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Introduction: The Japanese Encephalitis Virus (JEV) causes the acute inflammatory disease of the central nervous system known as Japanese encephalitis. JEV is a RNA virus (+strand) that is tiny, enclosed, and from the family Flavivirus. The envelope protein (E), which facilitates JEV entrance into the host cell, has been chosen as a possible molecular aim for therapeutic progress in this work. Materials and Methods: The 3D structure of E protein was retrieved from RCSB PDB (id: 3P54). The sdf files of four lead molecules namely etoposide, netropsin, nogalamycin, and novobiocin were downloaded from the PubChem and used for molecular docking against JEV E protein. We then assessed the fluorescence emission intensity of JEV alone and JEV bound to novobiocin at 280–500 nM to confirm the inhibition of JEV by Novobiocin. The secondary structure of JEV was ascertained by measuring its CD spectra. The CD spectra of JEV were examined as a function of temperature to evaluate the protein constancy. Results: Our docking and fluorescence emission spectra results showed that JEV E pro has good binding preference for novobiocin among these four test compounds. Moreover, fluorescence emission spectra of JEV E protein with novobiocin also revealed the 5 µM concentration is an effective novobiocin concentration to inhibit the activity of target protein. One top ranked lead molecule namely novobiocin with strong binding affinity (-8.574 Kcal/mol) to JEV E protein was known based on binding energy. Results of the CD Spectra made it quite evident that there is no random coil. Peaks in the negative range (troughs) at 210–230 nm in the CD spectra indicate that JEV has a secondary structure rich in helices. The data unambiguously show that there is no appreciable variation in the JEV curves. Conclusion: Conclusion of the current work offer a thorough understanding of how the JEV E protein is inhibited and provide information that will help novobiocin be developed as a therapeutic drug against JEV E protein in certain viral diseases. [ABSTRACT FROM AUTHOR]

Foliar anthocyanins shape a peculiar shade in a red leaf's interior leading to uneven energy distribution between the two photosystems. Accordingly, a readjustment of PSII/PSI stoichiometry could restore excitation balance. To test this hypothesis, 77 K fluorescence emission spectra of thylakoids from green and red leaves of seven species with different pigment profiles were compared. The ratio of F686/F736 served as an indication of the PSII/PSI functional ratio. To avoid possible species-dependent differences in the measured parameters, plants showing intra-individual, intra-species, or intra-leaf variation in the expression of the anthocyanic character were used. Red leaves or red leaf areas displayed higher PSII/PSI ratio, irrespectively of species and anthocyanin accumulation pattern. PSII/PSI ratio declined in parallel with anthocyanin decrease. In five species, red leaves displayed also a lower Chl a/b ratio. We conclude that red leaves growing in full sunlight develop adaptive adjustments in their chlorophyll and photosystem ratios, compatible with the shade-acclimation syndrome.

Foliar anthocyanins shape a peculiar shade in a red leaf's interior leading to uneven energy distribution between the two photosystems. Accordingly, a readjustment of PSII/PSI stoichiometry could restore excitation balance. To test this hypothesis, 77 K fluorescence emission spectra of thylakoids from green and red leaves of seven species with different pigment profiles were compared. The ratio of F686/F736 served as an indication of the PSII/PSI functional ratio. To avoid possible species-dependent differences in the measured parameters, plants showing intra-individual, intra-species, or intra-leaf variation in the expression of the anthocyanic character were used. Red leaves or red leaf areas displayed higher PSII/PSI ratio, irrespectively of species and anthocyanin accumulation pattern. PSII/PSI ratio declined in parallel with anthocyanin decrease. In five species, red leaves displayed also a lower Chl a/b ratio. We conclude that red leaves growing in full sunlight develop adaptive adjustments in their chlorophyll and photosystem ratios, compatible with the shade-acclimation syndrome. [ABSTRACT FROM AUTHOR]

To explore the effect of substituent attached to aromatic ring and the length of diamine chain in salen-type Schiff base molecules on the fluorescence emission spectra (FLem), the FLem of 63 diamine-salicylaldehyde condensates in an ethanol solution were obtained. The influence of substituent electronic effects and chain lengths on the wavenumber (νem) of fluorescence emission wavelengths (λem) was subsequently studied. The results show that the length of the diamine chain in the target compound has an effect on the νem, which can be quantified by the alkyl polarizability effect index (PEI), where compounds with alkyl of higher PEI have lower νem. Second, the λem of salen-type Schiff bases can be quantified by an equation of the seven parameters, PEI, σ(X)─OH, σ(X)─CH═N, σex CCðXÞ ─OH, &#963ex CC X ð Þ ─CH═N, Δσ2 p and Δσ2 m, form where the stability and predictive ability of the obtained equation was confirmed by leave-one-out cross validation. Lastly, it was observed that the influence on the λem of substituent X attached to the aromatic ring is related to its position relative to OH or CH═N groups as reference, whose Hammett constants (σ(X)─OH, σ(X)─CH═N) and the excited-state substituent constants (σex CC X ð Þ ─OH, σex CC X ð Þ ─CH═N) of the substituents X with varying locating methods have different effects on the λem; and that there is a "homoring competition effect" of substituent. [ABSTRACT FROM AUTHOR]

This work resulted in the development of a method based on fluorescence spectroscopy to differentiate between three corn varieties, standard, mutant and sweet, and to characterize the corn variety present in finished products. This was achieved by recording fluorescence emission spectra as a function of excitation wavelength. For a standard, non-transgenic and non-sweet corn, the maximum of the first peak is around 412–414 nm at the excitation wavelength equal to 280 nm and shifts to the longer emission wavelengths as the excitation wavelength increases. Also, the second peak is located at 535 nm or is slightly higher (537 to 540 nm) and does not vary for excitation wavelengths from 280 to 360 nm. For mutant corn, the position of the first peak is located at 420 nm and above for λex = 280 nm, while the second peak starts at 525–530 nm (depending on the mutant) and never reaches 535 nm. Finally, for a sweet corn, the position of the first fluorescence emission peak is around 430 nm. If the sweet corn is non-hybrid, the position of the second emission peak is at 535 nm. A hybrid sweet corn has its second peak around 530 nm. Thus, fluorescence emission at 530 is characteristic of corn that has undergone natural or artificial genetic transformation. Finally, we found simple mathematical equations to calculate the percentage of amylopectin and amylose in a given corn. [ABSTRACT FROM AUTHOR]

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Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Highlights • Different types of biomolecular markers in kidney cancer patients and in normal healthy controls. • Techniques used are Fluorescence emission spectra and synchronous fluorescence excitation spectra. • Accurate classification of the spectral features of kidney cancer patients relative to that of normal controls, in terms of the concentration ratios of biomolecules. • The specificity and sensitivity of the method were 90%. • Our current approach is to evolve an innovative protocol for the spectral characterization of in vitro optical analyses suitable for both small clinics and hospitals. Abstract In this study, we compared different types of biomolecular markers in kidney cancer patients and in normal healthy controls, using fluorescence emission spectra and synchronous fluorescence excitation spectra. We were able to provide an accurate classification of the spectral features of kidney cancer patients relative to that of normal controls, in terms of the concentration ratios of biomolecules (viz., tryptophan, NADH, FAD, basic porphyrin, and acidic porphyrin) based on the intensity of their spectral peaks. The specificity and sensitivity of the method were 90%. The rationale of our current approach is to evolve an innovative protocol for the spectral characterization of in vitro optical analyses suitable for both small clinics and hospitals. [ABSTRACT FROM AUTHOR]

Laccases (EC 1.10.3.2) have important industrial values in areas such as bioremediation, but they are often inactivated by heavy metal ions in real applications. In this report, laccase from a high laccase-producing Cerrena sp. HYB07 presented resistance to many metal ions except for Ag + , Hg 2+ , Li + and Pb 2+ , the inhibition of which on the laccase were all reversible. The presence of these four cations decreased Remazol Brilliant Blue R decolorization efficiencies catalyzed by the laccase, and the mediator 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) could restore the decolorization efficiency in spite of Hg 2+ inhibition. Hg 2+ had the lowest IC 50 value (0.17 mM) on the laccase activity, followed by Ag + , Li + and Pb 2+ . The inhibition type on laccase activity was competitive for Pb 2+ , noncompetitive for Hg 2+ , and mixed type for Ag + and Li + . The inhibition kinetic model of Hg 2+ on laccase activity was established by using the kinetic method of substrate reaction. The microscopic forward inhibition rate constant ( k +0 ) of Hg 2+ was 3.26 × 10 − 2 /s and the microscopic reverse inhibition rate constant ( k -0 ) was 1.36 × 10 − 3 /s, indicating the laccase would be completely inhibited when Hg 2+ concentration was sufficiently high because k +0 was much larger than k -0 . Furthermore, Hg 2+ reduced thermal and pH stability of the laccase. Fluorescence emission spectra demonstrated that Hg 2+ had one binding site per laccase protein regardless of pH, and the binding was stronger at pH 6.0 than that at pH 5.0 or 9.0, in accordance with the lowest stability of the enzyme at pH 6.0 with Hg 2+ . Dynamic simulation was performed to identify the binding sites of each ion on the Lac7 protein. [ABSTRACT FROM AUTHOR]

The absorption and fluorescence emission spectra of cyanidin and cyanidin 3-O-β-glucopyranoside (Cy3Glc) at pH 5.5 in aqueous solution have been studied. The most effective fluorescence excitations of cyanidin were at the UV absorption maxima at 220 and at 230 nm and at higher wavelengths at 270 and at 280 nm. Cyanidin exhibits fluorescence emission maxima at 310 nm and in the visible range at 615 nm. For the Cy3Glc most effective fluorescence excitation was at 220 and at 230 nm and at higher wavelengths at 300 and at 310 nm. Cy3Glc has fluorescence emission spectra with the maximum at 380 nm and does not show fluorescence emission in the visible range. If compare fluorescence emission spectra of cyanidin and Cy3Glc it can be seen that fluorescence emission intensity for cyanidin is significantly higher than that for Cy3Glc. These results reveals the impact of 3-glucosidic substitution at C-3 of aglycone (to form Cy3Glc) on the significantly decrease in fluorescence emission intensity, and disappearance of the fluorescence emission in visible wavelength range.

Purpose: Returning straw to soil improved soil carbon sequestration capacity and increase soil organic matter. However, in different soil depth, especially in subsoil, there were few studies on the effects of straw decomposition on soil carbon sequestration and the properties of humic substances. Therefore, an in-situ incubation study, with six different straw rates and three different soil depths, was carried out to explore the effects of straw decomposition on soil organic carbon and humic substance composition at different soil depths. Materials and methods: The experiment was composed of six straw rates: 0, 0.44, 0.88, 1.32, 2.64, and 5.28% of soil dry mass. The maize straw was proportionately mixed with soil and put into nylon bags. Then, the nylon bags were buried in soil at three depths (15, 30, and 45 cm) and the straw decomposition trial lasted for 17 consecutive months in-situ. Soil samples were collected after completion of the field trial. Humic substances were quantitatively and qualitatively analyzed using the modification method of humus composition and the methods specified by the International Humus Association. Fourier transform infrared spectroscopy and fluorescence spectroscopy were used in this study. Results and discussion: Results indicated that CO concentration increased with increase in soil depth. Compared with the 'zero' straw control, soil organic carbon contents in the treatments amended with 1.32, 2.64, and 5.28% maize straw increased significantly, and most accumulations were at 30-45 cm depths. FTIR and fluorescence emission spectra analyses indicated that the addition of straw enhanced the aliphatic structure and decreased the aromaticity of humic acid (HA), that was to say that HA molecular structure approaches to the development of simplification and younger. The maximum change in HA molecular structure was under the 5.28% treatment in the 30-45 cm depth. Conclusions: Returning maize straw to the subsoil layers is more conducive to the accumulation of soil organic carbon and improvement of the quality and activity of HA and the organic carbon in the subsoil can be renewed. [ABSTRACT FROM AUTHOR]

Two new azo-azomethine receptors, H 2 L 1 and H 2 L 2 , containing hydrazine, naphthalene and different electron withdrawing groups, Cl and NO 2 , have been designed and synthesized for qualitative and quantitative detection of Cu 2 + and Co 2 + in aqueous media. The crystal structure of H 2 L 1 is reported. The H 2 L 1 was used as a chemosensor for selective detection of trace amount of Cu 2 + in aqueous media. H 2 L 2 was also applied to naked-eye distinction of Cu 2 + and Co 2 + from other transition metal ions in aqueous media. Detection limit of Cu 2 + is 1.13 μM and 1.26 μM, in water, for H 2 L 1 and H 2 L 2 , respectively, which are lower than the World Health Organization (WHO) recommended level. The binuclear Cu 2 + and Co 2 + complexes of the receptors have been also prepared and characterized using spectroscopic methods and MALDI-TOF mass analysis. Furthermore, the binding stoichiometry between the receptors upon the addition Cu 2 + and Co 2 + has been investigated using Job's plot. Moreover, the fluorescence emission spectra of the receptors and their metal complexes are also reported. [ABSTRACT FROM AUTHOR]

Consistent search of plants for green synthesis of silver nanoparticles (SNPs) is an important arena in Nanomedicine. This study focuses on synthesis of SNPs using bioreduction of silver nitrate (AgNO3) by aqueous root extract of Decalepis hamiltonii. The biosynthesis of SNPs was monitored by UV–vis analysis at absorbance maxima 432 nm. The fluorescence emission spectra of SNPs illustrated the broad emission peak 450–483 nm at different excitation wavelengths. The surface characteristics were studied by scanning electron microscope and atomic force microscopy, showed spherical shape of SNPs and dynamic light scattering analysis confirmed the average particle size 32.5 nm and the presence of metallic silver was confirmed by energy dispersive X‐ray. Face centred cubic structure with crystal size 33.3 nm was revealed by powder X‐ray diffraction. Fourier transform infrared spectroscopy indicated the biomolecules involved in the reduction mainly polyols and phenols present in root extracts were found to be responsible for the synthesis of SNPs. The stability and charge on SNPs were revealed by zeta potential analysis. In addition, on therapeutic forum, the synthesised SNPs elicit antioxidant and antimicrobial activity against Bacillus cereus, Bacillus licheniformis, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. [ABSTRACT FROM AUTHOR]

[Zn(FZ)2Cl2] (1) (FZ= Voriconazole, (2R,3S)-2-(2,4-difluorophenyl)-3(5-fluoropyrimidin-4-yl)-1-(1H-1,2,4-triazol-1-yl)butan-2-ol), has been obtained through the reaction of zinc chloride andFZand has been characterized by FT-IR, UV–vis and fluorescence spectra, elemental analysis (EA), single crystal X-ray diffraction, powder X-ray diffraction and thermogravimetric analysis (TGA).FZwas also characterized by FT-IR, UV–vis spectra, single crystal X-ray diffraction and TGA.FZcrystallizes in the chiral space groupP21and1crystallizes in chiral space groupP1with a mononuclear structure. In1, there are three kinds of hydrogen bonding interactions and weak stacking interactions which generate a 3-D architecture. The primary antimicrobial results show that1exhibits potent activity againstAspergillus(Aspergillus niger,Aspergillus terreus,Aspergillus fumigatusandAspergillus flavus) andCandidaspecies (Candida albicans,Candida krusei,Candida glabrataandCryptococcus neoformans), higher than that of freeFZ. Fluorescence spectra of1andFZhave been discussed. [ABSTRACT FROM AUTHOR]

Calcium silicate hydrate (CSH) is a main component of cement-based material required for constructing the geological repository. As in many countries, since the repository in Japan is constructed below water table, we must consider the interaction of radionuclide with cement materials altered around the repository after the backfill. Using fluorescence emission spectra, so far, the authors have investigated the interaction of Eu(III) (as a chemical analog of Am(III)) with CSH gels as a secondary mineral formed without drying process, considering a condition saturated with groundwater. However, in such fluorescence emission behaviors, a deexcitation process of OH vibrators of light water and a quenching effect caused by Eu-Eu energy transfer between Eu atoms incorporated in the CSH gel must be considered. This study examined the fluorescence emission behavior of Eu(III) sorbed on CSH gels, by using La(III) (non-fluorescent ions) as a diluent of Eu(III). Furthermore, CSH samples were synthesized with CaO, SiO2, and heavy water (D2O) as a solvent in order to avoid the obvious deexcitation process of OH vibrators of light water. In the results, the peak around 618 nm was split into two peaks of 613 nm and 622 nm in the cases of Ca/Si=1.0 and 1.6. Then, the peak of 613 nm decreased with increment of Eu(III)/La(III) ratio. This means that the relative intensity of 613 nm is useful to quantify the amount of Eu(III) incorporated in CSH gel. Besides, the decay behavior of the fluorescence emission did not depend on the Eu/La concentration ratio. That is, such a quenching effect is neglectable. Additionally, the fluorescence emission spectra of Eu(III) showed that the state of Eu(III) depended on Ca/Si ratio of CSH. This suggested that there was several sites in CSH to incorporate Eu(III). When CSH is altered, whole cementitious material in repository must be altered forming cracks and leaching some calcium compositions. Therefore, the adsorptive capacity of CSH might also play a key role to retard the migration of nuclides released from the waste body. This study mentioned the fundamental behaviors on the interaction of radionuclides and the altered CSH around the repository.

Abstract: Chlorophyll-a derivatives possessing a pyridyl, 2,2′-bipyridinyl, or 2,2′:6′,2″-terpyridinyl group in the C3-substituent were synthesized by copper-free Sonogashira coupling of methyl 3-ethynyl-pyropheophorbide-a with the corresponding bromo/iodopyridine, bromobipyridine, or trifluoromethylsulfonyloxy-terpyridine, respectively. Their visible absorption spectra in dichloromethane showed that the maxima of all the coupling products gave similar peak positions and were shifted to a longer wavelength than those of the starting 3-ethynyl-chlorin. The red shifts are ascribable to the intramolecular π-conjugation between the chlorin ring and (oligo)pyridinyl moiety through the C C linker. The products in a diluted solution gave an intense fluorescence emission band at the red-side region of redmost absorption band. Their fluorescence quantum yields were about 25% and comparable to that of the starting unsubstituted 3-ethynyl-chlorin. [Copyright &y& Elsevier]

To model the binding to biomembranes, the interactions of potent N- m-tolylbenzamide (NTB) with a cationic surfactant, cetyltrimethylammonium bromide (CTAB) and an anionic surfactant, sodium dodecyl sulfate (SDS), have been investigated. The study was carried out by quantifying the absorption and fluorescence emission spectra of NTB as a function of pre-micellar to post-micellar surfactant concentrations in the temperature range of 25-50 °C. NTB is a strongly fluorescent compound that exhibits intense violet fluorescence. Using mathematical models, the water-micelle partition coefficient ( K), surfactant-NTB binding constant ( K), binding capacity ( n) and the degree of counter-ion binding ( α) are discussed from the thermodynamic viewpoint, considering the thermodynamic parameters of additive solubilization ( $$ \Delta G_{\text{p}}^{^\circ } ,\,\Delta H_{\text{p}}^{^\circ } ,\,\Delta S_{\text{p}}^{^\circ } $$ ). The high values of all interactions, especially when the surface charge of the organized medium is cationic, ensure that there are greater interactions between the NTB and CTAB than with SDS. The NTB molecule is found to be located at only one binding site of each surfactant and probably exhibits static quenching rather than a collisional quenching mechanism. These findings have been confirmed by the binding capacity for the NTB-surfactant combinational system and Stern-Volmer quenching constant ( K) values. The observed depression in binding strength of the counterions with temperature increase favors the promising solubilization of NTB in the palisade layer of micelles leading to penetration binding. [ABSTRACT FROM AUTHOR]

[Display omitted] • We investigate temperature sensitivity of rhodamines from molecular structure. • Substitute on the benzene carboxylate has little effect on temperature sensitivity. • Amino substituents of the three-ring xanthene enhance temperature sensitivity. • Methyl substituents on the three-ring xanthene reduce temperature sensitivity. • The above findings can be extended to other organic fluorescent dyes. As one of the most commonly used organic fluorescent dyes, recently rhodamines have been successfully employed in temperature sensing. However, few works have been reported on their temperature-sensitive properties, which inevitably limiting their further applications. In order to solve such problem, we investigated temperature-sensitive properties of rhodamine 110, 123, 19, 6G, B and 3B focusing on their fluorescence emission spectra; and analyzed them in the molecular structure perspective. It is demonstrated that the fluorescence emission intensities of all studied rhodamines decreased with higher temperature, which inevitably enhances the probability of collisions among molecules, thus definitely leads to energy loss in fluorescence emission. While these rhodamines still have various temperature sensitivities mainly due to the substitutes: the substitute on the benzene carboxylate has little effect; the amino substituents of the three-ring xanthene enhance the temperature sensitivity due to their rotation weakening the rigidity of the three-ring xanthene; and the methyl substituents on the three-ring xanthene reduce the temperature sensitivity by enhancing the rigidity and stability of the three-ring xanthene as well as hindering the rotation of ethylamino. These findings can also be extended to other organic fluorescent dyes proved by coumarins comparable to rhodamines. The results provided by this work can be useful reference and guidance to further develop organic fluorescent dyes especially for temperature sensing. [ABSTRACT FROM AUTHOR]

Omitting the far-red in LED lighting for bioreactors is inexplicable because it affects photosynthetic efficiency and photomorphogenetic activity. Therefore, this work compares three light sources (fluorescent-white light (WL), and LED: blue + red-BRL and blue + red + far-red-BRFRL) for cultures of Chlorella vulgaris. Metabolic activity was determined by isothermal calorimetry. Changes in the chemical composition of biomass were examined by spectrofluorimetry and Raman spectroscopy. Maximum quantum yield of photosystem II was determined on the basis of chlorophyll a fluorescence parameters. The algae grown under BRL produced significantly more thermal energy than those cultured under BRFRL and WL. The Raman spectra of cultures showed characteristic bands for carotenoids, chlorophyll, phenolics, lipids, aliphatic carbohydrates, pectins, and disaccharides. According to the cluster analysis, the chemical composition of cultures grown under BRL and BRFRL was very similar, whereas the WL represented a distinct group. BRL and BRFRL stimulated the biosynthesis of an unidentified compound(s) with fluorescence maximum at 614 nm. At the beginning of the cultivation, photosystem II had very weak photochemical activity. Under BRFRL, ratios of Fv/Fm reached the maximum after 4 days, whereas under BRL and WL, after 6 days of cultivation. The results point to the favorable influence of the far-red on the metabolism of microalgae. [ABSTRACT FROM AUTHOR]

Abstract: β-Carotene is an important molecule in the photosynthetic system, medicine and pharmacy, and has two important functions, photoprotection and light harvesting. Eleven different ionic liquids were designed, synthesized and purified for our experiment in order to obtain samples with predicted physicochemical parameters. The absorption and fluorescence emission spectra of all-trans and 15-cis-β-carotene, at concentrations of 5 μM and 50 μM, in different ionic liquids were recorded. The influence of temperature (in the physiological range important for the isomer stability) on the absorption and fluorescence emission spectra of the carotenes was investigated. [Copyright &y& Elsevier]

Abstract: Methyl 3-trifluoroacetyl-131-deoxo-pyropheophorbide-a (1) and its derivatives were prepared by modifying naturally occurring chlorophyll-a. The 3-trifluoroacetyl group of the synthetic pigments was reacted with amines in dichloromethane to give the hemiaminal-type adducts bearing blue-shifted absorption bands. The hemiaminal of metal-free chlorin 1 with butylamine was formed more preferably than were those of its metal complexes as well as its C17hyrin) and C7–C8 analogs (bacteriochlorin). An increase of the steric hindrance around the nitrogen atom of amines reduced the production of hemiaminals and primary amines possessing a primary alkyl group were selectively detected by absorption spectral change in 1. Polyamines bearing a (2-aminoethyl)amino group were readily added to the trifluoroacetyl group of 1 to afford the hemiaminals stabilized by intramolecular hydrogen bonding of the resulting hydroxy group with the nitrogen atom of the 2-aminoethyl group. Therefore, ethylenediamine was quantitatively analyzed by fluorescence emission spectroscopy and could be quickly detected even at 1 nmol (=0.1 equiv) using 10−5 M solution (1 mL) of 1 in aerated dichloromethane. [Copyright &y& Elsevier]

Origin of tryptophan residues fluorescence in β-lactoglobulin is analyzed. Fluorescence lifetimes and spectra of β-lactoglobulin solution are measured at pH going from 2 to 12 and in 6 M guanidine. Tryptophan residues emit with three lifetimes at all conditions. Two lifetimes (0.4-0.5 ns and 2-4 ns) are in the same range of those measured for tryptophan free in solution. Lifetimes in the denatured states are lower than those measured in the native state. Pre-exponential values are modified with the protein structure. Data are identical to those already obtained for other proteins. Fluorescence lifetimes characterize internal states of the tryptophan residues (Tryptophan sub-structures) independently of the tryptophan environments, the third lifetime results from the interaction that is occurring between the Trp residues and its environment. Pre-exponential values characterize substructures populations. In conclusion, tryptophan mission occurs from substates generated in the excited state. This is in good agreement with the theory we described in recent works. [ABSTRACT FROM AUTHOR]

A new computational procedure to resolve the contribution of Photosystem I (PSI) and Photosystem II (PSII) to the leaf chlorophyll fluorescence emission spectra at room temperature has been developed. It is based on the Principal Component Analysis (PCA) of the leaf fluorescence emission spectra measured during the OI photochemical phase of fluorescence induction kinetics. During this phase, we can assume that only two spectral components are present, one of which is constant (PSI) and the other variable in intensity (PSII). Application of the PCA method to the measured fluorescence emission spectra of Ficus benjamina L. evidences that the temporal variation in the spectra can be ascribed to a single spectral component (the first principal component extracted by PCA), which can be considered to be a good approximation of the PSII fluorescence emission spectrum. The PSI fluorescence emission spectrum was deduced by difference between measured spectra and the first principal component. A single-band spectrum for the PSI fluorescence emission, peaked at about 735 nm, and a 2-band spectrum with maxima at 685 and 740 nm for the PSII were obtained. A linear combination of only these two spectral shapes produced a good fit for any measured emission spectrum of the leaf under investigation and can be used to obtain the fluorescence emission contributions of photosystems under different conditions. With the use of our approach, the dynamics of energy distribution between the two photosystems, such as state transition, can be monitored in vivo, directly at physiological temperatures. Separation of the PSI and PSII emission components can improve the understanding of the fluorescence signal changes induced by environmental factors or stress conditions on plants. [ABSTRACT FROM AUTHOR]

The highly pure and active photosystem II (PSII) complex was isolated from Bangia fusco-purpurea (Dillw) Lyngb., an important economic red alga in China, through two steps of sucrose density gradient ultracentrifugation and characterized by the room absorption and fluorescence emission spectra, DCIP (2,6-dichloroindophenol) reduction, and oxygen evolution rates. The PSII complex from B. fusco-purpurea had the characteristic absorption peaks of chlorophyll (Chl) a (436 and 676 nm) and typical fluorescence emission peak at 685 nm (Ex = 436 nm). Moreover, the acquired PSII complex displayed high oxygen evolution (139 μmol O/(mg Chl h) in the presence of 2.5 mM 2,6-dimethybenzoqinone as an artificial acceptor and was active in photoreduction of DCIP (2,6-dichloroindophenol) by DPC (1,5-diphenylcarbazide) at 163 U/(mg Chl a h). SDS-PAGE also suggested that the purified PSII complex contained four intrinsic proteins (D1, D2, CP43, and CP47) and four extrinsic proteins (33-kD protein, 20-kD protein, cyt c-550, and 14-kD protein). [ABSTRACT FROM AUTHOR]

Abstract: Crystal structure of the imiquimod has been determined by single crystal X-ray analysis, imiquimod crystallizes in orthorhombic space group P212121 and the molecules are linked along the c axis by the strong N–H⋯N hydrogen bonds. A density functional theory (DFT) study on the electronic properties of imiquimod and its synthetic intermediates has been performed at B3LYP/6-31G∗ level, while taking solvent effects into account. Both the single configuration interaction (CIS) method and the time-dependent DFT (TDDFT) approaches have been used to calculate the electronic absorption spectra, and there is a good agreement between the calculated and experimental UV–visible absorption spectra. The fluorescence emission spectra of these three compounds in solution have also been measured, the relatively low fluorescence intensity is attributed to a chlorine-modulated heavy atom effect that enhances intersystem crossing between excited singlet and triplet states, and the relatively high fluorescence intensity of imiquimod results from an extended π-conjugated system which enhances S1 →S0 radiant transition. [Copyright &y& Elsevier]

Abstract: The steady-state and time-resolved fluorescence characteristics of protochlorophyll (Pchl) dissolved in neat Triton X-100 and in Triton X-100 micelles were investigated, and the fluorescence lifetimes of different Pchl spectral forms were studied. Varying the concentration of Pchl or diluting the micellar solutions either with a buffer or with a micellar solution, 631–634, 645–655, 680–692 and above 700nm emitting Pchl complexes were prepared, the ratios of which varied from one another. The fluorescence decay of the 631–634nm emitting (monomeric) form had a mono-exponential character with a 5.4-ns fluorescence lifetime. The long-wavelength Pchl complexes (aggregates) had two fluorescence lifetime values within a range of 1.4–3.9ns and 0.15–0.84ns, which showed high variability in different environments. Depending on the conditions, either mono- or double-exponential fluorescence decay was found for a fluorescence band at 680–685nm. These data show that despite their very similar steady-state fluorescence properties, Pchl complexes can differ in fluorescence lifetimes, which may reflect different molecular structures, intrinsic geometries or different molecular interactions. This underlines the importance of complex spectroscopic analysis for a precise description of native and artificial chlorophyllous pigment forms. [Copyright &y& Elsevier]

Abstract: The fluorescence emission spectra of Cr:Nd:YAG crystal are measured and the effective stimulated emission cross-section of the crystal is obtained from −80 to +80°C. A linear temperature dependence between −80 and +80°C is reported for the 1.064-μm peak stimulated emission cross-section of Cr:Nd:YAG crystal. [Copyright &y& Elsevier]

Abstract: Interaction of quercetin, one kind of flavonoid, with TritonX-100 organized molecular assemblies was investigated by electronic absorption spectra, fluorescence emission spectra, cyclic voltammetric measurements, freeze-fracture TEM (FF-TEM) images and the ab initio quantum calculation. Quercetin is located in the TritonX-100 micelles with the phenyl groups (B-ring part), which leads to the extension of π conjugation of the whole molecule and the enhancement of its ESPT fluorescence process. The embedment of two hydroxyl groups on the phenyl into a more hydrophobic microenvironment makes the oxidation peak of quercetin move to a higher potential with a decreased peak current. The binding of quercetin with TritonX-100 micelle is a spontaneous (ΔG <0) and endothermic process (ΔH >0), and the hydrophobic force is the main driving force for its location. [Copyright &y& Elsevier]

Distinct crystalloids were found in chloroplasts of transgenic P ssu-ipt tobacco ( Nicotiana tabacum L. cv. Petit Havana SR1) overproducing endogenous cytokinins. They were present both in rooted (T) and grafted (TC) transgenic plants contrary to control tobacco (C). The fractions enriched by crystalloids were isolated from chloroplasts using a continuous or a discontinuous Percoll gradient. Chlorophyll (Chl) fluorescence emission spectra at 77 K indicated the presence of aggregates of light-harvesting complex proteins (LHC2) that was not connected to reaction centres of photosystem 2 both in isolated chloroplasts and in the fraction of 80 % Percoll gradient from both types of transgenic tobacco. Further analyses, i.e. pigment contents, polypeptide composition by SDS-PAGE, and immunoblotting support our hypothesis that crystalloids inside chloroplasts of transgenic tobacco are formed by LHC2 aggregates. Treatment with two distinct detergents, chosen with respect to their effects ( i.e. β-dodecyl maltoside or Triton X-100), resulted in different degree of disintegration of Chl a/b proteins in transgenic plants compared to the control. Electron microscopic observations and immunogold labelling with specific LHC2 antibodies carried on the resin embedded leaf sections or free suspensions of chloroplasts showed that gold particles were bound preferentially on the outer surface of crystalloids. Three-dimensional reconstruction of chloroplasts and crystalloids proved that paracrystalline structures varied moderately in their size and took up a significant portion of total chloroplast volume. [ABSTRACT FROM AUTHOR]

Abstract: The fluorescence emission spectra of Cr:Yb:YAG crystal are measured and the effective stimulated emission cross section of the crystal are obtained from −80°C to +80°C. A linear temperature dependence between −80°C and +80°C is reported for the 1.03μm peak stimulated emission cross section of Cr:Yb:YAG crystal. [Copyright &y& Elsevier]

Abstract: There is a little available information about effects of heavy metal ions on greening process in angiosperms. The influence of Cd2+, Fe3+ and Cr2O72- ions on early steps of deetiolation process in wheat (Triticum aestivum) was investigated using fluorescence spectroscopy. Experiments were performed on prolamellar bodies (PLB) isolated from etiolated wheat leaves and the following aspects were studied: (i) stability of the phototransformable Pchlide pool (Pchlide655); (ii) the efficiency of Pchlide to chlorophyllide (Chlide) photoreduction; (iii) spectral transformation of the newly formed Chlide. Destruction of the phototransformable Pchlide655 leading to the lower efficiency of Pchlide to Chlide phototransformation was observed. This effect was more pronounced in the case of Cd(II) than for Cr(VI) and it was the lowest for Fe(III). The maximum of the fluorescence band of the newly formed Chlide in metal-treated samples was blue-shifted with respect to the untreated sample. The shift depended on the concentration of metal ions as well as on the time of incubation, and it was the largest for Cd(II), smaller for Fe(III), and the lowest for Cr(VI). This, in consequence, decreases the time needed to complete the blue Shibata-shift like spectral changes of Chlide. Different mechanisms of action of the investigated metal ions are discussed. [Copyright &y& Elsevier]

The interactions between the hemoprotein cytochrome P450 2B4 (CYP 2B4) and riboflavin – a low molecular weight component of the flavoprotein NADPH-dependent cytochrome P450 reductase – were investigated by fluorescence spectroscopy. Riboflavin fluorescence quenching by cytochrome P450 2B4 was used to probe the ligand–enzyme binding (λex=385 nm, λem=520 nm). Fluorescence titration experiments showed formation of a complex between cytochrome P450 2B4 and riboflavin with an apparent dissociation constant value, Kd=8.8 ± 1 μM. The fluorescence intensity of riboflavin was decreased with increasing the cytochrome P450 2B4 concentration, indicating the transfer of resonance excitation energy from riboflavin (energy donor) to the cytochrome P450 2B4 heme (energy acceptor). The data obtained are suggestive of the existence of riboflavin binding site(s) on the hemeprotein molecule. [Copyright &y& Elsevier]

Aqueous solutions containing a high yield of suspended pure silver, pure gold and silver-coated gold nanoshells have been synthesized via an electrochemical method. UV-vis absorption spectra and fluorescence emission spectra have been measured at room temperature. The absorption spectra show two peaks at 445 and 485 nm, which due to the plasmon resonance of silver-coated gold nanoparticles. Fluorescence emission peaks have been observed in the wavelength region of 550–700 nm. The emission peak corresponding to solid silver particles is more intensive than the peaks corresponding to silver-coated gold nanoshells and solid gold particles. The relationship between relative thickness of silver shell and fluorescence intensity has been illuminated from the quasi-static and local field theory. With decreasing the thickness of silver shell, the maximum of local field enhancement factor decrease and red shifts nonlinearly. [Copyright &y& Elsevier]

The activities of photosystem 2 (PS2) and whole chain electron transport declined in high temperature treated cells at the room temperature beyond 35 °C, while photosystem 1 (PS1) showed increased activity. Thylakoid membrane studies did not exhibit increase in PS1 activity indicating that the enhancement of PS1 activity is due to permeability change of cell membranes. However, the electron transport activity measured from reduced duroquinone to methylviologen which involves intersystem electron transport was extremely sensitive to high temperature. The activity of PS2 at different irradiance, which was accompanied by alterations in absorption and fluorescence emission properties, indicated changes in the energy transfer processes within phycobilisomes. Thus high temperature has multiple target sites in photosynthetic electron transport system of Spirulina platensis. [ABSTRACT FROM AUTHOR]

Fluorescent dye-anchored mesoporous MCM-48 silicate materials were fabricated by post-synthetic implantation of fluorescein isothocyanate dye molecules into MCM-48 framework. Surface modification allowed selective anchoring of the dye molecules into the host MCM-48 silica materials. [Copyright &y& Elsevier]

The effect of Hg++ was studied on the arrangement and photoactivity of NADPH:protochlorophyllide oxidoreductase (POR) in homogenates of dark-grown wheat ( Triticum aestivum L.) leaves. 77 K fluorescence emission spectra of the homogenates were recorded before and after the irradiation of the homogenates and the spectra were deconvoluted into Gaussian components. The mercury treatment caused a precipitation of the membrane particles, which was followed by a remarkable decrease of the fluorescence yield. 10-3 M Hg++ decreased the ratio of the 655 nm-emitting protochlorophyllide (Pchlide) form to the 633 nm-emitting form. 10-2 M Hg++ shifted the short wavelength band to 629–630 nm and a 655 nm form was observed which was inactive on irradiation. This inhibition may be caused by serious alteration of the enzyme structure resulting in the trans-localisation of NADPH within the active site of POR. [ABSTRACT FROM AUTHOR]

The effect of Cibacron Blue 3GA (CB) on the fluorescence emission spectra of bovine serum albumin (BSA) was investigated in cationic reversed micelles formed with cetyltrimethylammonium bromide (CTAB) compared with that in aqueous phase. The anionic CB had electrostatic interactions with cationic CTAB and affinity interactions with BSA in the reversed micelles. The addition of CB in the reversed micellar phase led to a great decrease in the fluorescence intensity of BSA and a remarkable red shift of the wavelength of emission maximum (λmax). The fluorescence intensity of BSA decreased and the λmax decreased 5 nm (blue shift) without the addition of CB in the reversed micellar phase. The fluorescence intensity of BSA with the addition of CB had the strongest value in the aqueous phase with the presence of CTAB, a less strong value in the reversed micellar phase, and a weak value in the aqueous phase without the presence of CTAB. The increase in λmax of BSA with the addition of CB in the reversed micellar phase might indicate the decrease in the hydrophobic microenvironment of the Trp residue of BSA, contrary to those microenvironments in the absence of CB. [ABSTRACT FROM AUTHOR]

Al3+ significantly delayed the loss of chlorophyll (Chl), protein, and carotenoids when compared to K+ and Mg2+ during dark-induced senescence of detached primary leaves of Triticum aestivum. Thylakoid membranes isolated from Al3+ - treated leaves showed a better retention of photosystem (PS) 2, PS1, and whole chain electron transport activities than thylakoids of K+- or Mg2+-treated leaves. These ions protected the electron transport activities and restored the DCMU-dependent fluorescence increase of thylakoid membranes in a valency-dependent manner. Al3+ also delayed the change of excitation energy distribution during senescence. [ABSTRACT FROM AUTHOR]

Salinised (150 mM NaCl for 15 d) roots excised from salt sensitive wheat cultivar Giza 163 showed about 15-fold increase in the ratio of Na/K while salt tolerant Sakha 92 exhibited only 7.5-fold increase compared to their control ratios. Root ratio of saturated/unsaturated fatty acids was stimulated twice in the sensitive cultivar versus 1.7-fold increase in the tolerant ones. Salinity enhanced greatly the accumulation of spermine (Spm) and spermidine (Spd) contents associated with a decrease in putrescine (Put) content in both wheat cultivars. Higher ratios of Spm+Spd/Put associated with lower content of proline and low ethylene evolution were detected in shoots and roots of salt tolerant cultivar. Chlorophyll a/b ratio showed an increase from 1.3 in control of both cultivars to 1.6 and 1.4 in stressed Giza 163 and Sakha 92, respectively. A reduced Hill reaction activity (19 %) was observed in stressed chloroplasts isolated from leaves of the tolerant cultivar versus 40 % inhibition in the sensitive ones. Moreover, chloroplasts isolated from stressed leaves of the sensitive cultivar showed about 25 % reduction in fluorescence emission at 685 nm as well as shifts in the peaks in the visible region. [ABSTRACT FROM AUTHOR]

Low-temperature fluorescence emission spectra of 6.5-day-old dark-grown epicotyls of pea (Pisum sativum) revealed the presence of protochlorophyll(ide). The upper part of the epicotyl contained 30% of the protochlorophyll(ide) content per fresh weight found in pea leaves, whereas the lower part contained 3%. Three discrete spectral forms of protochlorophyll(ide) were clearly distinguished after Gaussian deconvolution of fluorescence excitation and emission spectra. Adding the satellite bands of the Qy(0-0) transitions (the emission vibrational (Emv) bands with correlated amplitudes, gave the following delineation: Ex439-Em629-Emv684, Ex447-Em636-Emv700 and Ex456-Em650-Emv728. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) followed by immunodetection of whole tissue extracts of the epicotyl indicated the presence of NADPH-protochlorophyllide oxidoreductase (EC 1.3.1.33). Electron micrographs showed prolamellar bodies in at most 11% of the plastid profiles of the epicotyl cells. These prolamellar bodies were smaller, and many of them showed less regular structure than those of the leaves. Taken together, the results indicate that the protochlorophyll(ide) in epicotyls is arranged in a different way than in leaves. [ABSTRACT FROM AUTHOR]

Absorption spectra at ca 100 K from 400 to 750 nm and fluorescence emission spectra at 77 K from 600 to 750 nn were obtained from: 1) etiolated leaves of the Hordeum vulgare L. (barley) mutant albozonata 2 and SAN 9789-treated Avena sativa L. (oat) with low levels of carotenoids, and 2) preparations of protochlorophyllide holochrome from Phaseolus vulgaris L. cv. Commodore (bean). This allowed clear resolution for the first time of the Soret bands of the green pigments before and after light-induced accumulation of intermediate(s) in protochlorophyllide to chlorophyllide photoreduction and after conversion of the intermediates) to chlorophyllide by warming the samples to 233 K in darkness. Although the intermediate(s) differ(s) in absorption and fluorescence in the red wavelength region from both protochlorophyllide and chlorophyllide, the extinction in the Soret band is not distinguishable from that of chlorophyllide. These observations indicate that the C7–C8 double bond in ring IV of protochlorophyllide has been altered in intermediate(s) accumulated at low temperature in intense light, such that the transition state exhibits the character of a π complex. [ABSTRACT FROM AUTHOR]

Dark‐grown leaves of wheat (Triticum aestivum L. cv. Starke II, Weibull) were treated in darkness with 8‐hydroxyquinoline and δ‐aminolevulinic acid in order to accumulate magnesium‐protoporphyrin and/or magnesium‐protoporphyrin monomethylester. Prolamellar bodies and prothylakoids were separated from the treated leaves by sucrose density gradient centrifugation. About 90% of the recovered magnesium‐protoporphyrin/magnesium‐protoporphyrin monomethylester and about 75% of the recovered protochlorophyllide was found in the prothlakoid fraction. The significance of the distribution pattern of the chlorophyll precursors between the prolamellar bodies and the prothylakoids is discussed. The results indicate that the prothylakoids are the site for synthesis of membrane‐bound chlorophyll precursors and that phototransformable protochlorophyllide is a constituent of prolamellar bodies as well as of prothylakoids. [ABSTRACT FROM AUTHOR]

Two nuclear gene mutants of pea, chlorotica-887 and chlorina-5756, are temperature-sensitive in the development of photosystem II activity. Low temperature flourescence emission spectra of leaves show that the peak at 697 nm from the reaction center of photosystem II is present when the mutants have been grown at 18°C, but absent when they have been grown at 30°C. For leaves of chlorina-5756 grown at 18°C the relative size of the peak at 697 nm is reduced compared to that of leaves of the wild type or chlorotica-887 grown at this temperature. Flourescence induction curves of leaves from wild type plants and chlorotica-887 grown at 18°C possess two steps, while those of leaves from chlorina-5756 grown at 18°C or 30°C and chlorotica-887 grown at 30°C show at fast rise to the maximal level of fluorescence. Measurements on chloroplasts isolated from the mutants indicated that the photosystem I activity per g leaf material is comparable for plants grown at 18°C and plants grown at 30°C. In contrast, no photosystem II activity was detected when the mutants had been grown at 30°C. It is suggested that these mutants are affected in a component required for the assembly of functional photosystem II complexes. [ABSTRACT FROM AUTHOR]

Intracytoplasmic membranes of the mutant strain NK3 of Rhodopseudomonas capsulata lacking the lightharvesting complex B800-850 were fused with proteoliposomes containing the B800-850 complex. Fluorescence emission spectroscopy at 77K showed that after fusion the fluorescence of the B850 bacteriochlorophyll disappeared nearly completely and the B870 fluorescence became prominent. This result and control experiments with proteoliposome-chromatophore mixture and with chromatophore and solubilized B800-850 complexes, respectively, indicate that in fused membranes a reorientation of membrane particles took place and excitons migrated from B850 to B870 bacteriochlorophyll. In fused proteoliposome-chromatophore vesicles a light-induced carotenoid band shift was observed, reflecting the building of an electrical membrane potential due to chargeseparation. Carotenoid band shift was not observed in separated proteoliposomes and NK3 chromatophores. It is concluded that by membrane fusion and lateral diffusion of membrane particles reaction center-light-harvesting B870 complexes came in functional contact with B800-850 antenna complexes. [ABSTRACT FROM AUTHOR]

Spectral changes in the near infrared absorption region of chromatophores of Chromatium vinosum, strain D, were analyzed. Spectral changes dependent in growing cultures on temperature (33° C and 39° C, respectively) were compared to artificial changes which take place under the influence of the detergent Triton X-100. Like addition of Triton X-100 to chromatophores, transfer of cells from 39° C to 33° C leads to the reversible formation of an absorption band at 820 nm at the expense of a band at 850 nm. But in contrast to the influence of Triton X-100, chromatophores isolated from cells grown at 39° C (39° C chromatophores), contain on an identical bacteriochlorophyll basis, higher amounts of pigment absorbing at 880 nm and lower amounts of pigment absorbing at 800 nm than found in 33° C chromatophores. Triton X-100 treatment does not influence the production of light induced absorbance changes characteristic of photochemical reaction centers; it does, however, change absorption spectra of a subchromatophore fraction which does not exhibit the known light dependent reaction center responses. The spectral properties of this fraction are altered with Triton X-100 in a manner comparable to whole chromatophores, i.e. translocation of the 850 nm band to 820 nm. Subchromatophore fractions isolated from 33° C chromatophores, which display an absorption band at 820 nm show in the presence of menadione a light induced absorbance change at 835 nm. Subchromatophore fractions from 39° C chromatophores, which display no absorbance at 820 nm show a light induced adsorbance change at 835 nm only after addition of Triton X-100. Spectral changes in growing cultures are accompanied by changes in the fluorescence emission spectra of isolated chromatophores. While 33° C chromatophores exhibit a major fluorescence emission band at 929 nm plus a minor band at 890 nm 39° C chromatophores exhibit only one band at 937 nm. [ABSTRACT FROM AUTHOR]

In contrast to the granal thylakoids of mesophyll cells, the bundle sheath thylakoids of maize lack photosystem II activity and both of the chlorophyll a binding proteins of photosystem II. The chlorophyll-proteins from bundle sheath and mesophyll thylakoids are separated by undenaturing electrophoresis and after isolation characterized by SDS-urea-PAGE and spectroscopy. The chlorophyll-protein with the highest molecular mass (Chl-P1) is shown to consist of the reaction centre I containing chlorophyll-protein (Chl-P1) and 12 other polypeptides. Three of the polypeptides are components of the chlorophyll a/b-protein P3, which by its fluorescence emission and absorption spectrum is recognized as PSI antenna. The oligomeric chlorophyll a/b-protein 2 consists of the Chl=P2 polypeptides plus a polypeptide R with an apparent molecular weight of 7.800. The bundle sheath thylakoids contain large amounts of the light harvesting complex of the photosystem II which transfers energy efficiently to the PSI reaction centre in absence of the PSII reaction centre. [ABSTRACT FROM AUTHOR]