<i>Practical Fluorescence: Theory, Methods and Techniques</i>

Guilbault, G. G.; Norris, J.D.

doi:10.1063/1.3068881

Cited by 39 publications

(44 citation statements)

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“…The quenching of the tryptophanyl fluorescence of a protein by its prosthetic group is due to resonance-energy transfer, provided this group is within a limited distance and the emission spectrum of tryptophan overlaps the absorbance spectrum of the prosthetic group (Guilbault, 1973). A disruption of the conformational integrity at the active site and therefore the spatial arrangement between the bound nicotinamide ring of the added coenzyme and the indole ring of tryptophan at or near the active site could lead to a decrease in the efficiency of the resonanceenergy transfer.…”

Section: Discussionmentioning

confidence: 99%

Conformation and Microenvironment of the Active Site of Xylose Reductase Inferred by Fluorescent Chemoaffinity Labeling

Rawat

Rao

1997

European Journal of Biochemistry

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Conformation and microenvironment at the active site of xylose reductase (XR) from Neurospora crassa was probed with fluorescent chemoaffinity labeling (FCAL) using o-phthalaldehyde as a chemical initiator. Formation of a single isoindole derivative resulted in complete inactivation of the enzyme as judged by spectroscopic and fluorescence studies. Kinetic analysis of the 2,4,6-trinitrobenzenesulfonicacid-modified XR implicated the presence of an essential lysine residue at the active site of XR. Modification of lysine in XR abolished the ability of the enzyme to form isoindole derivative, indicating that the lysine residue involved in the reaction with 2,4,6-trinitrobenzenesulfonic acid and o-phthalaldehyde is the same and that the probe o-phthalaldehyde is directed to the active site.Fluorescence studies revealed that inactivation of XR by Gdn/HCl precedes gross conformational change and the possibility of secondary-conformational change was eliminated by acrylamide quenching studies. The enzyme inactivated by low concentrations of Gdn/HCl retained its ability to form the fluorescent XR-isoindole derivative indicating that inactivation is not due to conformational changes at or near the active site of XR. Gdn/HCI also had no effect on the high-affinity and low-affinity NADPH-binding sites of XR. Energy-transfer experiments further revealed structural integrity at the active site of the GdnlHCl-inactivated XR. Changes in the fluorescence emission maximum of l-@-hydroxyethylthio)-2-P hydroxyethyl isoindole (EA adduct) in solvents of varying polarity was studied, the data obtained were utilized to interpret the fluorescence behaviour of XR-isoindole derivative and assess the polarity at the active site. Experimental evidence presented here serves to suggest that the inactivation of XR by G d d HC1 precedes conformational changes at the active site located in a microenvironment of low polarity.

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Section: Discussionmentioning

confidence: 99%

Conformation and Microenvironment of the Active Site of Xylose Reductase Inferred by Fluorescent Chemoaffinity Labeling

Rawat

Rao

1997

European Journal of Biochemistry

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“…With the loss of energy due to molecular excitation, consequently, a decrease in frequency and an increase in wavelength will occur, causing a change in the light emitted. 16,17 Techniques that use fluorescence as a means of evaluation have been used in several areas of research.…”

Section: 5005/jp-journals-10024-2204mentioning

confidence: 99%

Effect of the Curing Temperature of Dental Composites evaluated with a Fluorescent Dye

Silva-Jñnior

Lizarelli

Bagnato

et al. 2018

The Journal of Contemporary Dental Practice

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Aim: With the development of the light-emitting diode (LED) to photo-activate composite resin, greater intensities could be reached without greater elevation of temperature in the mass of the composite resin and in the dental structure arisen from the irradiance in comparison to halogen equipments. This new scenario created a necessity to investigate the influence of temperature over the composite polymerization. Materials and methods:Several curing temperatures 25, 50, 75, and 100°C) were used to polymerize a composite resin (Filtek Z250, 3M ESPE) for 40 and 60 s, using the halogen equipment Gnatus Optilight Digital (halogen) and two LEDs that use a new technology to assembly the diodes: LEC 1000 and bright LEC (MM Optics) (LED 1 and LED 2 respectively). The influence of curing temperature, added by the other variables studied, was evaluated using a methodology developed and improved at IFSC/USP, in which the penetration of a fluorescent dye in the body of the photopolymerized composite resin was quantified using fluorescence spectroscopy.Results: According to the final data submitted to an analysis of variance, the presence of two groups of results could be verified: Between 0 and 25°C, both had a great percentage of the dye penetration compared with other Tcure with a variation in penetration from 69.26 ± 8.19% to 90.99 ± 3.38%. In this analysis, the effects of time and temperature were highly notable (p < 0.05) and the lesser value of dye penetration took place at 60 s of photoactivation This penetration was, in average, smaller with the Tcure of 25°C. The results showed that there was an Araraquara, 14801903, São Paulo, Brazil, e-mail: macieljr@hotmail.com interaction between the equipment and time and between time and temperature; the other group is regarding the Tcure was from 50, 75, and 100°C, despite the p = 0.05, the effect of temperature was notable. The penetration of the dye ranged from 8.87 ± 3.55 to 39.47 ± 8.9%. The effects of equipment and time were highly notable. The penetration with the time of 60 s was in average smaller. Except with the equipment LED 1, the percentages of the dye penetration were greater with the Tcure of 100°C. The smallest average was the Tcure of 50°C and 60 s of photoactivation. Conclusion:Based on the available data regarding the influence of curing temperature on the polymerization process of composite resins, was possible to concluded that small increments of heat increased the degree of conversion. We can assume that the energy supply through the generation of heat by the photopolymerizing devices can function as a heating medium for the reagent system by reducing its viscosity and increasing the mobility and agitation of its components. Clinical significance:The dentist must be aware of the effects that exist between the activation devices on the light output and their heat transmission to the composite and the tooth itself. This heat transmission might create a polymer with better characteristics.

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“…At low concentrations, the dependence of fluorescence irradiation, I f , on the concentration of the dye, C, can be expressed using the simple equation [40] …”

Section: Lif Thermometry Measurementsmentioning

confidence: 99%

Measurement of the temperature non-uniformity in a microchannel heat sink using microscale laser-induced fluorescence

Chamarthy¹,

Garimella²,

Wereley³

2010

International Journal of Heat and Mass Transfer

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Practical Fluorescence: Theory, Methods and Techniques

Cited by 39 publications

References 0 publications

Conformation and Microenvironment of the Active Site of Xylose Reductase Inferred by Fluorescent Chemoaffinity Labeling

Conformation and Microenvironment of the Active Site of Xylose Reductase Inferred by Fluorescent Chemoaffinity Labeling

Effect of the Curing Temperature of Dental Composites evaluated with a Fluorescent Dye

Measurement of the temperature non-uniformity in a microchannel heat sink using microscale laser-induced fluorescence

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