Fluorescence Spectral Properties Research Articles

Comparative study of the interaction of some meso-substituted anionic cyanine dyes with human serum albumin

Spectral-fluorescent properties of the meso-substituted anionic cyanine dye 3,3′-di-(γ-sulfopropyl)-4,5,4′,5′-dibenzo-9-methylthiacarbocyanine betaine (DMC) were studied in solutions and in the presence of human serum albumin (HSA). The properties of DMC were compared with those of the previously studied meso-substituted anionic dyes 3,3′-di(γ-sulfopropyl)-4,5,4′,5′-dibenzo-9-ethylthiacarbocyanine betaine (DEC), 3,3′-di-(γ-sulfopropyl)-9-methylthiacarbocyanine betaine (MTC) and 3,3′-di-(γ-sulfopropyl)-5,5′-diphenyl-9-ethyloxacarbocyanine betaine (OCC), which were studied here in more detail. In aqueous solutions, DMC, like DEC, is prone to dimerization; it also forms H– and J-aggregates. The noncovalent interaction of DMC with HSA leads to decomposition of the dimers with a shift in the cis–trans isomeric equilibrium toward the trans-monomer complexed with HSA, which is accompanied by a significant increase in fluorescence. The spectral-fluorescent data were used to estimate the binding constants of the dyes with HSA and other characteristics of the dyes, which are important when used as probes for HSA. The effect of structural rearrangements of HSA upon denaturation by urea on the spectral-fluorescent properties of the dyes was studied. Molecular docking of the dye–HSA systems was performed. A comparative assessment of the prospects for the use of the dyes as spectral-fluorescent probes for HSA in vitro was carried out.

Surface treatment on polymeric polymethyl methacrylate (PMMA) core via dip-coating photopolymerisation curing method

• Polymer optical was fabricated using co-extrusion followed by photopolymerization. • The lowest cladding thickness at 67.63 μm achieved using 13,000 mW/cm 2 UV irradiation. • The cladding with lowest thickness achieved power loss at −13.40 dBm. This work describes the fabrication and evaluation of fluoropolymer surface coating on polymer fibre core prepared from polymethyl methacrylate (PMMA) using ultraviolet (UV) photopolymerisation curing method. The curing condition has a significant influence on the coating adhesion on the core. The focus of this study was to evaluate an effective and simple process for polymer optical fabrication using UV curing with dip-coating method. The coating performance was evaluated through surface morphology analysis and physical properties. FESEM–EDX images indicate that the fluoropolymer coating formed a compact structure with a cladding thickness of 67.63 μm for the highest UV irradiation strength. FTIR analysis revealed the presence of fluorine elements on coated fibre with EDX surface mapping of fluorine dispersion. The performance of the fibre was studied and compared with commercially available polymer optical fibre in terms of fibre spectral fluorescence properties and light attenuation. The dip-coating photopolymerisation method was effective in forming the cladding for step-index polymer fibre with similar spectral excitation wavelength recorded at 620 to 630 nm with the lowest power loss at −13.40 dBm.

Investigated spectral-fluorescent properties of endogenous porphyrins of the wild boar hepatobiliary system optimize the diagnostics and treatment of cholangiocarcinoma with FD and PDT

The combined use of fluorescence diagnostics (FD) and photodynamic therapy (PDT) is a promising approach to the treatment of cholangiocarcinoma. Information about the probing depth of laser radiation at a therapeutic dose sufficient for the appearance of the photodynamic effect allows planning the PDT process. We aim to assess the probing depth of radiation at a therapeutic dose. The highest fluorescence intensity is observed in the gall bladder and liver tissues. A significant difference was noted in the intensity of backscattered laser radiation, depending on the segments of the wild boar hepatobiliary system. Analysis of the probing depth of radiation (λ = 660 nm) revealed that when the optical fiber is located outside the drainage, it increases by 2 to 4 mm, which improves the efficacy of treatment. The applicability of video FD of segments of the hepatobiliary system is investigated using the two-channel video fluorescence system. During video FD in the near-infrared range, the contrast of the fluorescence images of the hepatobiliary system is less than in the visible range. The results of the study will improve the quality of diagnostic information and optimize the FD and PDT algorithms for malignant neoplasms of the human hepatobiliary system.

In vivo detection of changes in cutaneous carotenoids after chemotherapy using shifted excitation resonance Raman difference and fluorescence spectroscopy.

Various cutaneous toxicities under chemotherapy indicate a local effect of chemotherapy by secretion after systemic application. Here, changes in the fluorescence and Raman spectral properties of the stratum corneum subsequent to intravenous chemotherapy were assessed. Twenty healthy subjects and 20 cancer patients undergoing chemotherapy were included. Measurement time points in cancer patients were before the first cycle of chemotherapy (Tbase ) and immediately after intravenous application of the chemotherapy (T1 ). Healthy subjects were measured once without any further intervention. Measurements were conducted using an individually manufactured system consisting of a handheld probe and a wavelength-tunable diode laser-based 488nm SHG light source. Hereby, changes in both skin fluorescence and shifted excitation resonance Raman difference spectroscopy (SERRDS) carotenoid signals were assessed. Healthy subjects showed significantly (P<.001) higher mean concentrations of carotenoids compared to cancer subjects at Tbase . An increase in fluorescence intensity was detected in almost all patients after chemotherapy, especially after doxorubicin infusion. Furthermore, a decrease in the carotenoid concentration in the skin after chemotherapy was found. The SERRDS based noninvasive detection can be used as an indirect quantitative assessment of fluorescent chemotherapeutics. The lower carotenoid SERRDS intensities at Tbase might be due to cancerous diseases and co-medication.

Absorption and fluorescence spectral properties of azo dyes based on 3-amido-6-hydroxy-4-methyl-2-pyridone: Solvent and substituent effects

A series of nine 5-(4-substituted phenylazo)-3-amido-6-hydroxy-4-methyl-2-pyridones were synthesized and characterized by FT–IR, 1H and 13C NMR, UV–Vis, and PL spectroscopy. Photophysical properties of the dyes were examined in solvents of various polarities and at different pH values. The solvent effects on the absorbance and emission spectral shift were analyzed using Lippert–Mataga, Reichardt–Dimroth and Kamlet-Taft equations. Moreover, UV–Vis absorption and emission frequencies were correlated with Hammett substituent constants applying the linear free energy relationships. DFT calculations of the investigated dyes were accomplished to determine their structural and electronic properties.

Lanthanide Doped Complexes and Organometallic Clusters: Design Strategies and their Applications in Biology and Photonics

In this review, we discuss the rational design of a new class of lanthanide-doped organometallic nanostructured materials called `molecular minerals`. Molecular minerals are nanostructured materials with a ceramic core made from chalcogenide groups and other heavy metals. Part of the central core atoms is replaced by suitable lanthanide atoms to impart fluorescent spectral properties. The ceramic core is surrounded by various types of organic networks thus making the structure partly ceramic and organic. The central core has superior optical properties and the surrounding organic ligand makes it easy to dissolve several kinds of organic solvents and fluoropolymers to make several kinds of active and passive photonic devices. This chapter starts with elaborate design strategies of lanthanidebased near-infrared emitting materials followed by the experimental results of selected near-infrared emitting lanthanide clusters. Finally, their potential applications in telecommunication, light-emitting diodes and medical imaging are discussed.

Meso-Substituted Carbocyanines as Effective Spectral-Fluorescent and Photochemical Probes for Structurally Organized Systems Based on Macromolecules

Studies of the photonics of dyes in structurally organized systems are of great fundamental and applied importance. In this regard, the search for simple and convenient methods for analyzing the composition and studying structurally organized systems based on biomolecules (proteins, nucleic acids, etc.) using dye probes is highly relevant. meso-substituted polymethine (carbocyanine) dyes can serve as such probes, as such dyes have a unique set of spectral-fluorescent and photochemical properties that are sensitive to the molecular environment. In structurally organized systems, the photonics of these dyes changes drastically, which allows them to be used in studies of such systems. One peculiarity of these dyes is the mobile equilibrium between the trans- and cis-isomers, which differently interact with biomolecules. The interaction of the dyes with components of structurally organized systems leads to an increase in fluorescence and intersystem crossing to the triplet state. We have developed and put into practice spectral-fluorescent and photochemical probes based on meso-substituted carbocyanines. In particular, we widely used one of the anionic carbocyanines as a probe in biological systems containing serum albumin and collagens. This review is devoted to the works of the authors on the interaction of meso-substituted carbocyanine dyes with biomolecules and the photonics of meso-substituted carbocyanines in complexes with biomolecules. The works on the use of these dyes as probes in biological systems are also considered.

DIPEA catalyzed step-by-step synthesis and photophysical properties of thieno[2,3-b]pyridine derivatives

A series of novel 5,6-disubstituted ethyl 3-amino-4-cyanothieno[2,3-b]pyridine-2-carboxylates was synthesized. The reaction conditions were thoroughly studied and intermediate ethyl 2-((3,4-dicyanopyridin-2-yl)thio)acetates were successfully isolated in good yields. For all synthesized compounds, spectral-fluorescent properties were carefully investigated and correlation thereof with chemical structure was found.

Electronic structure of merocyanine dyes derived from 3H-indole and malononitrile in the ground and excited states: DFT/TD-DFT analysis

The electronic structure and spectral-fluorescent properties of vinylogous positively solvatochromic merocyanines have been studied within the four-level scheme of electronic states using the DFT and TD-DFT computations. The calculations with the solvation taken into account have allowed us to interpret some non-trivial aspects of the merocyanine solvatochromism: weakening of the solvent influence in the fluorescent state, dependence of the shape and width of the spectral bands on the dye structure and environment polarity. It is found that the TD-DFT calculations of the higher electronic transitions agree well with the data obtained from the fluorescence excitation anisotropy spectra.

Spectral-fluorescent study of the interaction of polymethine dye probes with biological surfactants - bile salts.

Spectral-fluorescent properties of polymethine dye probes anionic 3,3'-di(sulfopropyl)-4,5,4',5'-dibenzo-9-ethylthiacarbocyanine-betaine (DEC) and cationic 3,3',9-trimethylthiacarbocyanine iodide (Cyan 2) in the presence of biological surfactants, bile salts sodium cholate (NaC), sodium deoxycholate (NaDC) and sodium taurocholate (NaTC), as well as sodium dodecyl sulfate (SDS), have been studied in a wide range of surfactant concentrations. When a surfactant is introduced into a solution of DEC, changes of the spectral-fluorescent properties are observed due to decomposition of dye dimers into cis-monomers and cis-trans conversion of the resulting monomers. In the presence of SDS, both processes occur in parallel, caused by noncovalent interaction of dye monomers with micelles, and mainly occur near the critical micelle concentration (CMC). In contrast, upon the introduction of increasing concentrations of bile salts, decomposition of dye dimers into the monomers begins at lower concentrations than cis-trans conversion. The former process is almost completed at concentrations close to CMC of secondary micelles (CMC2), while the latter process occurs even at concentrations of bile salts much higher than CMC2. Hence, DEC can serve as a probe that permits estimating the value of CMC2 and is indicative of reorganization of secondary micelles upon an increase in bile salt concentration. Aggregation of DEC and Cyan 2 on bile salts is also observed. Since it is observed at relatively low concentrations of bile salts (<CMC2), the aggregation probably occurs on monomeric molecules of bile salts and their small associates and primary micelles. Decomposition of the aggregates formed begins at concentrations of bile salts above CMC2 (that is, upon the interaction with secondary micelles).

Facile micelle-enhanced spectrofluorimetric method for picogram level determination of febuxostat; application in tablets and in real human plasma

Ultrasensitive, specific, rapid and economic spectrofluorimetric method was developed and validated for determination of a selective xanthine oxidase inhibitor; Febuxostat (FBX) in tablets and in human plasma. The proposed method is based on the enhancement of the fluorescence intensity of an aqueous acidic solution of FBX by using 1.0% w/v sodium dodecyl sulphate (SDS) as a micellar system. A great enhancement of the relative fluorescence intensity (RFI) of FBX was observed (about 2 and 30 folds compared to the aqueous acidic solution of FBX and the aqueous solution of FBX, respectively). RFI was measured at λex. 336 nm/ λem. 410 nm against a reagent blank treated similarly. A linear relationship between the fluorescence intensity of the formed FBX-SDS micellar system and the concentration of FBX was investigated. The reaction conditions and the fluorescence spectral properties of the formed micelle have been studied. The linearity range of the developed method was (0.100–25.0 ng/mL) with detection and quantitation limits of 15.08 and 45.71 pg/mL, respectively. This method was applied successfully for the estimation of FBX in its pharmaceutical dosage forms and in spiked plasma samples without matrices' interferences and with excellent recoveries (99.72–101.44%). This affords the ability to use the developed method for quantitation of FBX in real plasma samples with excellent reproducible % recoveries (96.51–101.32%). All obtained results of the developed method were statistically analyzed and validated according to ICH guidelines.

Leaf-Level Spectral Fluorescence Measurements: Comparing Methodologies for Broadleaves and Needles

Successful measurements of chlorophyll fluorescence (ChlF) spectral properties (typically in the wavelength range of 650–850 nm) across plant species, environmental conditions, and stress levels are a first step towards establishing a quantitative link between solar-induced chlorophyll fluorescence (SIF), which can only be measured at discrete ChlF spectral bands, and photosynthetic functionality. Despite its importance and significance, the various methodologies for the estimation of leaf-level ChlF spectral properties have not yet been compared, especially when applied to leaves with complex morphology, such as needles. Here we present, to the best of our knowledge, a first comparison of protocols for measuring leaf-level ChlF spectra: a custom-made system designed to measure ChlF spectra at ambient and 77 K temperatures (optical chamber, OC), the widely used FluoWat leaf clip (FW), and an integrating sphere setup (IS). We test the three methods under low-light conditions, across two broadleaf species and one needle-like species. For the conifer, we characterize the effect of needle arrangements: one needle, three needles, and needle mats with as little gap fraction as technically possible. We also introduce a simple baseline correction method to account for non-fluorescence-related contributions to spectral measurements. Baseline correction was found especially useful in recovering the spectra nearby the filter cut-off. Results show that the shape of the leaf-level ChlF spectra remained largely unaffected by the measurement methodology and geometry in OC and FW methods. Substantially smaller red/far-red ratios were observed in the IS method. The comparison of needle arrangements indicated that needle mats could be a practical solution to investigate temporal changes in ChlF spectra of needle-like leaves as they produced more reproducible results and higher signals.

Molecular design for novel sensing materials with self-screening interference effect (SSIE): Reversible recognizing Cu2+ in aqueous and biologic samples

In the work, self-screening interference effect (SSIE) was proposed for sensing trace Cu2+ by simply thermodynamic control reactions, using dipyridine as self-screening interference group, rhodamine as mother chromophore and cyanuric chloride as connecting bridge. After its UV–vis and fluorescent spectral properties were optimized in detail, it was noted to find that the present sensing material (RACD) could selectively and reversibly react Cu2+ with obvious colorimetric or fluorescent spectral and color changes from colorless to pink or orange-red. Some other concomitant ions, even trivalent Fe3+ or Al3+, had no interferences on it. Under the optimized conditions, RACD could multiple-mode sense trace Cu2+ in aqueous with a detection limit as low as 11.0 nmol/L. Especially with low toxicity, RACD was successfully applied for quantitatively monitoring Cu2+ and evaluating its toxicity in living cells and bio-tissues. RACD-functionalized paper-strips were also prepared to visibly recognize Cu2+ more conveniently. The selective action mechanism for RACD to Cu2+ was to form some stable 5-membered and 5-membered condensed rings between Cu2+ and O or N atoms.

Mapping the excitation energy migration pathways in phycobilisomes from the cyanobacterium Acaryochloris marina

In this study, we use ultrafast time-resolved absorption and fluorescence spectroscopies to examine A. marina phycobilisomes isolated from cells grown under light of different intensities and spectral regimes. Investigations were performed at room temperature and at 77 K. The study demonstrates that if complexes are stabilized by high phosphate (900 mM) buffer, there are no differences between them in temporal and spectral properties of fluorescence. However, when the complexes are allowed to disassemble into trimers in low phosphate (50 mM) buffer, differences are clearly observed. The fluorescence properties of intact or disassembled phycobilisomes from cells grown in low intensity white light are unresponsive to variation in phosphate concentration. This antenna complex was further studied in detail with application of femtosecond time-resolved absorption at room temperature. Combined spectroscopic and kinetic analysis of time-resolved fluorescence and absorption data of this antenna allowed us to identify spectrally different forms of phycocyanobilins and to propose a simplified model of how they could be distributed within the phycobilisome structure.

Merocyanines based on 1,2-diphenyl-3,5-pyrazolidinedione

The acceptor strength of the 1,2-diphenyl-3,5-pyrazolidinedione residue is re-evaluated based on the spectral-fluorescent properties of donor–acceptor dyes. Low fluorescence of the title compounds is explained by the low-lying forbidden ππ*-state.

Low-Temperature Effect on the Electronic Structure and Spectral-Fluorescent Properties of Highly Dipolar Merocyanines.

Absorption and fluorescence spectra of a vinylogous series of reversely solvatochromic merocyanines based on benzimidazole and malononitrile have been studied in frozen ethanol solutions at 77 K. It is found that they possess negative thermochromism-in contrast to both positively solvatochromic merocyanines and negatively solvatochromic symmetrical ionic polymethines-and even stronger negative thermofluorochromism. It has been deduced from the spectral data that at low temperature their electronic structure becomes more dipolar, deviating substantially from the virtual ideal polymethine in both the ground and the excited states. At that, owing probably to the high polarity and ordering of frozen ethanol, the dipolarity of the studied merocyanines increases with the polymethine chain lengthening-the tendency not observed for them in common solvents. The conclusions, based on the spectral data analysis, have been verified by the (TD)DFT-PCM simulations of the dyes within the four-level scheme of electronic transitions.

Effect of Temperature on the Spectral Fluorescent Properties of Positively Solvatochromic Merocyanines

Fluorescence quenching of positively solvatochromic merocyanines with a bridge group in the polymethine chain increases linearly with increasing temperature and is enhanced with increased chain length. Analysis of the kinetics of the fluorescence quenching gave the activation energy of this process. The absorption and fluorescence spectra in solvents of different viscosity and polarity at room temperature and 77 K showed that the major channel for fluorescence quenching is photoisomerization of the bonds in the polymethine chain. This conclusion was supported by TDDFT quantum-chemical calculations for the bond lengths of the merocyanines in the ground and excited states.

Generation and characterization of functional phosphoserine-incorporated neuronal nitric oxide synthase holoenzyme.

Phosphorylation is an important pathway for the regulation of nitric oxide synthase (NOS) at the posttranslational level. However, the molecular underpinnings of NOS regulation by phosphorylations remain unclear to date, mainly because of the problems in making a good amount of active phospho-NOS proteins. Herein, we have established a system in which recombinant rat nNOS holoprotein can be produced with site-specific incorporation of phosphoserine (pSer) at residue 1412, using a specialized bacterial host strain for pSer incorporation. The pSer1412 nNOS protein demonstrates UV-Vis, far-UV CD and fluorescence spectral properties that are identical to those of nNOS overexpressed in other bacterial strains. The protein is also functional, possessing normal NO production and NADPH oxidation activities in the presence of abundant substrate L-Arg. Conversely, the rate of FMN-heme interdomain electron transfer (IET) in pSer1412 nNOS is considerably lower than that of wild-type (wt) nNOS, while the phosphomimetic S1142E mutant possesses similar electron transfer kinetics to that of wt. The successful incorporation and high yield of pSer1412 into rat nNOS and the significant change in the IET kinetics upon the phosphorylation demonstrate a highly useful method for incorporating native phosphorylation sites as a substantial improvement to commonly used phosphomimetics.

Interaction of Amphotericin B with Ergosterol/Cholesterol‐Containing POPG Liposomes Studied by Absorption, Fluorescence and Second Harmonic Spectroscopy

AbstractThe membrane permeability induced by the polyene antibiotic Amphotericin B (AmB) against negatively charged L‐α‐phosphatidyl DL‐glycerol (POPG) membranes containing either Ergosterol (Ergo) or Cholesterol (Chol) has been investigated by monitoring the bilayer transport of the LDS‐698 (LDS+) ion using the interfacial selective second harmonic (SH) spectroscopy. The transport of LDS+ becomes faster at very low AmB/Liposome (A/L) ratio whereas Ergo present in the bilayer. As increasing A/L ratio, the average transport time constants (Tav) of the LDS+ ion fall into two kinetic regimes which observed for the different liposomes. In POPG‐Ergo liposomes, the effect of neutralizing either of the two charged functional groups of AmB reveals that interaction of AmB with Ergo is primarily dependent upon the charged amino group present in the mycosamine moiety of AmB. The spectral (absorption and fluorescence) properties of AmB were also studied to supplement the results obtained from SH studies. In summary, at low A/L ratio (&lt; 1), the membrane permeability of the POPG membrane were observed to dependent upon the membrane composition or the pH of the medium, whereas at higher A/L ratio (&gt; 1) the permeability becomes similar for all the cases. The spectroscopic properties of AmB with increasing A/L ratio suggest that the latter phenomena may be due to the aggregated states of AmB in the bilayer which enhance the bilayer permeability irrespective of the bilayer composition and solution pH.

Effects of carotenoids on the absorption and fluorescence spectral properties and fluorescence quenching of Chlorophyll a

Fluorescence and absorption characteristics of Chlorophyll a (Chl-a) were modulated by the carotenoids (Cars) with different numbers of conjugated carbon‑carbon double bonds in solutions. The Chl-a absorption appears the redshift phenomenon with the effective conjugated of Cars increasing. The absorption of Chl-a and Cars are linearly dependent on intrinsic factors, namely effective conjugate length and functional groups, and on environmental factors, such as the polarizability of the solvent. Cars can be able to quench the Chl-a fluorescence by producing the non-emitting exciplex intermediate. The effective conjugated length of Cars is one of the reasons that effect the fluorescence quenching of Chl-a. According to the Stern-Volmer plots, the Chl-a fluorescence quenching should be predominantly dynamic rather than static.