Chemistry Quiz: Fluorescence, Protein Folding, and DNA Helicase Reaction - Prof. Stefan Fr, Quizzes of Physical Chemistry

Download Chemistry Quiz: Fluorescence, Protein Folding, and DNA Helicase Reaction - Prof. Stefan Fr and more Quizzes Physical Chemistry in PDF only on Docsity! 1 North Carolina State University Physical Chemistry 331 Makeup Quiz #1 Name ___________________________ Section ______ Wednesday Oct. 30 1. A new fluorescent molecule called "phosphomol” is being studied by a startup company. The molecule is to be used as a label inside cells. The patent application states that the fluorescence quantum yield of the molecule is 0.2 and the phosphoresence yield is 0.8. There is no non-radiative process. A scientist measures the experimental lifetime for the fluorescence as twenty nanoseconds. Please determine the fluorescence rate constant (kf) and the intersystem crossing rate constant (kIC) that forms the phosphorescent triplet state. kf = ________________________ kIC = _______________________ 2. A protein is observed to fold with two intermediate states called I1 and I2. The experimental rate scheme is: k1 k2 k3 F ßà I1 ßà I2 à U k-1 k-2 Fill in the following blanks with the correct rate expressions: d[F]/dt = ________________________________. d[I1]/dt = ________________________________. d[I2]/dt = ________________________________. d[U]/dt = ________________________________. In this scheme the rate constant k3 >> k2 >> k1 and k2 ~ k-1. Write an expression for the rate of unfolding (d[U]/dt) in terms of only the concentration of the folded molecule [F]. d[U]/dt = __________________________ [F]. 3. Double helical 30-mer DNA is formed with an observed pseudo first-order rate constant of 105 s-1 and standard free energy change of -11.456 kJ/mol. kh The reaction is 2 ssDNA ßà dsDNA. kd a. Calculate the equilibrium constant at 300 K K = _________________________. b. Calculate the folding rate constant. kh = ________________________.