P17G.3 Dansyl chloride, which absorbs maximally at 330 nm and fluorescesmaximally at 510 nm, can be used to label amino acids in fluorescencemicroscopy and FRET studies. Tabulated below is the variation of thefluorescence intensity of an aqueous solution of dansyl chloride with timeafter excitation by a short laser pulse (with I, the initial fluorescence intensity).The ratio of intensities is equal to the ratio of the rates of photon emission.t/ns5.010.015.020.00.450.210.110.05(a) Calculate the observed fluorescence lifetime of dansyl chloride in water.(b) The fluorescence quantum yield of dansyl chloride in water is 0.70. Whatis the fluorescence rate constant?

P17G.3 (a) The expression for Fluorescence intensity can be given as follows: where If(t):…

Answered: P17G.3 Dansyl chloride, which absorbs…

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

Chapter19: Nuclear Magnetic Resonance Spectroscopy

Section: Chapter Questions

Problem 19.19QAP

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Consider the quenching of an organic fluorescent species with τ0 = 3.5 ns by a d-metal ion with kQ = 2.5 × 109 dm3 mol−1 s−1. Predict the concentration of quencher required to decrease the fluorescence intensity of the organic species to 75 per cent of the unquenched value.
An amino acid on the surface of an enzyme was labelled covalently with 1.5-I AEDANS and it is known that the active site contains a tryptophan residue. The fluorescence quantum yield of tryptophan decreased by 15 per cent due to quenching by 1.5-I AEDANS. What is the distance between the active site and the surface of the enzyme?
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.
Tungsten hexacarbonyl (W(CO)6) is reacted with (EtC≡N) and the product is W(CO)3(N≡CEt)3.However, the product can be a mixture of fac and mer isomers. But a Chemist can determine fromanalysis of the infrared spectrum if the product is indeed a mixture of isomers or not. In thesynthesis experiment, the product shows 3 carbonyl stretching frequencies in the infraredspectrum, at 2021, 1898 and 1840 cm-1. Determine the irreducible representations of the stretchesexpected for each of the two species in their respective point group. Can you confirm what isomerwas isolated?
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The first excited state of Cu is reached by absorption of 327-nm radiation. (a) What is the energy difference (J) between the ground and excited states? (b) The ratio of degeneracies is g*/g0 3 for Cu. Find N*/N0 at 2 400 K. (c) By what percentage will the fraction in (b) be changed by a 15-K rise in temperature? (d) What will the ratio N*/N0 be at 6 000 K?
Define a molar extinction coefficient and briefly describe how it is measured.
When a sample of 4-heptanone was irradiated for 100 sec with 313 nm radiation with a power output of 50 W under conditions of total absorption, it was found that 2.8 mmole C2H4 was formed. What is the quantum yield for the formation of ethane?
4c. Calculate the values of Mn, Mw, Mz and polydispersity index for a polymer mixture having equivalent moles of two polymers with exact molecular weight being 2,000 Dalton and 10,000 Dalton.
Estimate the spin-only molar susceptibility of CuSO4⋅5H2O at 25 °C.
The first step in plant photosynthesis is absorption of light by chlorophyll molecules bound to proteins known as ‘light-harvesting complexes’, where the fluorescence of a chlorophyll molecule is quenched by other nearby chlorophyll molecules. Given that for a pair of chlorophyll a molecules R0 = 5.6 nm, by what distance should two chlorophyll a molecules be separated to shorten the fluorescence lifetime from 1 ns (a typical value for monomeric chlorophyll a in organic solvents) to 10 ps?
The molar absorption coefficient of a solute at 540 nm is 386 dm3 mol−1 cm−1. When light of that wavelength passes through a 5.00 mm cell containing a solution of the solute, 38.5 per cent of the light was absorbed. What is the molar concentration of the solute?

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