In a FRET experiment designed to monitor conformational changes in T4 lysozyme, the fluorescence intensity fluctuates between 5000 and 10,000 counts per second. Assuming that 7500 counts represents a FRET efficiency of 0.6, what is the change in FRET pair separation distance during the reaction? For the tetramethylrhodamine-texas red FRET pair employed ro = 50. Å. Express your answer to two significant figures and include the appropriate units. HẢ ? Ar = Value Units

In a FRET experiment designed to monitor conformational changes in T4 lysozyme, the fluorescence intensity fluctuates between 5000 and 10,000 counts per second. Assuming that 7500 counts represents a FRET efficiency of 0.6, what is the change in FRET pair separation distance during the reaction? For the tetramethylrhodamine-texas red FRET pair employed ro = 50. Å. Express your answer to two significant figures and include the appropriate units. HẢ ? Ar = Value Units

Principles of Instrumental Analysis

7th Edition

ISBN:9781305577213

Author:Douglas A. Skoog, F. James Holler, Stanley R. Crouch

Publisher:Douglas A. Skoog, F. James Holler, Stanley R. Crouch

Chapter15: Molecular Luminescence Spectrometry

Section: Chapter Questions

Problem 15.15QAP: The following lifetimes were measured for the chloride quenching of quinine sulfate given in Example...

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Why is it reasonable that the Ksp of NiCl2 should be so high? given: NiCl2~~>Ni2+(aq)+2Cl-(aq) ksp=497.504 ksp=[Ni2+][Cl-]^2 [Ni2+]=4.992 [Cl-]=9.983
The observed fluorescence lifetime in the absenceof a quencher is 1.4 ns. In the presence of a quencher thefluorescence lifetime is 0.8 ns. Calculate the quenching efficiency. which is the ratio of the fluorescence quantum yieldsin the presence and absence of the quencher. ¢,/¢,_0
For a molecule, the phosphorescence lifetime without quenching is 1.0 s while with a quencher population of 10-2 M the phosphorescence lifetime is 0.10 s. Calculate the rate constant for phosphorescence assuming that kisc >> (kF + kec + kic). Calculate the rate constant for external conversion of the triplet state (kec’), the quenching rate constant for the triplet state (kq’), and the Stern-Volmer quenching constant. Assume that intersystem crossing from T1 to So is negligible.
During a spectroscopic evaluation of the several solutions of C6H5CH=CHCCl₂ in ethanol using a 1.0 cm spectrophotometric cell, different values of absorbance (A) were obtained, which are given in the following table: 105 x conc. mol dm-3 A time min A 0.446 0.080 0 0.560 C When the reaction of C6H5CH=CHCCl₂ with C₂H5O in an ethanolic medium is followed spectroscopically at a convenient wavelength (2), the following results are found: 0.812 0.145 40 0.283 1.335 1.711 0.240 0.305 80 0.217 120 2.105 0.378 0.168 140 0.149 The values of ε at λ and the rate constant for that reaction are: a. ε = 1.79x10-6 dm³ mol-¹ cm-¹ and k = 0.034 dm³ mol-¹ min-¹ b. ε = 1.79×104 dm³ mol-¹ cm-¹ and k = 0.034 dm³ mol-¹ min-¹ c. ε = 1.79x10-6 dm³ mol-¹ cm-1 and k = 8.9x10-³ dm³ mol-¹ min-¹ d. ε = 1.79×104 dm³ mol-¹ cm-¹ and k = 8.9x10-³ dm³ mol-¹ min¯¹
When benzophenone is illuminated with ultraviolet radiation it is excited into a singlet state. Th is singlet changes rapidly into a triplet, which phosphoresces. Triethylamine acts as a quencher for the triplet. In an experi ment in methanol as solvent, the phosphorescence intensity varied with amine concentration as shown below. A timeresolved laser spectroscopy experiment had also shown that the half-life of the fluorescence in the absence of quencher is 29μs. What is the value of the quenching rate constant kO ?
with amine concentration as shown below. A time-resolved laser spectroscopy experiment had also shown that the half-life of the phosphorescence in the absence of quencher is 29 us. What is the value of k,? [Q/(mmol dm) 1.0 5.0 10.0 I/(arbitrary units) 0.41 0.25 0.16 P17G.4 When benzophenone is exposed to ultraviolet radiation it is excited into a singlet state. This singlet changes rapidly into a triplet, which phosphoresces. Triethylamine acts as a quencher for the triplet. In an experiment in the solvent methanol, the phosphorescence intensity varied
c. Upon mixing CFP-a-p34 with GFP-a-p34 and 3-p34, the fluorescence of CFP drops from 100,000 to 96,000. When CFP-a-p34 is mixed with GFP-B-p34 in the presence of 0.5M GdnHCl the fluorescence of CFP drops from 100,000 to 63,900. If the Förster radius for the donor/acceptor pair is 50Å, how far apart are the donor and acceptor in each case?
The quenching of tryptophan fluorescence by dissolved O₂ gas was monitored by measuring the emission lifetimes at 348 nm in aqueous solutions. [0₂]/(10-² mol dm-³) T/(10-⁹ s) 0 2.3 5.5 8 10.8 2.6 1.5 0.92 0.71 0.57 A. 0.95 E-2 M B. 4.3 E-2 M C. 1.8 E-2 M D. 3.0 E-2 M E. None of the choices From the data above, predict the value of [0₂] required to decrease the intensity of tryptophan emission to 50% of the unquenched value.
Please label importank peaks (isotope peaks, fragments, molecular ions (if present)) please contain location of peaks and likely identity D-glucose C6H1206 (Mass of molecular ion: 180) 100 - MS-NU-9127 80 40 25 50 75 100 12 m/z Source Temperature: 200 °C Sample Temperature: 140 °C Direct, 75 ev 60 20 Relative Intensity
Fe2+ is used as a catalyst for the oxidation of luminal by H,02. The resulting chemiluminescence increases linearly with Fe2* concentration. Exactly 1.0 mL of water was added to a 5.0-mL sample of an unknown Fe2* solution, followed by 2.0 mL of H20, and 1.0 mL of luminol. The chemiluminescence intensity was found to be 16.1. When 1.0 mL of 4.75 x 10 SM Fe2+ solution was added to another 5.0-mL of the unknown Fe2+ solution, followed by 2.0 mL of H,0, and 1.0 mL of luminol, the chemiluminescence intensity was 39.6. Calculate the concentration of iron ions in the sample. O 6.5 x 106 M 9.0 x 10 5 M 1.4 x 10 5 M 1.3 x 104 M 1.6 x 104 M
The efficiency n of fluorescence resonance energy transfer (FRET) is given by: R + R° A solution is prepared containing linear molecules, each consisting of an anthracene donor and a tryptophyl peptide acceptor separated by n L-prolyl linker units. The solution absorbs 0.230 mJ of laser radiation with a wavelength of 273 nm and emits 1.35 ×10² mJ of fluorescence at a wavelength of 293 nm. Given that R. = 2.20 nm, ø= 0.36 for anthracene, and the approximate length of one linker unit is 0.34 nm, determine n.
A trypsin enzyme assay was performed by mixing 50 µL of trypsin with 950 µL of substrate in a cuvette with a pathlength of 1.00 cm. The absorption coefficient for the product formed by this reaction at 480 nm is 4130 M-'cm'. The rate of change in absorbance at 480 nm was 0.129 abs/min. What is the rate of this reaction in units of µmol/min?