quiz3 - Page 1 of 6 Name: BE.011/2772J Spring 2004 QUIZ III...

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Page 1 of 6 Name: BE.011/2772J Spring 2004 QUIZ III You have 1 hour for this exam. CLOSED BOOK 3 pages notes allowed 1 (45 points) 2 (30 points) 3 (25 points) total (100 points) Some formulas, constants, and conversions you may need: k = 1.38 × 10 -23 J/K N A = 6.02 × 10 23 0°C = 273K

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Page 2 of 6 Name: 1.) DNA supercoiling We saw that circular DNA plasmids can supercoil into right or left handed supercoils with τ number of turns: τ =-1 τ = 0 τ = 1 The energy in which it has τ turns is ε = τ 2 B where B is a constant. a) (10 pts) Draw the first few energy levels. Label the levels with their values of τ , and draw the energy levels to scale as much as possible (or label with its value of ε ). Include degeneracies. ε
Page 3 of 6 Name: b) (2 pts) What are the units of B? c) (18 pts) If T = B/k, what is the population of each of the energy levels at equilibrium? Which microstates are relevant (i.e., populated?). Levels which have less than 1% of the population can be considered negligible. Make a plot of population vs. energy justifying this.

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This note was uploaded on 11/11/2011 for the course BIO 20.010j taught by Professor Lindagriffith during the Spring '06 term at MIT.

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quiz3 - Page 1 of 6 Name: BE.011/2772J Spring 2004 QUIZ III...

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