Journal articles: 'Intrinsic UV fluorescence'

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Bhartia, Rohit, Everett C. Salas, William F. Hug, Ray D. Reid, Arthur L. Lane, Katrina J. Edwards, and Kenneth H. Nealson. "Label-Free Bacterial Imaging with Deep-UV-Laser-Induced Native Fluorescence." Applied and Environmental Microbiology 76, no. 21 (September 3, 2010): 7231–37. http://dx.doi.org/10.1128/aem.00943-10.

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ABSTRACT We introduce a near-real-time optical imaging method that works via the detection of the intrinsic fluorescence of life forms upon excitation by deep-UV (DUV) illumination. A DUV (<250-nm) source enables the detection of microbes in their native state on natural materials, avoiding background autofluorescence and without the need for fluorescent dyes or tags. We demonstrate that DUV-laser-induced native fluorescence can detect bacteria on opaque surfaces at spatial scales ranging from tens of centimeters to micrometers and from communities to single cells. Given exposure times of 100 μs and low excitation intensities, this technique enables rapid imaging of bacterial communities and cells without irreversible sample alteration or destruction. We also demonstrate the first noninvasive detection of bacteria on in situ-incubated environmental experimental samples from the deep ocean (Lo'ihi Seamount), showing the use of DUV native fluorescence for in situ detection in the deep biosphere and other nutrient-limited environments.

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Abd Halim, Adyani Azizah, Mohammed Suleiman Zaroog, Habsah Abdul Kadir, and Saad Tayyab. "Molten Globule-Like Partially Folded State ofBacillus licheniformis α-Amylase at Low pH Induced by 1,1,1,3,3,3-Hexafluoroisopropanol." Scientific World Journal 2014 (2014): 1–9. http://dx.doi.org/10.1155/2014/824768.

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Effect of 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) on acid-denaturedBacillus licheniformis α-amylase (BLA) at pH 2.0 was investigated by far-UV CD, intrinsic fluorescence, and ANS fluorescence measurements. Addition of increasing HFIP concentrations led to an increase in the mean residue ellipticity at 222 nm (MRE222 nm) up to 1.5 M HFIP concentration beyond which it sloped off. A small increase in the intrinsic fluorescence and a marked increase in the ANS fluorescence were also observed up to 0.4 M HFIP concentration, both of which decreased thereafter. Far- and near-UV CD spectra of the HFIP-induced state observed at 0.4 M HFIP showed significant retention of the secondary structures closer to native BLA but a disordered tertiary structure. Increase in the ANS fluorescence intensity was also observed with the HFIP-induced state, suggesting exposure of the hydrophobic clusters to the solvent. Furthermore, thermal denaturation of HFIP-induced state showed a non-cooperative transition. Taken together, all these results suggested that HFIP-induced state of BLA represented a molten globule-like state at pH 2.0.

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Meyer, Arne, Christian Betzel, and Marc Pusey. "Latest methods of fluorescence-based protein crystal identification." Acta Crystallographica Section F Structural Biology Communications 71, no. 2 (January 28, 2015): 121–31. http://dx.doi.org/10.1107/s2053230x15000114.

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Successful protein crystallization screening experiments are dependent upon the experimenter being able to identify positive outcomes. The introduction of fluorescence techniques has brought a powerful and versatile tool to the aid of the crystal grower. Trace fluorescent labeling, in which a fluorescent probe is covalently bound to a subpopulation (<0.5%) of the protein, enables the use of visible fluorescence. Alternatively, one can avoid covalent modification and use UV fluorescence, exploiting the intrinsic fluorescent amino acids present in most proteins. By the use of these techniques, crystals that had previously been obscured in the crystallization drop can readily be identified and distinguished from amorphous precipitate or salt crystals. Additionally, lead conditions that may not have been obvious as such under white-light illumination can be identified. In all cases review of the screening plate is considerably accelerated, as the eye can quickly note objects of increased intensity.

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Gagnon, Pete, Blaz Goricar, Nina Mencin, Timotej Zvanut, Sebastijan Peljhan, Maja Leskovec, and Ales Strancar. "Multiple-Monitor HPLC Assays for Rapid Process Development, In-Process Monitoring, and Validation of AAV Production and Purification." Pharmaceutics 13, no. 1 (January 17, 2021): 113. http://dx.doi.org/10.3390/pharmaceutics13010113.

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HPLC is established as a fast convenient analytical technology for characterizing the content of empty and full capsids in purified samples containing adeno-associated virus (AAV). UV-based monitoring unfortunately over-estimates the proportion of full capsids and offers little value for characterizing unpurified samples. The present study combines dual-wavelength UV monitoring with intrinsic fluorescence, extrinsic fluorescence, and light-scattering to extend the utility of HPLC for supporting development of therapeutic AAV-based drugs. Applications with anion exchange (AEC), cation exchange (CEC), and size exclusion chromatography (SEC) are presented. Intrinsic fluorescence increases sensitivity of AAV detection over UV and enables more objective estimation of empty and full capsid ratios by comparison of their respective peak areas. Light scattering enables identification of AAV capsids in complex samples, plus semiquantitative estimation of empty and full capsid ratios from relative peak areas of empty and full capsids. Extrinsic Picogreen fluorescence enables semiquantitative tracking of DNA with all HPLC methods at all stages of purification. It does not detect encapsidated DNA but reveals DNA associated principally with the exteriors of empty capsids. It also enables monitoring of host DNA contamination across chromatograms. These enhancements support many opportunities to improve characterization of raw materials and process intermediates, to accelerate process development, provide rapid in-process monitoring, and support process validation.

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Pottier, Fabien, Anne Michelin, Christine Andraud, Fabrice Goubard, and Bertrand Lavédrine. "Characterizing the Intrinsic Fluorescence Properties of Historical Painting Materials: The Case Study of a Sixteenth-Century Mesoamerican Manuscript." Applied Spectroscopy 72, no. 4 (December 14, 2017): 573–83. http://dx.doi.org/10.1177/0003702817747276.

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Ultraviolet visible (UV–Vis) fluorescence spectroscopy is widely used to study polychrome objects and can help to identify the nature of certain materials when they present specific fluorescent properties. However, given the complexity of the stratified and heterogeneous materials under study, the characterization of an intrinsic fluorescence related to a given constituent (a pigment or a binder composing a paint layer for example) is not straightforward, and the recorded raw data need to be corrected for a number of effects that can influence the detected spectral distribution. The application of standard correction procedures to experimental fluorescence data gathered on the polychromatic surface of the Codex Borbonicus, a 16th-century Aztec manuscript, is described. The results are confronted to an alternate new methodology that is based on the hypothesis of transparent non-scattering paint layers. This second approach allows to establish more clearly the material origin of the detected emission and to discriminate apparent fluorescence (emitted by the substrate and transmitted through the paint layers) from actual intrinsic emission generated by the coloring materials under study. The results show that most of the various emission profiles detected in the paint layers of the manuscript actually originate from a unique fluorophore (composing the substrate) and should not be used to characterize the coloring materials.

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Huang, Lei, Lianzhi Li, Haili Li, Chaohui Gao, Hui Cui, and Xiangshi Tan. "Multispectroscopic Study of the Interaction of Chloramphenicol with Human Neuroglobin." Spectroscopy: An International Journal 27 (2012): 143–54. http://dx.doi.org/10.1155/2012/192591.

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The interaction between chloramphenicol (CHL) and neuroglobin (Ngb) has been investigated by using fluorescence, synchronous fluorescence, UV-Vis and circular dichroism (CD) spectroscopy. It has been found that CHL molecule can quench the intrinsic fluorescence of Ngb in a way of dynamic quenching mechanism, which was supported by UV-Vis spectral data. Their effective quenching constants (KSV) are2.2×104,2.6×104,and 3.1×104 L⋅mol−1at 298 K, 303 K, and 308 K, respectively. The enthalpy change (ΔH) and entropy change (ΔS) for this reaction are 26.42 kJ⋅mol−1and 171.7 J⋅K−1, respectively. It means that the hydrophobic interaction is the main intermolecular force of the interaction between CHL and Ngb. Synchronous fluorescence spectra showed that the microenvironment of tryptophan and tyrosine residues of Ngb has been changed slightly. The fluorescence quenching efficiency of CHL to tyrosine residues is a little bit more than that to tryptophan residues of Ngb. Furthermore, CD spectra indicated that CHL can induce the formation of α-helix of Ngb.

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Jamme, Frederic, Sandrine Villette, Alexandre Giuliani, Valerie Rouam, Frank Wien, Bruno Lagarde, and Matthieu Réfrégiers. "Synchrotron UV Fluorescence Microscopy Uncovers New Probes in Cells and Tissues." Microscopy and Microanalysis 16, no. 5 (August 25, 2010): 507–14. http://dx.doi.org/10.1017/s1431927610093852.

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AbstractUse of deep ultraviolet (DUV, below 350 nm) fluorescence opens up new possibilities in biology because it does not need external specific probes or labeling but instead allows use of the intrinsic fluorescence that exists for many biomolecules when excited in this wavelength range. Indeed, observation of label free biomolecules or active drugs ensures that the label will not modify the biolocalization or any of its properties. In the past, it has not been easy to accomplish DUV fluorescence imaging due to limited sources and to microscope optics. Two worlds were coexisting: the spectrofluorometric measurements with full spectrum information with DUV excitation, which lacked high-resolution localization, and the microscopic world with very good spatial resolution but poor spectral resolution for which the wavelength range was limited to 350 nm. To combine the advantages of both worlds, we have developed a DUV fluorescence microscope for cell biology coupled to a synchrotron beamline, providing fine tunable excitation from 180 to 600 nm and full spectrum acquired on each point of the image, to study DUV excited fluorescence emitted from nanovolumes directly inside live cells or tissue biopsies.

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Xue, Mao-Yun, Ai-Ping Yang, Mei-Hua Ma, and Xiao-Hua Li. "The application of two-dimensional fluorescence correlation spectroscopy on the interaction between bovine serum albumin and prulifloxacin." Spectroscopy 23, no. 5-6 (2009): 257–63. http://dx.doi.org/10.1155/2009/565173.

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The interaction between bovine serum albumin (BSA) and prulifloxacin was investigated by ultraviolet spectrophotometer (UV) and fluorescence spectroscopy in this paper. Two-dimensional (2D) correlation spectroscopy was applied to the analysis of fluorescence spectra. The results of spectroscopic measurements suggested that prulifloxacin (PL) have a strong ability to quench the intrinsic fluorescence of bovine serum albumin through static quenching procedure. Thermodynamic parameter enthalpy changes (ΔH) and entropy changes (ΔS) were calculated. Owing to the spectral resolution enhancement in 2D correlation spectroscopy, the structure change of prulifloxacin can be observed.

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Lukk, Tiit, Richard E. Gillilan, Doletha M. E. Szebenyi, and Warren R. Zipfel. "A visible-light-excited fluorescence method for imaging protein crystals without added dyes." Journal of Applied Crystallography 49, no. 1 (February 1, 2016): 234–40. http://dx.doi.org/10.1107/s160057671502419x.

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Fluorescence microscopy methods have seen an increase in popularity in recent years for detecting protein crystals in screening trays. The fluorescence-based crystal detection methods have thus far relied on intrinsic UV-inducible tryptophan fluorescence, nonlinear optics or fluorescence in the visible light range dependent on crystals soaked with fluorescent dyes. In this paper data are presented on a novel visible-light-inducible autofluorescence arising from protein crystals as a result of general stabilization of conjugated double-bond systems and increased charge delocalization due to crystal packing. The visible-light-inducible autofluorescence serves as a complementary method to bright-field microscopy in beamline applications where accurate crystal centering about the rotation axis is essential. Owing to temperature-dependent chromophore stabilization, protein crystals exhibit tenfold higher fluorescence intensity at cryogenic temperatures, making the method ideal for experiments where crystals are cooled to 100 K with a cryostream. In addition to the non-damaging excitation wavelength and low laser power required for imaging, the method can also serve a useful role for differentiating protein crystals from salt crystals in screening trays.

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Abdelhameed, Ali Saber. "Insight into the Interaction between the HIV-1 Integrase Inhibitor Elvitegravir and Bovine Serum Albumin: A Spectroscopic Study." Journal of Spectroscopy 2015 (2015): 1–9. http://dx.doi.org/10.1155/2015/435674.

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The interaction between the anti-HIV drug Elvitegravir (EVG) and bovine serum albumin (BSA) was investigated by fluorescence spectroscopy and UV-visible absorption spectra. The mechanism for quenching the fluorescence of BSA by EVG is discussed. It was found that EVG can quench the intrinsic fluorescence of BSA through a static quenching procedure. The quenching type, association constant, and number of binding sites were investigated. The binding constant of EVG with BSA was calculated at different temperatures based on fluorescence quenching results. The thermodynamic parametersΔHθ,ΔGθ, andΔSθwere determined. The positiveΔSθand negativeΔHθandΔGθvalues showed that a spontaneous interaction may involve both roles of hydrophobic interaction and hydrogen bonding. The interaction of BSA with EVG was also confirmed by UV absorption spectra. The average distance,r, between donor (BSA) and acceptor (EVG) was obtained according to Förster’s theory of nonradiation energy transfer. Synchronous fluorescence and three-dimensional fluorescence spectra were used to investigate the conformational change of BSA molecules that occur upon addition of EVG and showed, upon binding, a possibility of increasing hydrophobicity around tryptophan residues of BSA.

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Zhu, Jin Lian, Jia He, Hua He, Shu Hua Tan, Xiao Mei He, Chuong Pham-Huy, and Lun Li. "Study on the interaction between ketoprofen and bovine serum albumin by molecular simulation and spectroscopic methods." Spectroscopy 26, no. 6 (2011): 337–48. http://dx.doi.org/10.1155/2011/840849.

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The interaction between ketoprofen and bovine serum albumin (BSA) was investigated by molecular simulation, fluorescence and UV-vis spectroscopy methods under the simulated physiological conditions. Molecular simulation method performed to reveal the possible binding mode or mechanism suggested the binding forces between ketoprofen and BSA were mainly hydrophobic interaction and hydrogen bond, which was in agreement with the thermodynamic study (ΔHΦand ΔSΦwere calculated to be 74.514 kJ/mol and 333.98 J/mol · K). The binding constants of ketoprofen and BSA at different temperatures (298, 310 and 318 K) were calculated according to the data obtained from fluorescence spectra and the results indicated that ketoprofen had strong ability to quench the intrinsic fluorescence of BSA via a combination of static and dynamic quenching. Meanwhile, the changes of the conformation of BSA caused by ketoprofen were qualitatively analyzed with the UV-vis and synchronous fluorescence spectroscopy. The distance between ketoprofen and tryptophan residue in BSA was calculated to be 1.58 nm.

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Fonin, Alexander V., Olga V. Stepanenko, Irina M. Kuznetsova, Konstantin K. Turoverov, Elena I. Kostyleva, and Vladimir I. Vorobyev. "Interaction between linker histone H1 and non-histone chromatin protein HMGB1." Spectroscopy 24, no. 1-2 (2010): 165–68. http://dx.doi.org/10.1155/2010/745671.

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The possibility of interaction between linker histone H1 and non-histone chromatin protein HMGB1 was studied by intrinsic UV-fluorescence, far and near-UV CD and light scattering. The obtained data allow us to assume that the increase of histone H1 content in the HMGB1 solutions in a low ionic strength is accompanied by the destruction of HMGB1 associates. The interaction between proteins causes the increase of ordered regions in the protein molecules and the minor changes in their tertiary structure.

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Striebel, Hans-Martin, Peter Schellenberg, Paulius Grigaravicius, and Karl Otto Greulich. "Readout of protein microarrays using intrinsic time resolved UV fluorescence for label-free detection." PROTEOMICS 4, no. 6 (April 20, 2004): 1703–11. http://dx.doi.org/10.1002/pmic.200300705.

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Liu, Qiong Yu. "Spectroscopic Studies on the Interaction between 2-Chlorophenol and Catalase." Advanced Materials Research 183-185 (January 2011): 206–10. http://dx.doi.org/10.4028/www.scientific.net/amr.183-185.206.

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The interaction characteristics of 2-chlorophenol (2-CP) with catalase (CAT) were investigated by employing fluorescence spectroscopy and UV-Vis absorption spectroscopy. The intrinsic fluorescence of CAT was quenched distinctly by 2-CP. The quenching mechanism of fluorescence of CAT by 2-CP was observed to be a static quenching procedure. The thermodynamic parameters indicated that the binding reaction was spontaneous and the hydrophobic force played the major role in stabilizing the 2-CP-CAT complex. The binding constant was 1.18×10-4L/mol. The binding distance r and critical distance R0was 1.90 nm and 1.64 nm, respectively.

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Yue, Qiaoli, Tongfei Shen, Changna Wang, Chaohui Gao, and Jifeng Liu. "Study on the Interaction of Bovine Serum Albumin with Ceftriaxone and the Inhibition Effect of Zinc (II)." International Journal of Spectroscopy 2012 (July 15, 2012): 1–9. http://dx.doi.org/10.1155/2012/284173.

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The mechanism of the interaction between bovine serum albumin (BSA) and ceftriaxone with and without zinc (II) (Zn2+) was studied employing fluorescence, ultraviolet (UV) absorption, circular dichroism (CD), and synchronous fluorescence spectral methods. The intrinsic fluorescence of BSA was quenched by ceftriaxone in a static quenching mode, which was authenticated by Stern-Volmer calculations. The binding constant, the number of binding sites, and the thermodynamic parameters were obtained, which indicated a spontaneous and hydrophobic interaction between BSA and ceftriaxone regardless of Zn2+. Changes in UV absorption, CD, and synchronous fluorescence spectral data are due to the microenvironment of amide moieties in BSA molecules. In the BSA-ceftriaxone-Zn2+ system, Zn2+ must first interact with ceftriaxone forming a complex, which inhibits BSA binding to ceftriaxone. The present work uses spectroscopy to elucidate the mechanism behind the interaction between BSA and ceftriaxone in the presence and absence of Zn2+. The BSA and ceftriaxone complex provides a model for studying drug-protein interactions and thus may further facilitate the study of drug metabolism and transportation.

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Han, Hui Kai, Jin Cheng Huang, Hang Qi, and Du You Lu. "Preparation of ZnSe Quantum Dots by Hydrothermal Method Assisted by Ammonia." Materials Science Forum 956 (June 2019): 99–106. http://dx.doi.org/10.4028/www.scientific.net/msf.956.99.

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ZnSe quantum dots (QDs) with high intrinsic fluorescence quantum efficiency (QY) and low defect luminescence were prepared by hydrothermal method assisted with ammonia, in which the selenium powder and zinc acetate were used as Se and Zn source, and the mercaptopropionic acid (MPA) was used as ligand. Effect of ammonia amount, Zn/Se ratio, Zn/MPA ratio, and reaction time was investigated in detail in this study. The as-prepared ZnSe QDs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-visible absorption spectrum (UV-Vis), fluorescence spectrum (PL). ZnSe QDs assisted with ammonia were sphalerite, and with emission peak in the range of 380~405nm. The optimal condition was following: Zn/Se ratio was 5, Zn/MPA ration was 0.25, reaction temperature was 110 °C and reaction time was 6 h. Under the optimal condition, ZnSe QDs with intrinsic emission QY of 47% and diameter of 3.8±0.3 nm can be obtained. The ZnSe QDs prepared in this study were expected to replace toxic Cd-related QDs in biomarkers, violet and blue light solid luminescent devices, and provide excellent parent materials for the doped ZnSe QDs system.

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Garoli, Denis, Andrea Schirato, Giorgia Giovannini, Sandro Cattarin, Paolo Ponzellini, Eugenio Calandrini, Remo Proietti Zaccaria, et al. "Galvanic Replacement Reaction as a Route to Prepare Nanoporous Aluminum for UV Plasmonics." Nanomaterials 10, no. 1 (January 4, 2020): 102. http://dx.doi.org/10.3390/nano10010102.

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There is a growing interest in extending plasmonics applications into the ultraviolet region of the electromagnetic spectrum. Noble metals are commonly used in plasmonic, but their intrinsic optical properties limit their use above 350 nm. Aluminum is probably the most suitable material for UV plasmonics, and in this work we fabricated substrates of nanoporous aluminum starting from an alloy of Al2Mg3. The porous metal is obtained by means of a galvanic replacement reaction. Such nanoporous metal can be exploited to achieve a plasmonic material suitable for enhanced UV Raman spectroscopy and fluorescence. Thanks to the large surface to volume ratio, this material represents a powerful platform for promoting interaction between plasmonic substrates and molecules in the UV.

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DARWISH, SAQER M. "SPECTROSCOPIC STUDY OF PROPOFOL BINDING TO HUMAN SERUM ALBUMIN." Biophysical Reviews and Letters 05, no. 04 (December 2010): 209–26. http://dx.doi.org/10.1142/s1793048010001202.

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The interaction of propofol and human serum albumin (HSA) has been investigated by UV-absorption, fluorescence spectroscopy and Fourier transform infrared (FT-IR) spectroscopy. Propofol has shown a strong ability to quench the intrinsic fluorescence of HSA through a static quenching procedure. The binding constant (k) is estimated at a low value of 2.55 × 103M-1at 293 K. FT-IR spectroscopy with Fourier self-deconvolution technique was used to determine the protein secondary structure in the amide regions I, II and III. The observed spectral changes of HSA-propofol complex indicate a larger intensity decrease in the absorption band of α-helix relative to that of β-sheets. This variation in intensity is related indirectly to the formation of H-bonding in the complex molecules, which accounts for the different intrinsic propensities of α-helix and β-sheets.

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Chen, Xu, Jia-Ming Ma, Ke-Lan Yong, Jing-Ci Lv, and Xia-Bing Zhang. "Fluorescence study on the interaction of human serum albumin with loureirin B." Spectroscopy 24, no. 5 (2010): 547–57. http://dx.doi.org/10.1155/2010/893430.

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The interaction between loureirin B (Lour B) and human serum albumin (HSA) was investigated by fluorescence and UV–vis absorption spectroscopy. Experimental results indicated that loureirin B had a strong ability to quench the intrinsic fluorescence of HSA through a dynamic quenching procedure. The fluorescence quenching data revealed that the quenching constants (KSV) 2.68×104, 3.30×104and 4.10×104l/mol at 300, 310 and 320 K, respectively. Based on the thermodynamic parameters obtained, the positive values of enthalpy change ΔH and entropy change ΔS suggested that hydrophobic forces played a major role in the interaction of Lour B with HSA. According to Förster theory of energy transfer, the distancerbetween HSA and Lour B was calculated to be 2.85 nm. Furthermore, the effect of Lour B on the conformation of HSA was analyzed by synchronous fluorescence and three-dimensional fluorescence spectra.

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Zipfel, Warren R., Rebecca M. Williams, and W. Watt. "Application of Multiphoton Imaging to Study of the Vasculature." Microscopy and Microanalysis 3, S2 (August 1997): 335–36. http://dx.doi.org/10.1017/s1431927600008564.

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Nonlinear or multiphoton fluorescence microscopy utilizes the simultaneous absorption of two (or three) longer wavelength photons to excite fluorophores (Denk et.al., 1990). For example, UV absorbing fluorophores such as DAPI or lndo-1 are excited using 700 nm near infrared light rather than 350 nm UV excitation. This relatively new form of laser scanning fluorescence microscopy has excellent optical sectioning capabilities in thick, highly scattering tissues. The high degree of intrinsic optical sectioning arises from the spatial nature of the excitation dependence, rather than from a confocal aperture or deconvolution algorithm. The fluorescence arising from any point in the specimen depends on the second or third power of the intensity (i.e. two and three photon excitation, respectively). This squaring (or cubing) of the illumination point spread function effectively confines the excitation to a tenth of a femtoliter optical volume when using a high NA lens. 680 to 1100 nm mode-locked lasers producing pulses of 100 femtosecond duration at a repetition rate of 80 Mhz are used to efficiently produce fluorescence excitation at average powers that are usually in the 0.5 to 10 mW range at the sample.

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Ren, Xiaofeng, Xi Zhang, Qiufang Liang, Ting Hou, and Huiji Zhou. "Effects of Different Working Modes of Ultrasound on Structural Characteristics of Zein and ACE Inhibitory Activity of Hydrolysates." Journal of Food Quality 2017 (2017): 1–8. http://dx.doi.org/10.1155/2017/7896037.

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Ultrasound was used as a new technology to pretreat protein prior to proteolysis to improve enzymolysis efficiency. The effects of different working modes of ultrasound on the angiotensin I-converting enzyme (ACE) inhibitory activity of zein hydrolysates and the structural characteristics of zein were investigated. The solubility, surface hydrophobicity (H0), ultraviolet-visible (UV-Vis) spectra, intrinsic fluorescence spectra, and circular dichroism (CD) spectra of zein pretreated with ultrasound were determined. All ultrasound pretreatments significantly improved the ACE inhibitory activity of zein hydrolysates (p<0.05). The highest ACE inhibitory activity, representing an increase of 99.21% over the control, was obtained with dual sweeping frequency ultrasound of 33±2 and 68±2 kHz. The effects of single sweeping frequency and dual fixed frequency ultrasound were stronger than those of single fixed frequency ultrasound for improving the ACE inhibitory activity of zein. Structural changes in zein were induced by ultrasound, as confirmed by changes in the solubility, H0, UV-Vis spectra, intrinsic fluorescence spectra, and CD spectra of zein, and these were consistent with the corresponding ACE inhibitory activities of zein hydrolysates. Thus, ultrasound working mode and frequency have significant effects on the structure of zein and the ACE inhibitory activity of zein hydrolysates.

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Gao, Limei, Ying Liu, Xiaofei Wang, Yongfeng Li, and Rong Han. "Lower levels of UV-B light trigger the adaptive responses by inducing plant antioxidant metabolism and flavonoid biosynthesis in Medicago sativa seedlings." Functional Plant Biology 46, no. 10 (2019): 896. http://dx.doi.org/10.1071/fp19007.

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Ultraviolet-B (UV-B) light, as an intrinsic part of sunlight, has more significant effects on plant growth and photomorphogenesis than other organisms due to plant’s sessile growth pattern. In our studies, we have observed that alfalfa (Medicago sativa L.) seedlings are very sensitive to UV-B performance. Seedlings have grown better at lower levels of UV-B light (UV-B irradiation dosage <17.35 μW cm–2 day–1), and have higher UV-resistance. However, the higher levels of UV-B light (UV-B irradiation dosage >17.35 μW cm–2 day–1) has caused severe stress injuries to alfalfa seedlings, and seriously inhibited its growth and development. Chlorophyll biosynthesis and chlorophyll fluorescence have been suppressed under all different dosage of UV-B light conditions. Plant antioxidant enzymes were induced by lower levels of UV-B, but greatly inhibited under higher levels of UV-B light. The contents of flavonoid compounds significantly increased under UV-B light compared with controls, and that was more significant under lower levels of UV-B than higher levels of UV-B. Therefore, we have assumed that the significant induction of plant antioxidant capacity and flavonoid excessive accumulation play a central role in alfalfa UV-B tolerance to lower levels of UV-B irradiation.

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Skandalis, Athanasios, Dimitrios Selianitis, and Stergios Pispas. "PnBA-b-PNIPAM-b-PDMAEA Thermo-Responsive Triblock Terpolymers and Their Quaternized Analogs as Gene and Drug Delivery Vectors." Polymers 13, no. 14 (July 19, 2021): 2361. http://dx.doi.org/10.3390/polym13142361.

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In this work, the ability of thermo-responsive poly [butyl acrylate-b-N-isopropylacrylamide-b-2-(dimethylamino) ethyl acrylate] (PnBA-b-PNIPAM-b-PDMAEA) triblock terpolymer self-assemblies, as well as of their quaternized analogs (PnBA-b-PNIPAM-b-QPDMAEA), to form polyplexes with DNA through electrostatic interactions was examined. Terpolymer/DNA polyplexes were prepared in three different amine over phosphate group ratios (N/P), and linear DNA with a 2000 base pair length was used. In aqueous solutions, the terpolymers formed aggregates of micelles with mixed PNIPAM/(Q)PDMAEA coronas and PnBA cores. The PnBA-b-PNIPAM-b-PDMAEA terpolymers’ micellar aggregates were also examined as carriers for the model hydrophobic drug curcumin (CUR). The complexation ability of the terpolymer with DNA was studied by UV–Vis spectroscopy and fluorescence spectroscopy by investigating ethidium bromide quenching. Fluorescence was also used for the determination of the intrinsic fluorescence of the CUR-loaded micellar aggregates. The structural characteristics of the polyplexes and the CUR-loaded aggregates were investigated by dynamic and electrophoretic light scattering techniques. Polyplexes were found to structurally respond to changes in solution temperature and ionic strength, while the intrinsic fluorescence of encapsulated CUR was increased at temperatures above ambient.

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Řezáčová, Barbora, Yves-Marie Coïc, Christian Zentz, Pierre-Yves Turpin, and Josef Štěpánek. "Spectroscopic Determination of pKa Constants of MADS Box Segments." Spectroscopy: An International Journal 27 (2012): 455–61. http://dx.doi.org/10.1155/2012/674032.

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We have introduced a new promising approach for the determination of pKa constants of oligopeptide intrinsic fluorophores and spectral components referring to their differently charged states. The method is based on the factor analysis of multiwavelength spectroscopic pH titration data. As an illustration, we present its application on the study of short segments of the MADS box, which is a highly conserved sequence of a so-called family of transcription factors, by techniques of UV absorption and fluorescence spectroscopies. Investigated oligopeptides contain no tryptophan but one tyrosine serving as an intrinsic fluorophore and absorber. The results indicate both good sensitivity and spectroscopic selectivity of our method, which thus may be considered as a complementary technique to conventional electrochemical methods.

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Gorgieva, Selestina, Darinka Fakin, and Alenka Ojstršek. "Confocal Fluorescence Microscopy as a Tool for Assessment of Photoluminescent Pigments Print on Polyester Fabric." TEKSTILEC 64, no. 1 (January 14, 2021): 16–24. http://dx.doi.org/10.14502/tekstilec2021.64.16-24.

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The size and distribution of the photoluminescent pigment particles within the selected binder may affect the quality and appearance of the final print significantly. Yet, the techniques for precise evaluation of size distri¬bution of the pigment particles within a 3D fabric space are rather limited, based on their intrinsic fluorescent properties. The presented work demonstrates a simple screen-printing process for the sustainable application of three different types of commercial fluorescent pigments on polyester (PES) fabric, using polydimethylsiloxane (PDMS) as a binder. A comprehensive toolbox was used to compare and study different commercial photo¬luminescent pigments and their corresponding prints, by means of size distribution and concentration effect of emission intensity, including Confocal Fluorescence Microscopy (CFM) and Scanning Electron Microscopy (SEM) in combination with complementary spectroscopic techniques, i.e. Energy Dispersive X-ray Spectroscopy (EDX) and Ultraviolet-visible (UV-vis) spectroscopy. The focus is on CFM utilised as a non-destructive tool, used for the evaluation of photoluminescent pigments´ spatial distribution within printing pastes, as well as on/within the PES fabrics.

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Mishra, Hirdyesh, Anatoliy Dragan, and Chris D. Geddes. "UV to NIR Surface Plasmon Coupled and Metal-Enhanced Fluorescence Using Indium Thin Films: Application to Intrinsic (Label-less) Protein Fluorescence Detection." Journal of Physical Chemistry C 115, no. 35 (August 11, 2011): 17227–36. http://dx.doi.org/10.1021/jp106671t.

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Kim, Min Sun, and Chong Sook Paik Sung. "Intrinsic UV reflection and fluorescence studies for water sorption in polycarbonate, polyurethane and poly(ethylene terephthalate) films." Fibers and Polymers 6, no. 2 (June 2005): 127–30. http://dx.doi.org/10.1007/bf02875603.

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Yan, Xiaodan, Dongjie Yuan, and Dandan Pan. "Interactions of Bromocarbazoles with Human Serum Albumin Using Spectroscopic Methods." Molecules 23, no. 12 (November 28, 2018): 3120. http://dx.doi.org/10.3390/molecules23123120.

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The 1,3,6,8-tetrabromocarbazole and 3-bromocarbazole have attracted great attention in the ecotoxicology field recently as hazardous environmental contaminants. In this study, the quenching mechanism of these two substances binding with human serum albumin (HSA) has been investigated with spectroscopic methods. Through fluorescence quenching and binding site experiments with steady-state fluorescence and UV-Vis spectra, the intrinsic fluorescence of HSA quenched by 1,3,6,8-tetrabromocarbazole and 3-bromocarbazole both in static process, are activated by binding to site II (subdomain IIIA) of the HSA. In addition, it was not only found that the conformation and secondary structure of the proteins changes, but also that their spontaneous binding processes were driven by electrostatic interactions as well as hydrophobic forces for HSA-1,3,6,8-tetrabromocarbazole, and by typical hydrophobic forces for HSA-3-bromocarbazole. The above studies are beneficial to enhance our understanding of the ecotoxicology and environmental behaviors of halogenated carbazoles.

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29

Amin, Fakhra, and Bilqees Bano. "Antidepressant Fluoxetine Modulates the In Vitro Inhibitory Activity of Buffalo Brain Cystatin: A Thermodynamic Study Using UV and Fluorescence Techniques." Biotechnology Research International 2014 (July 24, 2014): 1–7. http://dx.doi.org/10.1155/2014/319397.

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Cystatins constitute a superfamily of homologous proteins. The major role of cystatins is to regulate the unwanted proteolysis and to protect the organism against endogenous proteases released from lysosomes, invading microorganisms and parasites that use cysteine proteases to enter the body. Imbalance in regulation of proteolytic activity may lead to a wide range of human diseases. An enormous progress has been made in understanding of protein degradation process under normal and pathological conditions; infact proteases are now clearly viewed as important drug targets. Fluoxetine a selective serotonin reuptake inhibitor (SSRI) is an antidepressant. It is used to treat major depressive disorders. In the present study binding of fluoxetine to cystatin was studied by UV and fluorescence quenching technique. Intrinsic fluorescence of fluoxetine complexed with purified buffalo brain cystatin (BC) was measured by selectively exciting the tryptophan residues. Gradual quenching was observed on complex formation. When cystatin was added to fluoxetine solutions at a molar ratio of 1 : 0.5, it not only quenched more than half of its fluorescence but also reduced the activity of cystatin. Stern-Volmer plots obtained from experiments carried out at 25°C showed the quenching of fluorescence to be a collisional phenomenon. Our results suggest the prime binding site for fluoxetine on BC to be at or near tryptophan residues. Fluoxetine quenched the fluorescence by a static process, which specifically indicates the formation of a complex.

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30

Wiseman, P. W., J. C. Bouwer, S. Peltier, and M. H. Ellisman. "High Speed Two Photon Excitation Microscopy in Live Cell Imaging using Image Correlation Spectroscopy (ICS)." Microscopy and Microanalysis 7, S2 (August 2001): 22–23. http://dx.doi.org/10.1017/s1431927600026180.

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For live-cell imaging, two-photon excitation microscopy (TPEM) is proving to be a significant technological advancement. The unique features offered by TPEM are the ability to image thick sections, excellent optical sectioning capabilities, low damage to living cells, and less out of focus fluorescence and out of focus photobleaching. of these features, the most useful for the biological microscopist, is optical sectioning. Optical sectioning is an intrinsic property of the two-photon process, whereby, two infrared (IR) photons are absorbed quickly to excite a single UV/blue transition. The probability for exciting a two photon transition is proportional to the instantaneous excitation intensity squared. Therefore, for a focused laser beam, only light at the focal point of the excitation beam excites a fluorescent transition. Thus, the need for confocal apertures and time consuming deconvolution algorithms are, for the most part, eliminated.We have continued to develop and enhance our ability to perform high-speed, two-photon excitation fluorescence microscopy. in 1998, we successfully deployed a prototype, video-rate twophoton laser scanning system (30 frames/sec or faster at reduced scan width) developed with support from Nikon Corporation. That system was built upon a Nikon RCM 8000 confocal microscope.

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31

Pedersen, Morten E., Jesper Østergaard, and Henrik Jensen. "Quantification of Structural Integrity and Stability Using Nanograms of Protein by Flow-Induced Dispersion Analysis." Molecules 27, no. 8 (April 13, 2022): 2506. http://dx.doi.org/10.3390/molecules27082506.

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In the development of therapeutic proteins, analytical assessment of structural stability and integrity constitutes an important activity, as protein stability and integrity influence drug efficacy, and ultimately patient safety. Existing analytical methodologies solely rely on relative changes in optical properties such as fluorescence or scattering upon thermal or chemical perturbation. Here, we present an absolute analytical method for assessing protein stability, structure, and unfolding utilizing Taylor dispersion analysis (TDA) and LED-UV fluorescence detection. The developed TDA method measures the change in size (hydrodynamic radius) and intrinsic fluorescence of a protein during in-line denaturation with guanidinium hydrochloride (GuHCl). The conformational stability of the therapeutic antibody adalimumab and human serum albumin were characterized as a function of pH. The simple workflow and low sample consumption (40 ng protein per data point) of the methodology make it ideal for assessing protein characteristics related to stability in early drug development or when having a scarce amount of sample available.

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32

Steege Gall, Karen E., and Marinella Sandros. "Insulin Structure and Stability Assessed by Intrinsic Fluorescence and Simultaneous UV-vis Absorbance Spectroscopy Coupled with Chemometric Analysis." Biophysical Journal 112, no. 3 (February 2017): 197a. http://dx.doi.org/10.1016/j.bpj.2016.11.1091.

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33

SHING, CHRISTOPHER, LIQIAO QIN, and SHALYA SAWYER. "BIO-SENSING SENSITIVITY OF A NANOPARTICLE BASED ULTRAVIOLET PHOTODETECTOR." International Journal of High Speed Electronics and Systems 20, no. 03 (September 2011): 505–13. http://dx.doi.org/10.1142/s0129156411006799.

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Bio-sensing sensitivity of a spectrally selective nanoparticle based ultraviolet (UV) photodetector is characterized in comparison to a silicon photodiode and a photomultiplier tube (PMT). The nanoparticle based photodetector is comprised of poly-vinyl alcohol (PVA) coated zinc-oxide ( ZnO ) nanoparticles deposited on an aluminum-gallium-nitride ( AlGaN ) epitaxially grown substrate. The sensitivity was determined by measuring the fluorescence intensity of the native fluorophore, tryptophan, in Escherichia coli (E-coli, ATCC-25922) cells. Tryptophan intrinsically fluoresces with a peak at 340 nm under 280 nm UV light illumination. It is shown that this detector can sense the concentration of E-coli to 2.5 × 108 cfu/mL while the silicon photodiode cannot detect the intrinsic fluorescence at all. Nevertheless, the PMT outperformed the ZnO nanoparticle- AlGaN substrate based photodetector with the ability to sense E-coli concentrations to 3.91 × 106 cfu/mL. However, because PMT based systems are commonly limited by high dark current, susceptible to environmental changes, sensitive to ambient light, are not spectrally selective and have high power consumption, biological detection systems comprised of these ZnO nanoparticle- AlGaN substrate based photodetectors can be more effective for near real time characterization of potential bacterial contamination.

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Vasconcelos, Maydla dos Santos, Wilson Espíndola Passos, Caroline Honaiser Lescanos, Ivan Pires de Oliveira, Magno Aparecido Gonçalves Trindade, Anderson Rodrigues Lima Caires, and Rozanna Marques Muzzi. "Fluorescence Spectroscopy Applied to Monitoring Biodiesel Degradation: Correlation with Acid Value and UV Absorption Analyses." Journal of Analytical Methods in Chemistry 2018 (2018): 1–11. http://dx.doi.org/10.1155/2018/4175843.

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The techniques used to monitor the quality of the biodiesel are intensely discussed in the literature, partly because of the different oil sources and their intrinsic physicochemical characteristics. This study aimed to monitor the thermal degradation of the fatty acid methyl esters of Sesamum indicum L. and Raphanus sativus L. biodiesels (SILB and RSLB, resp.). The results showed that both biodiesels present a high content of unsaturated fatty acids, ∼84% (SILB) and ∼90% (RSLB). The SILB had a high content of polyunsaturated linoleic fatty acid (18 : 2), about 49%, and the oleic monounsaturated (18 : 1), ∼34%. On the other hand, RSLB presented a considerable content of linolenic fatty acid (18 : 3), ∼11%. The biodiesel samples were thermal degraded at 110°C for 48 hours, and acid value, UV absorption, and fluorescence spectroscopy analysis were carried out. The results revealed that both absorption and fluorescence presented a correlation with acid value as a function of degradation time by monitoring absorptions at 232 and 270 nm as well as the emission at 424 nm. Although the obtained correlation is not completely linear, a direct correlation was observed in both cases, revealing that both properties can be potentially used for monitoring the biodiesel degradation.

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35

Samaroo, Diana, Mai Zahran, Andrew C. Wills, Johnny Guevara, and Alexandra Tatonetti. "In vitro interaction and computational studies of glycosylated photosensitizers with plasma proteins." Journal of Porphyrins and Phthalocyanines 23, no. 04n05 (April 2019): 437–52. http://dx.doi.org/10.1142/s1088424619500275.

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A series of glycosylated photosensitizers (porphyrin, chlorin, and isobacteriochlorin) in the presence of plasma proteins: bovine serum albumin (BSA) and human serum albumin (HSA), were investigated in a buffer at pH 7.4, using ultraviolet-visible (UV-vis) absorption and fluorescence spectroscopies. Due to the excitation of the tryptophan residue of BSA and HSA, its fluorescence emission was monitored around 340 nm. During each titration experiment and with each addition of the corresponding glycosylated photosensitizer, there was a concentration-dependent quenching of the intrinsic fluorescence of BSA and HSA. Using Stern–Volmer and double logarithmic plots we determined that fluorescence quenching was static for all molecules. We calculated the average binding constant for BSA and HSA for each porphyrin-type compound. To support our experimental studies, computational molecular docking and molecular dynamics simulations were used to identify the binding sites and binding poses of the each of the glycosylated photosensitizers onto BSA and HSA. The three compounds are binding to the Hemin site located in the subdomain IB of BSA forming strong interactions with Trp134, while they are binding to the subdomain IIA of HSA close to the Sudlow’s site I, and interacting with Trp214.

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36

Zhou, Hong-Wei, Yan Xu, and Hai-Meng Zhou. "Activity and conformational changes of horseradish peroxidase in trifluoroethanol." Biochemistry and Cell Biology 80, no. 2 (April 1, 2002): 205–13. http://dx.doi.org/10.1139/o02-003.

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The effect of trifluoroethanol (TFE) on horseradish peroxidase (HRP) was determined using activity assay and spectral analysis including optical absorption, circular dichroism (CD), and intrinsic fluorescence. The enzyme activity increased nearly twofold after incubation with 525% (v/v) concentrations of TFE. At these TFE concentrations, the tertiary structure of the protein changed little, while small changes occurred at the active site. Further increases in the TFE concentration (2540%) decreased the enzyme activity until at 40% TFE the enzyme was completely inactivated. The α-helix content of the protein increased at high TFE concentrations, while near-UV CD, Soret CD, and intrinsic fluorescence indicated that the tertiary structure was destroyed. Polyacrylamide gel electrophoresis results indicated that the surface charge of the enzyme was changed at TFE concentrations greater than 20%, and increasing concentrations of TFE reduced the enzyme molecular compactness. A scheme for the unfolding of HRP in TFE was suggested based on these results. The kinetics of absorption change at 403 nm in 40% TFE followed a two-phase course. Finally, HRP incubated with TFE was more sensitive to urea denaturation, which suggested that the main effect of TFE on HRP was the disruption of hydrophobic interactions.Key words: horseradish peroxidase, trifluoroethanol, unfolding, Soret.

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37

Ranjbar, Samira, Yalda Shokoohinia, Sirous Ghobadi, Nooshin Bijari, Saeed Gholamzadeh, Nastaran Moradi, Mohammad Reza Ashrafi-Kooshk, Abbas Aghaei, and Reza Khodarahmi. "Studies of the Interaction between Isoimperatorin and Human Serum Albumin by Multispectroscopic Method: Identification of Possible Binding Site of the Compound Using Esterase Activity of the Protein." Scientific World Journal 2013 (2013): 1–13. http://dx.doi.org/10.1155/2013/305081.

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Isoimperatorin is one of the main components ofPrangos ferulaceaas a linear furanocoumarin and used as anti-inflammatory, analgesic, antispasmodic, and anticancer drug. Human serum albumin (HSA) is a principal extracellular protein with a high concentration in blood plasma and carrier for many drugs to different molecular targets. Since the carrying of drug by HSA may affect on its structure and action, we decided to investigate the interaction between HSA and isoimperatorin using fluorescence and UV spectroscopy. Fluorescence data indicated that isoimperatorin quenches the intrinsic fluorescence of the HSA via a static mechanism and hydrophobic interaction play the major role in the drug binding. The binding average distance between isoimperatorin and Trp 214 of HSA was estimated on the basis of the theory of Förster energy transfer. Decrease of protein surface hydrophobicity (PSH) was also documented upon isoimperatorin binding. Furthermore, the synchronous fluorescence spectra show that the microenvironment of the tryptophan residues does not have obvious changes. Site marker compettive and fluorescence experiments revealed that the binding of isoimperatorin to HSA occurred at or near site I. Finally, the binding details between isoimperatorin and HSA were further confirmed by molecular docking and esterase activity inhibition studies which revealed that drug was bound at subdomain IIA.

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38

Bundke, U., B. Reimann, B. Nillius, R. Jaenicke, and H. Bingemer. "Development of a bioaerosol single particle detector (BIO IN) for the fast ice nucleus chamber FINCH." Atmospheric Measurement Techniques Discussions 2, no. 5 (October 6, 2009): 2403–22. http://dx.doi.org/10.5194/amtd-2-2403-2009.

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Abstract. In this work we present the setup and first tests of our new BIO IN detector. This detector is designed to classify atmospheric ice nuclei (IN) for their biological content. Biological material is identified via its auto-fluorescence (intrinsic fluorescence) after irradiation with UV radiation. Ice nuclei are key substances for precipitation development via the Bergeron–Findeisen process. The level of scientific knowledge regarding origin and climatology (temporal and spatial distribution) of IN is very low. Some biological material is known to be active as IN even at relatively high temperatures of up to –2°C (e.g. pseudomonas syringae bacteria). These biological IN could have a strong influence on the formation of clouds and precipitation. We have designed the new BIO IN sensor to analyze the abundance of IN of biological origin. The instrument will be flown on one of the first missions of the new German research aircraft ''HALO'' (High Altitude and LOng Range).

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39

Liu, Linlin, Jianhua Zeng, Bingyu Sun, Na Zhang, Yinyuan He, Yanguo Shi, and Xiuqing Zhu. "Ultrasound-Assisted Mild Heating Treatment Improves the Emulsifying Properties of 11S Globulins." Molecules 25, no. 4 (February 17, 2020): 875. http://dx.doi.org/10.3390/molecules25040875.

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Ultrasonic technology is often used to modify proteins. Here, we investigated the effects of ultrasound alone or in combination with other heating methods on emulsifying properties and structure of glycinin (11S globulin). Structural alterations were assessed with Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS–PAGE), intrinsic fluorescence spectroscopy, ultraviolet (UV) absorption spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. The size distribution and zeta-potential of 11S globulin were evaluated with a particle size analyzer. An SDS-PAGE analysis showed no remarkable changes in the primary structure of 11S globulin. Ultrasound treatment disrupted the 11S globulin aggregates into small particles with uniform size, narrowed their distribution and increased their surface charge density. Fluorescent spectroscopy and second-derivative UV spectroscopy revealed that ultrasound coupled with heating induced partial unfolding of 11S globulin, increasing its flexibility and hydrophobicity. FTIR further showed that the random coil and α-helix contents were higher while β-turn and β-sheet contents were lower in ultrasound combined with heating group compared to the control group. Consequently, the oil-water interface entirely distributed protein and reduced the surface tension. Moreover, ultrasound combined with heating at 60 °C increased the emulsifying activity index and emulsifying stability index of 11S globulins by 6.49-folds and 2.90-folds, respectively. These findings suggest that ultrasound combined with mild heating modifies the emulsification properties of 11S globulin.

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40

RADU, LILIANA, I. MIHAILESCU, and DOINA GAZDARU. "Chromatin structure modification in an excimer laser field." Laser and Particle Beams 20, no. 2 (April 2002): 299–302. http://dx.doi.org/10.1017/s0263034602202219.

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Chromatin is the complex of deoxyribonucleic acid (DNA) with proteins that exists in eukaryotic cell nuclei. Chromatin was extracted from livers of Wistar rats and subjected to a 248-nm excimer laser radiation, in doses of 0.5–3 MJ/m2. An UV excimer laser Iofan 1701, with 40-mJ dose/pulse and frequency of 30 Hz was used. The radiolysis of chromatin was analyzed by (1) 1H-NMR spectroscopy, (2) steady-state fluorescence, (3) time-resolved fluorescence, and (4) fluorescence resonance energy transfer (FRET) methods. The laser action on chromatin determines bigger values of the transverse relaxation time (T2), which indicates less bound water in the chromatin structure, therefore a more injured one. The chromatin intrinsic fluorescence decreases on laser action, proving the destruction of the chromatin protein structure. By the time-resolved fluorescence we established that the relative contribution of the excited state lifetime of bound ethidium bromide to chromatin DNA diminishes with the laser dose. This denotes single- and double-strand breaks produced in DNA structure. By the FRET method, the energy transfer efficiency and the distance between dansyl chloride and acridine orange coupled at chromatin were determined. The distance increases with laser action. The determination of the chromatin structure modification in an excimer laser field can be of real interest in medical applications.

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Sun, Qifan, Xin Gao, Hongna Bi, Yingbo Xie, and Lin Tang. "Assessment of Binding Interaction between Bovine Lactoferrin and Tetracycline Hydrochloride: Multi-Spectroscopic Analyses and Molecular Modeling." Molecules 23, no. 8 (July 30, 2018): 1900. http://dx.doi.org/10.3390/molecules23081900.

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In this paper, the interaction between bovine lactoferrin (bLf) and tetracycline hydrochloride (TCH) was researched by microscale thermophoresis (MST), multi-spectroscopic methods, and molecular docking techniques. Normal fluorescence results showed that TCH effectively quenched the intrinsic fluorescence of bLf via static quenching. Moreover, MST confirmed that the combination force between bLf and TCH was very strong. Thermodynamic parameters and molecular docking further revealed that electrostatic forces, van der Waals, and hydrogen bonding forces played vital roles in the interaction between bLf and TCH. The binding distance and energy transfer efficiency between TCH and bLf were 2.81 nm and 0.053, respectively. Moreover, the results of circular dichroism spectra (CD), ultraviolet visible (UV-vis) absorption spectra, fluorescence Excitation-Emission Matrix (EEM) spectra, and molecular docking verified bLf indeed combined with TCH, and caused the changes of conformation of bLf. The influence of TCH on the functional changes of the protein was studied through the analysis of the change of the bLf surface hydrophobicity and research of the binding forces between bLf and iron ion. These results indicated that change in the structure and function of bLf were due to the interaction between bLf and TCH.

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42

Tang, Hong-Min, and Hong Yu. "Intermediate studies on refolding of arginine kinase denatured by guanidine hydrochloride." Biochemistry and Cell Biology 83, no. 2 (April 1, 2005): 109–14. http://dx.doi.org/10.1139/o04-131.

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The refolding course and intermediate of guanidine hydrochloride (GuHCl)-denatured arginine kinase (AK) were studied in terms of enzymatic activity, intrinsic fluorescence, 1-anilino-8-naphthalenesulfonte (ANS) fluorescence, and far-UV circular dichroism (CD). During AK refolding, the fluorescence intensity increased with a significantly blue shift of the emission maximum. The molar ellipticity of CD increased to close to that of native AK, as compared with the fully unfolded AK. In the AK refolding process, 2 refolding intermediates were observed at the concentration ranges of 0.8–1.0 mol/L and 0.3–0.5 mol GuHCl/L. The peak position of the fluorescence emission and the secondary structure of these conformation states remained roughly unchanged. The tryptophan fluorescence intensity increased a little. However, the ANS fluorescence intensity significantly increased, as compared with both the native and the fully unfolded states. The first refolding intermediate at the range of 0.8–1.0 mol GuHCl/L concentration represented a typical "pre-molten globule state structure" with inactivity. The second one, at the range of 0.3–0.5 mol GuHCl/L concentration, shared many structural characteristics of native AK, including its secondary and tertiary structure, and regained its catalytic function, although its activity was lower than that of native AK. The present results suggest that during the refolding of GuHCl-denatured AK there are at least 2 refolding intermediates; as well, the results provide direct evidence for the hierarchical mechanism of protein folding.Key words: arginine kinase, guanidine-denatured, refolding, intermediate, molten globule state.

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43

Pöhlker, C., J. A. Huffman, and U. Pöschl. "Autofluorescence of atmospheric bioaerosols – fluorescent biomolecules and potential interferences." Atmospheric Measurement Techniques 5, no. 1 (January 9, 2012): 37–71. http://dx.doi.org/10.5194/amt-5-37-2012.

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Abstract. Primary biological aerosol particles (PBAP) are an important subset of air particulate matter with a substantial contribution to the organic aerosol fraction and potentially strong effects on public health and climate. Recent progress has been made in PBAP quantification by utilizing real-time bioaerosol detectors based on the principle that specific organic molecules of biological origin such as proteins, coenzymes, cell wall compounds and pigments exhibit intrinsic fluorescence. The properties of many fluorophores have been well documented, but it is unclear which are most relevant for detection of atmospheric PBAP. The present study provides a systematic synthesis of literature data on potentially relevant biological fluorophores. We analyze and discuss their relative importance for the detection of fluorescent biological aerosol particles (FBAP) by online instrumentation for atmospheric measurements such as the ultraviolet aerodynamic particle sizer (UV-APS) or the wide issue bioaerosol sensor (WIBS). In addition, we provide new laboratory measurement data for selected compounds using bench-top fluorescence spectroscopy. Relevant biological materials were chosen for comparison with existing literature data and to fill in gaps of understanding. The excitation-emission matrices (EEM) exhibit pronounced peaks at excitation wavelengths of ~280 nm and ~360 nm, confirming the suitability of light sources used for online detection of FBAP. They also show, however, that valuable information is missed by instruments that do not record full emission spectra at multiple wavelengths of excitation, and co-occurrence of multiple fluorophores within a detected sample will likely confound detailed molecular analysis. Selected non-biological materials were also analyzed to assess their possible influence on FBAP detection and generally exhibit only low levels of background-corrected fluorescent emission. This study strengthens the hypothesis that ambient supermicron particle fluorescence in wavelength ranges used for most FBAP instruments is likely to be dominated by biological material and that such instrumentation is able to discriminate between FBAP and non-biological material in many situations. More detailed follow-up studies on single particle fluorescence are still required to reduce these uncertainties further, however.

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Pöhlker, C., J. A. Huffman, and U. Pöschl. "Autofluorescence of atmospheric bioaerosols – fluorescent biomolecules and potential interferences." Atmospheric Measurement Techniques Discussions 4, no. 5 (September 16, 2011): 5857–933. http://dx.doi.org/10.5194/amtd-4-5857-2011.

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Abstract. Primary biological aerosol particles (PBAP) are an important subset of air particulate matter with a substantial contribution to the organic aerosol fraction and potentially strong effects on public health and climate. Recent progress has been made in PBAP quantification by utilizing real-time bioaerosol detectors based on the principle that specific organic molecules of biological origin such as proteins, coenzymes, cell wall compounds and pigments exhibit intrinsic fluorescence. The properties of many fluorophores have been well documented, but it is unclear which are most relevant for detection of atmospheric PBAP. The present study provides a systematic synthesis of literature data on potentially relevant biological fluorophores. We analyze and discuss their relative importance for the detection of fluorescent biological aerosol particles (FBAP) by online instrumentation for atmospheric measurements such as the ultraviolet aerodynamic particle sizer (UV-APS) or the wide issue bioaerosol sensor (WIBS). In addition, we provide new laboratory measurement data for selected compounds using bench-top fluorescence spectroscopy. Relevant biological materials were chosen for comparison with existing literature data and to fill in gaps of understanding. The excitation-emission matrices (EEM) exhibit pronounced peaks at excitation wavelengths of ~280 nm and ~360 nm, confirming the suitability of light sources used for online detection of FBAP. They also show, however, that valuable information is missed by instruments that do not record full emission spectra at multiple wavelengths of excitation, and co-occurrence of multiple fluorophores within a detected sample will likely confound detailed molecular analysis. Selected non-biological materials were also analyzed to assess their possible influence on FBAP detection and generally exhibit only low levels of background-corrected fluorescent emission. This study strengthens the hypothesis that ambient supermicron particle fluorescence in wavelength ranges used for most FBAP instruments is likely to be dominated by biological material and that such instrumentation is able to discriminate between FBAP and non-biological material in many situations. More detailed follow-up studies on single particle fluorescence are still required to reduce these uncertainties further, however.

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45

Schneckenburger, H., P. Gessler, and I. Pavenstädt-Grupp. "Measurements of mitochondrial deficiencies in living cells by microspectrofluorometry." Journal of Histochemistry & Cytochemistry 40, no. 10 (October 1992): 1573–78. http://dx.doi.org/10.1177/40.10.1527376.

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Microspectrofluorometric methods were developed for detection of mitochondrial metabolites and marker molecules in living cells. After excitation in the near UV and blue spectral ranges, respiratory-deficient strains of Saccharomyces cerevisiae showed higher levels of intrinsic fluorescence than corresponding wild types. This may be attributed to an increased emission by NADH and flavin molecules of the mutants. After incubation with the mitochondrial marker rhodamine 123, there was a strong indication that an energy transfer from flavin to rhodamine molecules occurred, which was more pronounced for the respiratory-deficient yeast strains. Skin fibroblasts obtained from patients with mitochondrial diseases showed approximately the same levels of autofluorescence and energy transfer but higher variances than a control cell line. These higher variances may result from a coexistence of intact and defective mitochondria.

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Zhao, Chun Lin, Li Xing, Xiao Hong Liang, Jun Hui Xiang, Fu Shi Zhang, Li Jie Cui, Bo Song, Shi Wei Chen, Hua Zheng Sai, and Zhen You Li. "Photoluminescence Enhancement of CdS Nanocrystals Fabricated on Dithiocarbamate Functionalized PET Substrates." Key Engineering Materials 512-515 (June 2012): 1511–15. http://dx.doi.org/10.4028/www.scientific.net/kem.512-515.1511.

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Cadmium sulfide (CdS) nanocrystals (NCs) were self-assembled and in-situ immobilized on the dithiocarbamate (DTCs)-functionalized polyethylene glycol terephthalate (PET) substrates between the organic (carbon disulfide diffused in n-hexane) –aqueous (ethylenediamine and Cd2+ dissolved in water) interface at room temperature. Powder X-ray diffraction measurement revealed the hexagonal structure of CdS nanocrystals. Morphological studies performed by scanning electron microscopy (SEM) and high-resolution transmission electron microscope (HRTEM) showed the island-like structure of CdS nanocrystals on PET substrates, as well as energy-dispersive X-ray spectroscopy (EDS) confirmed the stoichiometries of CdS nanocrystals. The optical properties of DTCs modified CdS nanocrystals were thoroughly investigated by ultraviolet-visible absorption spectroscopy (UV-vis) and fluorescence spectroscopy. The as-prepared DTCs present intrinsic hydrophobicity and strong affinity for CdS nanocrystals.

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47

Al-Omari, Saleh. "Separation of static and dynamic thermodynamic parameters for the interaction between pyropheophorbide methyl ester and copper." Journal of Porphyrins and Phthalocyanines 18, no. 04 (April 2014): 297–304. http://dx.doi.org/10.1142/s1088424614500023.

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The interaction between pyropheophorbide methyl ester (PPME) and the ionic metal of copper ( Cu 2+) was investigated using fluorescence and UV-vis techniques. By analysis of the fluorescence spectra, it was observed that Cu 2+ has a strong ability to quench the intrinsic fluorescence of PPME through dynamic and static quenching process. The binding constants of Cu 2+ with PPME were determined at different temperatures depending on the results of fluorescence quenching. Based on the modified form of the Stern–Volmer equation, static binding constant (kS) and the dynamic binding constant (kD) of Cu 2+-PPME association were obtained at different temperatures. The static thermodynamic function of the enthalpy change (ΔHS), the dynamic thermodynamic function of the enthalpy change (ΔHD), the static thermodynamic function of the entropy change (ΔSS), and the dynamic thermodynamic function of the entropy change (ΔSD) for the binding interaction were determined according to the van't Hoff equation. The values of static Gibbs free energy change (ΔGS) and dynamic Gibbs free energy change (ΔGD) were determined to be negative indicating that the interaction process was a spontaneous. ΔHD and ΔSD values were positive indicating that the dynamic quenching process of Cu 2+-PPME interaction was driven mainly by hydrophobic forces. For the static binding quenching, ΔHS and ΔSS values were negative which indicated that hydrogen bond, electrostatic interaction, and van der Waals interaction were important driving forces for PPME- Cu 2+ association. Both static and dynamic fluorescence quenching were related to the distance between PPME and Cu 2+ indicating that the electron transfer process occurred.

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48

Chowdary, Tirumala Kumar, Bakthisaran Raman, Tangirala Ramakrishna, and Ch Mohan Rao. "Interaction of mammalian Hsp22 with lipid membranes." Biochemical Journal 401, no. 2 (December 21, 2006): 437–45. http://dx.doi.org/10.1042/bj20061046.

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Hsp22/HspB8 is a member of the small heat-shock protein family, whose function is not yet completely understood. Our immunolocalization studies in a human neuroblastoma cell line, SK-N-SH, using confocal microscopy show that a significant fraction of Hsp22 is localized to the plasma membrane. We therefore investigated its interactions with lipid vesicles in vitro. Intrinsic tryptophan fluorescence is quenched in the presence of lipid vesicles derived from either bovine brain lipid extract or purified lipids. Time-resolved fluorescence studies show a decrease in the lifetimes of the tryptophan residues. Both of these results indicate burial of some tryptophan residues of Hsp22 upon interaction with lipid vesicles. Membrane interactions also lead to increase in fluorescence polarization of Hsp22. Gel-filtration chromatography shows that Hsp22 binds stably with lipid vesicles; the extent of binding depends on the nature of the lipid. Hsp22 binds more strongly to vesicles made of lipids containing a phosphatidic acid, phosphatidylinositol or phosphatidylserine headgroup (known to be present in the inner leaflet of plasma membrane) compared with lipid vesicles made of a phosphatidylcholine head-group alone. Far-UV CD spectra reveal conformational changes upon binding to the lipid vesicles or in membrane-mimetic solvent, trifluoroethanol. Thus our fluorescence, CD and gel-filtration studies show that Hsp22 interacts with membrane and this interaction leads to stable binding and conformational changes. The present study therefore clearly demonstrates that Hsp22 exhibits potential membrane interaction that may play an important role in its cellular functions.

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TAYYAB, SAAD, TUAN NOR NAZIAN TUAN MAT, and ADYANI AZIZAH ABD HALIM. "DIFFERENTIAL STABILIZING EFFECTS OF BUFFERS ON STRUCTURAL STABILITY OF BOVINE SERUM ALBUMIN AGAINST UREA DENATURATION." Latin American Applied Research - An international journal 52, no. 1 (January 1, 2022): 7–13. http://dx.doi.org/10.52292/j.laar.2022.738.

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The conformational stability of bovine serum albumin (BSA) against urea denaturation was investigated in aqueous solutions both in the absence and presence of buffers. Various buffers differing in polar and nonpolar characters such as sodium phosphate, Tris-HCl, (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid) HEPES and [3-(N-morpholino)propanesulfonic acid] MOPS buffers were used in this study. Urea-induced structural changes were analyzed using different probes, i.e., intrinsic fluorescence, ANS fluorescence and UV-difference spectral signal. Presence of different buffers in the incubation medium offered different degrees of resistance to the protein against urea-induced structural changes compared to those obtained in water (in the absence of buffers). A similar trend of buffer-induced structural resistance was noticed with three different probes. The stabilizing effect of these buffers followed the order: MOPS > HEPES > sodium phosphate > Tris-HCl > water. As found in MOPS and HEPES buffers, the highest stability of BSA can be attributed to the presence of morpholine and piperazine rings, respectively, in their structures. These groups might have produced a hydrophobic environment around the protein surface, thus stabilizing protein conformation against urea denaturation.

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Stepanenko, Olga V., Olga I. Povarova, Olesya V. Stepanenko, Alexander V. Fonin, Irina M. Kuznetsova, Konstantin K. Turoverov, Maria Staiano, and Sabato D'Auria. "Structure and stability of D-galactose/D-glucose-binding protein. The role of D-glucose binding and Ca ion depletion." Spectroscopy 24, no. 3-4 (2010): 355–59. http://dx.doi.org/10.1155/2010/392428.

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The effects of guanidine hydrochloride (GdnHCl) on the structure and stability of the D-galactose/D-glucose-binding protein fromEscherichia coli(GGBP) and its complex with D-glucose (GGBP/Glc) were investigated by intrinsic protein fluorescence and far-UV circular dichroism (CD). The role of calcium in the stability of the protein structure was also studied. It was shown that the processes of GGBP and GGBP/Glc unfolding induced by GdnHCl followed one-step reversible denaturation mechanism. The obtained data showed that the binding of glucose to GGBP resulted in an increase of the protein stability towards the actions of the GdnHCl which made protein unfolding more cooperative. The stabilities of GGBP alone, GGBP in the presence of glucose, GGBP-depleted calcium (GGBP-Ca), and GGBP/Glc-depleted calcium (GGBP/Glc-Ca) were characterized by difference of Gibbs free energies.

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Journal articles on the topic 'Intrinsic UV fluorescence'

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