet molecular oxygen, a1Delta(g), can be detected from a single cell by its weak 1270 nm phosphorescence (a1Delta(g)-->X3Sigma(g)-) upon irradiation of the photosensitizer 5,10,15,20-tetrakis(N-methyl-4-pyridyl)-21H,23H-porphine (TMPyP) incorporated into the cell. The behavior of this sensitizer in a cell, and hence the behavior of the associated singlet oxygen phosphorescence signal, depends on the conditions under which the sample is exposed to light. Upon irradiation of a neuron freshly incubated with TMPyP, the intensity of TMPyP fluorescence initially increases and there is a concomitant increase in the singlet oxygen phosphorescence intensity from the cell. These results appear to reflect a photoinduced release of TMPyP bound to DNA in the nucleus of the cell, where TMPyP tends to localize, and the subsequent relocalization of TMPyP to a different microenvironment in the cell. Upon prolonged irradiation of the cell, TMPyP photobleaches and there is a corresponding decrease in the singlet oxygen phosphorescence intensity from the cell. The data reported herein provide insight into key factors that can influence photosensitized singlet oxygen experiments performed on biological samples.     

Resolution of uranium isotopes with kinetic phosphorescence analysis

This study was conducted to test the ability of the Chemchek? Kinetic Phosphorescence Analyzer Model KPA-11 with an auto-sampler to resolve the difference in phosphorescent decay rates of several different uranium isotopes, and therefore identify the uranium isotope ratios present in a sample. Kinetic phosphorescence analysis (KPA) is a technique that provides rapid, accurate, and precise determination of uranium concentration in aqueous solutions. Utilizing a pulsed-laser source to excite an aqueous solution of uranium, this technique measures the phosphorescent emission intensity over time to determine the phosphorescence decay profile. The phosphorescence intensity at the onset of decay is proportional to the uranium concentration in the sample. Calibration with uranium standards results in the accurate determination of actual concentration of the sample. Different isotopes of uranium, however, have unique properties which should result in different phosphorescence decay rates seen via KPA. Results show that a KPA is capable of resolving uranium isotopes.     

Phenyl‐functionalized silica‐coated magnetic nanoparticles for the extraction of chlorobenzenes,and their determination by GC‐electron capture detection

We have prepared a solid phase for the extraction of chlorobenzenes (CBs) by coating magnetic (Fe₃O₄) nanoparticles with silica via a sol‐gel process using a mixture of tetraethoxysilane and triethoxyphenylsilane. The nanoparticles were characterized by SEM, energy‐dispersive spectroscopy, and X‐ray diffractometry. The nanoparticles were used for the extraction of 1,4‐dichlorobenzene (1,4‐DCB), 1,2,3‐trichlorobenzene (1,2,3‐TCB), 1,2,4‐trichlorobenzene (1,2,4‐TCB), and 1,2,3,4‐tetrachlorobenzene (1,2,3,4‐TeCB) from water, followed by their determination by GC‐electron capture detection. Under optimal conditions, enrichment factors ranging from 220 to 360 were obtained. All determination coefficients (r²) are >0.99, and linear response is found in range 0.025–1.5 μg/L (at the lower end), and 6–120 μg/L (at the higher end). Detection limits are 6, 10, 11, and 500 ng/L for 1,2,3,4‐TeCB, 1,2,4‐TCB, 1,2,3‐TCB, and 1,4‐DCB, respectively. All RSDs are <6% (for n = 5). The method was successfully applied to the determination of CBs in environmental water samples.     

The development of room temperature phosphorescence into a new technique for chemical determinations : Part 1. Physical Aspects of Room Temperature Phosphorescence

The development and physical aspects of room temperature phosphorescence are reviewed in this first part of a two-part series. Certain fundamental aspects of phosphorescence are presented. The novel phenomenon of room temperature phosphorescence (strong phosphorescence for organic compounds adsorbed on appropriate substrates) is then treated in detail. Specific attention is given to the nature of the support-phosphor interaction and the quenching effects of moisture and oxygen on room temperature phosphorescence. Thorough coverage is also given to the heavy-atom effect. The effects of the sample matrix on certain phosphorescent properties, such as lifetime, intensity and spectral characteristics, are mentioned.     

A STUDY OF THE KINETICS OF INCLUSION OF HALONAPHTHALENES WITH ß-CYCLODEXTRIN VIA TIME CORRELATED PHOSPHORESCENCE

Abstract— The phosphorescence of 1-bromonaphthalene and 1-chloronaphthalene is readily observable in nitrogen purged aqueous solutions containing ß-cyclodextrin. Addition of acetonitrile increases both the phosphorescence intensity and lifetime. The quenching of halonaphthalene phosphorescence in aqueous solution by nitrite is substantially inhibited upon addition of ß-cyclodextrin, as a result of a guest-host complex. The rate constants for formation and dissociation of the l-bromonaphthalene/ß-cyclodextrin complex are evaluated from an analysis of the dependence of phosphorescence lifetimes on nitrite concentration.     

Analytical study of the phosphorescence of pyrimidine derivatives in frozen aqueous solution

Phosphorescence excitation and emission spectra, phosphorescence lifetimes, phosphorimetric analytical curves and limits of detection were determined at 77K in 10/90 v/v methanol/water solution for seven pyrimidine derivatives. The effect of pH on the phosphorescence intensity indicated an improvement of the sensitivity of the method in basic medium (pH reverse similar11). Low limits of detection, between 10(-5) and 10(-8)M, were obtained. The effect of sodium iodide on the phosphorescence efficiency led to heavy-atom enhancement factors ranging from 1.1 to 9.6, depending on the molecular structure and the pH conditions.     

Flexibility in Proteins: Tuning the Sensitivity to O2 Diffusion by Varying the Lifetime of a Phosphorescent Sensor in Horseradish Peroxidase¶

The heme in horseradish peroxidase (HRP) was replaced by phosphorescent Pt‐mesoporphyrin IX (PtMP), which acted as a phosphorescent marker of oxygen quenching and allowed comparison with another probe, Pd‐mesoporphyrin IX (Khajehpour et al. (2003) Proteins 53, 656–666). Benzohydroxamic acid (BHA), a competitive inhibitor of the enzyme, was also used to monitor its effects on phosphorescence quenching. With the addition of BHA, in the presence of oxygen, the phosphorescence intensity of the protein increased. In contrast, the addition of BHA, in the absence of oxygen, reduced the phosphorescence intensity of the protein. K_d= 18 μM when BHA binds to PtMP‐HRP. The effect of BHA can be explained by two factors: ( 1 ) BHA reduces the accessibility of O₂ to the protein interior and ( 2 ) BHA itself quenches the phosphorescence. Consistent with this, the oxygen quenching of the phosphorescence of PtMP‐HRP gave a quenching constant of k_q= 234 mm Hg^?1 s^?1 in the absence of BHA and k_q= 28.7 mm Hg^?1 s^?1 in the presence of BHA. The quenching rate of BHA is 4000 s^?1. The relative quantum yield of the phosphorescence of the Pt derivative is about six times that of the Pd derivative, whereas the phosphorescence lifetime is approximately eight times shorter. The high quantum yield and suitable lifetime make Pt‐porphyrins appropriate as sensors of O₂ diffusion and flexibility in heme proteins.     

Determination of the individual spin-lattice relaxation rates between the spin levels of phosphorescent triplet-state molecules

It is shown how one can determine the individual spir-lattice relaxation rates of a phosphorescent triplet-stale molecule from analysis of the recovery curve in the phosphorescence intensity upon a microwave sweep through one of the zero-field transitions.     

Irradiation-dependent equilibrium between open and closed form of UV absorbers of the 2-(2-hydroxyphenyl)-1,3,5-triazine type

2-(2-Hydroxyphenyl)-4,6-diaryl-1,3,5-triazines (HPTs) bearing one or more intramolecular hydrogen bonds (IMHBs) show phosphorescence in polar solvents at 77 K which increases in intensity with UV-irradiation time (λ_irr = 333 nm) until an equilibrium value is reached (phosphorescence evolution). Phosphorescence emission is produced from open conformers of the molecules with intermolecular rather than intramolecular hydrogen bonds, which are formed in polar solvents under the influence of UV radiation. All IMHBs of an individual molecule must be broken to enable triplet state population. Reformation of the closed form is observed for HPTs after dark periods resulting in a lower initial phosphorescence intensity upon renewed irradiation (relaxation). The methoxy derivatives (MPTs), where the OH groups are replaced by methoxy groups, can be employed as spectroscopic models for the open form; they emit phosphorescence independent of irradiation time. For the equilibrium between open and closed form of M-OH-P (2-(2-hydroxy-4-methoxyphenyl)-4,6-diphenyl-1,3,5-triazine) under constant irradiation (λ_irr = 333 nm, 100 W-HBO lamp) a proportion of 5% of open form was evaluated.     

Following Oxygen Consumption in Singlet Oxygen Reactions via Changes in Sensitizer Phosphorescence

This work reports an examination of singlet oxygen reactions with amino acid substrates by a method involving measurement of the change in phosphorescence intensity of the singlet oxygen sensitizer. The sensitizer, a Ru(II) bipyridyl complex covalently linked to pyrene, has long‐lived phosphorescence in N₂ purged aqueous solutions (τ₀ ~ 20 μs) that is nearly completely quenched by oxygen in aerated solutions. Irradiation of the complex in water containing sub mM concentrations of histidine, tryptophan and methionine results in a dramatic, easily visible increase in the phosphorescence intensity over a period of 10–100 s. Rate constants for singlet oxygen oxidation of each of the substrates can be obtained by using changes in the phosphorescence intensity in initial rate kinetic analysis. Rate constants obtained in this way compare favorably with those reported in the literature. The method represents a very simple approach for obtaining rate constants for singlet oxygen reactions with various substrates and the kinetics can be extended to nonaqueous solvents.     

EXTERNAL HEAVY ATOM EFFECTS ON THE S1 AND T1 ELECTRONIC STATES OF INDOLE

Abstract— The absorption, fluorescence and phosphorescence spectra along with the phosphorescence decay function of indole perturbed by various amounts of halocarbons have been studied in a 1:1 ethanol-ether glass at 77 K. For carbon tetrachloride. chloroform, halothane and methylene chloride used as quenchers. the biexponential nature of the phosphorescence decay prompted us to assume the existence of a triplet state complex (exciplex) between indole and the halocarbons. On the other hand. propyl bromide gives rise to a non-exponential decay and to an increase in the phosphorescence intensity suggesting the occurrence of a normal external spin-orbital coupling interaction between indole and the propyl bromide molecule.     

Dynamics of the tyrosine triplet state from magnetic resonance-saturated phosphorescence decay measurements

Analysis of the phosphorescence decays measured during magnetic resonance saturation of sublevel populations has been carried out on tyrosine and tyrosinate triplet states at 1.17°K in zero field. The individual sublevel decay constants and spin-lattice relaxation rate constants are derived. Relative intersystem crossing rates to the sublevels are obtained from flash excitation microwave-induced delayed phosphorescence measurements. Intersystem crossing is not spin-selective in tyrosine, but becomes so upon ionization near pH = 12. The spin-selective intersystem crossing mechanism in tyrosinate is discussed in terms of a model proposed by Bersohn.     

Magnetic field effects on the luminescence of Cs[Au(CN)2] at low temperatures

The effects of a magnetic field on the luminescence lifetime and spectrum of microcrystalline Cs[Au(CN)₂] from 2 to 20 K are reported. The lifetime of the 458 nm phosphorescence band at 4 K decreased. In addition, the field produces a blue shift of the band, reaching 75 cm⁻¹ at H = 1.0 T. These effects are in accord with our previously proposed model and are used to determine further details of that model. A new assignment of the 416 nm emission band as fluorescence is made based on its observed lifetime (τ < 10 ns), energy, and intensity variation with temperature.